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asm6502.cpp
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asm6502.cpp
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
enum address_mode
{
address_mode_undef,
address_mode_acc, // can merge with imp?
address_mode_imp,
address_mode_imm,
address_mode_zp,
address_mode_zp_x,
address_mode_zp_y,
address_mode_rel,
address_mode_abs,
address_mode_abs_x,
address_mode_abs_y,
address_mode_ind,
address_mode_ind_x,
address_mode_ind_y,
};
struct opcode
{
const char *mnemonic;
int length;
address_mode mode;
};
opcode opcodes[256];
inline void init_opcode(int id, const char *mnemonic, int length, address_mode mode)
{
opcodes[id].mnemonic = mnemonic;
opcodes[id].length = length;
opcodes[id].mode = mode;
}
int disasm_single(unsigned char *bytes, int offset, int base_address, FILE *file)
{
int id = bytes[offset];
const char *mnemonic = opcodes[id].mnemonic;
address_mode mode = opcodes[id].mode;
unsigned int address = offset + base_address;
unsigned int byte = bytes[offset + 1];
unsigned int word = (bytes[offset + 2] << 8) | (bytes[offset + 1] & 0xff);
unsigned int rel = offset + base_address + 2 + (signed char)byte;
fprintf(file, "$%04x ", address);
if (opcodes[id].length == 3)
{
fprintf(file, "%02x %02x %02x ", bytes[offset], bytes[offset + 1], bytes[offset + 2]);
}
else if (opcodes[id].length == 2)
{
fprintf(file, "%02x %02x ", bytes[offset], bytes[offset + 1]);
}
else
{
fprintf(file, "%02x ", bytes[offset]);
}
switch (mode)
{
case address_mode_abs:
fprintf(file, "%s $%04x\n", mnemonic, word);
break;
case address_mode_abs_x:
fprintf(file, "%s $%04x,X\n", mnemonic, word);
break;
case address_mode_abs_y:
fprintf(file, "%s $%04x,Y\n", mnemonic, word);
break;
case address_mode_imp:
fprintf(file, "%s\n", mnemonic);
break;
case address_mode_acc:
fprintf(file, "%s A\n", mnemonic);
break;
case address_mode_imm:
fprintf(file, "%s #$%02x\n", mnemonic, byte);
break;
case address_mode_ind:
fprintf(file, "%s ($%04x)\n", mnemonic, word);
break;
case address_mode_ind_x:
fprintf(file, "%s ($%02x,X)\n", mnemonic, byte);
break;
case address_mode_ind_y:
fprintf(file, "%s ($%02x),Y\n", mnemonic, byte);
break;
case address_mode_rel:
fprintf(file, "%s $%04x\n", mnemonic, rel);
break;
case address_mode_zp:
fprintf(file, "%s $%02x\n", mnemonic, byte);
break;
case address_mode_zp_x:
fprintf(file, "%s $%02x,X\n", mnemonic, byte);
break;
case address_mode_zp_y:
fprintf(file, "%s $%02x,Y\n", mnemonic, byte);
break;
default:
assert(!"invalid code path");
break;
}
return opcodes[id].length;
}
void disasm_program(unsigned char *bytes, int size, int base_address, FILE *file)
{
fprintf(file, "Address Hexdump Dissassembly\n");
fprintf(file, "-------------------------------\n");
for (int offset = 0; offset < size; )
{
