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