CLK/Analyser/Static/Acorn/StaticAnalyser.cpp

//
//  AcornAnalyser.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 29/08/2016.
//  Copyright 2016 Thomas Harte. All rights reserved.
//

#include "StaticAnalyser.hpp"

#include "Disk.hpp"
#include "Tape.hpp"
#include "Target.hpp"

#include "Numeric/StringSimilarity.hpp"

#include <algorithm>
#include <map>

using namespace Analyser::Static::Acorn;

namespace {
bool is_basic(const File &file) {
	std::size_t pointer = 0;
	const uint8_t *const data = file.data.data();
	const std::size_t data_size = file.data.size();
	while(true) {
		if(pointer >= data_size-1 || data[pointer] != 0x0d) {
			return false;
		}
		if((data[pointer+1]&0x7f) == 0x7f) break;
		pointer += data[pointer+3];
	}
	return true;
}

}

static std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>>
AcornCartridgesFrom(const std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>> &cartridges) {
	std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>> acorn_cartridges;

	for(const auto &cartridge : cartridges) {
		const auto &segments = cartridge->get_segments();

		// Only one mapped item is allowed.
		if(segments.size() != 1) continue;

		// Cartridges must be 8 or 16 kb in size.
		const Storage::Cartridge::Cartridge::Segment &segment = segments.front();
		if(segment.data.size() != 0x4000 && segment.data.size() != 0x2000) continue;

		// Check copyright string.
		const uint8_t copyright_offset = segment.data[7];
		if(
			segment.data[copyright_offset] != 0x00 ||
			segment.data[copyright_offset+1] != 0x28 ||
			segment.data[copyright_offset+2] != 0x43 ||
			segment.data[copyright_offset+3] != 0x29
		) continue;

		// Check language entry point.
		if(!(
			(segment.data[0] == 0x00 && segment.data[1] == 0x00 && segment.data[2] == 0x00) ||
			(segment.data[0] != 0x00 && segment.data[2] >= 0x80 && segment.data[2] < 0xc0)
			)) continue;

		// Check service entry point.
		if(!(segment.data[5] >= 0x80 && segment.data[5] < 0xc0)) continue;

		// Probability of a random binary blob that isn't an Acorn ROM proceeding to here:
		//		1/(2^32) *
		//		( ((2^24)-1)/(2^24)*(1/4)		+		1/(2^24)	) *
		//		1/4
		//	= something very improbable, around 1/16th of 1 in 2^32, but not exactly.
		acorn_cartridges.push_back(cartridge);
	}

	return acorn_cartridges;
}

Analyser::Static::TargetList Analyser::Static::Acorn::GetTargets(
	const Media &media,
	const std::string &file_name,
	TargetPlatform::IntType,
	bool
) {
	const auto early_exit = [](auto &ptr) {
		TargetList list;
		list.push_back(std::move(ptr));
		return list;
	};

	auto targetElectron = std::make_unique<ElectronTarget>();
	auto targetBBC = std::make_unique<BBCMicroTarget>();
	auto targetArchimedes = std::make_unique<ArchimedesTarget>();
	int bbc_hits = 0;
	int electron_hits = 0;
	int beebsid_hits = 0;
	bool format_prefers_bbc = false;

	// Copy appropriate cartridges to the 8-bit targets.
	targetElectron->media.cartridges = AcornCartridgesFrom(media.cartridges);
	targetBBC->media.cartridges = AcornCartridgesFrom(media.cartridges);

	// If there are tapes, attempt to get data from the first.
	if(!media.tapes.empty()) {
		std::shared_ptr<Storage::Tape::Tape> tape = media.tapes.front();
		auto serialiser = tape->serialiser();
		std::vector<File> files = GetFiles(*serialiser);

		// Continue only if there are any files.
		if(!files.empty()) {
			// Inspect first file. If it's protected or doesn't look like BASIC
			// then the loading command is *RUN. Otherwise it's CHAIN"".
			targetElectron->loading_command =
				(files.front().flags & File::Flags::ExecuteOnly) || !is_basic(files.front()) ? "*RUN\n" : "CHAIN\"\"\n";
			targetElectron->media.tapes = media.tapes;

			// TODO: my BBC Micro doesn't yet support tapes; evaluate here in the future.
		}
	}

	if(!media.disks.empty()) {
		std::shared_ptr<Storage::Disk::Disk> disk = media.disks.front();
		std::unique_ptr<Catalogue> dfs_catalogue, adfs_catalogue;

		// Get any sort of catalogue that can be found.
		dfs_catalogue = GetDFSCatalogue(disk);
		if(dfs_catalogue == nullptr) adfs_catalogue = GetADFSCatalogue(disk);

		// 8-bit options: DFS and Hugo-style ADFS.
		if(dfs_catalogue || (adfs_catalogue && !adfs_catalogue->has_large_sectors && adfs_catalogue->is_hugo)) {
			// Accept the disk and determine whether DFS or ADFS ROMs are implied.

