Merge pull request #1393 from TomHarte/ZXAnalysis

Improve Spectrum +3 disk analysis.

Analyser/Static/AmstradCPC/StaticAnalyser.cpp

@@ -228,26 +228,13 @@ Analyser::Static::TargetList Analyser::Static::AmstradCPC::GetTargets(const Medi
 	}
 
 	if(!media.disks.empty()) {
-		Storage::Disk::CPM::ParameterBlock data_format;
-		data_format.sectors_per_track = 9;
-		data_format.tracks = 40;
-		data_format.block_size = 1024;
-		data_format.first_sector = 0xc1;
-		data_format.catalogue_allocation_bitmap = 0xc000;
-		data_format.reserved_tracks = 0;
-
-		Storage::Disk::CPM::ParameterBlock system_format;
-		system_format.sectors_per_track = 9;
-		system_format.tracks = 40;
-		system_format.block_size = 1024;
-		system_format.first_sector = 0x41;
-		system_format.catalogue_allocation_bitmap = 0xc000;
-		system_format.reserved_tracks = 2;
+		const auto data_format = Storage::Disk::CPM::ParameterBlock::cpc_data_format();
+		const auto system_format = Storage::Disk::CPM::ParameterBlock::cpc_system_format();
 
 		for(auto &disk: media.disks) {
-			// Check for an ordinary catalogue.
+			// Check for an ordinary catalogue, making sure this isn't actually a ZX Spectrum disk.
 			std::unique_ptr<Storage::Disk::CPM::Catalogue> data_catalogue = Storage::Disk::CPM::GetCatalogue(disk, data_format);
-			if(data_catalogue) {
+			if(data_catalogue && !data_catalogue->is_zx_spectrum_booter()) {
 				InspectCatalogue(*data_catalogue, target);
 				target->media.disks.push_back(disk);
 				continue;
@@ -261,7 +248,7 @@ Analyser::Static::TargetList Analyser::Static::AmstradCPC::GetTargets(const Medi
 
 			// Failing that check for a system catalogue.
 			std::unique_ptr<Storage::Disk::CPM::Catalogue> system_catalogue = Storage::Disk::CPM::GetCatalogue(disk, system_format);
-			if(system_catalogue) {
+			if(system_catalogue && !system_catalogue->is_zx_spectrum_booter()) {
 				InspectCatalogue(*system_catalogue, target);
 				target->media.disks.push_back(disk);
 				continue;

Analyser/Static/ZXSpectrum/StaticAnalyser.cpp

@@ -8,11 +8,14 @@
 
 #include "StaticAnalyser.hpp"
 
+#include "../../../Storage/Disk/Parsers/CPM.hpp"
 #include "../../../Storage/Disk/Encodings/MFM/Parser.hpp"
 #include "../../../Storage/Tape/Parsers/Spectrum.hpp"
 
 #include "Target.hpp"
 
+#include <algorithm>
+
 namespace {
 
 bool IsSpectrumTape(const std::shared_ptr<Storage::Tape::Tape> &tape) {
@@ -35,23 +38,67 @@ bool IsSpectrumTape(const std::shared_ptr<Storage::Tape::Tape> &tape) {
 bool IsSpectrumDisk(const std::shared_ptr<Storage::Disk::Disk> &disk) {
 	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
-	// Get logical sector 1; the Spectrum appears to support various physical
-	// sectors as sector 1.
-	const Storage::Encodings::MFM::Sector *boot_sector = nullptr;
-	uint8_t sector_mask = 0;
-	while(!boot_sector) {
-		boot_sector = parser.sector(0, 0, sector_mask + 1);
-		sector_mask += 0x40;
-		if(!sector_mask) break;
-	}
+	// Grab absolutely any sector from the first track to determine general encoding.
+	const Storage::Encodings::MFM::Sector *any_sector = parser.any_sector(0, 0);
+	if(!any_sector) return false;
+
+	// Determine the sector base and get logical sector 1.
+	const uint8_t sector_base = any_sector->address.sector & 0xc0;
+	const Storage::Encodings::MFM::Sector *boot_sector = parser.sector(0, 0, sector_base + 1);
 	if(!boot_sector) return false;
 
