fileio.c

   1 /*
   2  * File IO utilities used in rsync.
   3  *
   4  * Copyright (C) 1998 Andrew Tridgell
   5  * Copyright (C) 2002 Martin Pool
   6  * Copyright (C) 2004-2007 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 #include "rsync.h"
  23
  24 #ifndef ENODATA
  25 #define ENODATA EAGAIN
  26 #endif
  27
  28 extern int sparse_files;
  29
  30 static char last_byte;
  31 static size_t sparse_seek = 0;
  32
  33 int sparse_end(int f)
  34 {
  35         int ret;
  36
  37         if (!sparse_seek)
  38                 return 0;
  39
  40         do_lseek(f, sparse_seek-1, SEEK_CUR);
  41         sparse_seek = 0;
  42
  43         do {
  44                 ret = write(f, "", 1);
  45         } while (ret < 0 && errno == EINTR);
  46
  47         return ret <= 0 ? -1 : 0;
  48 }
  49
  50
  51 static int write_sparse(int f, char *buf, size_t len)
  52 {
  53         size_t l1 = 0, l2 = 0;
  54         int ret;
  55
  56         for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
  57         for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}
  58
  59         /* XXX Riddle me this: why does this function SLOW DOWN when I
  60          * remove the following (unneeded) line?? Core Duo weirdness? */
  61         last_byte = buf[len-1];
  62
  63         sparse_seek += l1;
  64
  65         if (l1 == len)
  66                 return len;
  67
  68         if (sparse_seek)
  69                 do_lseek(f, sparse_seek, SEEK_CUR);
  70         sparse_seek = l2;
  71
  72         while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
  73                 if (ret < 0 && errno == EINTR)
  74                         continue;
  75                 return ret;
  76         }
  77
  78         if (ret != (int)(len - (l1+l2)))
  79                 return l1+ret;
  80
  81         return len;
  82 }
  83
  84
  85 static char *wf_writeBuf;
  86 static size_t wf_writeBufSize;
  87 static size_t wf_writeBufCnt;
  88
  89 int flush_write_file(int f)
  90 {
  91         int ret = 0;
  92         char *bp = wf_writeBuf;
  93
  94         while (wf_writeBufCnt > 0) {
  95                 if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
  96                         if (errno == EINTR)
  97                                 continue;
  98                         return ret;
  99                 }
 100                 wf_writeBufCnt -= ret;
 101                 bp += ret;
 102         }
 103         return ret;
 104 }
 105
 106
 107 /*
 108  * write_file does not allow incomplete writes.  It loops internally
 109  * until len bytes are written or errno is set.
 110  */
 111 int write_file(int f,char *buf,size_t len)
 112 {
 113         int ret = 0;
 114
 115         while (len > 0) {
 116                 int r1;
 117                 if (sparse_files > 0) {
 118                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
 119                         r1 = write_sparse(f, buf, len1);
 120                 } else {
 121                         if (!wf_writeBuf) {
 122                                 wf_writeBufSize = WRITE_SIZE * 8;
 123                                 wf_writeBufCnt  = 0;
 124                                 wf_writeBuf = new_array(char, wf_writeBufSize);
 125                                 if (!wf_writeBuf)
 126                                         out_of_memory("write_file");
 127                         }
 128                         r1 = MIN(len, wf_writeBufSize - wf_writeBufCnt);
 129                         if (r1) {
 130                                 memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
 131                                 wf_writeBufCnt += r1;
 132                         }
 133                         if (wf_writeBufCnt == wf_writeBufSize) {
 134                                 if (flush_write_file(f) < 0)
 135                                         return -1;
 136                                 if (!r1 && len)
 137                                         continue;
 138                         }
 139                 }
 140                 if (r1 <= 0) {
 141                         if (ret > 0)
 142                                 return ret;
 143                         return r1;
 144                 }
 145                 len -= r1;
 146                 buf += r1;
 147                 ret += r1;
 148         }
 149         return ret;
 150 }
 151
 152
 153 /* This provides functionality somewhat similar to mmap() but using read().
