+/* drive offset detection */
+int drvoff_detect(int type, unsigned int *off)
+{
+ if (bpbV40 <= type && type <= bpbVNT) {
+ *off = 0x24;
+ } else if (type == bpbV70) {
+ *off = 0x40;
+ } else
+ return 0;
+
+ return -1;
+}
+
+/*
+ * heuristics could certainly be improved
+ */
+int bpb_detect(const uint8_t *sec)
+{
+ int a, b, c, jmp = -1, rev = -1;
+
+ /* media descriptor check */
+ if ((sec[0x15] & 0xF0) != 0xF0)
+ return -1;
+
+ if (sec[0] == 0xEB) /* jump short */
+ jmp = 2 + *(int8_t *)(sec + 1);
+ else if (sec[0] == 0xE9) /* jump near */
+ jmp = 3 + *(int16_t *)(sec + 1);
+
+ if (jmp < 0) /* no boot code at all ? */
+ goto nocode;
+
+ /* sanity */
+ if (jmp < 0x18 || jmp > 0x1F0)
+ return -1;
+
+ /* detect by jump */
+ if (jmp >= 0x18 && jmp < 0x1E)
+ rev = bpbV20;
+ else if (jmp >= 0x1E && jmp < 0x20)
+ rev = bpbV30;
+ else if (jmp >= 0x20 && jmp < 0x24)
+ rev = bpbV32;
+ else if (jmp >= 0x24 && jmp < 0x46)
+ rev = bpbV34;
+
+ /* TODO: some better V2 - V3.4 checks ? */
+
+ if (rev >= 0)
+ return rev;
+
+nocode:
+ a = memcmp(sec + 0x03, "NTFS", 4);
+ b = memcmp(sec + 0x36, "FAT", 3);
+ c = memcmp(sec + 0x52, "FAT", 3); /* ext. DOS 7+ bs */
+
+ if ((sec[0x26] & 0xFE) == 0x28 && !b) {
+ rev = bpbV40;
+ } else if (sec[0x26] == 0x80 && !a) {
+ rev = bpbVNT;
+ } else if ((sec[0x42] & 0xFE) == 0x28 && !c) {
+ rev = bpbV70;
+ }
+
+ return rev;
+}
+
+