+/*-------------------------------------------------
+ header_guess_unitbytes - for older CHD formats,
+ guess at the bytes/unit based on metadata
+-------------------------------------------------*/
+
+static UINT32 header_guess_unitbytes(chd_file *chd)
+{
+ /* look for hard disk metadata; if found, then the unit size == sector size */
+ char metadata[512];
+ int i0, i1, i2, i3;
+ if (chd_get_metadata(chd, HARD_DISK_METADATA_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE &&
+ sscanf(metadata, HARD_DISK_METADATA_FORMAT, &i0, &i1, &i2, &i3) == 4)
+ return i3;
+
+ /* look for CD-ROM metadata; if found, then the unit size == CD frame size */
+ if (chd_get_metadata(chd, CDROM_OLD_METADATA_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE ||
+ chd_get_metadata(chd, CDROM_TRACK_METADATA_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE ||
+ chd_get_metadata(chd, CDROM_TRACK_METADATA2_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE ||
+ chd_get_metadata(chd, GDROM_OLD_METADATA_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE ||
+ chd_get_metadata(chd, GDROM_TRACK_METADATA_TAG, 0, metadata, sizeof(metadata), NULL, NULL, NULL) == CHDERR_NONE)
+ return CD_FRAME_SIZE;
+
+ /* otherwise, just map 1:1 with the hunk size */
+ return chd->header.hunkbytes;
+}