Mercenary by Woakes / Novagen

Refs #73

disk-analyse/formats

@@ -1051,6 +1051,11 @@ probe_amiga
     159 protec_longtrack
     * amigados menace
 
+"Mercenary"
+    0 amigados_unknown_length # Mastered long same as data tracks
+    1 ignore # Might be a protection track, but doesn't seem to be accessed
+    * mercenary
+
 "Micro Machines" = amigados_copylock
 
 "Microprose Formula One Grand Prix" = amigados

libdisk/format/amiga/mercenary.c

@@ -0,0 +1,107 @@
+/*
+ * disk/mercenary.c
+ * 
+ * Custom format as used on Mercenary by Paul Woakes (Novagen).
+ * 
+ * Written in 2020 by Keir Fraser
+ * 
+ * RAW TRACK LAYOUT:
+ *  u16 0xa89a,0xa89a :: Sync
+ *  u8  0x04,0x12,0x34,0x56,0x78,cyl
+ *  u8  dat[0x1800]
+ *  u8  csum_lo, csum_hi
+ * 
+ * TRKTYP_mercenary data layout:
+ *  u8 sector_data[0x1800]
+ */
+
+#include <libdisk/util.h>
+#include <private/disk.h>
+
+static const uint8_t exp[5] = { 0x04, 0x12, 0x34, 0x56, 0x78 };
+
+static void *mercenary_write_raw(
+    struct disk *d, unsigned int tracknr, struct stream *s)
+{
+    struct track_info *ti = &d->di->track[tracknr];
+
+    while (stream_next_bit(s) != -1) {
+
+        uint8_t dat[0x1800*2], hdr[6*2], sum[2*2];
+        uint16_t csum;
+        uint8_t *block;
+        unsigned int i;
+
+        if (s->word != 0xa89aa89a)
+            continue;
+
+        ti->data_bitoff = s->index_offset_bc - 31;
+
+        if (stream_next_bytes(s, hdr, 6*2) == -1)
+            goto fail;
+        mfm_decode_bytes(bc_mfm, 6, hdr, hdr);
+        if (memcmp(exp, hdr, 5) || (hdr[5] != tracknr>>1))
+            continue;
+
+        if (stream_next_bytes(s, dat, 0x1800*2) == -1)
+            goto fail;
+        mfm_decode_bytes(bc_mfm, 0x1800, dat, dat);
+        for (i = csum = 0; i < 0x1800; i++) {
+            uint8_t x = csum + dat[i];
+            csum = ((csum & 0xff00) << 1) | (csum >> 15) | (x << 1);
+        }
+
+        if (stream_next_bytes(s, sum, 2*2) == -1)
+            goto fail;
+        mfm_decode_bytes(bc_mfm, 2, sum, sum);
+        if (csum != (sum[0] | (sum[1]<<8)))
+            continue;
+
+        block = memalloc(ti->len);
+        memcpy(block, dat, ti->len);
+        set_all_sectors_valid(ti);
+        ti->total_bits = 102500;
+        return block;
+    }
+
+fail:
+    return NULL;
+}
+
+static void mercenary_read_raw(
+    struct disk *d, unsigned int tracknr, struct tbuf *tbuf)
+{
+    struct track_info *ti = &d->di->track[tracknr];
+    uint16_t csum;
+    uint8_t *dat = (uint8_t *)ti->dat;
+    unsigned int i;
+
+    tbuf_bits(tbuf, SPEED_AVG, bc_raw, 32, 0xa89aa89a);
+    tbuf_bytes(tbuf, SPEED_AVG, bc_mfm, sizeof(exp), (void *)exp);
+    tbuf_bits(tbuf, SPEED_AVG, bc_mfm, 8, tracknr>>1);
+    tbuf_bytes(tbuf, SPEED_AVG, bc_mfm, 0x1800, dat);
+
+    for (i = csum = 0; i < 0x1800; i++) {
+        uint8_t x = csum + dat[i];
+        csum = ((csum & 0xff00) << 1) | (csum >> 15) | (x << 1);
+    }
+    tbuf_bits(tbuf, SPEED_AVG, bc_mfm, 8, (uint8_t)(csum>>0));
+    tbuf_bits(tbuf, SPEED_AVG, bc_mfm, 8, (uint8_t)(csum>>8));
+}
+
+struct track_handler mercenary_handler = {
+    .bytes_per_sector = 0x1800,
+    .nr_sectors = 1,
+    .write_raw = mercenary_write_raw,
+    .read_raw = mercenary_read_raw
+};
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "Linux"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

libdisk/include/libdisk/track_types.h

@@ -207,3 +207,4 @@ X(turrican_3b, "Turrican 3 B")
 X(turrican_3c, "Turrican 3 C")
 X(head_over_heels, "Head Over Heels (Special FX)")
 X(f1, "F1")
+X(mercenary, "Mercenary")