262 lines
7.4 KiB
C++
262 lines
7.4 KiB
C++
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <inttypes.h>
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#include "../../file_io.h"
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static uint8_t hdr[512];
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enum HeaderField {
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CartName = 0x00,
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Mapper = 0x15,
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RomType = 0x16,
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RomSize = 0x17,
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RamSize = 0x18,
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CartRegion = 0x19,
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Company = 0x1a,
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Version = 0x1b,
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Complement = 0x1c, //inverse checksum
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Checksum = 0x1e,
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ResetVector = 0x3c,
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};
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static uint32_t score_header(const uint8_t *data, uint32_t size, uint32_t addr)
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{
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if (size < addr + 64) return 0; //image too small to contain header at this location?
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int score = 0;
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uint16_t resetvector = data[addr + ResetVector] | (data[addr + ResetVector + 1] << 8);
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uint16_t checksum = data[addr + Checksum] | (data[addr + Checksum + 1] << 8);
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uint16_t complement = data[addr + Complement] | (data[addr + Complement + 1] << 8);
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uint8_t resetop = data[(addr & ~0x7fff) | (resetvector & 0x7fff)]; //first opcode executed upon reset
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uint8_t mapper = data[addr + Mapper] & ~0x10; //mask off irrelevent FastROM-capable bit
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//$00:[0000-7fff] contains uninitialized RAM and MMIO.
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//reset vector must point to ROM at $00:[8000-ffff] to be considered valid.
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if (resetvector < 0x8000) return 0;
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//some images duplicate the header in multiple locations, and others have completely
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//invalid header information that cannot be relied upon.
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//below code will analyze the first opcode executed at the specified reset vector to
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//determine the probability that this is the correct header.
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//most likely opcodes
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if (resetop == 0x78 //sei
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|| resetop == 0x18 //clc (clc; xce)
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|| resetop == 0x38 //sec (sec; xce)
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|| resetop == 0x9c //stz $nnnn (stz $4200)
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|| resetop == 0x4c //jmp $nnnn
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|| resetop == 0x5c //jml $nnnnnn
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) score += 8;
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//plausible opcodes
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if (resetop == 0xc2 //rep #$nn
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|| resetop == 0xe2 //sep #$nn
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|| resetop == 0xad //lda $nnnn
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|| resetop == 0xae //ldx $nnnn
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|| resetop == 0xac //ldy $nnnn
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|| resetop == 0xaf //lda $nnnnnn
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|| resetop == 0xa9 //lda #$nn
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|| resetop == 0xa2 //ldx #$nn
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|| resetop == 0xa0 //ldy #$nn
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|| resetop == 0x20 //jsr $nnnn
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|| resetop == 0x22 //jsl $nnnnnn
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) score += 4;
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//implausible opcodes
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if (resetop == 0x40 //rti
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|| resetop == 0x60 //rts
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|| resetop == 0x6b //rtl
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|| resetop == 0xcd //cmp $nnnn
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|| resetop == 0xec //cpx $nnnn
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|| resetop == 0xcc //cpy $nnnn
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) score -= 4;
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//least likely opcodes
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if (resetop == 0x00 //brk #$nn
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|| resetop == 0x02 //cop #$nn
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|| resetop == 0xdb //stp
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|| resetop == 0x42 //wdm
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|| resetop == 0xff //sbc $nnnnnn,x
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) score -= 8;
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//at times, both the header and reset vector's first opcode will match ...
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//fallback and rely on info validity in these cases to determine more likely header.
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//a valid checksum is the biggest indicator of a valid header.
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if ((checksum + complement) == 0xffff && (checksum != 0) && (complement != 0)) score += 4;
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if (addr == 0x007fc0 && mapper == 0x20) score += 2; //0x20 is usually LoROM
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if (addr == 0x00ffc0 && mapper == 0x21) score += 2; //0x21 is usually HiROM
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if (addr == 0x007fc0 && mapper == 0x22) score += 2; //0x22 is usually SDD1
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if (addr == 0x40ffc0 && mapper == 0x25) score += 2; //0x25 is usually ExHiROM
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if (data[addr + Company] == 0x33) score += 2; //0x33 indicates extended header
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if (data[addr + RomType] < 0x08) score++;
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if (data[addr + RomSize] < 0x10) score++;
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if (data[addr + RamSize] < 0x08) score++;
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if (data[addr + CartRegion] < 14) score++;
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if (score < 0) score = 0;
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return score;
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}
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static uint32_t find_header(const uint8_t *data, uint32_t size)
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{
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uint32_t score_lo = score_header(data, size, 0x007fc0);
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uint32_t score_hi = score_header(data, size, 0x00ffc0);
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uint32_t score_ex = score_header(data, size, 0x40ffc0);
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if (score_ex) score_ex += 4; //favor ExHiROM on images > 32mbits
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if (score_lo >= score_hi && score_lo >= score_ex)
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{
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return score_lo ? 0x007fc0 : 0;
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}
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else if (score_hi >= score_ex)
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{
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return score_hi ? 0x00ffc0 : 0;
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}
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return score_ex ? 0x40ffc0 : 0;
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}
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uint8_t* snes_get_header(fileTYPE *f)
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{
