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iwereth/dis6502.c

Created July 12, 2017 06:04
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Disassembler 6502
Raw
dis6502.c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
static int Disassemble6502Op(unsigned char *codebuffer, int pc)
{
char opstr[256];
uint8_t *opcodes = &codebuffer[pc];
int count = 1;
switch (opcodes[0])
{
case 0x00:
sprintf(opstr, "BRK");
break;
case 0x01:
sprintf(opstr, "ORA ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0x05:
sprintf(opstr, "ORA $%02x", opcodes[1]);
count = 2;
break;
case 0x06:
sprintf(opstr, "ASL $%02x", opcodes[1]);
count = 2;
break;
case 0x08:
sprintf(opstr, "PHP");
break;
case 0x09:
sprintf(opstr, "ORA #$%02x", opcodes[1]);
count = 2;
break;
case 0x0a:
sprintf(opstr, "ASL A");
break;
case 0x0d:
sprintf(opstr, "ORA $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x0e:
sprintf(opstr, "ASL $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x10:
sprintf(opstr, "BPL $%02x", opcodes[1]);
count = 2;
break;
case 0x11:
sprintf(opstr, "ORA ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0x15:
sprintf(opstr, "ORA $%02x,X", opcodes[1]);
count = 2;
break;
case 0x16:
sprintf(opstr, "ASL $%02x,X", opcodes[1]);
count = 2;
break;
case 0x18:
sprintf(opstr, "CLC");
break;
case 0x19:
sprintf(opstr, "ORA $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x1d:
sprintf(opstr, "ORA $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x1e:
sprintf(opstr, "ASL $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x20:
sprintf(opstr, "JSR $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x21:
sprintf(opstr, "AND ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0x24:
sprintf(opstr, "BIT $%02x", opcodes[1]);
count = 2;
break;
case 0x25:
sprintf(opstr, "AND $%02x", opcodes[1]);
count = 2;
break;
case 0x26:
sprintf(opstr, "ROL $%02x", opcodes[1]);
count = 2;
break;
case 0x28:
sprintf(opstr, "PLP");
break;
case 0x29:
sprintf(opstr, "AND #$%02x", opcodes[1]);
count = 2;
break;
case 0x2a:
sprintf(opstr, "ROL A");
break;
case 0x2c:
sprintf(opstr, "BIT $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x2d:
sprintf(opstr, "AND $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x2e:
sprintf(opstr, "ROL $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x30:
sprintf(opstr, "BMI $%02x", opcodes[1]);
count = 2;
break;
case 0x31:
sprintf(opstr, "AND ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0x35:
sprintf(opstr, "AND $%02x,X", opcodes[1]);
count = 2;
break;
case 0x36:
sprintf(opstr, "ROL $%02x,X", opcodes[1]);
count = 2;
break;
case 0x38:
sprintf(opstr, "SEC");
break;
case 0x39:
sprintf(opstr, "AND $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x3d:
sprintf(opstr, "AND $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x3e:
sprintf(opstr, "ROL $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x40:
sprintf(opstr, "RTI");
break;
case 0x41:
sprintf(opstr, "EOR ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0x45:
sprintf(opstr, "EOR $%02x", opcodes[1]);
count = 2;
break;
case 0x46:
sprintf(opstr, "LSR $%02x", opcodes[1]);
count = 2;
break;
case 0x48:
sprintf(opstr, "PHA");
break;
case 0x49:
sprintf(opstr, "EOR #$%02x", opcodes[1]);
count = 2;
break;
case 0x4a:
sprintf(opstr, "LSR A");
break;
case 0x4c:
sprintf(opstr, "JMP $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x4d:
sprintf(opstr, "EOR $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x4e:
sprintf(opstr, "LSR $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x50:
sprintf(opstr, "BVC $%02x", opcodes[1]);
count = 2;
break;
case 0x51:
sprintf(opstr, "EOR ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0x55:
sprintf(opstr, "EOR $%02x,X", opcodes[1]);
count = 2;
break;
case 0x56:
sprintf(opstr, "LSR $%02x,X", opcodes[1]);
count = 2;
break;
case 0x58:
sprintf(opstr, "CLI");
break;
case 0x59:
sprintf(opstr, "EOR $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x5d:
sprintf(opstr, "EOR $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x5e:
sprintf(opstr, "LSR $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x60:
sprintf(opstr, "RTS");
break;
case 0x61:
sprintf(opstr, "ADC ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0x65:
sprintf(opstr, "ADC $%02x", opcodes[1]);
count = 2;
break;
case 0x66:
sprintf(opstr, "ROR $%02x", opcodes[1]);
count = 2;
break;
case 0x68:
sprintf(opstr, "PLA");
break;
case 0x69:
sprintf(opstr, "ADC #$%02x", opcodes[1]);
count = 2;
break;
case 0x6a:
sprintf(opstr, "ROR A");
break;
case 0x6c:
sprintf(opstr, "JMP ($%02x%02x)", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x6d:
sprintf(opstr, "ADC $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x6e:
sprintf(opstr, "ROR $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x70:
sprintf(opstr, "BVS $%02x", opcodes[1]);
count = 2;
break;
case 0x71:
sprintf(opstr, "ADC ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0x75:
sprintf(opstr, "ADC $%02x,X", opcodes[1]);
count = 2;
break;
case 0x76:
sprintf(opstr, "ROR $%02x,X", opcodes[1]);
count = 2;
break;
case 0x78:
sprintf(opstr, "SEI");
break;
case 0x79:
sprintf(opstr, "ADC $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x7d:
sprintf(opstr, "ADC $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x7e:
sprintf(opstr, "ROR $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x81:
sprintf(opstr, "STA ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0x84:
sprintf(opstr, "STY $%02x", opcodes[1]);
count = 2;
break;
case 0x85:
sprintf(opstr, "STA $%02x", opcodes[1]);
count = 2;
break;
case 0x86:
sprintf(opstr, "STX $%02x", opcodes[1]);
count = 2;
break;
case 0x88:
sprintf(opstr, "DEY");
break;
case 0x8a:
sprintf(opstr, "TXA");
break;
case 0x8c:
sprintf(opstr, "STY $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x8d:
sprintf(opstr, "STA $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x8e:
sprintf(opstr, "STX $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x90:
sprintf(opstr, "BCC $%02x", opcodes[1]);
count = 2;
break;
case 0x91:
sprintf(opstr, "STA ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0x94:
sprintf(opstr, "STY $%02x,X", opcodes[1]);
count = 2;
break;
case 0x95:
sprintf(opstr, "STA $%02x,X", opcodes[1]);
count = 2;
break;
case 0x96:
sprintf(opstr, "STX $%02x,Y", opcodes[1]);
count = 2;
break;
case 0x98:
sprintf(opstr, "TYA");
break;
case 0x99:
sprintf(opstr, "STA $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0x9a:
sprintf(opstr, "TXS");
break;
case 0x9d:
sprintf(opstr, "STA $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xa0:
sprintf(opstr, "LDY #$%02x", opcodes[1]);
count = 2;
break;
case 0xa1:
sprintf(opstr, "LDA ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0xa2:
sprintf(opstr, "LDX #$%02x", opcodes[1]);
count = 2;
break;
case 0xa4:
sprintf(opstr, "LDY $%02x", opcodes[1]);
count = 2;
break;
case 0xa5:
sprintf(opstr, "LDA $%02x", opcodes[1]);
count = 2;
break;
case 0xa6:
sprintf(opstr, "LDX $%02x", opcodes[1]);
count = 2;
break;
case 0xa8:
sprintf(opstr, "TAY");
break;
case 0xa9:
sprintf(opstr, "LDA #$%02x", opcodes[1]);
count = 2;
break;
case 0xaa:
sprintf(opstr, "TAX");
break;
case 0xac:
sprintf(opstr, "LDY $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xad:
sprintf(opstr, "LDA $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xae:
sprintf(opstr, "LDX $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xb0:
sprintf(opstr, "BCS $%02x", opcodes[1]);
count = 2;
break;
case 0xb1:
sprintf(opstr, "LDA ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0xb4:
sprintf(opstr, "LDY $%02x,X", opcodes[1]);
count = 2;
break;
case 0xb5:
sprintf(opstr, "LDA $%02x,X", opcodes[1]);
count = 2;
break;
case 0xb6:
sprintf(opstr, "LDX $%02x,Y", opcodes[1]);
count = 2;
break;
case 0xb8:
sprintf(opstr, "CLV");
break;
case 0xb9:
sprintf(opstr, "LDA $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xba:
sprintf(opstr, "TSX");
break;
case 0xbc:
sprintf(opstr, "LDY $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xbd:
sprintf(opstr, "LDA $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xbe:
sprintf(opstr, "LDX $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xc0:
sprintf(opstr, "CPY #$%02x", opcodes[1]);
count = 2;
break;
case 0xc1:
sprintf(opstr, "CMP ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0xc4:
sprintf(opstr, "CPY $%02x", opcodes[1]);
count = 2;
break;
case 0xc5:
sprintf(opstr, "CMP $%02x", opcodes[1]);
count = 2;
break;
case 0xc6:
sprintf(opstr, "DEC $%02x", opcodes[1]);
count = 2;
break;
case 0xc8:
sprintf(opstr, "INY");
break;
case 0xc9:
sprintf(opstr, "CMP #$%02x", opcodes[1]);
count = 2;
break;
case 0xca:
sprintf(opstr, "DEX");
break;
case 0xcc:
sprintf(opstr, "CPY $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xcd:
sprintf(opstr, "CMP $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xce:
sprintf(opstr, "DEC $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xd0:
sprintf(opstr, "BNE $%02x", opcodes[1]);
count = 2;
break;
case 0xd1:
sprintf(opstr, "CMP ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0xd5:
sprintf(opstr, "CMP $%02x,X", opcodes[1]);
count = 2;
break;
case 0xd6:
sprintf(opstr, "DEC $%02x,X", opcodes[1]);
count = 2;
break;
case 0xd8:
sprintf(opstr, "CLD");
break;
case 0xd9:
sprintf(opstr, "CMP $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xdd:
sprintf(opstr, "CMP $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xde:
sprintf(opstr, "DEC $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xe0:
sprintf(opstr, "CPX #$%02x", opcodes[1]);
count = 2;
break;
case 0xe1:
sprintf(opstr, "SBC ($%02x,X)", opcodes[1]);
count = 2;
break;
case 0xe4:
sprintf(opstr, "CPX $%02x", opcodes[1]);
count = 2;
break;
case 0xe5:
sprintf(opstr, "SBC $%02x", opcodes[1]);
count = 2;
break;
case 0xe6:
sprintf(opstr, "INC $%02x", opcodes[1]);
count = 2;
break;
case 0xe8:
sprintf(opstr, "INX");
break;
case 0xe9:
sprintf(opstr, "SBC #$%02x", opcodes[1]);
count = 2;
break;
case 0xea:
sprintf(opstr, "NOP");
break;
case 0xec:
sprintf(opstr, "CPX $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xed:
sprintf(opstr, "SBC $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xee:
sprintf(opstr, "INC $%02x%02x", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xf0:
sprintf(opstr, "BEQ $%02x", opcodes[1]);
count = 2;
break;
case 0xf1:
sprintf(opstr, "SBC ($%02x),Y", opcodes[1]);
count = 2;
break;
case 0xf5:
sprintf(opstr, "SBC $%02x,X", opcodes[1]);
count = 2;
break;
case 0xf6:
sprintf(opstr, "INC $%02x,X", opcodes[1]);
count = 2;
break;
case 0xf8:
sprintf(opstr, "SED");
break;
case 0xf9:
sprintf(opstr, "SBC $%02x%02x,Y", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xfd:
sprintf(opstr, "SBC $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
case 0xfe:
sprintf(opstr, "INC $%02x%02x,X", opcodes[2], opcodes[1]);
count = 3;
break;
default:
sprintf(opstr, ".db $%02x", opcodes[0]);
break;
}
printf("%04X %02X ", 0x5000 + pc, opcodes[0]);
if (count > 1)
printf("%02X ", opcodes[1]);
else
printf(" ");
if (count > 2)
printf("%02X ", opcodes[2]);
else
printf(" ");
printf("%-s", opstr);
switch (opcodes[0])
{
case 0x90:
case 0xB0:
case 0xF0:
case 0x30:
case 0xD0:
case 0x10:
case 0x50:
case 0x70:
// print branch target
printf("\t\t; $%04x", 0x5000 + pc + 2 + (int8_t) opcodes[1]);
}
printf("\n");
return count;
}
int main(int argc, char **argv)
{
FILE *f = fopen(argv[1], "rb");
if (f == NULL)
{
printf("error: Couldn't open %s\n", argv[1]);
exit(1);
}
// Get the file size
fseek(f, 0L, SEEK_END);
int fsize = ftell(f);
fseek(f, 0L, SEEK_SET);
unsigned char *buffer = malloc(fsize);
fread(buffer, fsize, 1, f);
fclose(f);
int pc = 0;
while (pc < fsize)
{
pc += Disassemble6502Op(buffer, pc);
}
return 0;
}
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