			// Electron: use the Pres ADFS if using an ADFS, as it leaves Page at &E00.
			targetElectron->media.disks = media.disks;
			targetElectron->has_dfs = bool(dfs_catalogue);
			targetElectron->has_pres_adfs = bool(adfs_catalogue);

			// BBC: only the 1770 DFS is currently supported, so use that.
			targetBBC->media.disks = media.disks;
			targetBBC->has_1770dfs = bool(dfs_catalogue);
			targetBBC->has_adfs = bool(adfs_catalogue);

			// Special case: if there's only one file, and it is called CPMDISC,
			// select a BBC with the Z80 second processor.
			const auto &files = dfs_catalogue ? dfs_catalogue->files : adfs_catalogue->files;
			if(files.size() == 1 && files[0].name == "$.CPMDISC") {
				targetBBC->tube_processor = BBCMicroTarget::TubeProcessor::Z80;
				return early_exit(targetBBC);
			}

			// Check whether a simple shift+break will do for loading this disk.
			const auto bootOption = (dfs_catalogue ?: adfs_catalogue)->bootOption;
			if(bootOption != Catalogue::BootOption::None) {
				targetBBC->should_shift_restart = targetElectron->should_shift_restart = true;
			} else {
				// Otherwise: if there's only one BASIC program then chain it.
				// Failing that, do a *CAT to be communicative.

				const File *sole_basic_file = nullptr;
				for(const auto &file: dfs_catalogue ? dfs_catalogue->files : adfs_catalogue->files) {
					if(is_basic(file)) {
						if(!sole_basic_file) {
							sole_basic_file = &file;
						} else {
							sole_basic_file = nullptr;
							break;
						}
					}
				}

				targetBBC->loading_command = targetElectron->loading_command =
					sole_basic_file ? "CHAIN \"" + sole_basic_file->name + "\"\n" : "*CAT\n";
			}

			// Further special case: if any of the files have a top word of 0x0003 then
			// they're for a 6502 second processor, so provide a BBC with one of those.
			for(const auto &file: files) {
				if((file.load_address >> 16) == 3) {
					targetBBC->tube_processor = BBCMicroTarget::TubeProcessor::WDC65C02;
					return early_exit(targetBBC);
				}
			}

			// Add a slight preference for the BBC over the Electron, all else being equal, if this is a DFS floppy.
			format_prefers_bbc = bool(dfs_catalogue);

			for(const auto &file: files) {
				// Electron: check whether adding the AP6 ROM is justified.
				// For now this is an incredibly dense text search;
				// if any of the commands that aren't usually present
				// on a stock Electron are here, add the AP6 ROM and
				// some sideways RAM such that the SR commands are useful.
				for(const auto &command: {
					"AQRPAGE", "BUILD", "DUMP", "FORMAT", "INSERT", "LANG", "LIST", "LOADROM",
					"LOCK", "LROMS", "RLOAD", "ROMS", "RSAVE", "SAVEROM", "SRLOAD", "SRPAGE",
					"SRUNLOCK", "SRWIPE", "TUBE", "TYPE", "UNLOCK", "UNPLUG", "UROMS",
					"VERIFY", "ZERO"
				}) {
					if(std::search(
						file.data.begin(),
						file.data.end(),
						command,
						command + strlen(command)
					) != file.data.end()) {
						targetElectron->has_ap6_rom = true;
						targetElectron->has_sideways_ram = true;
					}
				}

				// Look for any 'BBC indicators', i.e. direct access to BBC-specific hardware.
				// Also currently a dense search.
				const auto hits = [&](const std::initializer_list<uint16_t> collection) {
					int hits = 0;
					for(const auto address: collection) {
						const uint8_t sta_address[3] = {
							0x8d, uint8_t(address & 0xff), uint8_t(address >> 8)
						};

						if(std::search(
							file.data.begin(), file.data.end(),
							std::begin(sta_address), std::end(sta_address)
						) != file.data.end()) {
							++hits;
						}

						// I think I'll want std::ranges::contains_subrange if/when building for C++23.
					}
					return hits;
				};

				bbc_hits += hits({
					// The video control registers.
					0xfe20, 0xfe21,

					// The system VIA.
					0xfe40, 0xfe41, 0xfe42, 0xfe43, 0xfe44, 0xfe45, 0xfe46, 0xfe47,
					0xfe48, 0xfe49, 0xfe4a, 0xfe4b, 0xfe4c, 0xfe4d, 0xfe4e, 0xfe4f,