-	// Test that the contents of the boot sector sum to 3, modulo 256.
-	uint8_t byte_sum = 0;
-	for(auto byte: boot_sector->samples[0]) {
-		byte_sum += byte;
+	Storage::Disk::CPM::ParameterBlock cpm_format{};
+	switch(sector_base) {
+		case 0x40:	cpm_format = Storage::Disk::CPM::ParameterBlock::cpc_system_format();	break;
+		case 0xc0:	cpm_format = Storage::Disk::CPM::ParameterBlock::cpc_data_format();		break;
+
+		default: {
+			// Check the first ten bytes of the first sector for the disk format; if these are all
+			// the same value then instead substitute a default format.
+			std::array<uint8_t, 10> format;
+			std::copy(boot_sector->samples[0].begin(), boot_sector->samples[0].begin() + 10, format.begin());
+			if(std::all_of(format.begin(), format.end(), [&](const uint8_t v) { return v == format[0]; })) {
+				format = {0x00, 0x00, 0x28, 0x09, 0x02, 0x01, 0x03, 0x02, 0x2a, 0x52};
+			}
+
+			// Parse those ten bytes as:
+			//
+			// Byte 0: disc type
+			// Byte 1: sidedness
+			//		bits 0-6: arrangement
+			//			0 => single sided
+			//			1 => double sided, flip sides
+			//			2 => double sided, up and over
+			//		bit 7: double-track
+			// Byte 2: number of tracks per side
+			// Byte 3: number of sectors per track
+			// Byte 4: Log2(sector size) - 7
+			// Byte 5: number of reserved tracks
+			// Byte 6: Log2(block size) - 7
+			// Byte 7: number of directory blocks
+			// Byte 8: gap length (read/write)
+			// Byte 9: gap length(format)
+			cpm_format.sectors_per_track = format[3];
+			cpm_format.tracks = format[2];
+			cpm_format.block_size = 128 << format[6];
+			cpm_format.first_sector = sector_base + 1;
+			cpm_format.reserved_tracks = format[5];
+
+			// i.e. bits set downward from 0x4000 for as many blocks as form the catalogue.
+			cpm_format.catalogue_allocation_bitmap = 0x8000 - (0x8000 >> format[7]);
+		} break;
 	}
-	return byte_sum == 3;
+
+	// If the boot sector sums to 3 modulo 256 then this is a Spectrum disk.
+	const auto byte_sum = static_cast<uint8_t>(
+		std::accumulate(boot_sector->samples[0].begin(), boot_sector->samples[0].end(), 0));
+	if(byte_sum == 3) {
+		return true;
+	}
+
+	// ... otherwise read a CPM directory and look for a BASIC program called "DISK".
+	const auto catalogue = Storage::Disk::CPM::GetCatalogue(disk, cpm_format);
+	return catalogue && catalogue->is_zx_spectrum_booter();
 }
 
 }

Storage/Disk/Encodings/MFM/Parser.cpp

@@ -71,3 +71,15 @@ const Sector *Parser::sector(int head, int track, uint8_t sector) {
 
 	return &stored_sector->second;
 }
+
+const Sector *Parser::any_sector(int head, int track) {
+	const Disk::Track::Address address(head, Storage::Disk::HeadPosition(track));
+	install_track(address);
+
+	const auto sectors = sectors_by_address_by_track_.find(address);
+	if(sectors == sectors_by_address_by_track_.end()) {
+		return nullptr;
+	}
+
+	return &sectors->second.begin()->second;
+}

Storage/Disk/Encodings/MFM/Parser.hpp

@@ -37,6 +37,14 @@ class Parser {
 		*/
 		const Storage::Encodings::MFM::Sector *sector(int head, int track, uint8_t sector);
 
+
+		/*!
+			Seeks to the physical track at @c head and @c track. Searches on it for any sector.
+
+			@returns a sector if one was found; @c nullptr otherwise.
+		*/
+		const Storage::Encodings::MFM::Sector *any_sector(int head, int track);
+
 		// TODO: set_sector.
 
 	private:

Storage/Disk/Parsers/CPM.cpp

@@ -158,3 +158,13 @@ std::unique_ptr<Storage::Disk::CPM::Catalogue> Storage::Disk::CPM::GetCatalogue(
 
 	return result;
 }
+
+bool Catalogue::is_zx_spectrum_booter() {
+	// Check for a file called 'DISK'.
+	const auto file = std::find_if(files.begin(), files.end(), [](const auto &file) { return file.name == "DISK    "; });
+	if(file == files.end()) return false;
+
+	// TODO: check the file is valid ZX Spectrum BASIC.
+
+	return true;
+}

Storage/Disk/Parsers/CPM.hpp

@@ -24,6 +24,29 @@ struct ParameterBlock {
 	int first_sector;
 	uint16_t catalogue_allocation_bitmap;
 	int reserved_tracks;
+
+	// Some well-known formats.
+	static ParameterBlock cpc_data_format() {
+		Storage::Disk::CPM::ParameterBlock data_format;
+		data_format.sectors_per_track = 9;
+		data_format.tracks = 40;
+		data_format.block_size = 1024;
+		data_format.first_sector = 0xc1;
+		data_format.catalogue_allocation_bitmap = 0xc000;
+		data_format.reserved_tracks = 0;
+		return data_format;
+	}
+
+	static ParameterBlock cpc_system_format() {
+		Storage::Disk::CPM::ParameterBlock system_format;
+		system_format.sectors_per_track = 9;
+		system_format.tracks = 40;
+		system_format.block_size = 1024;
+		system_format.first_sector = 0x41;
+		system_format.catalogue_allocation_bitmap = 0xc000;
+		system_format.reserved_tracks = 2;
+		return system_format;
+	}
 };
 
 struct File {
@@ -37,6 +60,8 @@ struct File {
 
 struct Catalogue {
 	std::vector<File> files;
+
+	bool is_zx_spectrum_booter();
 };
 
 std::unique_ptr<Catalogue> GetCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk, const ParameterBlock &parameters);