make module cache just about everything, but never return items

[httpd-crcsyncproxy.git] / crccache / mod_crccache_client.c

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* crcsync/crccache apache client module
 *
 * This module is designed to run as a cache server on the local end of a slow
 * internet link. This module uses a crc running hash algorithm to reduce
 * data transfer in cached but modified upstream files.
 *
 * CRC algorithm uses the crcsync library created by Rusty Russel
 *
 * Author: Toby Collett (2009)
 * Contributor: Alex Wulms (2009)
 *
 */



#include <assert.h>

#include <apr-1.0/apr_file_io.h>
#include <apr-1.0/apr_strings.h>
#include <apr-1.0/apr_base64.h>
#include <apr-1.0/apr_lib.h>
#include <apr-1.0/apr_date.h>
#include "ap_provider.h"
#include "util_filter.h"
#include "util_script.h"
#include "util_charset.h"
#include <http_log.h>
#include <http_protocol.h>

#include "crccache.h"
#include "ap_wrapper.h"
#include <crcsync/crcsync.h>
#include <zlib.h>

#include "mod_crccache_client.h"

static ap_filter_rec_t *crccache_decode_filter_handle;

/* Handles for cache filters, resolved at startup to eliminate
 * a name-to-function mapping on each request
 */
static ap_filter_rec_t *cache_save_filter_handle;
static ap_filter_rec_t *cache_save_subreq_filter_handle;
static ap_filter_rec_t *cache_out_filter_handle;
static ap_filter_rec_t *cache_out_subreq_filter_handle;
static ap_filter_rec_t *cache_remove_url_filter_handle;

/*
 * mod_disk_cache: Disk Based HTTP 1.1 Cache.
 *
 * Flow to Find the .data file:
 *   Incoming client requests URI /foo/bar/baz
 *   Generate <hash> off of /foo/bar/baz
 *   Open <hash>.header
 *   Read in <hash>.header file (may contain Format #1 or Format #2)
 *   If format #1 (Contains a list of Vary Headers):
 *      Use each header name (from .header) with our request values (headers_in) to
 *      regenerate <hash> using HeaderName+HeaderValue+.../foo/bar/baz
 *      re-read in <hash>.header (must be format #2)
 *   read in <hash>.data
 *
 * Format #1:
 *   apr_uint32_t format;
 *   apr_time_t expire;
 *   apr_array_t vary_headers (delimited by CRLF)
 *
 * Format #2:
 *   disk_cache_info_t (first sizeof(apr_uint32_t) bytes is the format)
 *   entity name (dobj->name) [length is in disk_cache_info_t->name_len]
 *   r->headers_out (delimited by CRLF)
 *   CRLF
 *   r->headers_in (delimited by CRLF)
 *   CRLF
 */

module AP_MODULE_DECLARE_DATA crccache_client_module;
APR_OPTIONAL_FN_TYPE(ap_cache_generate_key) *cache_generate_key;


static int cache_post_config(apr_pool_t *p, apr_pool_t *plog,
                             apr_pool_t *ptemp, server_rec *s)
{
    /* This is the means by which unusual (non-unix) os's may find alternate
     * means to run a given command (e.g. shebang/registry parsing on Win32)
     */
    cache_generate_key = APR_RETRIEVE_OPTIONAL_FN(ap_cache_generate_key);
    if (!cache_generate_key) {
        cache_generate_key = cache_generate_key_default;
    }
    return OK;
}


/*
 * Local static functions
 */

static char *header_file(apr_pool_t *p, crccache_client_conf *conf,
                disk_cache_object_t *dobj, const char *name) {
        if (!dobj->hashfile) {
                dobj->hashfile = ap_cache_generate_name(p, conf->dirlevels,
                                conf->dirlength, name);
        }

        if (dobj->prefix) {
                return apr_pstrcat(p, dobj->prefix, CACHE_VDIR_SUFFIX, "/",
                                dobj->hashfile, CACHE_HEADER_SUFFIX, NULL);
        } else {
                return apr_pstrcat(p, conf->cache_root, "/", dobj->hashfile,
                                CACHE_HEADER_SUFFIX, NULL);
        }
}

static char *data_file(apr_pool_t *p, crccache_client_conf *conf,
                disk_cache_object_t *dobj, const char *name) {
        if (!dobj->hashfile) {
                dobj->hashfile = ap_cache_generate_name(p, conf->dirlevels,
                                conf->dirlength, name);
        }

        if (dobj->prefix) {
                return apr_pstrcat(p, dobj->prefix, CACHE_VDIR_SUFFIX, "/",
                                dobj->hashfile, CACHE_DATA_SUFFIX, NULL);
        } else {
                return apr_pstrcat(p, conf->cache_root, "/", dobj->hashfile,
                                CACHE_DATA_SUFFIX, NULL);
        }
}

static void mkdir_structure(crccache_client_conf *conf, const char *file,
                apr_pool_t *pool) {
        apr_status_t rv;
        char *p;

        for (p = (char*) file + conf->cache_root_len + 1;;) {
                p = strchr(p, '/');
                if (!p)
                        break;
                *p = '\0';

                rv = apr_dir_make(file, APR_UREAD | APR_UWRITE | APR_UEXECUTE, pool);
                if (rv != APR_SUCCESS && !APR_STATUS_IS_EEXIST(rv)) {
                        /* XXX */
                }
                *p = '/';
                ++p;
        }
}

/* htcacheclean may remove directories underneath us.
 * So, we'll try renaming three times at a cost of 0.002 seconds.
 */
static apr_status_t safe_file_rename(crccache_client_conf *conf, const char *src,
                const char *dest, apr_pool_t *pool) {
        apr_status_t rv;

        rv = apr_file_rename(src, dest, pool);

        if (rv != APR_SUCCESS) {
                int i;

                for (i = 0; i < 2 && rv != APR_SUCCESS; i++) {
                        /* 1000 micro-seconds aka 0.001 seconds. */
                        apr_sleep(1000);

                        mkdir_structure(conf, dest, pool);

                        rv = apr_file_rename(src, dest, pool);
                }
        }

        return rv;
}

static apr_status_t file_cache_el_final(disk_cache_object_t *dobj,
                request_rec *r) {
        /* move the data over */
        if (dobj->tfd) {
                apr_status_t rv;

                apr_file_close(dobj->tfd);

                /* This assumes that the tempfile is on the same file system
                 * as the cache_root. If not, then we need a file copy/move
                 * rather than a rename.
                 */
                rv = apr_file_rename(dobj->tempfile, dobj->datafile, r->pool);
                if (rv != APR_SUCCESS) {
                        ap_log_error(APLOG_MARK, APLOG_WARNING, rv,r->server, "disk_cache: rename tempfile to datafile failed:"
                        " %s -> %s", dobj->tempfile, dobj->datafile);
                        apr_file_remove(dobj->tempfile, r->pool);
                }

                dobj->tfd = NULL;
        }

        return APR_SUCCESS;
}

static apr_status_t file_cache_errorcleanup(disk_cache_object_t *dobj,
                request_rec *r) {
        /* Remove the header file and the body file. */
        apr_file_remove(dobj->hdrsfile, r->pool);
        apr_file_remove(dobj->datafile, r->pool);

        /* If we opened the temporary data file, close and remove it. */
        if (dobj->tfd) {
                apr_file_close(dobj->tfd);
                apr_file_remove(dobj->tempfile, r->pool);
                dobj->tfd = NULL;
        }

        return APR_SUCCESS;
}

/* These two functions get and put state information into the data
 * file for an ap_cache_el, this state information will be read
 * and written transparent to clients of this module
 */
static int file_cache_recall_mydata(apr_file_t *fd, cache_info *info,
                disk_cache_object_t *dobj, request_rec *r) {
        apr_status_t rv;
        char *urlbuff;
        disk_cache_info_t disk_info;
        apr_size_t len;

        /* read the data from the cache file */
        len = sizeof(disk_cache_info_t);
        rv = apr_file_read_full(fd, &disk_info, len, &len);
        if (rv != APR_SUCCESS) {
                return rv;
        }

        /* Store it away so we can get it later. */
        dobj->disk_info = disk_info;

        info->status = disk_info.status;
        info->date = disk_info.date;
        info->expire = disk_info.expire;
        info->request_time = disk_info.request_time;
        info->response_time = disk_info.response_time;

        /* Note that we could optimize this by conditionally doing the palloc
         * depending upon the size. */
        urlbuff = apr_palloc(r->pool, disk_info.name_len + 1);
        len = disk_info.name_len;
        rv = apr_file_read_full(fd, urlbuff, len, &len);
        if (rv != APR_SUCCESS) {
                return rv;
        }
        urlbuff[disk_info.name_len] = '\0';

        /* check that we have the same URL */
        /* Would strncmp be correct? */
        if (strcmp(urlbuff, dobj->name) != 0) {
                return APR_EGENERAL;
        }

        return APR_SUCCESS;
}

static const char* regen_key(apr_pool_t *p, apr_table_t *headers,
                apr_array_header_t *varray, const char *oldkey) {
        struct iovec *iov;
        int i, k;
        int nvec;
        const char *header;
        const char **elts;

        nvec = (varray->nelts * 2) + 1;
        iov = apr_palloc(p, sizeof(struct iovec) * nvec);
        elts = (const char **) varray->elts;

        /* TODO:
         *    - Handle multiple-value headers better. (sort them?)
         *    - Handle Case in-sensitive Values better.
         *        This isn't the end of the world, since it just lowers the cache
         *        hit rate, but it would be nice to fix.
         *
         * The majority are case insenstive if they are values (encoding etc).
         * Most of rfc2616 is case insensitive on header contents.
         *
         * So the better solution may be to identify headers which should be
         * treated case-sensitive?
         *  HTTP URI's (3.2.3) [host and scheme are insensitive]
         *  HTTP method (5.1.1)
         *  HTTP-date values (3.3.1)
         *  3.7 Media Types [exerpt]
         *     The type, subtype, and parameter attribute names are case-
         *     insensitive. Parameter values might or might not be case-sensitive,
         *     depending on the semantics of the parameter name.
         *  4.20 Except [exerpt]
         *     Comparison of expectation values is case-insensitive for unquoted
         *     tokens (including the 100-continue token), and is case-sensitive for
         *     quoted-string expectation-extensions.
         */

        for (i = 0, k = 0; i < varray->nelts; i++) {
                header = apr_table_get(headers, elts[i]);
                if (!header) {
                        header = "";
                }
                iov[k].iov_base = (char*) elts[i];
                iov[k].iov_len = strlen(elts[i]);
                k++;
                iov[k].iov_base = (char*) header;
                iov[k].iov_len = strlen(header);
                k++;
        }
        iov[k].iov_base = (char*) oldkey;
        iov[k].iov_len = strlen(oldkey);
        k++;

        return apr_pstrcatv(p, iov, k, NULL);
}

static int array_alphasort(const void *fn1, const void *fn2) {
        return strcmp(*(char**) fn1, *(char**) fn2);
}

static void tokens_to_array(apr_pool_t *p, const char *data,
                apr_array_header_t *arr) {
        char *token;

        while ((token = ap_get_list_item(p, &data)) != NULL) {
                *((const char **) apr_array_push(arr)) = token;
        }

