MDOS disk format support

Motorola DOS, used on the EXORciser etc.

scripts/src/formats.lua

@@ -1193,6 +1193,18 @@ if (FORMATS["MBEE_CAS"]~=null  or _OPTIONS["with-tools"]) then
 	}
 end
 
+--------------------------------------------------
+--
+--@src/lib/formats/mdos_dsk.h,FORMATS["MDOS_DSK"] = true
+--------------------------------------------------
+
+if (FORMATS["MDOS_DSK"]~=null  or _OPTIONS["with-tools"]) then
+	files {
+		MAME_DIR.. "src/lib/formats/mdos_dsk.cpp",
+		MAME_DIR.. "src/lib/formats/mdos_dsk.h",
+	}
+end
+
 --------------------------------------------------
 --
 --@src/lib/formats/mfm_hd.h,FORMATS["MFM_HD"] = true

src/lib/formats/mdos_dsk.cpp

@@ -0,0 +1,250 @@
+// license:BSD-3-Clause
+// copyright-holders: 68bit
+/*
+ * mdos_dsk.c  -  MDOS compatible disk images
+ *
+ * The format is largely IBM 3740 compatible, with 77 tracks, and 26 sectors
+ * per track, and a sector size of 128 bytes. Single sided disks were initially
+ * supported and later software supported double sided disk with 52 sectors per
+ * cylinder. The sectors are numbered from one, and the sectors indexes on the
+ * second side continue from the first side rather than starting again at
+ * one.
+ *
+ * TODO The MDOS 3 FORMAT command writes a zero in the address mark 'head'
+ * field irrespective of the disk head and the software ignores this field when
+ * read.
+ */
+
+#include "mdos_dsk.h"
+#include "formats/imageutl.h"
+
+
+mdos_format::mdos_format() : wd177x_format(formats)
+{
+}
+
+const char *mdos_format::name() const
+{
+	return "mdos";
+}
+
+const char *mdos_format::description() const
+{
+	return "MDOS compatible disk image";
+}
+
+const char *mdos_format::extensions() const
+{
+	return "dsk";
+}
+
+int mdos_format::identify(io_generic *io, uint32_t form_factor)
+{
+	int type = find_size(io, form_factor);
+
+	if (type != -1)
+		return 75;
+	return 0;
+}
+
+bool mdos_format::check_ascii(uint8_t *str, size_t len, const char* name)
+{
+	LOG_FORMATS(" %s: \"", name);
+	for (int i = 0; i < len; i++) {
+		uint8_t ch = str[i];
+		if (ch == 0) {
+			LOG_FORMATS("\\0");
+		} else if (ch < 0x20 || ch > 0x7f) {
+			return 0;
+		} else {
+			LOG_FORMATS("%c", ch);
+		}
+	}
+	LOG_FORMATS("\"\n");
+	return 1;
+}
+
+int mdos_format::parse_date_field(uint8_t *str)
+{
+	uint8_t high = str[0];
+	uint8_t low = str[1];
+
+	if (high < 0x30 || high > 0x39 || low < 0x30 || low > 0x39)
+		return -1;
+
+	return (high - 0x30) * 10 + (low - 0x30);
+}
+
+int mdos_format::find_size(io_generic *io, uint32_t form_factor)
+{
+	uint64_t size = io_generic_size(io);
+
+	// Look at the disk id sector.
+	io_generic_read(io, &info, 0, sizeof(struct disk_id_sector));
+
+	LOG_FORMATS("MDOS floppy dsk: size %d bytes, %d total sectors, %d remaining bytes, expected form factor %x\n", (uint32_t)size, (uint32_t)size / 128, (uint32_t)size % 128, form_factor);
+
+	// The 'unused' area is not necessarily zero filled and is ignoded
+	// in the identification of a MDOS format image.
+
+	// Expect an ASCII id, version, revision, and 'user name' strings.
+	if (!check_ascii(info.id, sizeof(info.id), "id"))
+		return -1;
+
+	if (!check_ascii(info.version, sizeof(info.version), "version"))
+		return -1;
+
+	if (!check_ascii(info.revision, sizeof(info.revision), "revision"))
+		return -1;
+
+	if (!check_ascii(info.date, sizeof(info.date), "date"))
+		return -1;
+	
+	if (!check_ascii(info.username, sizeof(info.username), "username"))
+		return -1;
+
+	// The date should be the numeric day, month and year.
+	int month = parse_date_field(info.date);
+	int day = parse_date_field(info.date + 2);
+	int year = parse_date_field(info.date + 4);
+
+	LOG_FORMATS(" day %d, month %d, year %d\n", day, month, year);
+	if (day < 1 || day > 32 || month < 1 || month > 12 || year < 0)
+		return -1;
+
+	// The RIB address seems to be a sequence of 16 bit cluster numbers,
+	// ending in a zero word. The maximum size appears to be 20 bytes, or
