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 static char last_byte;
  26 static int last_sparse;
  27 extern int sparse_files;
  28
  29 int sparse_end(int f)
  30 {
  31         if (last_sparse) {
  32                 do_lseek(f,-1,SEEK_CUR);
  33                 return (write(f,&last_byte,1) == 1 ? 0 : -1);
  34         }
  35         last_sparse = 0;
  36         return 0;
  37 }
  38
  39
  40 static int write_sparse(int f,char *buf,size_t len)
  41 {
  42         size_t l1=0, l2=0;
  43         int ret;
  44
  45         for (l1=0;l1<len && buf[l1]==0;l1++) ;
  46         for (l2=0;l2<(len-l1) && buf[len-(l2+1)]==0;l2++) ;
  47
  48         last_byte = buf[len-1];
  49
  50         if (l1 == len || l2 > 0)
  51                 last_sparse=1;
  52
  53         if (l1 > 0) {
  54                 do_lseek(f,l1,SEEK_CUR);
  55         }
  56
  57         if (l1 == len)
  58                 return len;
  59
  60         ret = write(f, buf + l1, len - (l1+l2));
  61         if (ret == -1 || ret == 0)
  62                 return ret;
  63         else if (ret != (int) (len - (l1+l2)))
  64                 return (l1+ret);
  65
  66         if (l2 > 0)
  67                 do_lseek(f,l2,SEEK_CUR);
  68
  69         return len;
  70 }
  71
  72 /*
  73  * write_file does not allow incomplete writes.  It loops internally
  74  * until len bytes are written or errno is set.
  75  */
  76 int write_file(int f,char *buf,size_t len)
  77 {
  78         int ret = 0;
  79
  80         while (len>0) {
  81                 int r1;
  82                 if (sparse_files) {
  83                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
  84                         r1 = write_sparse(f, buf, len1);
  85                 } else {
  86                         r1 = write(f, buf, len);
  87                 }
  88                 if (r1 <= 0) {
  89                         if (ret > 0) return ret;
  90                         return r1;
  91                 }
  92                 len -= r1;
  93                 buf += r1;
  94                 ret += r1;
  95         }
  96         return ret;
  97 }
  98
  99
 100
 101 /* this provides functionality somewhat similar to mmap() but using
 102    read(). It gives sliding window access to a file. mmap() is not
 103    used because of the possibility of another program (such as a
 104    mailer) truncating the file thus giving us a SIGBUS */
 105 struct map_struct *map_file(int fd,OFF_T len)
 106 {
 107         struct map_struct *map;
 108         map = new(struct map_struct);
 109         if (!map) out_of_memory("map_file");
 110
 111         map->fd = fd;
 112         map->file_size = len;
 113         map->p = NULL;
 114         map->p_size = 0;
 115         map->p_offset = 0;
 116         map->p_fd_offset = 0;
 117         map->p_len = 0;
 118         map->status = 0;
 119
 120         return map;
 121 }
 122
 123 /* slide the read window in the file */
 124 char *map_ptr(struct map_struct *map,OFF_T offset,int len)
 125 {
 126         int nread;
 127         OFF_T window_start, read_start;
 128         int window_size, read_size, read_offset;
 129
 130         if (len == 0) {
 131                 return NULL;
 132         }
 133
 134         /* can't go beyond the end of file */
 135         if (len > (map->file_size - offset)) {
 136                 len = map->file_size - offset;
 137         }
 138
 139         /* in most cases the region will already be available */
 140         if (offset >= map->p_offset &&
 141             offset+len <= map->p_offset+map->p_len) {
 142                 return (map->p + (offset - map->p_offset));
 143         }
 144
 145
 146         /* nope, we are going to have to do a read. Work out our desired window */
 147         if (offset > 2*CHUNK_SIZE) {
 148                 window_start = offset - 2*CHUNK_SIZE;
 149                 window_start &= ~((OFF_T)(CHUNK_SIZE-1)); /* assumes power of 2 */
 150         } else {
 151                 window_start = 0;
 152         }
 153         window_size = MAX_MAP_SIZE;
 154         if (window_start + window_size > map->file_size) {
 155                 window_size = map->file_size - window_start;
 156         }
 157         if (offset + len > window_start + window_size) {
 158                 window_size = (offset+len) - window_start;
 159         }
 160
 161         /* make sure we have allocated enough memory for the window */
 162         if (window_size > map->p_size) {
 163                 map->p = realloc_array(map->p, char, window_size);
 164                 if (!map->p) out_of_memory("map_ptr");
 165                 map->p_size = window_size;
 166         }
 167
 168         /* now try to avoid re-reading any bytes by reusing any bytes from the previous
 169            buffer. */
 170         if (window_start >= map->p_offset &&
 171             window_start < map->p_offset + map->p_len &&
 172             window_start + window_size >= map->p_offset + map->p_len) {
 173                 read_start = map->p_offset + map->p_len;
 174                 read_offset = read_start - window_start;
 175                 read_size = window_size - read_offset;
 176                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 177         } else {
 178                 read_start = window_start;
 179                 read_size = window_size;
 180                 read_offset = 0;
 181         }
 182
 183         if (read_size <= 0) {
 184                 rprintf(FINFO,"Warning: unexpected read size of %d in map_ptr\n", read_size);
 185         } else {
 186                 if (map->p_fd_offset != read_start) {
 187                         if (do_lseek(map->fd,read_start,SEEK_SET) != read_start) {
 188                                 rprintf(FERROR,"lseek failed in map_ptr\n");
 189                                 exit_cleanup(RERR_FILEIO);
 190                         }
 191                         map->p_fd_offset = read_start;
 192                 }
 193
 194                 if ((nread=read(map->fd,map->p + read_offset,read_size)) != read_size) {
 195                         if (nread < 0) {
 196                                 nread = 0;
 197                                 if (!map->status)
 198                                         map->status = errno;
 199                         }
 200                         /* the best we can do is zero the buffer - the file
 201                            has changed mid transfer! */
 202                         memset(map->p+read_offset+nread, 0, read_size - nread);
 203                 }
 204                 map->p_fd_offset += nread;
 205         }
 206
 207         map->p_offset = window_start;
 208         map->p_len = window_size;
 209
 210         return map->p + (offset - map->p_offset);
 211 }
 212
 213
 214 int unmap_file(struct map_struct *map)
 215 {
 216         int     ret;
 217
 218         if (map->p) {
 219                 free(map->p);
 220                 map->p = NULL;
 221         }
 222         ret = map->status;
 223         memset(map, 0, sizeof(*map));
 224         free(map);
 225
 226         return ret;
 227 }
 228