        /* Sort it so that "Vary: A, B" and "Vary: B, A" are stored the same. */
        qsort((void *) arr->elts, arr->nelts, sizeof(char *), array_alphasort);
}

/*
 * Hook and mod_cache callback functions
 */
int create_entity(cache_handle_t *h, request_rec *r, const char *key,
                apr_off_t len) {
        crccache_client_conf *conf = ap_get_module_config(r->server->module_config,
                        &crccache_client_module);
        cache_object_t *obj;
        disk_cache_object_t *dobj;

        if (conf->cache_root == NULL) {
                return DECLINED;
        }

        /* Allocate and initialize cache_object_t and disk_cache_object_t */
        h->cache_obj = obj = apr_pcalloc(r->pool, sizeof(*obj));
        obj->vobj = dobj = apr_pcalloc(r->pool, sizeof(*dobj));

        obj->key = apr_pstrdup(r->pool, key);

        dobj->name = obj->key;
        dobj->prefix = NULL;
        /* Save the cache root */
        dobj->root = apr_pstrndup(r->pool, conf->cache_root, conf->cache_root_len);
        dobj->root_len = conf->cache_root_len;
        dobj->datafile = data_file(r->pool, conf, dobj, key);
        dobj->hdrsfile = header_file(r->pool, conf, dobj, key);
        dobj->tempfile = apr_pstrcat(r->pool, conf->cache_root, AP_TEMPFILE, NULL);

        return OK;
}

int open_entity(cache_handle_t *h, request_rec *r, const char *key) {
        apr_uint32_t format;
        apr_size_t len;
        const char *nkey;
        apr_status_t rc;
        static int error_logged = 0;
        crccache_client_conf *conf = ap_get_module_config(r->server->module_config,
                        &crccache_client_module);
        apr_finfo_t finfo;
        cache_object_t *obj;
        cache_info *info;
        disk_cache_object_t *dobj;
        int flags;
        h->cache_obj = NULL;

        /* Look up entity keyed to 'url' */
        if (conf->cache_root == NULL) {
                if (!error_logged) {
                        error_logged = 1;
                        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                                        "disk_cache: Cannot cache files to disk without a CacheRootClient specified.");
        }
        return DECLINED;
    }

    /* Create and init the cache object */
    h->cache_obj = obj = apr_pcalloc(r->pool, sizeof(cache_object_t));
    obj->vobj = dobj = apr_pcalloc(r->pool, sizeof(disk_cache_object_t));

    info = &(obj->info);

    /* Open the headers file */
    dobj->prefix = NULL;

    /* Save the cache root */
    dobj->root = apr_pstrndup(r->pool, conf->cache_root, conf->cache_root_len);
    dobj->root_len = conf->cache_root_len;

    dobj->hdrsfile = header_file(r->pool, conf, dobj, key);
    flags = APR_READ|APR_BINARY|APR_BUFFERED;
    rc = apr_file_open(&dobj->hfd, dobj->hdrsfile, flags, 0, r->pool);
    if (rc != APR_SUCCESS) {
        return DECLINED;
    }

    /* read the format from the cache file */
    len = sizeof(format);
    apr_file_read_full(dobj->hfd, &format, len, &len);

    if (format == VARY_FORMAT_VERSION) {
        apr_array_header_t* varray;
        apr_time_t expire;

        len = sizeof(expire);
        apr_file_read_full(dobj->hfd, &expire, len, &len);

        varray = apr_array_make(r->pool, 5, sizeof(char*));
        rc = read_array(r, varray, dobj->hfd);
        if (rc != APR_SUCCESS) {
            ap_log_error(APLOG_MARK, APLOG_ERR, rc, r->server,
                         "disk_cache: Cannot parse vary header file: %s",
                         dobj->hdrsfile);
            return DECLINED;
        }
        apr_file_close(dobj->hfd);

        nkey = regen_key(r->pool, r->headers_in, varray, key);

        dobj->hashfile = NULL;
        dobj->prefix = dobj->hdrsfile;
        dobj->hdrsfile = header_file(r->pool, conf, dobj, nkey);

        flags = APR_READ|APR_BINARY|APR_BUFFERED;
        rc = apr_file_open(&dobj->hfd, dobj->hdrsfile, flags, 0, r->pool);
        if (rc != APR_SUCCESS) {
            return DECLINED;
        }
    }
    else if (format != DISK_FORMAT_VERSION) {
        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                     "cache_disk: File '%s' has a version mismatch. File had version: %d.",
                     dobj->hdrsfile, format);
        return DECLINED;
    }
    else {
        apr_off_t offset = 0;
        /* This wasn't a Vary Format file, so we must seek to the
         * start of the file again, so that later reads work.
         */
        apr_file_seek(dobj->hfd, APR_SET, &offset);
        nkey = key;
    }

    obj->key = nkey;
    dobj->key = nkey;
    dobj->name = key;
    dobj->datafile = data_file(r->pool, conf, dobj, nkey);
    dobj->tempfile = apr_pstrcat(r->pool, conf->cache_root, AP_TEMPFILE, NULL);

    /* Open the data file */
    flags = APR_READ|APR_BINARY;
#ifdef APR_SENDFILE_ENABLED
    flags |= APR_SENDFILE_ENABLED;
#endif
    rc = apr_file_open(&dobj->fd, dobj->datafile, flags, 0, r->pool);
    if (rc != APR_SUCCESS) {
        /* XXX: Log message */
        return DECLINED;
    }

    rc = apr_file_info_get(&finfo, APR_FINFO_SIZE, dobj->fd);
    if (rc == APR_SUCCESS) {
        dobj->file_size = finfo.size;
    }

    /* Read the bytes to setup the cache_info fields */
    rc = file_cache_recall_mydata(dobj->hfd, info, dobj, r);
    if (rc != APR_SUCCESS) {
        /* XXX log message */
        return DECLINED;
    }

    /* Initialize the cache_handle callback functions */
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "disk_cache: Recalled cached URL info header %s",  dobj->name);
    return OK;
}

int remove_entity(cache_handle_t *h) {
        /* Null out the cache object pointer so next time we start from scratch  */
        h->cache_obj = NULL;

        return OK;
}

int remove_url(cache_handle_t *h, apr_pool_t *p) {
        apr_status_t rc;
        disk_cache_object_t *dobj;

        /* Get disk cache object from cache handle */
        dobj = (disk_cache_object_t *) h->cache_obj->vobj;
        if (!dobj) {
                return DECLINED;
        }

        /* Delete headers file */
        if (dobj->hdrsfile) {
                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL,
                "disk_cache: Deleting %s from cache.", dobj->hdrsfile);

                rc = apr_file_remove(dobj->hdrsfile, p);
                if ((rc != APR_SUCCESS) && !APR_STATUS_IS_ENOENT(rc)) {
                        /* Will only result in an output if httpd is started with -e debug.
                         * For reason see log_error_core for the case s == NULL.
                         */
                        ap_log_error(APLOG_MARK, APLOG_DEBUG, rc, NULL,
                        "disk_cache: Failed to delete headers file %s from cache.",
                        dobj->hdrsfile);
                        return DECLINED;
                }
        }

        /* Delete data file */
        if (dobj->datafile) {
                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL,
                "disk_cache: Deleting %s from cache.", dobj->datafile);

                rc = apr_file_remove(dobj->datafile, p);
                if ((rc != APR_SUCCESS) && !APR_STATUS_IS_ENOENT(rc)) {
                        /* Will only result in an output if httpd is started with -e debug.
                         * For reason see log_error_core for the case s == NULL.
                         */
                        ap_log_error(APLOG_MARK, APLOG_DEBUG, rc, NULL,
                        "disk_cache: Failed to delete data file %s from cache.",
                        dobj->datafile);
                        return DECLINED;
                }
        }

        /* now delete directories as far as possible up to our cache root */
        if (dobj->root) {
                const char *str_to_copy;

                str_to_copy = dobj->hdrsfile ? dobj->hdrsfile : dobj->datafile;
                if (str_to_copy) {
                        char *dir, *slash, *q;

                        dir = apr_pstrdup(p, str_to_copy);

                        /* remove filename */
                        slash = strrchr(dir, '/');
                        *slash = '\0';

                        /*
                         * now walk our way back to the cache root, delete everything
                         * in the way as far as possible
                         *
                         * Note: due to the way we constructed the file names in
                         * header_file and data_file, we are guaranteed that the
                         * cache_root is suffixed by at least one '/' which will be
                         * turned into a terminating null by this loop.  Therefore,
                         * we won't either delete or go above our cache root.
                         */
                        for (q = dir + dobj->root_len; *q; ) {
                                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL,
                                "disk_cache: Deleting directory %s from cache",
                                dir);

                                rc = apr_dir_remove(dir, p);
                                if (rc != APR_SUCCESS && !APR_STATUS_IS_ENOENT(rc)) {
                                        break;
                                }
                                slash = strrchr(q, '/');
                                *slash = '\0';
                        }
                }
        }

        return OK;
}

apr_status_t read_array(request_rec *r, apr_array_header_t* arr,
                apr_file_t *file) {
        char w[MAX_STRING_LEN];
        int p;
        apr_status_t rv;

        while (1) {
                rv = apr_file_gets(w, MAX_STRING_LEN - 1, file);
                if (rv != APR_SUCCESS) {
                        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                                        "Premature end of vary array.");
                        return rv;
                }

                p = strlen(w);
                if (p> 0 && w[p - 1] == '\n') {
                        if (p> 1 && w[p - 2] == CR) {
                                w[p - 2] = '\0';
                        }
                        else {
                                w[p - 1] = '\0';
                        }
                }

                /* If we've finished reading the array, break out of the loop. */
                if (w[0] == '\0') {
                        break;
                }

                *((const char **) apr_array_push(arr)) = apr_pstrdup(r->pool, w);
        }

        return APR_SUCCESS;
}

static apr_status_t store_array(apr_file_t *fd, apr_array_header_t* arr) {
        int i;
        apr_status_t rv;
        struct iovec iov[2];
        apr_size_t amt;
        const char **elts;

        elts = (const char **) arr->elts;

        for (i = 0; i < arr->nelts; i++) {
                iov[0].iov_base = (char*) elts[i];
                iov[0].iov_len = strlen(elts[i]);
                iov[1].iov_base = CRLF;
                iov[1].iov_len = sizeof(CRLF) - 1;

                rv = apr_file_writev(fd, (const struct iovec *) &iov, 2,
                                &amt);
                if (rv != APR_SUCCESS) {
                        return rv;
                }
        }

        iov[0].iov_base = CRLF;
        iov[0].iov_len = sizeof(CRLF) - 1;

        return apr_file_writev(fd, (const struct iovec *) &iov, 1,
                        &amt);
}

apr_status_t read_table(cache_handle_t *handle, request_rec *r,
                apr_table_t *table, apr_file_t *file) {
        char w[MAX_STRING_LEN];
        char *l;
        int p;
        apr_status_t rv;

        while (1) {

                /* ### What about APR_EOF? */
                rv = apr_file_gets(w, MAX_STRING_LEN - 1, file);
                if (rv != APR_SUCCESS) {
                        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                                        "Premature end of cache headers.");
                        return rv;
                }