offset += disasm_single(bytes + base_address, offset, base_address, file);
}
}
void init()
{
for (int i = 0; i < 256; i++)
{
init_opcode(i, "???", 1, address_mode_imp);
}
init_opcode(0x69, "ADC", 2, address_mode_imm);
init_opcode(0x65, "ADC", 2, address_mode_zp);
init_opcode(0x75, "ADC", 2, address_mode_zp_x);
init_opcode(0x6D, "ADC", 3, address_mode_abs);
init_opcode(0x7D, "ADC", 3, address_mode_abs_x);
init_opcode(0x79, "ADC", 3, address_mode_abs_y);
init_opcode(0x61, "ADC", 2, address_mode_ind_x);
init_opcode(0x71, "ADC", 2, address_mode_ind_y);
init_opcode(0x29, "AND", 2, address_mode_imm);
init_opcode(0x25, "AND", 2, address_mode_zp);
init_opcode(0x35, "AND", 2, address_mode_zp_x);
init_opcode(0x2D, "AND", 3, address_mode_abs);
init_opcode(0x3D, "AND", 3, address_mode_abs_x);
init_opcode(0x39, "AND", 3, address_mode_abs_y);
init_opcode(0x21, "AND", 2, address_mode_ind_x);
init_opcode(0x31, "AND", 2, address_mode_ind_y);
init_opcode(0x0A, "ASL", 1, address_mode_acc);
init_opcode(0x06, "ASL", 2, address_mode_zp);
init_opcode(0x16, "ASL", 2, address_mode_zp_x);
init_opcode(0x0E, "ASL", 3, address_mode_abs);
init_opcode(0x1E, "ASL", 3, address_mode_abs_x);
init_opcode(0x24, "BIT", 2, address_mode_zp);
init_opcode(0x2C, "BIT", 3, address_mode_abs);
init_opcode(0x00, "BRK", 1, address_mode_imp);
init_opcode(0xC9, "CMP", 2, address_mode_imm);
init_opcode(0xC5, "CMP", 2, address_mode_zp);
init_opcode(0xD5, "CMP", 2, address_mode_zp_x);
init_opcode(0xCD, "CMP", 3, address_mode_abs);
init_opcode(0xDD, "CMP", 3, address_mode_abs_x);
init_opcode(0xD9, "CMP", 3, address_mode_abs_y);
init_opcode(0xC1, "CMP", 2, address_mode_ind_x);
init_opcode(0xD1, "CMP", 2, address_mode_ind_y);
init_opcode(0xE0, "CPX", 2, address_mode_imm);
init_opcode(0xE4, "CPX", 2, address_mode_zp);
init_opcode(0xEC, "CPX", 3, address_mode_abs);
init_opcode(0xC0, "CPY", 2, address_mode_imm);
init_opcode(0xC4, "CPY", 2, address_mode_zp);
init_opcode(0xCC, "CPY", 3, address_mode_abs);
init_opcode(0xC6, "DEC", 2, address_mode_zp);
init_opcode(0xD6, "DEC", 2, address_mode_zp_x);
init_opcode(0xCE, "DEC", 3, address_mode_abs);
init_opcode(0xDE, "DEC", 3, address_mode_abs_x);
init_opcode(0x42, "WDM", 2, address_mode_imm); // 65C816
init_opcode(0x49, "EOR", 2, address_mode_imm);
init_opcode(0x45, "EOR", 2, address_mode_zp);
init_opcode(0x55, "EOR", 2, address_mode_zp_x);
init_opcode(0x4D, "EOR", 3, address_mode_abs);
init_opcode(0x5D, "EOR", 3, address_mode_abs_x);
init_opcode(0x59, "EOR", 3, address_mode_abs_y);
init_opcode(0x41, "EOR", 2, address_mode_ind_x);
init_opcode(0x51, "EOR", 2, address_mode_ind_y);
init_opcode(0xE6, "INC", 2, address_mode_zp);
init_opcode(0xF6, "INC", 2, address_mode_zp_x);
init_opcode(0xEE, "INC", 3, address_mode_abs);
init_opcode(0xFE, "INC", 3, address_mode_abs_x);
