Fixing comment in merge strategies

[git/builtin-gsoc.git] / convert.c

#include "cache.h"
#include "attr.h"
#include "run-command.h"

/*
 * convert.c - convert a file when checking it out and checking it in.
 *
 * This should use the pathname to decide on whether it wants to do some
 * more interesting conversions (automatic gzip/unzip, general format
 * conversions etc etc), but by default it just does automatic CRLF<->LF
 * translation when the "auto_crlf" option is set.
 */

#define CRLF_GUESS      (-1)
#define CRLF_BINARY     0
#define CRLF_TEXT       1
#define CRLF_INPUT      2

struct text_stat {
        /* CR, LF and CRLF counts */
        unsigned cr, lf, crlf;

        /* These are just approximations! */
        unsigned printable, nonprintable;
};

static void gather_stats(const char *buf, unsigned long size, struct text_stat *stats)
{
        unsigned long i;

        memset(stats, 0, sizeof(*stats));

        for (i = 0; i < size; i++) {
                unsigned char c = buf[i];
                if (c == '\r') {
                        stats->cr++;
                        if (i+1 < size && buf[i+1] == '\n')
                                stats->crlf++;
                        continue;
                }
                if (c == '\n') {
                        stats->lf++;
                        continue;
                }
                if (c == 127)
                        /* DEL */
                        stats->nonprintable++;
                else if (c < 32) {
                        switch (c) {
                                /* BS, HT, ESC and FF */
                        case '\b': case '\t': case '\033': case '\014':
                                stats->printable++;
                                break;
                        default:
                                stats->nonprintable++;
                        }
                }
                else
                        stats->printable++;
        }
}

/*
 * The same heuristics as diff.c::mmfile_is_binary()
 */
static int is_binary(unsigned long size, struct text_stat *stats)
{

        if ((stats->printable >> 7) < stats->nonprintable)
                return 1;
        /*
         * Other heuristics? Average line length might be relevant,
         * as might LF vs CR vs CRLF counts..
         *
         * NOTE! It might be normal to have a low ratio of CRLF to LF
         * (somebody starts with a LF-only file and edits it with an editor
         * that adds CRLF only to lines that are added..). But do  we
         * want to support CR-only? Probably not.
         */
        return 0;
}

static char *crlf_to_git(const char *path, const char *src, unsigned long *sizep, int action)
{
        char *buffer, *dst;
        unsigned long size, nsize;
        struct text_stat stats;

        if ((action == CRLF_BINARY) || !auto_crlf)
                return NULL;

        size = *sizep;
        if (!size)
                return NULL;

        gather_stats(src, size, &stats);

        /* No CR? Nothing to convert, regardless. */
        if (!stats.cr)
                return NULL;

        if (action == CRLF_GUESS) {
                /*
                 * We're currently not going to even try to convert stuff
                 * that has bare CR characters. Does anybody do that crazy
                 * stuff?
                 */
                if (stats.cr != stats.crlf)
                        return NULL;

                /*
                 * And add some heuristics for binary vs text, of course...
                 */
                if (is_binary(size, &stats))
                        return NULL;
        }

        /*
         * Ok, allocate a new buffer, fill it in, and return it
         * to let the caller know that we switched buffers.
         */
        nsize = size - stats.crlf;
        buffer = xmalloc(nsize);
        *sizep = nsize;

        dst = buffer;
        if (action == CRLF_GUESS) {
                /*
                 * If we guessed, we already know we rejected a file with
                 * lone CR, and we can strip a CR without looking at what
                 * follow it.
                 */
                do {
                        unsigned char c = *src++;
                        if (c != '\r')
                                *dst++ = c;
                } while (--size);
        } else {
                do {
                        unsigned char c = *src++;
                        if (! (c == '\r' && (1 < size && *src == '\n')))
                                *dst++ = c;
                } while (--size);
        }

        return buffer;
}

static char *crlf_to_worktree(const char *path, const char *src, unsigned long *sizep, int action)
{
        char *buffer, *dst;
        unsigned long size, nsize;
        struct text_stat stats;
        unsigned char last;

        if ((action == CRLF_BINARY) || (action == CRLF_INPUT) ||
            auto_crlf <= 0)
                return NULL;

        size = *sizep;
        if (!size)
                return NULL;

        gather_stats(src, size, &stats);

        /* No LF? Nothing to convert, regardless. */
        if (!stats.lf)
                return NULL;