                /* Delete terminal (CR?)LF */

                p = strlen(w);
                /* Indeed, the host's '\n':
                 '\012' for UNIX; '\015' for MacOS; '\025' for OS/390
                 -- whatever the script generates.
                 */
                if (p> 0 && w[p - 1] == '\n') {
                        if (p> 1 && w[p - 2] == CR) {
                                w[p - 2] = '\0';
                        }
                        else {
                                w[p - 1] = '\0';
                        }
                }

                /* If we've finished reading the headers, break out of the loop. */
                if (w[0] == '\0') {
                        break;
                }

#if APR_CHARSET_EBCDIC
                        /* Chances are that we received an ASCII header text instead of
                         * the expected EBCDIC header lines. Try to auto-detect:
                         */
                        if (!(l = strchr(w, ':'))) {
                                int maybeASCII = 0, maybeEBCDIC = 0;
                                unsigned char *cp, native;
                                apr_size_t inbytes_left, outbytes_left;

                                for (cp = w; *cp != '\0'; ++cp) {
                                        native = apr_xlate_conv_byte(ap_hdrs_from_ascii, *cp);
                                        if (apr_isprint(*cp) && !apr_isprint(native))
                                        ++maybeEBCDIC;
                                        if (!apr_isprint(*cp) && apr_isprint(native))
                                        ++maybeASCII;
                                }
                                if (maybeASCII> maybeEBCDIC) {
                                        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                                                        "CGI Interface Error: Script headers apparently ASCII: (CGI = %s)",
                             r->filename);
                inbytes_left = outbytes_left = cp - w;
                apr_xlate_conv_buffer(ap_hdrs_from_ascii,
                                      w, &inbytes_left, w, &outbytes_left);
            }
        }
#endif /*APR_CHARSET_EBCDIC*/

        /* if we see a bogus header don't ignore it. Shout and scream */
        if (!(l = strchr(w, ':'))) {
            return APR_EGENERAL;
        }

        *l++ = '\0';
        while (*l && apr_isspace(*l)) {
            ++l;
        }

        apr_table_add(table, w, l);
    }

    return APR_SUCCESS;
}

/**
 * Clean-up memory used by helper libraries, that don't know about apr_palloc
 * and that (probably) use classical malloc/free
 */
apr_status_t deflate_ctx_cleanup(void *data)
{
        crccache_client_ctx *ctx = (crccache_client_ctx *)data;

        if (ctx != NULL)
        {
                if (ctx->decompression_state != DECOMPRESSION_ENDED)
                {
                        inflateEnd(ctx->decompression_stream);
                        ctx->decompression_state = DECOMPRESSION_ENDED;
                }
        }
        return APR_SUCCESS;
}


/*
 * Reads headers from a buffer and returns an array of headers.
 * Returns NULL on file error
 * This routine tries to deal with too long lines and continuation lines.
 * @@@: XXX: FIXME: currently the headers are passed thru un-merged.
 * Is that okay, or should they be collapsed where possible?
 */
apr_status_t recall_headers(cache_handle_t *h, request_rec *r) {
        const char *data;
        apr_size_t len;
        apr_bucket *e;
        unsigned i;
        int z_RC;

        disk_cache_object_t *dobj = (disk_cache_object_t *) h->cache_obj->vobj;

        /* This case should not happen... */
        if (!dobj->hfd) {
                /* XXX log message */
                return APR_NOTFOUND;
        }

        h->req_hdrs = apr_table_make(r->pool, 20);
        h->resp_hdrs = apr_table_make(r->pool, 20);

        /* Call routine to read the header lines/status line */
        read_table(h, r, h->resp_hdrs, dobj->hfd);
        read_table(h, r, h->req_hdrs, dobj->hfd);

        // TODO: We only really want to add our block hashes if the cache is not fresh
        // TODO: We could achieve that by adding a filter here on sending the request
        // and then doing all of this in the filter 'JIT'
        e = apr_bucket_file_create(dobj->fd, 0, (apr_size_t) dobj->file_size, r->pool,
        r->connection->bucket_alloc);

        /* read */
        apr_bucket_read(e, &data, &len, APR_BLOCK_READ);

        // this will be rounded down, but thats okay
        // TODO: I think that we should just add %  to the trailing block, otherwise our extra block
        // is always limited to max of BLOCK_COUNT size.
        size_t blocksize = len/FULL_BLOCK_COUNT;
        size_t tail_block_size = len % FULL_BLOCK_COUNT;
        size_t block_count_including_final_block = FULL_BLOCK_COUNT + (tail_block_size != 0);
        // sanity check for very small files
        if (blocksize> 4)
        {
                //ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"crccache: %d blocks of %ld bytes",FULL_BLOCK_COUNT,blocksize);

                crccache_client_ctx * ctx;
                ctx = apr_pcalloc(r->pool, sizeof(*ctx));
                ctx->bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);
                ctx->block_size = blocksize;
                ctx->tail_block_size = tail_block_size;
                ctx->state = DECODING_NEW_SECTION;
                ctx->cached_bucket = e;

                // Setup inflate for decompressing non-matched literal data
                ctx->decompression_stream = apr_palloc(r->pool, sizeof(*(ctx->decompression_stream)));
                ctx->decompression_stream->zalloc = Z_NULL;
                ctx->decompression_stream->zfree = Z_NULL;
                ctx->decompression_stream->opaque = Z_NULL;
                ctx->decompression_stream->avail_in = 0;
                ctx->decompression_stream->next_in = Z_NULL;
                z_RC = inflateInit(ctx->decompression_stream);
                if (z_RC != Z_OK)
                {
                        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, r->server,
                        "Can not initialize decompression engine, return code: %d", z_RC);
                        return APR_SUCCESS;
                }
                ctx->decompression_state = DECOMPRESSION_INITIALIZED;

                // Register a cleanup function to cleanup internal libz resources
                apr_pool_cleanup_register(r->pool, ctx, deflate_ctx_cleanup,
                                  apr_pool_cleanup_null);

                // All OK to go for the crcsync decoding: add the headers
                // and set-up the decoding filter

                // add one for base 64 overflow and null terminator
                char hash_set[HASH_HEADER_SIZE+1];

                uint64_t crcs[block_count_including_final_block];
                crc_of_blocks(data, len, blocksize, HASH_SIZE, crcs);

                // swap to network byte order
                for (i = 0; i < block_count_including_final_block;++i)
                {
                        htobe64(crcs[i]);
                }

                apr_base64_encode (hash_set, (char *)crcs, block_count_including_final_block*sizeof(crcs[0]));
                hash_set[HASH_HEADER_SIZE] = '\0';
                //apr_bucket_delete(e);

                // TODO; bit of a safety margin here, could calculate exact size
                const int block_header_max_size = HASH_HEADER_SIZE+32;
                char block_header_txt[block_header_max_size];
                snprintf(block_header_txt, block_header_max_size,"fs=%zu, h=%s",len,hash_set);
                apr_table_set(r->headers_in, BLOCK_HEADER, block_header_txt);
                // TODO: do we want to cache the hashes here?

                // initialise the context for our sha1 digest of the unencoded response
                EVP_MD_CTX_init(&ctx->mdctx);
                const EVP_MD *md = EVP_sha1();
                EVP_DigestInit_ex(&ctx->mdctx, md, NULL);

                // we want to add a filter here so that we can decode the response.
                // we need access to the original cached data when we get the response as
                // we need that to fill in the matched blocks.
                ap_add_output_filter_handle(crccache_decode_filter_handle,
                ctx, r, r->connection);

                // TODO: why is hfd file only closed in this case?
                apr_file_close(dobj->hfd);
        }
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
        "crccache_client: Recalled headers for URL %s", dobj->name);
        return APR_SUCCESS;
}

apr_status_t recall_body(cache_handle_t *h, apr_pool_t *p,
                apr_bucket_brigade *bb) {
        apr_bucket *e;
        disk_cache_object_t *dobj = (disk_cache_object_t*) h->cache_obj->vobj;

        e = apr_bucket_file_create(dobj->fd, 0, (apr_size_t) dobj->file_size, p,
                        bb->bucket_alloc);

        APR_BRIGADE_INSERT_HEAD(bb, e);
        e = apr_bucket_eos_create(bb->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(bb, e);

        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL,  "crccache_client: Recalled body for URL %s", dobj->name);
        return APR_SUCCESS;
}

apr_status_t store_table(apr_file_t *fd, apr_table_t *table) {
        int i;
        apr_status_t rv;
        struct iovec iov[4];
        apr_size_t amt;
        apr_table_entry_t *elts;

        elts = (apr_table_entry_t *) apr_table_elts(table)->elts;
        for (i = 0; i < apr_table_elts(table)->nelts; ++i) {
                if (elts[i].key != NULL) {
                        iov[0].iov_base = elts[i].key;
                        iov[0].iov_len = strlen(elts[i].key);
                        iov[1].iov_base = ": ";
                        iov[1].iov_len = sizeof(": ") - 1;
                        iov[2].iov_base = elts[i].val;
                        iov[2].iov_len = strlen(elts[i].val);
                        iov[3].iov_base = CRLF;
                        iov[3].iov_len = sizeof(CRLF) - 1;

                        rv = apr_file_writev(fd, (const struct iovec *) &iov, 4,
                                        &amt);
                        if (rv != APR_SUCCESS) {
                                return rv;
                        }
                }
        }
        iov[0].iov_base = CRLF;
        iov[0].iov_len = sizeof(CRLF) - 1;
        rv = apr_file_writev(fd, (const struct iovec *) &iov, 1,
                        &amt);
        return rv;
}

apr_status_t store_headers(cache_handle_t *h, request_rec *r,
                cache_info *info) {
        crccache_client_conf *conf = ap_get_module_config(r->server->module_config,
                        &crccache_client_module);

        apr_status_t rv;
        apr_size_t amt;
        disk_cache_object_t *dobj = (disk_cache_object_t*) h->cache_obj->vobj;

        disk_cache_info_t disk_info;
        struct iovec iov[2];

        /* This is flaky... we need to manage the cache_info differently */
        h->cache_obj->info = *info;

        if (r->headers_out) {
                const char *tmp;

                tmp = apr_table_get(r->headers_out, "Vary");

                if (tmp) {
                        apr_array_header_t* varray;
                        apr_uint32_t format = VARY_FORMAT_VERSION;

                        /* If we were initially opened as a vary format, rollback
                         * that internal state for the moment so we can recreate the
                         * vary format hints in the appropriate directory.
                         */
                        if (dobj->prefix) {
                                dobj->hdrsfile = dobj->prefix;
                                dobj->prefix = NULL;
                        }

                        mkdir_structure(conf, dobj->hdrsfile, r->pool);

                        rv = apr_file_mktemp(&dobj->tfd, dobj->tempfile,
                                        APR_CREATE | APR_WRITE | APR_BINARY | APR_EXCL,
                                        r->pool);

                        if (rv != APR_SUCCESS) {
                                return rv;
                        }

