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◆ main openmsx / Contrib / dmk / analyze-dmk.cc
6.0 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#include "dmk-common.hh"
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#include <cassert>
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#include <cstdlib>
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#include <span>
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#include <string>
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#include <vector>
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[[nodiscard]] static int modulo(int x, int y) {
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	int z = x % y; // this calculates the remainder, not modulo!
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	if (z < 0) z += y;
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	return z;
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}
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struct DmkTrackData {
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public:
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	void read(const File& file, int dmkTrackLen) {
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		assert(dmkTrackLen > 128);
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		buffer.resize(dmkTrackLen);
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		file.read(buffer.data(), dmkTrackLen);
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	}
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	[[nodiscard]] int readDmkIndex(unsigned i) const {
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		assert(i < 64);
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		return buffer[2 * i + 0] + 256 * buffer[2 * i + 1];
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	}
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	[[nodiscard]] uint8_t readCircular(int idx) const
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	{
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		return buffer[128 + trackIdx(idx)];
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	}
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	[[nodiscard]] int trackIdx(int idx) const {
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		return modulo(idx, trackLength());
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	}
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	[[nodiscard]] int trackLength() const {
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		assert(buffer.size() > 128);
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		return int(buffer.size() - 128);
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	}
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private:
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	std::vector<uint8_t> buffer;
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};
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static bool isValidDmkHeader(const DmkHeader& header)
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{
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	if ((header.writeProtected != 0x00) &&
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	    (header.writeProtected != 0xff)) {
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		return false;
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	}
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	int trackLen = header.trackLen[0] + 256 * header.trackLen[1];
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	if (trackLen >= 0x4000) return false; // too large track length
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	if (trackLen <= 128)    return false; // too small
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	if (header.flags & ~0xd0) return false; // unknown flag set
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	for (int i = 0; i < 7 + 4; ++i) {
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		if (header.reserved[i] != 0) return false;
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	}
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	return true;
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}
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static void analyzeTrack(const DmkTrackData& track)
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{
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	for (int i = 0; i < 64; ++i) {
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		// Get (and check) pointer into track data
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		int dmkIdx = track.readDmkIndex(i);
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		if (dmkIdx == 0) {
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			// end of table reached
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			break;
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		}
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		printf("%2d: ", i);
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		if ((dmkIdx & 0xC000) != 0x8000) {
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			printf("... skipping single-density sector\n");
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			continue;
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		}
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		dmkIdx &= ~0xC000; // clear flags
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		if ((dmkIdx < 128) || ((dmkIdx + 128) >= track.trackLength())) {
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			printf("... skipping invalid IDAM offset (wrong DMK file)\n");
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			continue;
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		}
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		dmkIdx -= 128;
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		// read (and check) address mark
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		int addrIdx = track.trackIdx(dmkIdx - 3);
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		uint8_t d0 = track.readCircular(addrIdx + 0);
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		uint8_t d1 = track.readCircular(addrIdx + 1);
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		uint8_t d2 = track.readCircular(addrIdx + 2);
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		uint8_t d3 = track.readCircular(addrIdx + 3);
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		uint8_t c  = track.readCircular(addrIdx + 4);
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		uint8_t h  = track.readCircular(addrIdx + 5);
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		uint8_t r  = track.readCircular(addrIdx + 6);
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		uint8_t n  = track.readCircular(addrIdx + 7);
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		uint8_t ch = track.readCircular(addrIdx + 8);
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		uint8_t cl = track.readCircular(addrIdx + 9);
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		if ((d0 != 0xA1) || (d1 != 0xA1) || (d2 != 0xA1) || (d3 != 0xFE)) {
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			printf("... skipping wrong IDAM entry, does not point to an address mark\n");
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			continue;
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		}
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		// address mark CRC
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		uint16_t addrCrc = 0xFFFF;
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		updateCrc(addrCrc, d0);
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		updateCrc(addrCrc, d1);
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		updateCrc(addrCrc, d2);
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		updateCrc(addrCrc, d3);
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		updateCrc(addrCrc, c);
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		updateCrc(addrCrc, h);
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		updateCrc(addrCrc, r);
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		updateCrc(addrCrc, n);
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		int onDiskAddrCrc = 256 * ch + cl;