        /* Was it already in CRLF format? */
        if (stats.lf == stats.crlf)
                return NULL;

        if (action == CRLF_GUESS) {
                /* If we have any bare CR characters, we're not going to touch it */
                if (stats.cr != stats.crlf)
                        return NULL;

                if (is_binary(size, &stats))
                        return NULL;
        }

        /*
         * Ok, allocate a new buffer, fill it in, and return it
         * to let the caller know that we switched buffers.
         */
        nsize = size + stats.lf - stats.crlf;
        buffer = xmalloc(nsize);
        *sizep = nsize;
        last = 0;

        dst = buffer;
        do {
                unsigned char c = *src++;
                if (c == '\n' && last != '\r')
                        *dst++ = '\r';
                *dst++ = c;
                last = c;
        } while (--size);

        return buffer;
}

static int filter_buffer(const char *path, const char *src,
                         unsigned long size, const char *cmd)
{
        /*
         * Spawn cmd and feed the buffer contents through its stdin.
         */
        struct child_process child_process;
        int pipe_feed[2];
        int write_err, status;

        memset(&child_process, 0, sizeof(child_process));

        if (pipe(pipe_feed) < 0) {
                error("cannot create pipe to run external filter %s", cmd);
                return 1;
        }

        child_process.pid = fork();
        if (child_process.pid < 0) {
                error("cannot fork to run external filter %s", cmd);
                close(pipe_feed[0]);
                close(pipe_feed[1]);
                return 1;
        }
        if (!child_process.pid) {
                dup2(pipe_feed[0], 0);
                close(pipe_feed[0]);
                close(pipe_feed[1]);
                execlp("sh", "sh", "-c", cmd, NULL);
                return 1;
        }
        close(pipe_feed[0]);

        write_err = (write_in_full(pipe_feed[1], src, size) < 0);
        if (close(pipe_feed[1]))
                write_err = 1;
        if (write_err)
                error("cannot feed the input to external filter %s", cmd);

        status = finish_command(&child_process);
        if (status)
                error("external filter %s failed %d", cmd, -status);
        return (write_err || status);
}

static char *apply_filter(const char *path, const char *src,
                          unsigned long *sizep, const char *cmd)
{
        /*
         * Create a pipeline to have the command filter the buffer's
         * contents.
         *
         * (child --> cmd) --> us
         */
        const int SLOP = 4096;
        int pipe_feed[2];
        int status;
        char *dst;
        unsigned long dstsize, dstalloc;
        struct child_process child_process;

        if (!cmd)
                return NULL;

        memset(&child_process, 0, sizeof(child_process));

        if (pipe(pipe_feed) < 0) {
                error("cannot create pipe to run external filter %s", cmd);
                return NULL;
        }

        fflush(NULL);
        child_process.pid = fork();
        if (child_process.pid < 0) {
                error("cannot fork to run external filter %s", cmd);
                close(pipe_feed[0]);
                close(pipe_feed[1]);
                return NULL;
        }
        if (!child_process.pid) {
                dup2(pipe_feed[1], 1);
                close(pipe_feed[0]);
                close(pipe_feed[1]);
                exit(filter_buffer(path, src, *sizep, cmd));
        }
        close(pipe_feed[1]);

        dstalloc = *sizep;
        dst = xmalloc(dstalloc);
        dstsize = 0;

        while (1) {
                ssize_t numread = xread(pipe_feed[0], dst + dstsize,
                                        dstalloc - dstsize);

                if (numread <= 0) {
                        if (!numread)
                                break;
                        error("read from external filter %s failed", cmd);
                        free(dst);
                        dst = NULL;
                        break;
                }
                dstsize += numread;
                if (dstalloc <= dstsize + SLOP) {
                        dstalloc = dstsize + SLOP;
                        dst = xrealloc(dst, dstalloc);
                }
        }
        if (close(pipe_feed[0])) {
                error("read from external filter %s failed", cmd);
                free(dst);
                dst = NULL;
        }

        status = finish_command(&child_process);
        if (status) {
                error("external filter %s failed %d", cmd, -status);
                free(dst);
                dst = NULL;
        }

        if (dst)
                *sizep = dstsize;
        return dst;
}

static struct convert_driver {
        const char *name;
        struct convert_driver *next;
        char *smudge;
        char *clean;
} *user_convert, **user_convert_tail;

static int read_convert_config(const char *var, const char *value)
{
        const char *ep, *name;
        int namelen;
        struct convert_driver *drv;

