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) 2004-2009 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 extern int sparse_files;
  30
  31 static char last_byte;
  32 static OFF_T sparse_seek = 0;
  33
  34 int sparse_end(int f)
  35 {
  36         int ret;
  37
  38         if (!sparse_seek)
  39                 return 0;
  40
  41         do_lseek(f, sparse_seek-1, SEEK_CUR);
  42         sparse_seek = 0;
  43
  44         do {
  45                 ret = write(f, "", 1);
  46         } while (ret < 0 && errno == EINTR);
  47
  48         return ret <= 0 ? -1 : 0;
  49 }
  50
  51
  52 static int write_sparse(int f, char *buf, int len)
  53 {
  54         int l1 = 0, l2 = 0;
  55         int ret;
  56
  57         for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
  58         for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}
  59
  60         /* XXX Riddle me this: why does this function SLOW DOWN when I
  61          * remove the following (unneeded) line?? Core Duo weirdness? */
  62         last_byte = buf[len-1];
  63
  64         sparse_seek += l1;
  65
  66         if (l1 == len)
  67                 return len;
  68
  69         if (sparse_seek)
  70                 do_lseek(f, sparse_seek, SEEK_CUR);
  71         sparse_seek = l2;
  72
  73         while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
  74                 if (ret < 0 && errno == EINTR)
  75                         continue;
  76                 return ret;
  77         }
  78
  79         if (ret != (int)(len - (l1+l2)))
  80                 return l1+ret;
  81
  82         return len;
  83 }
  84
  85
  86 static char *wf_writeBuf;
  87 static size_t wf_writeBufSize;
  88 static size_t wf_writeBufCnt;
  89
  90 int flush_write_file(int f)
  91 {
  92         int ret = 0;
  93         char *bp = wf_writeBuf;
  94
  95         while (wf_writeBufCnt > 0) {
  96                 if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
  97                         if (errno == EINTR)
  98                                 continue;
  99                         return ret;
 100                 }
 101                 wf_writeBufCnt -= ret;
 102                 bp += ret;
 103         }
 104         return ret;
 105 }
 106
 107
 108 /*
 109  * write_file does not allow incomplete writes.  It loops internally
 110  * until len bytes are written or errno is set.
 111  */
 112 int write_file(int f, char *buf, int len)
 113 {
 114         int ret = 0;
 115
 116         while (len > 0) {
 117                 int r1;
 118                 if (sparse_files > 0) {
 119                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
 120                         r1 = write_sparse(f, buf, len1);
 121                 } else {
 122                         if (!wf_writeBuf) {
 123                                 wf_writeBufSize = WRITE_SIZE * 8;
 124                                 wf_writeBufCnt  = 0;
 125                                 wf_writeBuf = new_array(char, wf_writeBufSize);
 126                                 if (!wf_writeBuf)
 127                                         out_of_memory("write_file");
 128                         }
 129                         r1 = (int)MIN((size_t)len, wf_writeBufSize - wf_writeBufCnt);
 130                         if (r1) {
 131                                 memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
 132                                 wf_writeBufCnt += r1;
 133                         }
 134                         if (wf_writeBufCnt == wf_writeBufSize) {
 135                                 if (flush_write_file(f) < 0)
 136                                         return -1;
 137                                 if (!r1 && len)
 138                                         continue;
 139                         }
 140                 }
 141                 if (r1 <= 0) {
 142                         if (ret > 0)
 143                                 return ret;
 144                         return r1;
 145                 }
 146                 len -= r1;
 147                 buf += r1;
 148                 ret += r1;
 149         }
 150         return ret;
 151 }
 152
 153
 154 /* This provides functionality somewhat similar to mmap() but using read().
 155  * It gives sliding window access to a file.  mmap() is not used because of
 156  * the possibility of another program (such as a mailer) truncating the
 157  * file thus giving us a SIGBUS. */
 158 struct map_struct *map_file(int fd, OFF_T len, int32 read_size,
 159                             int32 blk_size)
 160 {
 161         struct map_struct *map;
 162
 163         if (!(map = new0(struct map_struct)))
 164                 out_of_memory("map_file");
 165
 166         if (blk_size && (read_size % blk_size))
 167                 read_size += blk_size - (read_size % blk_size);
 168
 169         map->fd = fd;
 170         map->file_size = len;
 171         map->def_window_size = read_size;
 172
 173         return map;
 174 }
 175
 176
 177 /* slide the read window in the file */
 178 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 179 {
 180         int32 nread;
 181         OFF_T window_start, read_start;
 182         int32 window_size, read_size, read_offset;
 183
 184         if (len == 0)
 185                 return NULL;
 186         if (len < 0) {
 187                 rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
 188                         (long)len);
 189                 exit_cleanup(RERR_FILEIO);
 190         }
 191
 192         /* in most cases the region will already be available */
 193         if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
 194                 return map->p + (offset - map->p_offset);
 195
 196         /* nope, we are going to have to do a read. Work out our desired window */
 197         window_start = offset;
 198         window_size = map->def_window_size;
 199         if (window_start + window_size > map->file_size)
 200                 window_size = (int32)(map->file_size - window_start);
 201         if (len > window_size)
 202                 window_size = len;
 203
 204         /* make sure we have allocated enough memory for the window */
 205         if (window_size > map->p_size) {
 206                 map->p = realloc_array(map->p, char, window_size);
 207                 if (!map->p)
 208                         out_of_memory("map_ptr");
 209                 map->p_size = window_size;
 210         }
 211
 212         /* Now try to avoid re-reading any bytes by reusing any bytes
 213          * from the previous buffer. */
 214         if (window_start >= map->p_offset &&
 215             window_start < map->p_offset + map->p_len &&
 216             window_start + window_size >= map->p_offset + map->p_len) {
 217                 read_start = map->p_offset + map->p_len;
 218                 read_offset = (int32)(read_start - window_start);
 219                 read_size = window_size - read_offset;
 220                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 221         } else {
 222                 read_start = window_start;
 223                 read_size = window_size;
 224                 read_offset = 0;
 225         }
 226
 227         if (read_size <= 0) {
 228                 rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
 229                         (long)read_size);
 230                 exit_cleanup(RERR_FILEIO);
 231         }
 232
 233         if (map->p_fd_offset != read_start) {
 234                 OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
 235                 if (ret != read_start) {
 236                         rsyserr(FERROR, errno, "lseek returned %s, not %s",
 237                                 big_num(ret), big_num(read_start));
 238                         exit_cleanup(RERR_FILEIO);
 239                 }
 240                 map->p_fd_offset = read_start;
 241         }
 242         map->p_offset = window_start;
 243         map->p_len = window_size;
 244
 245         while (read_size > 0) {
 246                 nread = read(map->fd, map->p + read_offset, read_size);
 247                 if (nread <= 0) {
 248                         if (!map->status)
 249                                 map->status = nread ? errno : ENODATA;
 250                         /* The best we can do is zero the buffer -- the file
 251                          * has changed mid transfer! */
 252                         memset(map->p + read_offset, 0, read_size);
 253                         break;
 254                 }
 255                 map->p_fd_offset += nread;
 256                 read_offset += nread;
 257                 read_size -= nread;
 258         }
 259
 260         return map->p;
 261 }
 262
 263
 264 int unmap_file(struct map_struct *map)
 265 {
 266         int     ret;
 267
 268         if (map->p) {
 269                 free(map->p);
 270                 map->p = NULL;
 271         }
 272         ret = map->status;
 273         memset(map, 0, sizeof map[0]);
 274         free(map);
 275
 276         return ret;
 277 }