+	// 10 words. The area beyond the zero word is not always zero filled,
+	// and is ignored here. Check that it is consistent with this.
+	for (int i = 0; i < 10; i++) {
+		uint8_t high = info.rib_addr[i * 2];
+		uint8_t low = info.rib_addr[i * 2 + 1];
+		uint16_t cluster = (high << 8) | low;
+
+		if (cluster == 0)
+			break;
+
+		// The lowest value cluster here appears to be 92, just after
+		// the director sectors.
+		if (cluster < 92) {
+			LOG_FORMATS(" id sector rib address %d unexpectedly low\n", cluster);
+			return -1;
+		}
+
+		if (cluster * 4 * 128 + 4 * 128 > size) {
+			LOG_FORMATS(" id sector rib address %d beyond disk extent\n", cluster);
+			return -1;
+		}
+	}
+
+	// Check that the cluster allocation table and the cluster available
+	// table are consistent with the disk size, that no clusters beyond
+	// the extent of the disk are free or available.
+
+	uint8_t cluster_allocation[128], cluster_available[128];
+	io_generic_read(io, &cluster_allocation, 1 * 128, sizeof(cluster_allocation));
+	io_generic_read(io, &cluster_available, 2 * 128, sizeof(cluster_available));
+
+	for (int cluster = 0; cluster < sizeof(cluster_allocation) * 8; cluster++) {
+		if (cluster * 4 * 128 + 4 * 128 > size) {
+			// This cluster does not fit within the disk size, so
+			// should be marked as not free and not available.
+			uint8_t mask = 1 << (7 - (cluster & 7));
+			uint8_t offset = cluster >> 3;
+			if ((cluster_allocation[offset] & mask) == 0) {
+				LOG_FORMATS("  unexpected free cluster %d beyond disk extent\n", cluster);
+				return -1;
+			}
+			if ((cluster_available[offset] & mask) == 0) {
+				LOG_FORMATS("  unexpected available cluster %d beyond disk extent\n", cluster);
+				return -1;
+			}
+		}
+	}
+
+	for (int i=0; formats[i].form_factor; i++) {
+		const format &f = formats[i];
+		LOG_FORMATS(" checking format %d with form factor %02x, %d sectors, %d heads\n",
+				i, f.form_factor, f.sector_count, f.head_count);
+		if (form_factor != floppy_image::FF_UNKNOWN && form_factor != f.form_factor)
+			continue;
+
+		unsigned int format_size = 0;
+		for (int track=0; track < f.track_count; track++) {
+			for (int head=0; head < f.head_count; head++) {
+				const format &tf = get_track_format(f, head, track);
+				format_size += compute_track_size(tf);
+			}
+		}
+
+		LOG_FORMATS(" image size %u\n", format_size);
+		if (format_size != size)
+			continue;
+
+		LOG_FORMATS("MDOS matching format index %d\n", i);
+		return i;
+	}
+	return -1;
+}
+
+const wd177x_format::format &mdos_format::get_track_format(const format &f, int head, int track)
+{
+	int n = -1;
+
+	for (int i = 0; formats[i].form_factor; i++) {
+		if (&formats[i] == &f) {
+			n = i;
+			break;
+		}
+	}
+
+	if (n < 0) {
+		LOG_FORMATS("Error format not found\n");
+		return f;
+	}
+
+	if (head >= f.head_count) {
+		LOG_FORMATS("Error invalid head %d\n", head);
+		return f;
+	}
+
+	if (track >= f.track_count) {
+		LOG_FORMATS("Error invalid track %d\n", track);
+		return f;
+	}
+
+	if (head == 1) {
+		const format &fh1 = formats_head1[n];
+		if (!fh1.form_factor) {
+			LOG_FORMATS("Error expected a head 1 format\n");
+			return f;
+		}
+		return fh1;
+	}
+
+	return f;
+}
+
+const mdos_format::format mdos_format::formats[] = {
+	{ // 55 250.25K 8 inch single sided single density
+		floppy_image::FF_8, floppy_image::SSSD, floppy_image::FM,
+		2000, 26, 77, 1, 128, {}, 1, {}, 32, 17, 33
+	},
+	{ // 57 500.5K 8 inch double sided single density
+		floppy_image::FF_8, floppy_image::DSSD, floppy_image::FM,
+		2000, 26, 77, 2, 128, {}, 1, {}, 32, 17, 33
+	},
+	{}
+};
+
+const mdos_format::format mdos_format::formats_head1[] = {
+	{ // 55 250.25K 8 inch single sided single density
+	},
+	{ // 57 500.5K 8 inch double sided single density
+		floppy_image::FF_8, floppy_image::DSSD, floppy_image::FM,
+		2000, 26, 77, 2, 128, {}, 27, {}, 32, 17, 33
+	},
+	{}
+};
+
+const floppy_format_type FLOPPY_MDOS_FORMAT = &floppy_image_format_creator<mdos_format>;

