fileio.c

   1 /*
   2    Copyright (C) Andrew Tridgell 1998
   3    Copyright (C) 2002 by Martin Pool
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18 */
  19
  20 /*
  21   File IO utilities used in rsync
  22   */
  23 #include "rsync.h"
  24
  25 extern int sparse_files;
  26
  27 static char last_byte;
  28 static int last_sparse;
  29
  30 int sparse_end(int f)
  31 {
  32         if (last_sparse) {
  33                 do_lseek(f,-1,SEEK_CUR);
  34                 return (write(f,&last_byte,1) == 1 ? 0 : -1);
  35         }
  36         last_sparse = 0;
  37         return 0;
  38 }
  39
  40
  41 static int write_sparse(int f,char *buf,size_t len)
  42 {
  43         size_t l1=0, l2=0;
  44         int ret;
  45
  46         for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
  47         for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}
  48
  49         last_byte = buf[len-1];
  50
  51         if (l1 == len || l2 > 0)
  52                 last_sparse=1;
  53
  54         if (l1 > 0) {
  55                 do_lseek(f,l1,SEEK_CUR);
  56         }
  57
  58         if (l1 == len)
  59                 return len;
  60
  61         ret = write(f, buf + l1, len - (l1+l2));
  62         if (ret == -1 || ret == 0)
  63                 return ret;
  64         else if (ret != (int) (len - (l1+l2)))
  65                 return (l1+ret);
  66
  67         if (l2 > 0)
  68                 do_lseek(f,l2,SEEK_CUR);
  69
  70         return len;
  71 }
  72
  73
  74 static char *wf_writeBuf;
  75 static size_t wf_writeBufSize;
  76 static size_t wf_writeBufCnt;
  77
  78 int flush_write_file(int f)
  79 {
  80         int ret = 0;
  81         char *bp = wf_writeBuf;
  82
  83         while (wf_writeBufCnt > 0) {
  84                 if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
  85                         if (errno == EINTR)
  86                                 continue;
  87                         return ret;
  88                 }
  89                 wf_writeBufCnt -= ret;
  90                 bp += ret;
  91         }
  92         return ret;
  93 }
  94
  95
  96 /*
  97  * write_file does not allow incomplete writes.  It loops internally
  98  * until len bytes are written or errno is set.
  99  */
 100 int write_file(int f,char *buf,size_t len)
 101 {
 102         int ret = 0;
 103
 104         while (len > 0) {
 105                 int r1;
 106                 if (sparse_files) {
 107                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
 108                         r1 = write_sparse(f, buf, len1);
 109                 } else {
 110                         if (!wf_writeBuf) {
 111                                 wf_writeBufSize = WRITE_SIZE * 8;
 112                                 wf_writeBufCnt  = 0;
 113                                 wf_writeBuf = new_array(char, wf_writeBufSize);
 114                                 if (!wf_writeBuf)
 115                                         out_of_memory("write_file");
 116                         }
 117                         r1 = MIN(len, wf_writeBufSize - wf_writeBufCnt);
 118                         if (r1) {
 119                                 memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
 120                                 wf_writeBufCnt += r1;
 121                         }
 122                         if (wf_writeBufCnt == wf_writeBufSize) {
 123                                 if (flush_write_file(f) < 0)
 124                                         return -1;
 125                                 if (!r1 && len)
 126                                         continue;
 127                         }
 128                 }
 129                 if (r1 <= 0) {
 130                         if (ret > 0)
 131                                 return ret;
 132                         return r1;
 133                 }
 134                 len -= r1;
 135                 buf += r1;
 136                 ret += r1;
 137         }
 138         return ret;
 139 }
 140
 141
 142 /* This provides functionality somewhat similar to mmap() but using read().
 143  * It gives sliding window access to a file.  mmap() is not used because of
 144  * the possibility of another program (such as a mailer) truncating the
 145  * file thus giving us a SIGBUS. */
 146 struct map_struct *map_file(int fd, OFF_T len, int32 read_size,
 147                             int32 blk_size)
 148 {
 149         struct map_struct *map;
 150
 151         if (!(map = new(struct map_struct)))
 152                 out_of_memory("map_file");
 153
 154         if (blk_size && (read_size % blk_size))
 155                 read_size += blk_size - (read_size % blk_size);
 156
 157         memset(map, 0, sizeof map[0]);
 158         map->fd = fd;
 159         map->file_size = len;
 160         map->def_window_size = read_size;
 161
 162         return map;
 163 }
 164
 165
 166 /* slide the read window in the file */
 167 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 168 {
 169         int32 nread;
 170         OFF_T window_start, read_start;
 171         int32 window_size, read_size, read_offset;
 172
 173         if (len == 0)
 174                 return NULL;
 175         if (len < 0) {
 176                 rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
 177                         (long)len);
 178                 exit_cleanup(RERR_FILEIO);
 179         }
 180
 181         /* in most cases the region will already be available */
 182         if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
 183                 return map->p + (offset - map->p_offset);
 184
 185         /* nope, we are going to have to do a read. Work out our desired window */
 186         window_start = offset;
 187         window_size = map->def_window_size;
 188         if (window_start + window_size > map->file_size)
 189                 window_size = map->file_size - window_start;
 190         if (len > window_size)
 191                 window_size = len;
 192
 193         /* make sure we have allocated enough memory for the window */
 194         if (window_size > map->p_size) {
 195                 map->p = realloc_array(map->p, char, window_size);
 196                 if (!map->p)
 197                         out_of_memory("map_ptr");
 198                 map->p_size = window_size;
 199         }
 200
 201         /* Now try to avoid re-reading any bytes by reusing any bytes
 202          * from the previous buffer. */
 203         if (window_start >= map->p_offset &&
 204             window_start < map->p_offset + map->p_len &&
 205             window_start + window_size >= map->p_offset + map->p_len) {
 206                 read_start = map->p_offset + map->p_len;
 207                 read_offset = read_start - window_start;
 208                 read_size = window_size - read_offset;
 209                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 210         } else {
 211                 read_start = window_start;
 212                 read_size = window_size;
 213                 read_offset = 0;
 214         }
 215
 216         if (read_size <= 0) {
 217                 rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
 218                         (long)read_size);
 219                 exit_cleanup(RERR_FILEIO);
 220         } else {
 221                 if (map->p_fd_offset != read_start) {
 222                         OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
 223                         if (ret != read_start) {
 224                                 rsyserr(FERROR, errno,
 225                                         "lseek returned %.0f, not %.0f",
 226                                         (double)ret, (double)read_start);
 227                                 exit_cleanup(RERR_FILEIO);
 228                         }
 229                         map->p_fd_offset = read_start;
 230                 }
 231
 232                 if ((nread=read(map->fd,map->p + read_offset,read_size)) != read_size) {
 233                         if (nread < 0) {
 234                                 nread = 0;
 235                                 if (!map->status)
 236                                         map->status = errno;
 237                         }
 238                         /* the best we can do is zero the buffer - the file
 239                            has changed mid transfer! */
 240                         memset(map->p+read_offset+nread, 0, read_size - nread);
 241                 }
 242                 map->p_fd_offset += nread;
 243         }
 244
 245         map->p_offset = window_start;
 246         map->p_len = window_size;
 247
 248         return map->p;
 249 }
 250
 251
 252 int unmap_file(struct map_struct *map)
 253 {
 254         int     ret;
 255
 256         if (map->p) {
 257                 free(map->p);
 258                 map->p = NULL;
 259         }
 260         ret = map->status;
 261         memset(map, 0, sizeof map[0]);
 262         free(map);
 263
 264         return ret;
 265 }