+ int nread;
+
+ if (len == 0)
+ return NULL;
+
+ if (len > (map->size-offset))
+ len = map->size-offset;
+
+#ifdef USE_MMAP
+ if (map->map) {
+ if (offset >= map->p_offset &&
+ offset+len <= map->p_offset+map->p_len) {
+ return (map->map + (offset - map->p_offset));
+ }
+ if (munmap(map->map, map->p_len) != 0) {
+ rprintf(FERROR,"munmap failed : %s\n", strerror(errno));
+ exit_cleanup(1);
+ }
+
+ /* align the mmap region on a nice boundary back a bit from
+ where it is asked for to allow for some seeking */
+ if (offset > 2*CHUNK_SIZE) {
+ map->p_offset = offset - 2*CHUNK_SIZE;
+ map->p_offset &= ~((OFF_T)(CHUNK_SIZE-1));
+ } else {
+ map->p_offset = 0;
+ }
+
+ /* map up to MAX_MAP_SIZE */
+ map->p_len = MAX(len, MAX_MAP_SIZE);
+ map->p_len = MIN(map->p_len, map->size - map->p_offset);
+
+ map->map = (char *)do_mmap(NULL,map->p_len,PROT_READ,
+ MAP_SHARED,map->fd,map->p_offset);
+
+ if (map->map == (char *)-1) {
+ map->map = NULL;
+ map->p_len = 0;
+ map->p_offset = 0;
+ } else {
+ return (map->map + (offset - map->p_offset));
+ }
+ }
+#endif
+
+ if (offset >= map->p_offset &&
+ offset+len <= map->p_offset+map->p_len) {
+ return (map->p + (offset - map->p_offset));
+ }
+
+ len = MAX(len,CHUNK_SIZE);
+ if (len > (map->size-offset))
+ len = map->size-offset;
+
+ if (len > map->p_size) {
+ if (map->p) free(map->p);
+ map->p = (char *)malloc(len);
+ if (!map->p) out_of_memory("map_ptr");
+ map->p_size = len;
+ }
+
+ map->p_offset = offset;
+ map->p_len = len;
+
+ if (do_lseek(map->fd,offset,SEEK_SET) != offset) {
+ rprintf(FERROR,"lseek failed in map_ptr\n");
+ exit_cleanup(1);
+ }
+
+ if ((nread=read(map->fd,map->p,len)) != len) {
+ if (nread < 0) nread = 0;
+ /* the best we can do is zero the buffer - the file
+ has changed mid transfer! */
+ memset(map->p+nread, 0, len - nread);
+ }
+
+ return map->p;