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CLK/Analyser/Static/Sega/StaticAnalyser.cpp

81 lines
2.7 KiB
C++

//
// StaticAnalyser.cpp
// Clock Signal
//
// Created by Thomas Harte on 20/09/2018.
// Copyright © 2018 Thomas Harte. All rights reserved.
//
#include "StaticAnalyser.hpp"
#include "Target.hpp"
#include <algorithm>
#include <cstring>
Analyser::Static::TargetList Analyser::Static::Sega::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType) {
if(media.cartridges.empty())
return {};
TargetList targets;
auto target = std::make_unique<Target>();
// Files named .sg are treated as for the SG1000; otherwise assume a Master System.
if(file_name.size() >= 2 && *(file_name.end() - 2) == 's' && *(file_name.end() - 1) == 'g') {
target->model = Target::Model::SG1000;
} else {
target->model = Target::Model::MasterSystem;
}
// If this is a Master System title, look for a ROM header.
if(target->model == Target::Model::MasterSystem) {
const auto &data = media.cartridges.front()->get_segments()[0].data;
// First try to locate a header.
size_t header_offset = 0;
size_t potential_offsets[] = {0x1ff0, 0x3ff0, 0x7ff0};
for(auto potential_offset: potential_offsets) {
if(!memcmp(&data[potential_offset], "TMR SEGA", 8)) {
header_offset = potential_offset;
break;
}
}
// If a header was found, use it to crib region.
if(header_offset) {
// Treat export titles as European by default; decline to
// do so only if (US) or (NTSC) is in the file name.
const uint8_t region = data[header_offset + 0x0f] >> 4;
switch(region) {
default: break;
case 4: {
std::string lowercase_name = file_name;
std::transform(lowercase_name.begin(), lowercase_name.end(), lowercase_name.begin(), ::tolower);
if(lowercase_name.find("(jp)") == std::string::npos) {
target->region =
(lowercase_name.find("(us)") == std::string::npos &&
lowercase_name.find("(ntsc)") == std::string::npos) ? Target::Region::Europe : Target::Region::USA;
}
} break;
}
// Also check for a Codemasters header.
// If one is found, set the paging scheme appropriately.
const uint16_t inverse_checksum = uint16_t(0x10000 - (data[0x7fe6] | (data[0x7fe7] << 8)));
if(
data[0x7fe3] >= 0x87 && data[0x7fe3] < 0x96 && // i.e. game is dated between 1987 and 1996
(inverse_checksum&0xff) == data[0x7fe8] &&
(inverse_checksum >> 8) == data[0x7fe9] && // i.e. the standard checksum appears to be present
!data[0x7fea] && !data[0x7feb] && !data[0x7fec] && !data[0x7fed] && !data[0x7fee] && !data[0x7fef]
) {
target->paging_scheme = Target::PagingScheme::Codemasters;
target->model = Target::Model::MasterSystem2;
}
}
}
target->media.cartridges = media.cartridges;
targets.push_back(std::move(target));
return targets;
}