                        amt = sizeof(format);
                        apr_file_write(dobj->tfd, &format, &amt);

                        amt = sizeof(info->expire);
                        apr_file_write(dobj->tfd, &info->expire, &amt);

                        varray = apr_array_make(r->pool, 6, sizeof(char*));
                        tokens_to_array(r->pool, tmp, varray);

                        store_array(dobj->tfd, varray);

                        apr_file_close(dobj->tfd);

                        dobj->tfd = NULL;

                        rv = safe_file_rename(conf, dobj->tempfile, dobj->hdrsfile,
                                        r->pool);
                        if (rv != APR_SUCCESS) {
                                ap_log_error(APLOG_MARK, APLOG_WARNING, rv, r->server,
                                                "disk_cache: rename tempfile to varyfile failed: %s -> %s",
                    dobj->tempfile, dobj->hdrsfile);
                apr_file_remove(dobj->tempfile, r->pool);
                return rv;
            }

            dobj->tempfile = apr_pstrcat(r->pool, conf->cache_root, AP_TEMPFILE, NULL);
            tmp = regen_key(r->pool, r->headers_in, varray, dobj->name);
            dobj->prefix = dobj->hdrsfile;
            dobj->hashfile = NULL;
            dobj->datafile = data_file(r->pool, conf, dobj, tmp);
            dobj->hdrsfile = header_file(r->pool, conf, dobj, tmp);
        }
    }


    rv = apr_file_mktemp(&dobj->hfd, dobj->tempfile,
                         APR_CREATE | APR_WRITE | APR_BINARY |
                         APR_BUFFERED | APR_EXCL, r->pool);

    if (rv != APR_SUCCESS) {
        return rv;
    }

    disk_info.format = DISK_FORMAT_VERSION;
    disk_info.date = info->date;
    disk_info.expire = info->expire;
    disk_info.entity_version = dobj->disk_info.entity_version++;
    disk_info.request_time = info->request_time;
    disk_info.response_time = info->response_time;
    disk_info.status = info->status;

    disk_info.name_len = strlen(dobj->name);

    iov[0].iov_base = (void*)&disk_info;
    iov[0].iov_len = sizeof(disk_cache_info_t);
    iov[1].iov_base = (void*)dobj->name;
    iov[1].iov_len = disk_info.name_len;

    rv = apr_file_writev(dobj->hfd, (const struct iovec *) &iov, 2, &amt);
    if (rv != APR_SUCCESS) {
        return rv;
    }

    if (r->headers_out) {
        apr_table_t *headers_out;

        headers_out = ap_cache_cacheable_hdrs_out(r->pool, r->headers_out,
                                                  r->server);

        if (!apr_table_get(headers_out, "Content-Type")
            && r->content_type) {
            apr_table_setn(headers_out, "Content-Type",
                           ap_make_content_type(r, r->content_type));
        }

        headers_out = apr_table_overlay(r->pool, headers_out,
                                        r->err_headers_out);
        rv = store_table(dobj->hfd, headers_out);
        if (rv != APR_SUCCESS) {
            return rv;
        }
    }

    /* Parse the vary header and dump those fields from the headers_in. */
    /* FIXME: Make call to the same thing cache_select calls to crack Vary. */
    if (r->headers_in) {
        apr_table_t *headers_in;

        headers_in = ap_cache_cacheable_hdrs_out(r->pool, r->headers_in,
                                                 r->server);
        rv = store_table(dobj->hfd, headers_in);
        if (rv != APR_SUCCESS) {
            return rv;
        }
    }

    apr_file_close(dobj->hfd); /* flush and close */

    /* Remove old file with the same name. If remove fails, then
     * perhaps we need to create the directory tree where we are
     * about to write the new headers file.
     */
    rv = apr_file_remove(dobj->hdrsfile, r->pool);
    if (rv != APR_SUCCESS) {
        mkdir_structure(conf, dobj->hdrsfile, r->pool);
    }

    rv = safe_file_rename(conf, dobj->tempfile, dobj->hdrsfile, r->pool);
    if (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_WARNING, rv, r->server,
                     "disk_cache: rename tempfile to hdrsfile failed: %s -> %s",
                     dobj->tempfile, dobj->hdrsfile);
        apr_file_remove(dobj->tempfile, r->pool);
        return rv;
    }

    dobj->tempfile = apr_pstrcat(r->pool, conf->cache_root, AP_TEMPFILE, NULL);

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "disk_cache: Stored headers for URL %s",  dobj->name);
    return APR_SUCCESS;
}

apr_status_t store_body(cache_handle_t *h, request_rec *r,
                apr_bucket_brigade *bb) {
        apr_bucket *e;
        apr_status_t rv;

        disk_cache_object_t *dobj = (disk_cache_object_t *) h->cache_obj->vobj;
        crccache_client_conf *conf = ap_get_module_config(r->server->module_config,
                        &crccache_client_module);

        /* We write to a temp file and then atomically rename the file over
         * in file_cache_el_final().
         */
        if (!dobj->tfd) {
                rv = apr_file_mktemp(&dobj->tfd, dobj->tempfile, APR_CREATE | APR_WRITE
                                | APR_BINARY | APR_BUFFERED | APR_EXCL, r->pool);
                if (rv != APR_SUCCESS) {
                        return rv;
                }
                dobj->file_size = 0;
        }

        for (e = APR_BRIGADE_FIRST(bb); e != APR_BRIGADE_SENTINEL(bb); e = APR_BUCKET_NEXT(e)) {
                const char *str;
                apr_size_t length, written;
                rv = apr_bucket_read(e, &str, &length, APR_BLOCK_READ);
                if (rv != APR_SUCCESS) {
                        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                        "cache_disk: Error when reading bucket for URL %s",
                        h->cache_obj->key);
                        /* Remove the intermediate cache file and return non-APR_SUCCESS */
                        file_cache_errorcleanup(dobj, r);
                        return rv;
                }
                rv = apr_file_write_full(dobj->tfd, str, length, &written);
                if (rv != APR_SUCCESS) {
                        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                                        "cache_disk: Error when writing cache file for URL %s",
                                        h->cache_obj->key);
                        /* Remove the intermediate cache file and return non-APR_SUCCESS */
                        file_cache_errorcleanup(dobj, r);
                        return rv;
                }
                dobj->file_size += written;
                if (dobj->file_size> conf->maxfs) {
                        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                                        "cache_disk: URL %s failed the size check "
                                        "(%" APR_OFF_T_FMT " > %" APR_OFF_T_FMT ")",
                                        h->cache_obj->key, dobj->file_size, conf->maxfs);
                        /* Remove the intermediate cache file and return non-APR_SUCCESS */
                        file_cache_errorcleanup(dobj, r);
                        return APR_EGENERAL;
                }
        }

        /* Was this the final bucket? If yes, close the temp file and perform
         * sanity checks.
         */
        if (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(bb))) {
                if (r->connection->aborted || r->no_cache) {
                        ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
                                        "disk_cache: Discarding body for URL %s "
                                        "because connection has been aborted.",
                                        h->cache_obj->key);
                        /* Remove the intermediate cache file and return non-APR_SUCCESS */
                        file_cache_errorcleanup(dobj, r);
                        return APR_EGENERAL;
                }
                if (dobj->file_size < conf->minfs) {
                        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                                        "cache_disk: URL %s failed the size check "
                                        "(%" APR_OFF_T_FMT " < %" APR_OFF_T_FMT ")",
                                        h->cache_obj->key, dobj->file_size, conf->minfs);
                        /* Remove the intermediate cache file and return non-APR_SUCCESS */
                        file_cache_errorcleanup(dobj, r);
                        return APR_EGENERAL;
                }

                /* All checks were fine. Move tempfile to final destination */
                /* Link to the perm file, and close the descriptor */
                file_cache_el_final(dobj, r);
                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                                "disk_cache: Body for URL %s cached.", dobj->name);
        }

        return APR_SUCCESS;
}

/*
 * CACHE_DECODE filter
 * ----------------
 *
 * Deliver cached content (headers and body) up the stack.
 */
static int crccache_decode_filter(ap_filter_t *f, apr_bucket_brigade *bb) {
        apr_bucket *e;
        request_rec *r = f->r;
        // TODO: set up context type struct
        crccache_client_ctx *ctx = f->ctx;

        // if this is the first pass in decoding we should check the headers etc
        // and fix up those headers that we modified as part of the encoding
        if (ctx->headers_checked == 0)
        {
                ctx->headers_checked = 1;

                ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                                "CRCSYNC retuned status code (%d)", r->status);

                // TODO: make this work if we have multiple encodings
                const char * content_encoding;
                content_encoding = apr_table_get(r->headers_out, ENCODING_HEADER);
                if (content_encoding == NULL || strcmp(CRCCACHE_ENCODING, content_encoding)
                                != 0) {
                        ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                        "CRCSYNC not decoding, content encoding bad (%s)", content_encoding?content_encoding:"NULL");
                        ap_remove_output_filter(f);
                        return ap_pass_brigade(f->next, bb);
                }
                // TODO: Remove crcsync from the content encoding header

                // TODO: we should only set the status back to 200 if there are no
                // other instance codings used
                //r->status = 200;
                //r->status_line = "200 OK";


                // TODO: Fix up the etag as well
        }



        /* Do nothing if asked to filter nothing. */
        if (APR_BRIGADE_EMPTY(bb)) {
                return ap_pass_brigade(f->next, bb);
        }

        /* We require that we have a context already, otherwise we dont have our cached file
         * to fill in the gaps with.
         */
        if (!ctx) {
                ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                                "No context available %s", r->uri);
                ap_remove_output_filter(f);
                return ap_pass_brigade(f->next, bb);
        }

        while (!APR_BRIGADE_EMPTY(bb))
        {
                const char *data;
                apr_size_t len;

                e = APR_BRIGADE_FIRST(bb);

                if (APR_BUCKET_IS_EOS(e)) {

                        /* Remove EOS from the old list, and insert into the new. */
                        APR_BUCKET_REMOVE(e);
                        APR_BRIGADE_INSERT_TAIL(ctx->bb, e);

                        /* This filter is done once it has served up its content */
                        ap_remove_output_filter(f);

                        // TODO: check strong hash here
                        unsigned md_len;
                        unsigned char md_value[EVP_MAX_MD_SIZE];
                        EVP_DigestFinal_ex(&ctx->mdctx, md_value, &md_len);
                        EVP_MD_CTX_cleanup(&ctx->mdctx);

                        if (memcmp(md_value, ctx->md_value_rx, 20) != 0)
                        {
                                // TODO: Actually signal this to the user
                                ap_log_error_wrapper(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"CRCSYNC-DECODE HASH CHECK FAILED");
                        }
                        else
                        {
                                ap_log_error_wrapper(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"CRCSYNC-DECODE HASH CHECK PASSED");
                        }

                        /* Okay, we've seen the EOS.
                         * Time to pass it along down the chain.
                         */
                        return ap_pass_brigade(f->next, ctx->bb);
                }

                if (APR_BUCKET_IS_FLUSH(e)) {
                        apr_status_t rv;

