fileio.c

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/*
   Copyright (C) Andrew Tridgell 1998
   Copyright (C) 2002 by Martin Pool

   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
  File IO utilities used in rsync
  */
#include "rsync.h"

#ifndef ENODATA
#define ENODATA EAGAIN
#endif

extern int sparse_files;

static char last_byte;
static int last_sparse;

int sparse_end(int f)
{
        if (last_sparse) {
                do_lseek(f,-1,SEEK_CUR);
                return (write(f,&last_byte,1) == 1 ? 0 : -1);
        }
        last_sparse = 0;
        return 0;
}


static int write_sparse(int f,char *buf,size_t len)
{
        size_t 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++) {}

        last_byte = buf[len-1];

        if (l1 == len || l2 > 0)
                last_sparse=1;

        if (l1 > 0) {
                do_lseek(f,l1,SEEK_CUR);
        }

        if (l1 == len)
                return len;

        ret = write(f, buf + l1, len - (l1+l2));
        if (ret == -1 || ret == 0)
                return ret;
        else if (ret != (int) (len - (l1+l2)))
                return (l1+ret);

        if (l2 > 0)
                do_lseek(f,l2,SEEK_CUR);

        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.
 */
int write_file(int f,char *buf,size_t len)
{
        int ret = 0;

        while (len > 0) {
                int r1;
                if (sparse_files) {
                        int len1 = MIN(len, SPARSE_WRITE_SIZE);
                        r1 = write_sparse(f, buf, len1);
                } else {
                        if (!wf_writeBuf) {
                                wf_writeBufSize = WRITE_SIZE * 8;
                                wf_writeBufCnt  = 0;
                                wf_writeBuf = new_array(char, wf_writeBufSize);
                                if (!wf_writeBuf)
                                        out_of_memory("write_file");
                        }
                        r1 = MIN(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;
}


/* 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;

        if (!(map = new(struct map_struct)))
                out_of_memory("map_file");

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

        memset(map, 0, sizeof map[0]);
        map->fd = fd;
        map->file_size = len;
        map->def_window_size = read_size;

        return map;
}


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

        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 */
        window_start = offset;
        window_size = map->def_window_size;
        if (window_start + window_size > map->file_size)
                window_size = map->file_size - window_start;
        if (len > window_size)
                window_size = len;

        /* 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);
                if (!map->p)
                        out_of_memory("map_ptr");
                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 = 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 %.0f, not %.0f",
                                (double)ret, (double)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) {
                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;
}


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

        if (map->p) {
                free(map->p);
                map->p = NULL;
        }
        ret = map->status;
        memset(map, 0, sizeof map[0]);
        free(map);

        return ret;
}

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