+#else
+ fprintf(stderr, "sorry mincore only works with mmap");
+#endif
+}
+
+
+/* drop cache except for the header and the active pages */
+void
+rrd_dontneed (
+ rrd_file_t *rrd_file,
+ rrd_t *rrd){
+ unsigned long dontneed_start;
+ unsigned long rra_start;
+ unsigned long active_block;
+ unsigned long i;
+ ssize_t _page_size = sysconf(_SC_PAGESIZE);
+
+#if defined DEBUG && DEBUG > 1
+ mincore_print(rrd_file,"before");
+#endif
+
+ /* ignoring errors from RRDs that are smaller then the file_len+rounding */
+ rra_start = rrd_file->header_len;
+ dontneed_start = PAGE_START(rra_start)+_page_size;
+ for (i = 0; i < rrd->stat_head->rra_cnt; ++i) {
+ active_block =
+ PAGE_START(rra_start
+ + rrd->rra_ptr[i].cur_row
+ * rrd->stat_head->ds_cnt
+ * sizeof(rrd_value_t));
+ if (active_block > dontneed_start){
+#ifdef USE_MADVISE
+ _madvise(rrd_file->file_start + dontneed_start,
+ active_block-dontneed_start-1,
+ MADV_DONTNEED);
+#endif
+/* in linux at least only fadvise DONTNEED seems to purge pages from cache */
+#ifdef HAVE_POSIX_FADVISE
+ posix_fadvise(rrd_file->fd, dontneed_start, active_block-dontneed_start-1, POSIX_FADV_DONTNEED);
+#endif
+ }
+ dontneed_start = active_block + _page_size;
+ rra_start += rrd->rra_def[i].row_cnt * rrd->stat_head->ds_cnt * sizeof(rrd_value_t);
+ }
+#ifdef USE_MADVISE
+ _madvise(rrd_file->file_start + dontneed_start,
+ rrd_file->file_len - dontneed_start,
+ MADV_DONTNEED);
+#endif
+#ifdef HAVE_POSIX_FADVISE
+ posix_fadvise(rrd_file->fd, dontneed_start, rrd_file->file_len-dontneed_start, POSIX_FADV_DONTNEED);
+#endif
+#if defined DEBUG && DEBUG > 1
+ mincore_print(rrd_file,"after");
+#endif
+}
+
+int rrd_close(
+ rrd_file_t *rrd_file)
+{
+ int ret;
+#ifdef HAVE_MMAP
+ ret = munmap(rrd_file->file_start, rrd_file->file_len);
+ if (ret != 0)
+ rrd_set_error("munmap rrd_file: %s", rrd_strerror(errno));
+#endif
+ ret = close(rrd_file->fd);
+ if (ret != 0)
+ rrd_set_error("closing file: %s", rrd_strerror(errno));
+ free(rrd_file);
+ rrd_file = NULL;
+ return ret;
+}
+
+
+/* Set position of rrd_file. */
+
+off_t rrd_seek(
+ rrd_file_t *rrd_file,
+ off_t off,
+ int whence)
+{
+ off_t ret = 0;
+
+#ifdef HAVE_MMAP
+ if (whence == SEEK_SET)
+ rrd_file->pos = off;
+ else if (whence == SEEK_CUR)
+ rrd_file->pos += off;
+ else if (whence == SEEK_END)
+ rrd_file->pos = rrd_file->file_len + off;
+#else
+ ret = lseek(rrd_file->fd, off, whence);
+ if (ret < 0)
+ rrd_set_error("lseek: %s", rrd_strerror(errno));
+ rrd_file->pos = ret;
+#endif
+//XXX: mimic fseek, which returns 0 upon success
+ return ret == -1; //XXX: or just ret to mimic lseek
+}
+
+
+/* Get current position in rrd_file. */
+
+inline off_t rrd_tell(
+ rrd_file_t *rrd_file)
+{
+ return rrd_file->pos;
+}
+
+
+/* read count bytes into buffer buf, starting at rrd_file->pos.
+ * Returns the number of bytes read or <0 on error. */
+
+inline ssize_t rrd_read(
+ rrd_file_t *rrd_file,
+ void *buf,
+ size_t count)
+{
+#ifdef HAVE_MMAP
+ size_t _cnt = count;
+ ssize_t _surplus = rrd_file->pos + _cnt - rrd_file->file_len;
+
+ if (_surplus > 0) { /* short read */
+ _cnt -= _surplus;