                        /* Remove flush bucket from old brigade anf insert into the new. */
                        APR_BUCKET_REMOVE(e);
                        APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
                        rv = ap_pass_brigade(f->next, ctx->bb);
                        if (rv != APR_SUCCESS) {
                                return rv;
                        }
                        continue;
                }

                if (APR_BUCKET_IS_METADATA(e)) {
                        /*
                         * Remove meta data bucket from old brigade and insert into the
                         * new.
                         */
                        APR_BUCKET_REMOVE(e);
                        APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
                        continue;
                }

                /* read */
                apr_bucket_read(e, &data, &len, APR_BLOCK_READ);
                //ap_log_error_wrapper(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"CRCSYNC-DECODE read %zd bytes",len);

                apr_size_t consumed_bytes = 0;
                while (consumed_bytes < len)
                {
                        //ap_log_error_wrapper(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"CRCSYNC-DECODE remaining %zd bytes",len - consumed_bytes);
                        // no guaruntee that our buckets line up with our encoding sections
                        // so we need a processing state machine stored in our context
                        switch (ctx->state)
                        {
                                case DECODING_NEW_SECTION:
                                {
                                        // check if we have a compressed section or a block section
                                        if (data[consumed_bytes] == ENCODING_COMPRESSED)
                                                ctx->state = DECODING_COMPRESSED;
                                        else if (data[consumed_bytes] == ENCODING_BLOCK)
                                                ctx->state = DECODING_BLOCK_HEADER;
                                        else if (data[consumed_bytes] == ENCODING_LITERAL)
                                                ctx->state = DECODING_LITERAL;
                                        else if (data[consumed_bytes] == ENCODING_HASH)
                                        {
                                                ctx->state = DECODING_HASH;
                                                ctx->md_value_rx_count = 0;
                                        }
                                        else
                                        {
                                                ap_log_error(APLOG_MARK, APLOG_ERR, APR_SUCCESS, r->server,
                                                                "CRCSYNC-DECODE, unknown section %d(%c)",data[consumed_bytes],data[consumed_bytes]);
                                                apr_brigade_cleanup(bb);
                                                return APR_EGENERAL;
                                        }
                                        //ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,"CRCSYNC-DECODE found a new section %d",ctx->state);
                                        consumed_bytes++;
                                        break;
                                }
                                case DECODING_BLOCK_HEADER:
                                {
                                        unsigned char block_number = data[consumed_bytes];
                                        consumed_bytes++;
                                        ctx->state = DECODING_NEW_SECTION;

                                        // TODO: Output the indicated block here
                                        size_t current_block_size = block_number < FULL_BLOCK_COUNT ? ctx->block_size : ctx->tail_block_size;
                                        ap_log_error_wrapper(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                                                        "CRCSYNC-DECODE block section, block %d, size %zu" ,block_number, current_block_size);

                                        char * buf = apr_palloc(r->pool, current_block_size);
                                        const char * source_data;
                                        size_t source_len;
                                        apr_bucket_read(ctx->cached_bucket, &source_data, &source_len, APR_BLOCK_READ);
                                        assert(block_number < (FULL_BLOCK_COUNT + (ctx->tail_block_size != 0)));
                                        memcpy(buf,&source_data[block_number*ctx->block_size],current_block_size);
                                        // update our sha1 hash
                                        EVP_DigestUpdate(&ctx->mdctx, buf, current_block_size);
                                        apr_bucket * b = apr_bucket_pool_create(buf, current_block_size, r->pool, f->c->bucket_alloc);
                                        APR_BRIGADE_INSERT_TAIL(ctx->bb, b);
                                        break;
                                }
                                case DECODING_HASH:
                                {
                                        unsigned avail_in = len - consumed_bytes;
                                        // 20 bytes for an SHA1 hash
                                        unsigned needed = MIN(20-ctx->md_value_rx_count, avail_in);
                                        memcpy(&ctx->md_value_rx[ctx->md_value_rx_count], &data[consumed_bytes],needed);
                                        ctx->md_value_rx_count+=needed;
                                        consumed_bytes += needed;
                                        if (ctx->md_value_rx_count == 20)
                                        {
                                                ctx->state = DECODING_NEW_SECTION;
                                        }
                                        break;
                                }
                                case DECODING_COMPRESSED:
                                {
                                        unsigned char decompressed_data_buf[30000];
                                        int z_RC;
                                        z_stream *strm = ctx->decompression_stream;
                                        strm->avail_in = len - consumed_bytes;
                                        strm->next_in = (Bytef *)(data + consumed_bytes);
                                        // ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server, "CRCSYNC-DECODE inflating %d bytes", strm.avail_in);
                                        // ap_log_hex(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server, strm.next_in, strm.avail_in);
                                        do {
                                                strm->avail_out = sizeof(decompressed_data_buf);
                                                strm->next_out = decompressed_data_buf;
                                                uInt avail_in_pre_inflate = strm->avail_in;
                                                z_RC = inflate(strm, Z_NO_FLUSH);
                                                if (z_RC == Z_NEED_DICT || z_RC == Z_DATA_ERROR || z_RC == Z_MEM_ERROR)
                                                {
                                                        ap_log_error(APLOG_MARK, APLOG_ERR, APR_EGENERAL, r->server, "CRCSYNC-DECODE inflate error: %d", z_RC);
                                                        apr_brigade_cleanup(bb);
                                                        return APR_EGENERAL;
                                                }
                                                int have = sizeof(decompressed_data_buf) - strm->avail_out;
                                                ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                                                                "CRCSYNC-DECODE inflate rslt %d, consumed %d, produced %d",
                                                                z_RC, avail_in_pre_inflate - strm->avail_in, have);
                                                if (have)
                                                {
                                                        // write output data
                                                        char * buf = apr_palloc(r->pool, have);
                                                        memcpy(buf,decompressed_data_buf,have);
                                                        EVP_DigestUpdate(&ctx->mdctx, buf, have);
                                                        apr_bucket * b = apr_bucket_pool_create(buf, have, r->pool, f->c->bucket_alloc);
                                                        APR_BRIGADE_INSERT_TAIL(ctx->bb, b);
                                                }
                                        } while (strm->avail_out == 0);
                                        consumed_bytes = len - strm->avail_in;
                                        if (z_RC == Z_STREAM_END)
                                        {
                                                ctx->state = DECODING_NEW_SECTION;
                                                inflateReset(strm);
                                        }
                                        break;
                                }
                                default:
                                {
                                        ap_log_error(APLOG_MARK, APLOG_ERR, APR_SUCCESS, r->server,
                                                        "CRCSYNC-DECODE, unknown state %d, terminating transaction",ctx->state);
                                        apr_brigade_cleanup(bb);
                                        return APR_EGENERAL; // TODO: figure out how to pass the error on to the client
                                }
                        }
                        APR_BUCKET_REMOVE(e);
                }
        }

        apr_brigade_cleanup(bb);
        return APR_SUCCESS;
}

static void *create_config(apr_pool_t *p, server_rec *s) {
        crccache_client_conf *conf = apr_pcalloc(p, sizeof(crccache_client_conf));
    /* array of URL prefixes for which caching is enabled */
    conf->cacheenable = apr_array_make(p, 10, sizeof(struct cache_enable));
    /* array of URL prefixes for which caching is enabled */
    conf->cacheenable = apr_array_make(p, 10, sizeof(struct cache_enable));
    /* array of URL prefixes for which caching is disabled */
    conf->cachedisable = apr_array_make(p, 10, sizeof(struct cache_disable));
    /* maximum time to cache a document */
    conf->maxex = DEFAULT_CACHE_MAXEXPIRE;
    conf->maxex_set = 0;
    conf->minex = DEFAULT_CACHE_MINEXPIRE;
    conf->minex_set = 0;
    /* default time to cache a document */
    conf->defex = DEFAULT_CACHE_EXPIRE;
    conf->defex_set = 0;
    /* factor used to estimate Expires date from LastModified date */
    conf->factor = DEFAULT_CACHE_LMFACTOR;
    conf->factor_set = 0;
    conf->no_last_mod_ignore_set = 0;
    conf->no_last_mod_ignore = 0;
    conf->ignorecachecontrol = 0;
    conf->ignorecachecontrol_set = 0;
    conf->store_private = 0;
    conf->store_private_set = 0;
    conf->store_nostore = 0;
    conf->store_nostore_set = 0;
    /* array of headers that should not be stored in cache */
    conf->ignore_headers = apr_array_make(p, 10, sizeof(char *));
    conf->ignore_headers_set = CACHE_IGNORE_HEADERS_UNSET;
    /* flag indicating that query-string should be ignored when caching */
    conf->ignorequerystring = 0;
    conf->ignorequerystring_set = 0;

        /* XXX: Set default values */
        conf->dirlevels = DEFAULT_DIRLEVELS;
        conf->dirlength = DEFAULT_DIRLENGTH;
        conf->maxfs = DEFAULT_MAX_FILE_SIZE;
        conf->minfs = DEFAULT_MIN_FILE_SIZE;

        conf->cache_root = NULL;
        conf->cache_root_len = 0;

        return conf;
}

/*
 * mod_disk_cache configuration directives handlers.
 */
static const char *set_cache_root(cmd_parms *parms, void *in_struct_ptr,
                const char *arg) {
        crccache_client_conf *conf = ap_get_module_config(parms->server->module_config,
                        &crccache_client_module);
        conf->cache_root = arg;
        conf->cache_root_len = strlen(arg);
        /* TODO: canonicalize cache_root and strip off any trailing slashes */

        return NULL;
}

/*
 * Consider eliminating the next two directives in favor of
 * Ian's prime number hash...
 * key = hash_fn( r->uri)
 * filename = "/key % prime1 /key %prime2/key %prime3"
 */
static const char *set_cache_dirlevels(cmd_parms *parms, void *in_struct_ptr,
                const char *arg) {
        crccache_client_conf *conf = ap_get_module_config(parms->server->module_config,
                        &crccache_client_module);
        int val = atoi(arg);
        if (val < 1)
                return "CacheDirLevelsClient value must be an integer greater than 0";
        if (val * conf->dirlength > CACHEFILE_LEN)
                return "CacheDirLevelsClient*CacheDirLengthClient value must not be higher than 20";
        conf->dirlevels = val;
        return NULL;
}
static const char *set_cache_dirlength(cmd_parms *parms, void *in_struct_ptr,
                const char *arg) {
        crccache_client_conf *conf = ap_get_module_config(parms->server->module_config,
                        &crccache_client_module);
        int val = atoi(arg);
        if (val < 1)
                return "CacheDirLengthClient value must be an integer greater than 0";
        if (val * conf->dirlevels > CACHEFILE_LEN)
                return "CacheDirLevelsClient*CacheDirLengthClient value must not be higher than 20";

        conf->dirlength = val;
        return NULL;
}

static const char *set_cache_minfs(cmd_parms *parms, void *in_struct_ptr,
                const char *arg) {
        crccache_client_conf *conf = ap_get_module_config(parms->server->module_config,
                        &crccache_client_module);

