fileio.c

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