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) 2004-2013 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 #include "inums.h"
  24
  25 #ifndef ENODATA
  26 #define ENODATA EAGAIN
  27 #endif
  28
  29 /* We want all reads to be aligned on 1K boundries. */
  30 #define ALIGN_BOUNDRY 1024
  31 /* How far past the boundary is an offset? */
  32 #define ALIGNED_OVERSHOOT(oft) ((oft) & (ALIGN_BOUNDRY-1))
  33 /* Round up a length to the next boundary */
  34 #define ALIGNED_LENGTH(len) ((((len) - 1) | (ALIGN_BOUNDRY-1)) + 1)
  35
  36 extern int sparse_files;
  37
  38 static OFF_T sparse_seek = 0;
  39
  40 int sparse_end(int f, OFF_T size)
  41 {
  42         int ret;
  43
  44         if (!sparse_seek)
  45                 return 0;
  46
  47 #ifdef HAVE_FTRUNCATE
  48         ret = do_ftruncate(f, size);
  49 #else
  50         if (do_lseek(f, sparse_seek-1, SEEK_CUR) != size-1)
  51                 ret = -1;
  52         else {
  53                 do {
  54                         ret = write(f, "", 1);
  55                 } while (ret < 0 && errno == EINTR);
  56
  57                 ret = ret <= 0 ? -1 : 0;
  58         }
  59 #endif
  60
  61         sparse_seek = 0;
  62
  63         return ret;
  64 }
  65
  66
  67 static int write_sparse(int f, char *buf, int len)
  68 {
  69         int l1 = 0, l2 = 0;
  70         int ret;
  71
  72         for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
  73         for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}
  74
  75         sparse_seek += l1;
  76
  77         if (l1 == len)
  78                 return len;
  79
  80         if (sparse_seek)
  81                 do_lseek(f, sparse_seek, SEEK_CUR);
  82         sparse_seek = l2;
  83
  84         while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
  85                 if (ret < 0 && errno == EINTR)
  86                         continue;
  87                 return ret;
  88         }
  89
  90         if (ret != (int)(len - (l1+l2)))
  91                 return l1+ret;
  92
  93         return len;
  94 }
  95
  96
  97 static char *wf_writeBuf;
  98 static size_t wf_writeBufSize;
  99 static size_t wf_writeBufCnt;
 100
 101 int flush_write_file(int f)
 102 {
 103         int ret = 0;
 104         char *bp = wf_writeBuf;
 105
 106         while (wf_writeBufCnt > 0) {
 107                 if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
 108                         if (errno == EINTR)
 109                                 continue;
 110                         return ret;
 111                 }
 112                 wf_writeBufCnt -= ret;
 113                 bp += ret;
 114         }
 115         return ret;
 116 }
 117
 118
 119 /*
 120  * write_file does not allow incomplete writes.  It loops internally
 121  * until len bytes are written or errno is set.
 122  */
 123 int write_file(int f, char *buf, int len)
 124 {
 125         int ret = 0;
 126
 127         while (len > 0) {
 128                 int r1;
 129                 if (sparse_files > 0) {
 130                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
 131                         r1 = write_sparse(f, buf, len1);
 132                 } else {
 133                         if (!wf_writeBuf) {
 134                                 wf_writeBufSize = WRITE_SIZE * 8;
 135                                 wf_writeBufCnt  = 0;
 136                                 wf_writeBuf = new_array(char, wf_writeBufSize);
 137                                 if (!wf_writeBuf)
 138                                         out_of_memory("write_file");
 139                         }
 140                         r1 = (int)MIN((size_t)len, wf_writeBufSize - wf_writeBufCnt);
 141                         if (r1) {
 142                                 memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
 143                                 wf_writeBufCnt += r1;
 144                         }
 145                         if (wf_writeBufCnt == wf_writeBufSize) {
 146                                 if (flush_write_file(f) < 0)
 147                                         return -1;
 148                                 if (!r1 && len)
 149                                         continue;
 150                         }
 151                 }
 152                 if (r1 <= 0) {
 153                         if (ret > 0)
 154                                 return ret;
 155                         return r1;
 156                 }
 157                 len -= r1;
 158                 buf += r1;
 159                 ret += r1;
 160         }
 161         return ret;
 162 }
 163
 164
 165 /* This provides functionality somewhat similar to mmap() but using read().