        if (apr_strtoff(&conf->minfs, arg, NULL, 0) != APR_SUCCESS || conf->minfs
                        < 0) {
                return "CacheMinFileSizeClient argument must be a non-negative integer representing the min size of a file to cache in bytes.";
        }
        return NULL;
}

static const char *set_cache_maxfs(cmd_parms *parms, void *in_struct_ptr,
                const char *arg) {
        crccache_client_conf *conf = ap_get_module_config(parms->server->module_config,
                        &crccache_client_module);
        if (apr_strtoff(&conf->maxfs, arg, NULL, 0) != APR_SUCCESS || conf->maxfs
                        < 0) {
                return "CacheMaxFileSizeClient argument must be a non-negative integer representing the max size of a file to cache in bytes.";
        }
        return NULL;
}

static const char *add_crc_client_enable(cmd_parms *parms, void *dummy,
                                    const char *type,
                                    const char *url)
{
        crccache_client_conf *conf;
    struct cache_enable *new;

    if (*type == '/') {
        return apr_psprintf(parms->pool,
          "provider (%s) starts with a '/'.  Are url and provider switched?",
          type);
    }

    conf =
        (crccache_client_conf *)ap_get_module_config(parms->server->module_config,
                                                  &crccache_client_module);
    new = apr_array_push(conf->cacheenable);
    new->type = type;
    if (apr_uri_parse(parms->pool, url, &(new->url))) {
        return NULL;
    }
    if (new->url.path) {
        new->pathlen = strlen(new->url.path);
    } else {
        new->pathlen = 1;
        new->url.path = "/";
    }
    return NULL;
}

static const command_rec disk_cache_cmds[] =
{
    AP_INIT_TAKE2("CRCClientEnable", add_crc_client_enable, NULL, RSRC_CONF, "A cache type and partial URL prefix below which caching is enabled"),
        AP_INIT_TAKE1("CacheRootClient", set_cache_root, NULL, RSRC_CONF,"The directory to store cache files"),
        AP_INIT_TAKE1("CacheDirLevelsClient", set_cache_dirlevels, NULL, RSRC_CONF, "The number of levels of subdirectories in the cache"),
        AP_INIT_TAKE1("CacheDirLengthClient", set_cache_dirlength, NULL, RSRC_CONF, "The number of characters in subdirectory names"),
        AP_INIT_TAKE1("CacheMinFileSizeClient", set_cache_minfs, NULL, RSRC_CONF, "The minimum file size to cache a document"),
        AP_INIT_TAKE1("CacheMaxFileSizeClient", set_cache_maxfs, NULL, RSRC_CONF, "The maximum file size to cache a document"),
        { NULL }
};

int ap_run_insert_filter(request_rec *r);

int cache_url_handler(request_rec *r, int lookup)
{
    apr_status_t rv;
    const char *auth;
    cache_request_rec *cache;
    crccache_client_conf *conf;
    apr_bucket_brigade *out;
    ap_filter_t *next;
    ap_filter_rec_t *cache_out_handle;

    /* Delay initialization until we know we are handling a GET */
    if (r->method_number != M_GET) {
        return DECLINED;
    }

    conf = (crccache_client_conf *) ap_get_module_config(r->server->module_config,
                                                      &crccache_client_module);

    /* make space for the per request config */
    cache = (cache_request_rec *) ap_get_module_config(r->request_config,
                                                       &crccache_client_module);
    if (!cache) {
        cache = apr_pcalloc(r->pool, sizeof(cache_request_rec));
        ap_set_module_config(r->request_config, &crccache_client_module, cache);
    }

    /*
     * Are we allowed to serve cached info at all?
     */

    /* find certain cache controlling headers */
    auth = apr_table_get(r->headers_in, "Authorization");

    /* First things first - does the request allow us to return
     * cached information at all? If not, just decline the request.
     */
    if (auth) {
        return DECLINED;
    }

    /*
     * Try to serve this request from the cache.
     *
     * If no existing cache file (DECLINED)
     *   add cache_save filter
     * If cached file (OK)
     *   clear filter stack
     *   add cache_out filter
     *   return OK
     */
    rv = cache_select(r);
    if (rv != OK) {
        if (rv == DECLINED) {
            if (!lookup) {

                /*
                 * Add cache_save filter to cache this request. Choose
                 * the correct filter by checking if we are a subrequest
                 * or not.
                 */
                if (r->main) {
                    ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS,
                                 r->server,
                                 "Adding CACHE_SAVE_SUBREQ filter for %s",
                                 r->uri);
                    ap_add_output_filter_handle(cache_save_subreq_filter_handle,
                                                NULL, r, r->connection);
                }
                else {
                    ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS,
                                 r->server, "Adding CACHE_SAVE filter for %s",
                                 r->uri);
                    ap_add_output_filter_handle(cache_save_filter_handle,
                                                NULL, r, r->connection);
                }

                ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                             "Adding CACHE_REMOVE_URL filter for %s",
                             r->uri);

                /* Add cache_remove_url filter to this request to remove a
                 * stale cache entry if needed. Also put the current cache
                 * request rec in the filter context, as the request that
                 * is available later during running the filter maybe
                 * different due to an internal redirect.
                 */
                cache->remove_url_filter =
                    ap_add_output_filter_handle(cache_remove_url_filter_handle,
                                                cache, r, r->connection);
            }
            else {
                if (cache->stale_headers) {
                    ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS,
                                 r->server, "Restoring request headers for %s",
                                 r->uri);

                    r->headers_in = cache->stale_headers;
                }

                /* Delete our per-request configuration. */
                ap_set_module_config(r->request_config, &crccache_client_module, NULL);
            }
        }
        else {
            /* error */
            ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
                         "cache: error returned while checking for cached "
                         "file by cache");
        }
        return DECLINED;
    }

    /* if we are a lookup, we are exiting soon one way or another; Restore
     * the headers. */
    if (lookup) {
        if (cache->stale_headers) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                         "Restoring request headers.");
            r->headers_in = cache->stale_headers;
        }

        /* Delete our per-request configuration. */
        ap_set_module_config(r->request_config, &crccache_client_module, NULL);
    }

    rv = ap_meets_conditions(r);
    if (rv != OK) {
        /* If we are a lookup, we have to return DECLINED as we have no
         * way of knowing if we will be able to serve the content.
         */
        if (lookup) {
            return DECLINED;
        }

        /* Return cached status. */
        return rv;
    }

    /* If we're a lookup, we can exit now instead of serving the content. */
    if (lookup) {
        return OK;
    }

    /* Serve up the content */

    /* We are in the quick handler hook, which means that no output
     * filters have been set. So lets run the insert_filter hook.
     */
    ap_run_insert_filter(r);

    /*
     * Add cache_out filter to serve this request. Choose
     * the correct filter by checking if we are a subrequest
     * or not.
     */
    if (r->main) {
        cache_out_handle = cache_out_subreq_filter_handle;
    }
    else {
        cache_out_handle = cache_out_filter_handle;
    }
    ap_add_output_filter_handle(cache_out_handle, NULL, r, r->connection);

    /*
     * Remove all filters that are before the cache_out filter. This ensures
     * that we kick off the filter stack with our cache_out filter being the
     * first in the chain. This make sense because we want to restore things
     * in the same manner as we saved them.
     * There may be filters before our cache_out filter, because
     *
     * 1. We call ap_set_content_type during cache_select. This causes
     *    Content-Type specific filters to be added.
     * 2. We call the insert_filter hook. This causes filters e.g. like
     *    the ones set with SetOutputFilter to be added.
     */
    next = r->output_filters;
    while (next && (next->frec != cache_out_handle)) {
        ap_remove_output_filter(next);
        next = next->next;
    }

    /* kick off the filter stack */
    out = apr_brigade_create(r->pool, r->connection->bucket_alloc);
    rv = ap_pass_brigade(r->output_filters, out);
    if (rv != APR_SUCCESS) {
        if (rv != AP_FILTER_ERROR) {
            ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
                         "cache: error returned while trying to return "
                         "cached data");
        }
        return rv;
    }

    return OK;
}



/*
 * CACHE_OUT filter
 * ----------------
 *
 * Deliver cached content (headers and body) up the stack.
 */
int cache_out_filter(ap_filter_t *f, apr_bucket_brigade *bb)
{
    request_rec *r = f->r;
    cache_request_rec *cache;

    cache = (cache_request_rec *) ap_get_module_config(r->request_config,
                                                       &crccache_client_module);

    if (!cache) {
        /* user likely configured CACHE_OUT manually; they should use mod_cache
         * configuration to do that */
        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                     "CACHE_OUT enabled unexpectedly");
        ap_remove_output_filter(f);
        return ap_pass_brigade(f->next, bb);
    }

    ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                 "cache: running CACHE_OUT filter");

    /* restore status of cached response */
    /* XXX: This exposes a bug in mem_cache, since it does not
     * restore the status into it's handle. */
    r->status = cache->handle->cache_obj->info.status;

    /* recall_headers() was called in cache_select() */
    recall_body(cache->handle, r->pool, bb);

    /* This filter is done once it has served up its content */
    ap_remove_output_filter(f);

    ap_log_error(APLOG_MARK, APLOG_DEBUG, APR_SUCCESS, r->server,
                 "cache: serving %s", r->uri);
    return ap_pass_brigade(f->next, bb);
}


/*
 * CACHE_SAVE filter
 * ---------------
 *
 * Decide whether or not this content should be cached.
 * If we decide no it should not:
 *   remove the filter from the chain
 * If we decide yes it should:
 *   Have we already started saving the response?
 *      If we have started, pass the data to the storage manager via store_body
 *      Otherwise:
 *        Check to see if we *can* save this particular response.
 *        If we can, call cache_create_entity() and save the headers and body
 *   Finally, pass the data to the next filter (the network or whatever)
 */

int cache_save_filter(ap_filter_t *f, apr_bucket_brigade *in)
{
    int rv = !OK;
    request_rec *r = f->r;
    cache_request_rec *cache;
    crccache_client_conf *conf;
    //const char *cc_out, *cl;
    const char *cl;
    const char *exps, /* *lastmods,*/ *dates;//, *etag;
    apr_time_t exp, date,/* lastmod,*/ now;
    apr_off_t size;
    cache_info *info = NULL;
    char *reason;
    apr_pool_t *p;

    conf = (crccache_client_conf *) ap_get_module_config(r->server->module_config,
                                                      &crccache_client_module);

    /* Setup cache_request_rec */
    cache = (cache_request_rec *) ap_get_module_config(r->request_config,
                                                       &crccache_client_module);
    if (!cache) {
        /* user likely configured CACHE_SAVE manually; they should really use
         * mod_cache configuration to do that
         */
        cache = apr_pcalloc(r->pool, sizeof(cache_request_rec));
        ap_set_module_config(r->request_config, &crccache_client_module, cache);
    }

    reason = NULL;
    p = r->pool;
    /*
     * Pass Data to Cache
     * ------------------
     * This section passes the brigades into the cache modules, but only
     * if the setup section (see below) is complete.
     */
    if (cache->block_response) {
        /* We've already sent down the response and EOS.  So, ignore
         * whatever comes now.
         */
        return APR_SUCCESS;
    }