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memset(hdr, 0, sizeof(hdr));
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uint32_t size = f->size;
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uint8_t *prebuf = (uint8_t*)malloc(size);
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if (prebuf)
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{
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FileSeekLBA(f, 0);
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if (FileReadAdv(f, prebuf, size))
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{
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uint8_t *buf = prebuf;
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if (size & 512)
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{
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buf += 512;
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size -= 512;
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}
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*(uint32_t*)(&hdr[8]) = size;
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uint32_t addr = find_header(buf, size);
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if (addr)
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{
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uint8_t ramsz = buf[addr + RamSize];
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if (ramsz >= 0x08) ramsz = 0;
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//re-calc rom size
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uint8_t romsz = 15;
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size--;
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if (!(size & 0xFF000000))
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{
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while (!(size & 0x1000000))
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{
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romsz--;
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size <<= 1;
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}
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}
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//Rom type: 0-Low, 1-High, 2-ExHigh
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hdr[1] = (addr == 0x00ffc0) ? 1 : (addr == 0x40ffc0) ? 2 : 0;
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//DSPn types 8..B
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if ((buf[addr + Mapper] == 0x20 || buf[addr + Mapper] == 0x21) && buf[addr + RomType] == 0x03)
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{ //DSP1
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hdr[1] |= 0x80;
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}
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else if (buf[addr + Mapper] == 0x30 && buf[addr + RomType] == 0x05 && buf[addr + Company] != 0xb2)
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{ //DSP1
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hdr[1] |= 0x80;
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}
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else if (buf[addr + Mapper] == 0x31 && (buf[addr + RomType] == 0x03 || buf[addr + RomType] == 0x05))
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{ //DSP1
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hdr[1] |= 0x80;
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}
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else if (buf[addr + Mapper] == 0x20 && buf[addr + RomType] == 0x05)
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{ //DSP2
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hdr[1] |= 0x90;
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}
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else if (buf[addr + Mapper] == 0x30 && buf[addr + RomType] == 0x05 && buf[addr + Company] == 0xb2)
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{ //DSP3
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hdr[1] |= 0xA0;
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}
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else if (buf[addr + Mapper] == 0x30 && buf[addr + RomType] == 0x03)
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{ //DSP4
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hdr[1] |= 0xB0;
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}
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else if (buf[addr + Mapper] == 0x30 && buf[addr + RomType] == 0xf6)
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{ //ST010
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hdr[1] |= 0x88;
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ramsz = 1;
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if(buf[addr + RomSize] < 10) hdr[1] |= 0x20; // ST011
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}
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else if (buf[addr + Mapper] == 0x30 && buf[addr + RomType] == 0x25)
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{ //OBC1
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hdr[1] |= 0xC0;
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}
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if (buf[addr + Mapper] == 0x3a && (buf[addr + RomType] == 0xf5 || buf[addr + RomType] == 0xf9)) {
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//SPC7110
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hdr[1] |= 0xD0;
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if(buf[addr + RomType] == 0xf9) hdr[1] |= 0x08; // with RTC
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}
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if (buf[addr + Mapper] == 0x35 && buf[addr + RomType] == 0x55)
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{
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//S-RTC (+ExHigh)
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hdr[1] |= 0x08;
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}
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//CX4 4
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if (buf[addr + Mapper] == 0x20 && buf[addr + RomType] == 0xf3)
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{
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hdr[1] |= 0x40;
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}
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//SDD1 5
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if (buf[addr + Mapper] == 0x32 && (buf[addr + RomType] == 0x43 || buf[addr + RomType] == 0x45))
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{
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if (romsz < 14) hdr[1] |= 0x50; // except Star Ocean un-SDD1
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}
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//SA1 6
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if (buf[addr + Mapper] == 0x23 && (buf[addr + RomType] == 0x32 || buf[addr + RomType] == 0x34 || buf[addr + RomType] == 0x35))
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{
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hdr[1] |= 0x60;
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}
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//GSU 7
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if (buf[addr + Mapper] == 0x20 && (buf[addr + RomType] == 0x13 || buf[addr + RomType] == 0x14 || buf[addr + RomType] == 0x15 || buf[addr + RomType] == 0x1a))
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{
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ramsz = buf[addr - 3];
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if (ramsz == 0xFF) ramsz = 5; //StarFox
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if (ramsz > 6) ramsz = 6;
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hdr[1] |= 0x70;
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}
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//1..3,E..F - reserved for other mappers.
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hdr[2] = 0;
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//PAL Regions
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if ((buf[addr + CartRegion] >= 0x02 && buf[addr + CartRegion] <= 0x0C) || buf[addr + CartRegion] == 0x11)
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{
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hdr[3] |= 1;
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}
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hdr[0] = (ramsz << 4) | romsz;
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printf("Size from header: 0x%X, calculated size: 0x%X\n", buf[addr + RomSize], romsz);
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}
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*(uint32_t*)(&hdr[4]) = addr;
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}
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FileSeekLBA(f, 0);
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free(prebuf);
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}
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return hdr;
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}
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