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[rsync.git] / fileio.c

/*
 * File IO utilities used in rsync.
 *
 * Copyright (C) 1998 Andrew Tridgell
 * Copyright (C) 2002 Martin Pool
 * Copyright (C) 2004-2020 Wayne Davison
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, visit the http://fsf.org website.
 */

#include "rsync.h"
#include "inums.h"

#ifndef ENODATA
#define ENODATA EAGAIN
#endif

/* We want all reads to be aligned on 1K boundaries. */
#define ALIGN_BOUNDARY 1024
/* How far past the boundary is an offset? */
#define ALIGNED_OVERSHOOT(oft) ((oft) & (ALIGN_BOUNDARY-1))
/* Round up a length to the next boundary */
#define ALIGNED_LENGTH(len) ((((len) - 1) | (ALIGN_BOUNDARY-1)) + 1)

extern int sparse_files;

OFF_T preallocated_len = 0;

static OFF_T sparse_seek = 0;
static OFF_T sparse_past_write = 0;

int sparse_end(int f, OFF_T size)
{
        int ret;

        sparse_past_write = 0;

        if (!sparse_seek)
                return 0;

#ifdef HAVE_FTRUNCATE
        ret = do_ftruncate(f, size);
#else
        if (do_lseek(f, sparse_seek-1, SEEK_CUR) != size-1)
                ret = -1;
        else {
                do {
                        ret = write(f, "", 1);
                } while (ret < 0 && errno == EINTR);

                ret = ret <= 0 ? -1 : 0;
        }
#endif

        sparse_seek = 0;

        return ret;
}

/* Note that the offset is just the caller letting us know where
 * the current file position is in the file. The use_seek arg tells
 * us that we should seek over matching data instead of writing it. */
static int write_sparse(int f, int use_seek, OFF_T offset, const char *buf, int len)
{
        int l1 = 0, l2 = 0;
        int ret;

        for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
        for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}

        sparse_seek += l1;

        if (l1 == len)
                return len;

        if (sparse_seek) {
                if (sparse_past_write >= preallocated_len) {
                        if (do_lseek(f, sparse_seek, SEEK_CUR) < 0)
                                return -1;
                } else if (do_punch_hole(f, sparse_past_write, sparse_seek) < 0) {
                        sparse_seek = 0;
                        return -1;
                }
        }
        sparse_seek = l2;
        sparse_past_write = offset + len - l2;

        if (use_seek) {
                /* The in-place data already matches. */
                if (do_lseek(f, len - (l1+l2), SEEK_CUR) < 0)
                        return -1;
                return len;
        }

        while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
                if (ret < 0 && errno == EINTR)
                        continue;
                sparse_seek = 0;
                return ret;
        }

        if (ret != (int)(len - (l1+l2))) {
                sparse_seek = 0;
                return l1+ret;
        }

        return len;
}

static char *wf_writeBuf;
static size_t wf_writeBufSize;
static size_t wf_writeBufCnt;

int flush_write_file(int f)
{
        int ret = 0;
        char *bp = wf_writeBuf;

        while (wf_writeBufCnt > 0) {
                if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
                        if (errno == EINTR)
                                continue;
                        return ret;
                }
                wf_writeBufCnt -= ret;
                bp += ret;
        }
        return ret;
}

/* write_file does not allow incomplete writes.  It loops internally
 * until len bytes are written or errno is set.  Note that use_seek and
 * offset are only used in sparse processing (see write_sparse()). */
int write_file(int f, int use_seek, OFF_T offset, const char *buf, int len)
{
        int ret = 0;

        while (len > 0) {
                int r1;
                if (sparse_files > 0) {
                        int len1 = MIN(len, SPARSE_WRITE_SIZE);
                        r1 = write_sparse(f, use_seek, offset, buf, len1);
                        offset += r1;
                } else {
                        if (!wf_writeBuf) {
                                wf_writeBufSize = WRITE_SIZE * 8;
                                wf_writeBufCnt  = 0;
                                wf_writeBuf = new_array(char, wf_writeBufSize);
                        }
                        r1 = (int)MIN((size_t)len, wf_writeBufSize - wf_writeBufCnt);
                        if (r1) {
                                memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
                                wf_writeBufCnt += r1;
                        }
                        if (wf_writeBufCnt == wf_writeBufSize) {
                                if (flush_write_file(f) < 0)
                                        return -1;
                                if (!r1 && len)
                                        continue;
                        }
                }
                if (r1 <= 0) {
                        if (ret > 0)
                                return ret;
                        return r1;
                }
                len -= r1;
                buf += r1;
                ret += r1;
        }
        return ret;
}