        /*
         * External conversion drivers are configured using
         * "filter.<name>.variable".
         */
        if (prefixcmp(var, "filter.") || (ep = strrchr(var, '.')) == var + 6)
                return 0;
        name = var + 7;
        namelen = ep - name;
        for (drv = user_convert; drv; drv = drv->next)
                if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
                        break;
        if (!drv) {
                char *namebuf;
                drv = xcalloc(1, sizeof(struct convert_driver));
                namebuf = xmalloc(namelen + 1);
                memcpy(namebuf, name, namelen);
                namebuf[namelen] = 0;
                drv->name = namebuf;
                drv->next = NULL;
                *user_convert_tail = drv;
                user_convert_tail = &(drv->next);
        }

        ep++;

        /*
         * filter.<name>.smudge and filter.<name>.clean specifies
         * the command line:
         *
         *      command-line
         *
         * The command-line will not be interpolated in any way.
         */

        if (!strcmp("smudge", ep)) {
                if (!value)
                        return error("%s: lacks value", var);
                drv->smudge = strdup(value);
                return 0;
        }

        if (!strcmp("clean", ep)) {
                if (!value)
                        return error("%s: lacks value", var);
                drv->clean = strdup(value);
                return 0;
        }
        return 0;
}

static void setup_convert_check(struct git_attr_check *check)
{
        static struct git_attr *attr_crlf;
        static struct git_attr *attr_ident;
        static struct git_attr *attr_filter;

        if (!attr_crlf) {
                attr_crlf = git_attr("crlf", 4);
                attr_ident = git_attr("ident", 5);
                attr_filter = git_attr("filter", 6);
                user_convert_tail = &user_convert;
                git_config(read_convert_config);
        }
        check[0].attr = attr_crlf;
        check[1].attr = attr_ident;
        check[2].attr = attr_filter;
}

static int count_ident(const char *cp, unsigned long size)
{
        /*
         * "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"
         */
        int cnt = 0;
        char ch;

        while (size) {
                ch = *cp++;
                size--;
                if (ch != '$')
                        continue;
                if (size < 3)
                        break;
                if (memcmp("Id", cp, 2))
                        continue;
                ch = cp[2];
                cp += 3;
                size -= 3;
                if (ch == '$')
                        cnt++; /* $Id$ */
                if (ch != ':')
                        continue;

                /*
                 * "$Id: ... "; scan up to the closing dollar sign and discard.
                 */
                while (size) {
                        ch = *cp++;
                        size--;
                        if (ch == '$') {
                                cnt++;
                                break;
                        }
                }
        }
        return cnt;
}

static char *ident_to_git(const char *path, const char *src, unsigned long *sizep, int ident)
{
        int cnt;
        unsigned long size;
        char *dst, *buf;

        if (!ident)
                return NULL;
        size = *sizep;
        cnt = count_ident(src, size);
        if (!cnt)
                return NULL;
        buf = xmalloc(size);

        for (dst = buf; size; size--) {
                char ch = *src++;
                *dst++ = ch;
                if ((ch == '$') && (3 <= size) &&
                    !memcmp("Id:", src, 3)) {
                        unsigned long rem = size - 3;
                        const char *cp = src + 3;
                        do {
                                ch = *cp++;
                                if (ch == '$')
                                        break;
                                rem--;
                        } while (rem);
                        if (!rem)
                                continue;
                        memcpy(dst, "Id$", 3);
                        dst += 3;
                        size -= (cp - src);
                        src = cp;
                }
        }

        *sizep = dst - buf;
        return buf;
}

static char *ident_to_worktree(const char *path, const char *src, unsigned long *sizep, int ident)
{
        int cnt;
        unsigned long size;
        char *dst, *buf;
        unsigned char sha1[20];

        if (!ident)
                return NULL;

        size = *sizep;
        cnt = count_ident(src, size);
        if (!cnt)
                return NULL;

        hash_sha1_file(src, size, "blob", sha1);
        buf = xmalloc(size + cnt * 43);

        for (dst = buf; size; size--) {
                const char *cp;
                /* Fetch next source character, move the pointer on */
                char ch = *src++;
                /* Copy the current character to the destination */
                *dst++ = ch;
                /* If the current character is "$" or there are less than three
                 * remaining bytes or the two bytes following this one are not
                 * "Id", then simply read the next character */
                if ((ch != '$') || (size < 3) || memcmp("Id", src, 2))
                        continue;
                /*
                 * Here when
                 *  - There are more than 2 bytes remaining
                 *  - The current three bytes are "$Id"
                 * with
                 *  - ch == "$"
                 *  - src[0] == "I"
                 */

                /*
                 * It's possible that an expanded Id has crept its way into the
                 * repository, we cope with that by stripping the expansion out
                 */
                if (src[2] == ':') {
                        /* Expanded keywords have "$Id:" at the front */