    /* have we already run the cachability check and set up the
     * cached file handle?
     */
    if (cache->in_checked) {
        /* pass the brigades into the cache, then pass them
         * up the filter stack
         */
        rv = store_body(cache->handle, r, in);
        if (rv != APR_SUCCESS) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server,
                         "cache: Cache provider's store_body failed!");
            ap_remove_output_filter(f);
        }
        return ap_pass_brigade(f->next, in);
    }

    /*
     * Setup Data in Cache
     * -------------------
     * This section opens the cache entity and sets various caching
     * parameters, and decides whether this URL should be cached at
     * all. This section is* run before the above section.
     */

    /* read expiry date; if a bad date, then leave it so the client can
     * read it
     */
    exps = apr_table_get(r->err_headers_out, "Expires");
    if (exps == NULL) {
        exps = apr_table_get(r->headers_out, "Expires");
    }
    if (exps != NULL) {
        if (APR_DATE_BAD == (exp = apr_date_parse_http(exps))) {
            exps = NULL;
        }
    }
    else {
        exp = APR_DATE_BAD;
    }
// we dont care about these
#if 0
    /* read the last-modified date; if the date is bad, then delete it */
    lastmods = apr_table_get(r->err_headers_out, "Last-Modified");
    if (lastmods == NULL) {
        lastmods = apr_table_get(r->headers_out, "Last-Modified");
    }
    if (lastmods != NULL) {
        lastmod = apr_date_parse_http(lastmods);
        if (lastmod == APR_DATE_BAD) {
            lastmods = NULL;
        }
    }
    else {
        lastmod = APR_DATE_BAD;
    }

    /* read the etag and cache-control from the entity */
    etag = apr_table_get(r->err_headers_out, "Etag");
    if (etag == NULL) {
        etag = apr_table_get(r->headers_out, "Etag");
    }
    cc_out = apr_table_get(r->err_headers_out, "Cache-Control");
    if (cc_out == NULL) {
        cc_out = apr_table_get(r->headers_out, "Cache-Control");
    }
#endif
    /*
     * what responses should we not cache?
     *
     * At this point we decide based on the response headers whether it
     * is appropriate _NOT_ to cache the data from the server. There are
     * a whole lot of conditions that prevent us from caching this data.
     * They are tested here one by one to be clear and unambiguous.
     */
    if (r->status != HTTP_OK && r->status != HTTP_NON_AUTHORITATIVE
        && r->status != HTTP_MULTIPLE_CHOICES
        && r->status != HTTP_MOVED_PERMANENTLY
        && r->status != HTTP_NOT_MODIFIED) {
        /* RFC2616 13.4 we are allowed to cache 200, 203, 206, 300, 301 or 410
         * We don't cache 206, because we don't (yet) cache partial responses.
         * We include 304 Not Modified here too as this is the origin server
         * telling us to serve the cached copy.
         */
#if 0
        if (exps != NULL || cc_out != NULL) {
            /* We are also allowed to cache any response given that it has a
             * valid Expires or Cache Control header. If we find a either of
             * those here,  we pass request through the rest of the tests. From
             * the RFC:
             *
             * A response received with any other status code (e.g. status
             * codes 302 and 307) MUST NOT be returned in a reply to a
             * subsequent request unless there are cache-control directives or
             * another header(s) that explicitly allow it. For example, these
             * include the following: an Expires header (section 14.21); a
             * "max-age", "s-maxage",  "must-revalidate", "proxy-revalidate",
             * "public" or "private" cache-control directive (section 14.9).
             */
        }
        else {
            reason = apr_psprintf(p, "Response status %d", r->status);
        }
#endif
    }

    if (reason) {
        /* noop */
    }
#if 0
    else if (exps != NULL && exp == APR_DATE_BAD) {
        /* if a broken Expires header is present, don't cache it */
        reason = apr_pstrcat(p, "Broken expires header: ", exps, NULL);
    }
    else if (exp != APR_DATE_BAD && exp < r->request_time)
    {
        /* if a Expires header is in the past, don't cache it */
        reason = "Expires header already expired, not cacheable";
    }
    else if (!conf->ignorequerystring && r->parsed_uri.query && exps == NULL &&
             !ap_cache_liststr(NULL, cc_out, "max-age", NULL)) {
        /* if a query string is present but no explicit expiration time,
         * don't cache it (RFC 2616/13.9 & 13.2.1)
         */
        reason = "Query string present but no explicit expiration time";
    }
#endif
    else if (r->status == HTTP_NOT_MODIFIED &&
             !cache->handle && !cache->stale_handle) {
        /* if the server said 304 Not Modified but we have no cache
         * file - pass this untouched to the user agent, it's not for us.
         */
        reason = "HTTP Status 304 Not Modified";
    }
#if 0
    else if (r->status == HTTP_OK && lastmods == NULL && etag == NULL
             && (exps == NULL) && (conf->no_last_mod_ignore ==0)) {
        /* 200 OK response from HTTP/1.0 and up without Last-Modified,
         * Etag, or Expires headers.
         */
        /* Note: mod-include clears last_modified/expires/etags - this
         * is why we have an optional function for a key-gen ;-)
         */
        reason = "No Last-Modified, Etag, or Expires headers";
    }
#endif
    else if (r->header_only && !cache->stale_handle) {
        /* Forbid HEAD requests unless we have it cached already */
        reason = "HTTP HEAD request";
    }
#if 0
    else if (!conf->store_nostore &&
             ap_cache_liststr(NULL, cc_out, "no-store", NULL)) {
        /* RFC2616 14.9.2 Cache-Control: no-store response
         * indicating do not cache, or stop now if you are
         * trying to cache it.
         */
        /* FIXME: The Cache-Control: no-store could have come in on a 304,
         * FIXME: while the original request wasn't conditional.  IOW, we
         * FIXME:  made the the request conditional earlier to revalidate
         * FIXME: our cached response.
         */
        reason = "Cache-Control: no-store present";
    }
    else if (!conf->store_private &&
             ap_cache_liststr(NULL, cc_out, "private", NULL)) {
        /* RFC2616 14.9.1 Cache-Control: private response
         * this object is marked for this user's eyes only. Behave
         * as a tunnel.
         */
        /* FIXME: See above (no-store) */
        reason = "Cache-Control: private present";
    }
    else if (apr_table_get(r->headers_in, "Authorization") != NULL
             && !(ap_cache_liststr(NULL, cc_out, "s-maxage", NULL)
                  || ap_cache_liststr(NULL, cc_out, "must-revalidate", NULL)
                  || ap_cache_liststr(NULL, cc_out, "public", NULL))) {
        /* RFC2616 14.8 Authorisation:
         * if authorisation is included in the request, we don't cache,
         * but we can cache if the following exceptions are true:
         * 1) If Cache-Control: s-maxage is included
         * 2) If Cache-Control: must-revalidate is included
         * 3) If Cache-Control: public is included
         */
        reason = "Authorization required";
    }

    else if (ap_cache_liststr(NULL,
                              apr_table_get(r->headers_out, "Vary"),
                              "*", NULL)) {
        reason = "Vary header contains '*'";
    }
    else if (apr_table_get(r->subprocess_env, "no-cache") != NULL) {
        reason = "environment variable 'no-cache' is set";
    }
    else if (r->no_cache) {
        /* or we've been asked not to cache it above */
        reason = "r->no_cache present";
    }
#endif
    if (reason) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                     "cache: %s not cached. Reason: %s", r->unparsed_uri,
                     reason);

        /* remove this filter from the chain */
        ap_remove_output_filter(f);

        /* ship the data up the stack */
        return ap_pass_brigade(f->next, in);
    }

    /* Make it so that we don't execute this path again. */
    cache->in_checked = 1;

    /* Set the content length if known.
     */
    cl = apr_table_get(r->err_headers_out, "Content-Length");
    if (cl == NULL) {
        cl = apr_table_get(r->headers_out, "Content-Length");
    }
    if (cl) {
        char *errp;
        if (apr_strtoff(&size, cl, &errp, 10) || *errp || size < 0) {
            cl = NULL; /* parse error, see next 'if' block */
        }
    }

    if (!cl) {
        /* if we don't get the content-length, see if we have all the
         * buckets and use their length to calculate the size
         */
        apr_bucket *e;
        int all_buckets_here=0;
        int unresolved_length = 0;
        size=0;
        for (e = APR_BRIGADE_FIRST(in);
             e != APR_BRIGADE_SENTINEL(in);
             e = APR_BUCKET_NEXT(e))
        {
            if (APR_BUCKET_IS_EOS(e)) {
                all_buckets_here=1;
                break;
            }
            if (APR_BUCKET_IS_FLUSH(e)) {
                unresolved_length = 1;
                continue;
            }
            if (e->length == (apr_size_t)-1) {
                break;
            }
            size += e->length;
        }
        if (!all_buckets_here) {
            size = -1;
        }
    }

    /* It's safe to cache the response.
     *
     * There are two possiblities at this point:
     * - cache->handle == NULL. In this case there is no previously
     * cached entity anywhere on the system. We must create a brand
     * new entity and store the response in it.
     * - cache->stale_handle != NULL. In this case there is a stale
     * entity in the system which needs to be replaced by new
     * content (unless the result was 304 Not Modified, which means
     * the cached entity is actually fresh, and we should update
     * the headers).
     */

    /* Did we have a stale cache entry that really is stale?
     *
     * Note that for HEAD requests, we won't get the body, so for a stale
     * HEAD request, we don't remove the entity - instead we let the
     * CACHE_REMOVE_URL filter remove the stale item from the cache.
     */
    if (cache->stale_handle) {
        if (r->status == HTTP_NOT_MODIFIED) {
            /* Oh, hey.  It isn't that stale!  Yay! */
            cache->handle = cache->stale_handle;
            info = &cache->handle->cache_obj->info;
            rv = OK;
        }
        else if (!r->header_only) {
            /* Oh, well.  Toss it. */
            remove_entity(cache->stale_handle);
            /* Treat the request as if it wasn't conditional. */
            cache->stale_handle = NULL;
            /*
             * Restore the original request headers as they may be needed
             * by further output filters like the byterange filter to make
             * the correct decisions.
             */
            r->headers_in = cache->stale_headers;
        }
    }

    /* no cache handle, create a new entity only for non-HEAD requests */
    if (!cache->handle && !r->header_only) {
        rv = cache_create_entity(r, size);
        info = apr_pcalloc(r->pool, sizeof(cache_info));
        /* We only set info->status upon the initial creation. */
        info->status = r->status;
    }

    if (rv != OK) {
        /* Caching layer declined the opportunity to cache the response */
        ap_remove_output_filter(f);
        return ap_pass_brigade(f->next, in);
    }

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "cache: Caching url: %s", r->unparsed_uri);

    /* We are actually caching this response. So it does not
     * make sense to remove this entity any more.
     */
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "cache: Removing CACHE_REMOVE_URL filter.");
    ap_remove_output_filter(cache->remove_url_filter);

    /*
     * We now want to update the cache file header information with
     * the new date, last modified, expire and content length and write
     * it away to our cache file. First, we determine these values from
     * the response, using heuristics if appropriate.
     *
     * In addition, we make HTTP/1.1 age calculations and write them away
     * too.
     */