 154  * It gives sliding window access to a file.  mmap() is not used because of
 155  * the possibility of another program (such as a mailer) truncating the
 156  * file thus giving us a SIGBUS. */
 157 struct map_struct *map_file(int fd, OFF_T len, int32 read_size,
 158                             int32 blk_size)
 159 {
 160         struct map_struct *map;
 161
 162         if (!(map = new0(struct map_struct)))
 163                 out_of_memory("map_file");
 164
 165         if (blk_size && (read_size % blk_size))
 166                 read_size += blk_size - (read_size % blk_size);
 167
 168         map->fd = fd;
 169         map->file_size = len;
 170         map->def_window_size = read_size;
 171
 172         return map;
 173 }
 174
 175
 176 /* slide the read window in the file */
 177 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 178 {
 179         int32 nread;
 180         OFF_T window_start, read_start;
 181         int32 window_size, read_size, read_offset;
 182
 183         if (len == 0)
 184                 return NULL;
 185         if (len < 0) {
 186                 rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
 187                         (long)len);
 188                 exit_cleanup(RERR_FILEIO);
 189         }
 190
 191         /* in most cases the region will already be available */
 192         if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
 193                 return map->p + (offset - map->p_offset);
 194
 195         /* nope, we are going to have to do a read. Work out our desired window */
 196         window_start = offset;
 197         window_size = map->def_window_size;
 198         if (window_start + window_size > map->file_size)
 199                 window_size = (int32)(map->file_size - window_start);
 200         if (len > window_size)
 201                 window_size = len;
 202
 203         /* make sure we have allocated enough memory for the window */
 204         if (window_size > map->p_size) {
 205                 map->p = realloc_array(map->p, char, window_size);
 206                 if (!map->p)
 207                         out_of_memory("map_ptr");
 208                 map->p_size = window_size;
 209         }
 210
 211         /* Now try to avoid re-reading any bytes by reusing any bytes
 212          * from the previous buffer. */
 213         if (window_start >= map->p_offset &&
 214             window_start < map->p_offset + map->p_len &&
 215             window_start + window_size >= map->p_offset + map->p_len) {
 216                 read_start = map->p_offset + map->p_len;
 217                 read_offset = (int32)(read_start - window_start);
 218                 read_size = window_size - read_offset;
 219                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 220         } else {
 221                 read_start = window_start;
 222                 read_size = window_size;
 223                 read_offset = 0;
 224         }
 225
 226         if (read_size <= 0) {
 227                 rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
 228                         (long)read_size);
 229                 exit_cleanup(RERR_FILEIO);
 230         }
 231
 232         if (map->p_fd_offset != read_start) {
 233                 OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
 234                 if (ret != read_start) {
 235                         rsyserr(FERROR, errno, "lseek returned %.0f, not %.0f",
 236                                 (double)ret, (double)read_start);
 237                         exit_cleanup(RERR_FILEIO);
 238                 }
 239                 map->p_fd_offset = read_start;
 240         }
 241         map->p_offset = window_start;
 242         map->p_len = window_size;
 243
 244         while (read_size > 0) {
 245                 nread = read(map->fd, map->p + read_offset, read_size);
 246                 if (nread <= 0) {
 247                         if (!map->status)
 248                                 map->status = nread ? errno : ENODATA;
 249                         /* The best we can do is zero the buffer -- the file
 250                          * has changed mid transfer! */
 251                         memset(map->p + read_offset, 0, read_size);
 252                         break;
 253                 }
 254                 map->p_fd_offset += nread;
 255                 read_offset += nread;
 256                 read_size -= nread;
 257         }
 258
 259         return map->p;
 260 }
 261
 262
 263 int unmap_file(struct map_struct *map)
 264 {
 265         int     ret;
 266
 267         if (map->p) {
 268                 free(map->p);
 269                 map->p = NULL;
 270         }
 271         ret = map->status;
 272         memset(map, 0, sizeof map[0]);
 273         free(map);
 274
 275         return ret;
 276 }