                        /* discard up to but not including the closing $ */
                        unsigned long rem = size - 3;
                        /* Point at first byte after the ":" */
                        cp = src + 3;
                        /*
                         * Throw away characters until either
                         *  - we reach a "$"
                         *  - we run out of bytes (rem == 0)
                         */
                        do {
                                ch = *cp;
                                if (ch == '$')
                                        break;
                                cp++;
                                rem--;
                        } while (rem);
                        /* If the above finished because it ran out of characters, then
                         * this is an incomplete keyword, so don't run the expansion */
                        if (!rem)
                                continue;
                } else if (src[2] == '$')
                        cp = src + 2;
                else
                        /* Anything other than "$Id:XXX$" or $Id$ and we skip the
                         * expansion */
                        continue;

                /* cp is now pointing at the last $ of the keyword */

                memcpy(dst, "Id: ", 4);
                dst += 4;
                memcpy(dst, sha1_to_hex(sha1), 40);
                dst += 40;
                *dst++ = ' ';

                /* Adjust for the characters we've discarded */
                size -= (cp - src);
                src = cp;

                /* Copy the final "$" */
                *dst++ = *src++;
                size--;
        }

        *sizep = dst - buf;
        return buf;
}

static int git_path_check_crlf(const char *path, struct git_attr_check *check)
{
        const char *value = check->value;

        if (ATTR_TRUE(value))
                return CRLF_TEXT;
        else if (ATTR_FALSE(value))
                return CRLF_BINARY;
        else if (ATTR_UNSET(value))
                ;
        else if (!strcmp(value, "input"))
                return CRLF_INPUT;
        return CRLF_GUESS;
}

static struct convert_driver *git_path_check_convert(const char *path,
                                             struct git_attr_check *check)
{
        const char *value = check->value;
        struct convert_driver *drv;

        if (ATTR_TRUE(value) || ATTR_FALSE(value) || ATTR_UNSET(value))
                return NULL;
        for (drv = user_convert; drv; drv = drv->next)
                if (!strcmp(value, drv->name))
                        return drv;
        return NULL;
}

static int git_path_check_ident(const char *path, struct git_attr_check *check)
{
        const char *value = check->value;

        return !!ATTR_TRUE(value);
}

char *convert_to_git(const char *path, const char *src, unsigned long *sizep)
{
        struct git_attr_check check[3];
        int crlf = CRLF_GUESS;
        int ident = 0;
        char *filter = NULL;
        char *buf, *buf2;

        setup_convert_check(check);
        if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
                struct convert_driver *drv;
                crlf = git_path_check_crlf(path, check + 0);
                ident = git_path_check_ident(path, check + 1);
                drv = git_path_check_convert(path, check + 2);
                if (drv && drv->clean)
                        filter = drv->clean;
        }

        buf = apply_filter(path, src, sizep, filter);

        buf2 = crlf_to_git(path, buf ? buf : src, sizep, crlf);
        if (buf2) {
                free(buf);
                buf = buf2;
        }

        buf2 = ident_to_git(path, buf ? buf : src, sizep, ident);
        if (buf2) {
                free(buf);
                buf = buf2;
        }

        return buf;
}

char *convert_to_working_tree(const char *path, const char *src, unsigned long *sizep)
{
        struct git_attr_check check[3];
        int crlf = CRLF_GUESS;
        int ident = 0;
        char *filter = NULL;
        char *buf, *buf2;

        setup_convert_check(check);
        if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
                struct convert_driver *drv;
                crlf = git_path_check_crlf(path, check + 0);
                ident = git_path_check_ident(path, check + 1);
                drv = git_path_check_convert(path, check + 2);
                if (drv && drv->smudge)
                        filter = drv->smudge;
        }

        buf = ident_to_worktree(path, src, sizep, ident);

        buf2 = crlf_to_worktree(path, buf ? buf : src, sizep, crlf);
        if (buf2) {
                free(buf);
                buf = buf2;
        }

        buf2 = apply_filter(path, buf ? buf : src, sizep, filter);
        if (buf2) {
                free(buf);
                buf = buf2;
        }

        return buf;
}

void *convert_sha1_file(const char *path, const unsigned char *sha1,
                        unsigned int mode, enum object_type *type,
                        unsigned long *size)
{
        void *buffer = read_sha1_file(sha1, type, size);
        if (S_ISREG(mode) && buffer) {
                void *converted = convert_to_working_tree(path, buffer, size);
                if (converted) {
                        free(buffer);
                        buffer = converted;
                }
        }
        return buffer;
}