/* An in-place update found identical data at an identical location. We either
 * just seek past it, or (for an in-place sparse update), we give the data to
 * the sparse processor with the use_seek flag set. */
int skip_matched(int fd, OFF_T offset, const char *buf, int len)
{
        OFF_T pos;

        if (sparse_files > 0) {
                if (write_file(fd, 1, offset, buf, len) != len)
                        return -1;
                return 0;
        }

        if (flush_write_file(fd) < 0)
                return -1;

        if ((pos = do_lseek(fd, len, SEEK_CUR)) != offset + len) {
                rsyserr(FERROR_XFER, errno, "lseek returned %s, not %s",
                        big_num(pos), big_num(offset));
                return -1;
        }

        return 0;
}

/* This provides functionality somewhat similar to mmap() but using read().
 * It gives sliding window access to a file.  mmap() is not used because of
 * the possibility of another program (such as a mailer) truncating the
 * file thus giving us a SIGBUS. */
struct map_struct *map_file(int fd, OFF_T len, int32 read_size, int32 blk_size)
{
        struct map_struct *map;

        map = new0(struct map_struct);

        if (blk_size && (read_size % blk_size))
                read_size += blk_size - (read_size % blk_size);

        map->fd = fd;
        map->file_size = len;
        map->def_window_size = ALIGNED_LENGTH(read_size);

        return map;
}


/* slide the read window in the file */
char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
{
        OFF_T window_start, read_start;
        int32 window_size, read_size, read_offset, align_fudge;

        if (len == 0)
                return NULL;
        if (len < 0) {
                rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
                        (long)len);
                exit_cleanup(RERR_FILEIO);
        }

        /* in most cases the region will already be available */
        if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
                return map->p + (offset - map->p_offset);

        /* nope, we are going to have to do a read. Work out our desired window */
        align_fudge = (int32)ALIGNED_OVERSHOOT(offset);
        window_start = offset - align_fudge;
        window_size = map->def_window_size;
        if (window_start + window_size > map->file_size)
                window_size = (int32)(map->file_size - window_start);
        if (window_size < len + align_fudge)
                window_size = ALIGNED_LENGTH(len + align_fudge);

        /* make sure we have allocated enough memory for the window */
        if (window_size > map->p_size) {
                map->p = realloc_array(map->p, char, window_size);
                map->p_size = window_size;
        }

        /* Now try to avoid re-reading any bytes by reusing any bytes from the previous buffer. */
        if (window_start >= map->p_offset && window_start < map->p_offset + map->p_len
         && window_start + window_size >= map->p_offset + map->p_len) {
                read_start = map->p_offset + map->p_len;
                read_offset = (int32)(read_start - window_start);
                read_size = window_size - read_offset;
                memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
        } else {
                read_start = window_start;
                read_size = window_size;
                read_offset = 0;
        }

        if (read_size <= 0) {
                rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
                        (long)read_size);
                exit_cleanup(RERR_FILEIO);
        }

        if (map->p_fd_offset != read_start) {
                OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
                if (ret != read_start) {
                        rsyserr(FERROR, errno, "lseek returned %s, not %s",
                                big_num(ret), big_num(read_start));
                        exit_cleanup(RERR_FILEIO);
                }
                map->p_fd_offset = read_start;
        }
        map->p_offset = window_start;
        map->p_len = window_size;

        while (read_size > 0) {
                int32 nread = read(map->fd, map->p + read_offset, read_size);
                if (nread <= 0) {
                        if (!map->status)
                                map->status = nread ? errno : ENODATA;
                        /* The best we can do is zero the buffer -- the file
                         * has changed mid transfer! */
                        memset(map->p + read_offset, 0, read_size);
                        break;
                }
                map->p_fd_offset += nread;
                read_offset += nread;
                read_size -= nread;
        }

        return map->p + align_fudge;
}

int unmap_file(struct map_struct *map)
{
        int     ret;

        if (map->p) {
                free(map->p);
                map->p = NULL;
        }
        ret = map->status;
#if 0 /* I don't think we really need this. */
        force_memzero(map, sizeof map[0]);
#endif
        free(map);

        return ret;
}