src/lib/formats/mdos_dsk.h

@@ -0,0 +1,45 @@
+// license:BSD-3-Clause
+// copyright-holders:68bit
+/*
+ * mdos_dsk.h
+ */
+#ifndef MAME_FORMATS_MDOS_DSK_H
+#define MAME_FORMATS_MDOS_DSK_H
+
+#pragma once
+
+#include "flopimg.h"
+#include "wd177x_dsk.h"
+
+class mdos_format : public wd177x_format
+{
+public:
+	mdos_format();
+
+	virtual const char *name() const override;
+	virtual const char *description() const override;
+	virtual const char *extensions() const override;
+	virtual int identify(io_generic *io, uint32_t form_factor) override;
+	virtual int find_size(io_generic *io, uint32_t form_factor) override;
+	virtual const wd177x_format::format &get_track_format(const format &f, int head, int track) override;
+
+private:
+	struct disk_id_sector
+	{
+		uint8_t id[8];
+		uint8_t version[2];
+		uint8_t revision[2];
+		uint8_t date[6];
+		uint8_t username[20];
+		uint8_t rib_addr[20];
+		uint8_t unused[70];
+	} info;
+	static const format formats[];
+	static const format formats_head1[];
+	bool check_ascii(uint8_t *, size_t len, const char* name);
+	int parse_date_field(uint8_t *str);
+};
+
+extern const floppy_format_type FLOPPY_MDOS_FORMAT;
+
+#endif // MAME_FORMATS_MDOS_DSK_H

src/tools/floptool.cpp

@@ -62,6 +62,8 @@
 #include "formats/flex_dsk.h"
 #include "formats/uniflex_dsk.h"
 
+#include "formats/mdos_dsk.h"
+
 
 static floppy_format_type floppy_formats[] = {
 	FLOPPY_MFI_FORMAT,
@@ -112,7 +114,9 @@ static floppy_format_type floppy_formats[] = {
 	FLOPPY_OS9_FORMAT,
 
 	FLOPPY_FLEX_FORMAT,
-	FLOPPY_UNIFLEX_FORMAT
+	FLOPPY_UNIFLEX_FORMAT,
+
+	FLOPPY_MDOS_FORMAT
 };
 
 void CLIB_DECL ATTR_PRINTF(1,2) logerror(const char *format, ...)