 166  * It gives sliding window access to a file.  mmap() is not used because of
 167  * the possibility of another program (such as a mailer) truncating the
 168  * file thus giving us a SIGBUS. */
 169 struct map_struct *map_file(int fd, OFF_T len, int32 read_size, int32 blk_size)
 170 {
 171         struct map_struct *map;
 172
 173         if (!(map = new0(struct map_struct)))
 174                 out_of_memory("map_file");
 175
 176         if (blk_size && (read_size % blk_size))
 177                 read_size += blk_size - (read_size % blk_size);
 178
 179         map->fd = fd;
 180         map->file_size = len;
 181         map->def_window_size = ALIGNED_LENGTH(read_size);
 182
 183         return map;
 184 }
 185
 186
 187 /* slide the read window in the file */
 188 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 189 {
 190         OFF_T window_start, read_start;
 191         int32 window_size, read_size, read_offset, align_fudge;
 192
 193         if (len == 0)
 194                 return NULL;
 195         if (len < 0) {
 196                 rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
 197                         (long)len);
 198                 exit_cleanup(RERR_FILEIO);
 199         }
 200
 201         /* in most cases the region will already be available */
 202         if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
 203                 return map->p + (offset - map->p_offset);
 204
 205         /* nope, we are going to have to do a read. Work out our desired window */
 206         align_fudge = (int32)ALIGNED_OVERSHOOT(offset);
 207         window_start = offset - align_fudge;
 208         window_size = map->def_window_size;
 209         if (window_start + window_size > map->file_size)
 210                 window_size = (int32)(map->file_size - window_start);
 211         if (window_size < len + align_fudge)
 212                 window_size = ALIGNED_LENGTH(len + align_fudge);
 213
 214         /* make sure we have allocated enough memory for the window */
 215         if (window_size > map->p_size) {
 216                 map->p = realloc_array(map->p, char, window_size);
 217                 if (!map->p)
 218                         out_of_memory("map_ptr");
 219                 map->p_size = window_size;
 220         }
 221
 222         /* Now try to avoid re-reading any bytes by reusing any bytes from the previous buffer. */
 223         if (window_start >= map->p_offset && window_start < map->p_offset + map->p_len
 224          && window_start + window_size >= map->p_offset + map->p_len) {
 225                 read_start = map->p_offset + map->p_len;
 226                 read_offset = (int32)(read_start - window_start);
 227                 read_size = window_size - read_offset;
 228                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 229         } else {
 230                 read_start = window_start;
 231                 read_size = window_size;
 232                 read_offset = 0;
 233         }
 234
 235         if (read_size <= 0) {
 236                 rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
 237                         (long)read_size);
 238                 exit_cleanup(RERR_FILEIO);
 239         }
 240
 241         if (map->p_fd_offset != read_start) {
 242                 OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
 243                 if (ret != read_start) {
 244                         rsyserr(FERROR, errno, "lseek returned %s, not %s",
 245                                 big_num(ret), big_num(read_start));
 246                         exit_cleanup(RERR_FILEIO);
 247                 }
 248                 map->p_fd_offset = read_start;
 249         }
 250         map->p_offset = window_start;
 251         map->p_len = window_size;
 252
 253         while (read_size > 0) {
 254                 int32 nread = read(map->fd, map->p + read_offset, read_size);
 255                 if (nread <= 0) {
 256                         if (!map->status)
 257                                 map->status = nread ? errno : ENODATA;
 258                         /* The best we can do is zero the buffer -- the file
 259                          * has changed mid transfer! */
 260                         memset(map->p + read_offset, 0, read_size);
 261                         break;
 262                 }
 263                 map->p_fd_offset += nread;
 264                 read_offset += nread;
 265                 read_size -= nread;
 266         }
 267
 268         return map->p + align_fudge;
 269 }
 270
 271
 272 int unmap_file(struct map_struct *map)
 273 {
 274         int     ret;
 275
 276         if (map->p) {
 277                 free(map->p);
 278                 map->p = NULL;
 279         }
 280         ret = map->status;
 281         memset(map, 0, sizeof map[0]);
 282         free(map);
 283
 284         return ret;
 285 }