					// The user VIA.
					0xfe60, 0xfe61, 0xfe62, 0xfe63, 0xfe64, 0xfe65, 0xfe66, 0xfe67,
					0xfe68, 0xfe69, 0xfe6a, 0xfe6b, 0xfe6c, 0xfe6d, 0xfe6e, 0xfe6f,
				});
				// BASIC for "MODE7".
				static constexpr uint8_t mode7[] = {0xeb, 0x37};
				bbc_hits += std::search(
							file.data.begin(), file.data.end(),
							std::begin(mode7), std::end(mode7)
						) != file.data.end();

				electron_hits += hits({
					// ULA addresses that aren't also the BBC's CRTC.
					0xfe03, 0xfe04, 0xfe05,
					0xfe06, 0xfe07, 0xfe08,
					0xfe09, 0xfe0a, 0xfe0b,
					0xfe0c, 0xfe0d, 0xfe0e,
					0xfe0f,
				});

				// While here, look for attempted SID accesses.
				beebsid_hits += hits({
					// ULA addresses that aren't also the BBC's CRTC.
					0xfc20, 0xfc21, 0xfc22,	0xfc23,
					0xfc24, 0xfc25, 0xfc26,	0xfc27,
					0xfc28, 0xfc29, 0xfc2a,	0xfc2b,
					0xfc2c, 0xfc2d, 0xfc2e,	0xfc2f,
					0xfc30, 0xfc31, 0xfc32,	0xfc33,
					0xfc34, 0xfc35, 0xfc36,	0xfc37,
					0xfc38,
				});
			}
		} else if(adfs_catalogue) {
			// Archimedes options, implicitly: ADFS, non-Hugo.
			targetArchimedes->media.disks = media.disks;

			// Also look for the best possible startup program name, if it can be discerned.
			std::multimap<double, std::string, std::greater<double>> options;
			for(const auto &file: adfs_catalogue->files) {
				// Skip non-Pling files.
				if(file.name[0] != '!') continue;

				// Take whatever else comes with a preference for things that don't
				// have 'boot' or 'read' in them (the latter of which will tend to be
				// read_me or read_this or similar).
				static constexpr char read[] = "read";
				static constexpr char boot[] = "boot";
				const auto has = [&](const char *begin, const char *end) {
					return  std::search(
						file.name.begin(), file.name.end(),
						begin, end - 1, // i.e. don't compare the trailing NULL.
						[](char lhs, char rhs) {
							return std::tolower(lhs) == rhs;
						}
					) != file.name.end();
				};
				const auto has_read = has(std::begin(read), std::end(read));
				const auto has_boot = has(std::begin(boot), std::end(boot));

				const auto probability =
					Numeric::similarity(file.name, adfs_catalogue->name) +
					Numeric::similarity(file.name, file_name) -
					((has_read || has_boot) ? 0.2 : 0.0);
				options.emplace(probability, file.name);
			}

			if(!options.empty()) {
				targetArchimedes->main_program = options.begin()->second;
			}
		}
	}

	// Enable the Acorn ADFS if a mass-storage device is attached;
	// unlike the Pres ADFS it retains SCSI logic.
	if(!media.mass_storage_devices.empty()) {
		targetElectron->has_pres_adfs = false;	// To override a floppy selection, if one was made.
		targetElectron->has_acorn_adfs = true;

		// Assume some sort of later-era Acorn work is likely to happen;
		// so ensure *TYPE, etc are present.
		targetElectron->has_ap6_rom = true;
		targetElectron->has_sideways_ram = true;

		targetElectron->media.mass_storage_devices = media.mass_storage_devices;

		// Check for a boot option.
		const auto sector = targetElectron->media.mass_storage_devices.front()->get_block(1);
		if(sector[0xfd]) {
			targetElectron->should_shift_restart = true;
		} else {
			targetElectron->loading_command = "*CAT\n";
		}
	}

	// Make a BeebSID guess.
	targetBBC->has_beebsid = beebsid_hits > 20;

	TargetList targets;
	if(!targetElectron->media.empty() && !targetBBC->media.empty()) {
		if(bbc_hits > electron_hits || (bbc_hits == electron_hits && format_prefers_bbc)) {
			targets.push_back(std::move(targetBBC));
		} else {
			targets.push_back(std::move(targetElectron));
		}
	} else {
		if(!targetElectron->media.empty()) {
			targets.push_back(std::move(targetElectron));
		} else if(!targetBBC->media.empty()) {
			targets.push_back(std::move(targetBBC));
		}
	}
	if(!targetArchimedes->media.empty()) {
		targets.push_back(std::move(targetArchimedes));
	}
	return targets;
}