    /* Read the date. Generate one if one is not supplied */
    dates = apr_table_get(r->err_headers_out, "Date");
    if (dates == NULL) {
        dates = apr_table_get(r->headers_out, "Date");
    }
    if (dates != NULL) {
        info->date = apr_date_parse_http(dates);
    }
    else {
        info->date = APR_DATE_BAD;
    }

    now = apr_time_now();
    if (info->date == APR_DATE_BAD) {  /* No, or bad date */
        /* no date header (or bad header)! */
        info->date = now;
    }
    date = info->date;

    /* set response_time for HTTP/1.1 age calculations */
    info->response_time = now;

    /* get the request time */
    info->request_time = r->request_time;
#if 0
    /* check last-modified date */
    if (lastmod != APR_DATE_BAD && lastmod > date) {
        /* if it's in the future, then replace by date */
        lastmod = date;
        lastmods = dates;
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0,
                     r->server,
                     "cache: Last modified is in the future, "
                     "replacing with now");
    }

    /* if no expiry date then
     *   if Cache-Control: max-age
     *      expiry date = date + max-age
     *   else if lastmod
     *      expiry date = date + min((date - lastmod) * factor, maxexpire)
     *   else
     *      expire date = date + defaultexpire
     */
    if (exp == APR_DATE_BAD) {
        char *max_age_val;

        if (ap_cache_liststr(r->pool, cc_out, "max-age", &max_age_val) &&
            max_age_val != NULL) {
            apr_int64_t x;

            errno = 0;
            x = apr_atoi64(max_age_val);
            if (errno) {
                x = conf->defex;
            }
            else {
                x = x * MSEC_ONE_SEC;
            }
            if (x < conf->minex) {
                x = conf->minex;
            }
            if (x > conf->maxex) {
                x = conf->maxex;
            }
            exp = date + x;
        }
        else if ((lastmod != APR_DATE_BAD) && (lastmod < date)) {
            /* if lastmod == date then you get 0*conf->factor which results in
             * an expiration time of now. This causes some problems with
             * freshness calculations, so we choose the else path...
             */
            apr_time_t x = (apr_time_t) ((date - lastmod) * conf->factor);

            if (x < conf->minex) {
                x = conf->minex;
            }
            if (x > conf->maxex) {
                x = conf->maxex;
            }
            exp = date + x;
        }
        else {
            exp = date + conf->defex;
        }
    }
#endif
    info->expire = exp;

    /* We found a stale entry which wasn't really stale. */
    if (cache->stale_handle) {
        /* Load in the saved status and clear the status line. */
        r->status = info->status;
        r->status_line = NULL;

        /* RFC 2616 10.3.5 states that entity headers are not supposed
         * to be in the 304 response.  Therefore, we need to combine the
         * response headers with the cached headers *before* we update
         * the cached headers.
         *
         * However, before doing that, we need to first merge in
         * err_headers_out and we also need to strip any hop-by-hop
         * headers that might have snuck in.
         */
        r->headers_out = ap_cache_cacheable_headers_out(r);

        /* Merge in our cached headers.  However, keep any updated values. */
        ap_cache_accept_headers(cache->handle, r, 1);
    }

    /* Write away header information to cache. It is possible that we are
     * trying to update headers for an entity which has already been cached.
     *
     * This may fail, due to an unwritable cache area. E.g. filesystem full,
     * permissions problems or a read-only (re)mount. This must be handled
     * later.
     */
    rv = store_headers(cache->handle, r, info);

    /* Did we just update the cached headers on a revalidated response?
     *
     * If so, we can now decide what to serve to the client.  This is done in
     * the same way as with a regular response, but conditions are now checked
     * against the cached or merged response headers.
     */
    if (cache->stale_handle) {
        apr_bucket_brigade *bb;
        apr_bucket *bkt;
        int status;

        bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);

        /* Restore the original request headers and see if we need to
         * return anything else than the cached response (ie. the original
         * request was conditional).
         */
        r->headers_in = cache->stale_headers;
        status = ap_meets_conditions(r);
        if (status != OK) {
            r->status = status;

            bkt = apr_bucket_flush_create(bb->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(bb, bkt);
        }
        else {
            recall_body(cache->handle, r->pool, bb);
        }

        cache->block_response = 1;

        /* Before returning we need to handle the possible case of an
         * unwritable cache. Rather than leaving the entity in the cache
         * and having it constantly re-validated, now that we have recalled
         * the body it is safe to try and remove the url from the cache.
         */
        if (rv != APR_SUCCESS) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server,
                         "cache: updating headers with store_headers failed. "
                         "Removing cached url.");

            rv = remove_url(cache->stale_handle, r->pool);
            if (rv != OK) {
                /* Probably a mod_disk_cache cache area has been (re)mounted
                 * read-only, or that there is a permissions problem.
                 */
                ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server,
                     "cache: attempt to remove url from cache unsuccessful.");
            }
        }

        return ap_pass_brigade(f->next, bb);
    }

    if(rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server,
                     "cache: store_headers failed");
        ap_remove_output_filter(f);

        return ap_pass_brigade(f->next, in);
    }

    rv = store_body(cache->handle, r, in);
    if (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server,
                     "cache: store_body failed");
        ap_remove_output_filter(f);
    }

    return ap_pass_brigade(f->next, in);
}


/*
 * CACHE_REMOVE_URL filter
 * ---------------
 *
 * This filter gets added in the quick handler every time the CACHE_SAVE filter
 * gets inserted. Its purpose is to remove a confirmed stale cache entry from
 * the cache.
 *
 * CACHE_REMOVE_URL has to be a protocol filter to ensure that is run even if
 * the response is a canned error message, which removes the content filters
 * and thus the CACHE_SAVE filter from the chain.
 *
 * CACHE_REMOVE_URL expects cache request rec within its context because the
 * request this filter runs on can be different from the one whose cache entry
 * should be removed, due to internal redirects.
 *
 * Note that CACHE_SAVE_URL (as a content-set filter, hence run before the
 * protocol filters) will remove this filter if it decides to cache the file.
 * Therefore, if this filter is left in, it must mean we need to toss any
 * existing files.
 */
int cache_remove_url_filter(ap_filter_t *f, apr_bucket_brigade *in)
{
    request_rec *r = f->r;
    cache_request_rec *cache;

    /* Setup cache_request_rec */
    cache = (cache_request_rec *) f->ctx;

    if (!cache) {
        /* user likely configured CACHE_REMOVE_URL manually; they should really
         * use mod_cache configuration to do that. So:
         * 1. Remove ourselves
         * 2. Do nothing and bail out
         */
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                     "cache: CACHE_REMOVE_URL enabled unexpectedly");
        ap_remove_output_filter(f);
        return ap_pass_brigade(f->next, in);
    }
    /* Now remove this cache entry from the cache */
    cache_remove_url(cache, r->pool);

    /* remove ourselves */
    ap_remove_output_filter(f);
    return ap_pass_brigade(f->next, in);
}


/*static const cache_provider crccache_client_provider = { &remove_entity,
                &store_headers, &store_body, &recall_headers, &recall_body,
                &create_entity, &open_entity, &remove_url, };
*/
static void disk_cache_register_hook(apr_pool_t *p) {
        ap_log_error(APLOG_MARK, APLOG_INFO, 0, NULL,
                        "Registering crccache client module, (C) 2009, Toby Collett");

    /* cache initializer */
    /* cache handler */
    ap_hook_quick_handler(cache_url_handler, NULL, NULL, APR_HOOK_FIRST);
    /* cache filters
     * XXX The cache filters need to run right after the handlers and before
     * any other filters. Consider creating AP_FTYPE_CACHE for this purpose.
     *
     * Depending on the type of request (subrequest / main request) they
     * need to be run before AP_FTYPE_CONTENT_SET / after AP_FTYPE_CONTENT_SET
     * filters. Thus create two filter handles for each type:
     * cache_save_filter_handle / cache_out_filter_handle to be used by
     * main requests and
     * cache_save_subreq_filter_handle / cache_out_subreq_filter_handle
     * to be run by subrequest
     */
    /*
     * CACHE_SAVE must go into the filter chain after a possible DEFLATE
     * filter to ensure that the compressed content is stored.
     * Incrementing filter type by 1 ensures his happens.
     */
    cache_save_filter_handle =
        ap_register_output_filter("CACHE_SAVE",
                                  cache_save_filter,
                                  NULL,
                                  AP_FTYPE_CONTENT_SET+1);
    /*
     * CACHE_SAVE_SUBREQ must go into the filter chain before SUBREQ_CORE to
     * handle subrequsts. Decrementing filter type by 1 ensures this
     * happens.
     */
    cache_save_subreq_filter_handle =
        ap_register_output_filter("CACHE_SAVE_SUBREQ",
                                  cache_save_filter,
                                  NULL,
                                  AP_FTYPE_CONTENT_SET-1);
    /*
     * CACHE_OUT must go into the filter chain after a possible DEFLATE
     * filter to ensure that already compressed cache objects do not
     * get compressed again. Incrementing filter type by 1 ensures
     * his happens.
     */
    cache_out_filter_handle =
        ap_register_output_filter("CACHE_OUT",
                                  cache_out_filter,
                                  NULL,
                                  AP_FTYPE_CONTENT_SET+1);
    /*
     * CACHE_OUT_SUBREQ must go into the filter chain before SUBREQ_CORE to
     * handle subrequsts. Decrementing filter type by 1 ensures this
     * happens.
     */
    cache_out_subreq_filter_handle =
        ap_register_output_filter("CACHE_OUT_SUBREQ",
                                  cache_out_filter,
                                  NULL,
                                  AP_FTYPE_CONTENT_SET-1);
    /* CACHE_REMOVE_URL has to be a protocol filter to ensure that is
     * run even if the response is a canned error message, which
     * removes the content filters.
     */
    cache_remove_url_filter_handle =
        ap_register_output_filter("CACHE_REMOVE_URL",
                                  cache_remove_url_filter,
                                  NULL,
                                  AP_FTYPE_PROTOCOL);

        /* cache initializer */
//      ap_register_provider(p, CACHE_PROVIDER_GROUP, "crccache_client", "0",
//                      &crccache_client_provider);
        /*
         * CACHE_OUT must go into the filter chain after a possible DEFLATE
         * filter to ensure that already compressed cache objects do not
         * get compressed again. Incrementing filter type by 1 ensures
         * his happens.
         */
        crccache_decode_filter_handle = ap_register_output_filter(
                        "CRCCACHE_DECODE", crccache_decode_filter, NULL,
                        AP_FTYPE_CONTENT_SET + 1);

        ap_hook_post_config(cache_post_config, NULL, NULL, APR_HOOK_REALLY_FIRST);

}

module AP_MODULE_DECLARE_DATA crccache_client_module = {
                STANDARD20_MODULE_STUFF, NULL, /* create per-directory config structure */
                NULL ,                       /* merge per-directory config structures */
    create_config, /* create per-server config structure */
NULL            , /* merge per-server config structures */
                disk_cache_cmds, /* command apr_table_t */
                disk_cache_register_hook /* register hooks */
        };