}
-/* this provides functionality somewhat similar to mmap() but using
- read(). It gives sliding window access to a file. mmap() is not
- used because of the possibility of another program (such as a
- mailer) truncating the file thus giving us a SIGBUS */
-struct map_struct *map_file(int fd, OFF_T len, size_t block_size)
+/* This provides functionality somewhat similar to mmap() but using read().
+ * It gives sliding window access to a file. mmap() is not used because of
+ * the possibility of another program (such as a mailer) truncating the
+ * file thus giving us a SIGBUS. */
+struct map_struct *map_file(int fd, OFF_T len, OFF_T map_size,
+ size_t block_size)
{
struct map_struct *map;
if (!(map = new(struct map_struct)))
out_of_memory("map_file");
+ if (block_size && (map_size % block_size))
+ map_size += block_size - (map_size % block_size);
+
memset(map, 0, sizeof map[0]);
map->fd = fd;
map->file_size = len;
- map->def_window_size = MAX(MAX_MAP_SIZE, block_size * 32);
+ map->def_window_size = map_size;
return map;
}
}
/* nope, we are going to have to do a read. Work out our desired window */
- if (offset > 2*CHUNK_SIZE) {
- window_start = offset - 2*CHUNK_SIZE;
- window_start &= ~((OFF_T)(CHUNK_SIZE-1)); /* assumes power of 2 */
- } else {
- window_start = 0;
- }
+ window_start = offset;
window_size = map->def_window_size;
if (window_start + window_size > map->file_size) {
window_size = map->file_size - window_start;