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		bool addrCrcErr = onDiskAddrCrc != addrCrc;
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		// print address mark info
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		printf("AOfst=%4d C=%3d H=%3d R=%3d N=%3d ACrc=%04x,%s",
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		       addrIdx, c, h, r, n, onDiskAddrCrc,
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		       (addrCrcErr ? "ERR\n" : "ok "));
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		if (onDiskAddrCrc != addrCrc) {
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			continue;
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		}
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		// locate data mark, should be within 43 bytes from end
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		// of address mark (according to WD2793 datasheet)
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		int j;
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		for (j = 10; j < 53; ++j) {
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			int dataIdx = addrIdx + j;
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			uint8_t a0 = track.readCircular(dataIdx + 0);
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			uint8_t a1 = track.readCircular(dataIdx + 1);
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			uint8_t a2 = track.readCircular(dataIdx + 2);
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			uint8_t t  = track.readCircular(dataIdx + 3);
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			if ((a0 != 0xA1) || (a1 != 0xA1) || (a2 != 0xA1)) {
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				continue;
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			}
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			// calculate data CRC, data mark part
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			uint16_t dataCrc = 0xFFFF;
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			updateCrc(dataCrc, a0);
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			updateCrc(dataCrc, a1);
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			updateCrc(dataCrc, a2);
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			updateCrc(dataCrc, t);
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			// actual sector data
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			int sectorSize = 128 << (n & 7);
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			for (int k = 0; k < sectorSize; ++k) {
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				uint8_t d = track.readCircular(dataIdx + 4 + k);
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				updateCrc(dataCrc, d);
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			}
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			uint8_t crc1 = track.readCircular(dataIdx + 4 + sectorSize + 0);
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			uint8_t crc2 = track.readCircular(dataIdx + 4 + sectorSize + 1);
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			int onDiskDataCrc = 256 * crc1 + crc2;
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			bool dataCrcErr = onDiskDataCrc != dataCrc;
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			char type = (t == 0xFB) ? 'n' :
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			            (t == 0xF8) ? 'd' :
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			                          '?';
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			printf(" DOfst=%4d T=%c DCrc=%04x,%s\n",
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			       dataIdx, type, onDiskDataCrc,
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			       (dataCrcErr ? "ERR" : "ok "));
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			break;
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		}
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		if (j == 53) {
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			printf(" data mark not found within 43 bytes from address mark\n");
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		}
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	}
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}
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static void analyzeDisk(const std::string& input)
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{
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	File inf(input, "rb");
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	DmkHeader header;
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	inf.read(&header, sizeof(header));
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	if (!isValidDmkHeader(header)) {
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		throw std::runtime_error("Invalid DMK header");
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	}
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	int numCylinders = header.numTracks;
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	int numSides = (header.flags & 0x10) ? 1 : 2;
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	int dmkTrackLen = header.trackLen[0] + 256 * header.trackLen[1];
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	printf("Legend:\n"
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	       "  AOfst:  address mark offset in track\n"
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	       "  C:      cylinder\n"
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	       "  H:      head\n"
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	       "  R:      record (sector number)\n"
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	       "  N:      sector size  (in bytes: 128 << N)\n"
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	       "  ACrc:   CRC value of the address block\n"
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	       "  DOfst:  data mark offset in track\n"
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	       "  T:      data mark type (n = normal, d = deleted, ? = unknown)\n"
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	       "  DCrc:   CRC value of data block\n"
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	       "\n");
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	printf("Raw track length = %d bytes\n\n", dmkTrackLen - 128);
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	DmkTrackData track;
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	for (int t = 0; t < numCylinders; ++t) {
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		for (int h = 0; h < numSides; ++h) {
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			printf("-- physical track %d, head %d\n", t, h);
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			track.read(inf, dmkTrackLen);
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			analyzeTrack(track);
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		}
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	}
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}
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int main(int argc, const char** argv)
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{
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	std::span arg(argv, argc);
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	if (arg.size() != 2) {
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		printf("analyze-dmk\n"
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		       "\n"
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		       "Analyze the content of a DMK disk image.\n"
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		       "\n"
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		       "usage: %s <file.dmk>\n", arg[0]);
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		exit(1);
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	}
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	try {
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		analyzeDisk(arg[1]);
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	} catch (std::exception& e) {
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		fprintf(stderr, "Error: %s\n", e.what());
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	}
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}