init_opcode(0x4C, "JMP", 3, address_mode_abs);
init_opcode(0x6C, "JMP", 3, address_mode_ind);
init_opcode(0x20, "JSR", 3, address_mode_abs);
init_opcode(0xA9, "LDA", 2, address_mode_imm);
init_opcode(0xA5, "LDA", 2, address_mode_zp);
init_opcode(0xB5, "LDA", 2, address_mode_zp_x);
init_opcode(0xAD, "LDA", 3, address_mode_abs);
init_opcode(0xBD, "LDA", 3, address_mode_abs_x);
init_opcode(0xB9, "LDA", 3, address_mode_abs_y);
init_opcode(0xA1, "LDA", 2, address_mode_ind_x);
init_opcode(0xB1, "LDA", 2, address_mode_ind_y);
init_opcode(0xA2, "LDX", 2, address_mode_imm);
init_opcode(0xA6, "LDX", 2, address_mode_zp);
init_opcode(0xB6, "LDX", 2, address_mode_zp_y);
init_opcode(0xAE, "LDX", 3, address_mode_abs);
init_opcode(0xBE, "LDX", 3, address_mode_abs_y);
init_opcode(0xA0, "LDY", 2, address_mode_imm);
init_opcode(0xA4, "LDY", 2, address_mode_zp);
init_opcode(0xB4, "LDY", 2, address_mode_zp_x);
init_opcode(0xAC, "LDY", 3, address_mode_abs);
init_opcode(0xBC, "LDY", 3, address_mode_abs_x);
init_opcode(0x4A, "LSR", 1, address_mode_acc);
init_opcode(0x46, "LSR", 2, address_mode_zp);
init_opcode(0x56, "LSR", 2, address_mode_zp_x);
init_opcode(0x4E, "LSR", 3, address_mode_abs);
init_opcode(0x5E, "LSR", 3, address_mode_abs_x);
init_opcode(0xEA, "NOP", 1, address_mode_imp);
init_opcode(0x09, "ORA", 2, address_mode_imm);
init_opcode(0x05, "ORA", 2, address_mode_zp);
init_opcode(0x15, "ORA", 2, address_mode_zp_x);
init_opcode(0x0D, "ORA", 3, address_mode_abs);
init_opcode(0x1D, "ORA", 3, address_mode_abs_x);
init_opcode(0x19, "ORA", 3, address_mode_abs_y);
init_opcode(0x01, "ORA", 2, address_mode_ind_x);
init_opcode(0x11, "ORA", 2, address_mode_ind_y);
init_opcode(0x2A, "ROL", 1, address_mode_acc);
init_opcode(0x26, "ROL", 2, address_mode_zp);
init_opcode(0x36, "ROL", 2, address_mode_zp_x);
init_opcode(0x2E, "ROL", 3, address_mode_abs);
init_opcode(0x3E, "ROL", 3, address_mode_abs_x);
init_opcode(0x6A, "ROR", 1, address_mode_acc);
init_opcode(0x66, "ROR", 2, address_mode_zp);
init_opcode(0x76, "ROR", 2, address_mode_zp_x);
init_opcode(0x6E, "ROR", 3, address_mode_abs);
init_opcode(0x7E, "ROR", 3, address_mode_abs_x);
init_opcode(0x40, "RTI", 1, address_mode_imp);
init_opcode(0x60, "RTS", 1, address_mode_imp);
init_opcode(0xE9, "SBC", 2, address_mode_imm);
init_opcode(0xE5, "SBC", 2, address_mode_zp);
init_opcode(0xF5, "SBC", 2, address_mode_zp_x);
init_opcode(0xED, "SBC", 3, address_mode_abs);
init_opcode(0xFD, "SBC", 3, address_mode_abs_x);
init_opcode(0xF9, "SBC", 3, address_mode_abs_y);
init_opcode(0xE1, "SBC", 2, address_mode_ind_x);
init_opcode(0xF1, "SBC", 2, address_mode_ind_y);
init_opcode(0x85, "STA", 2, address_mode_zp);
init_opcode(0x95, "STA", 2, address_mode_zp_x);
init_opcode(0x8D, "STA", 3, address_mode_abs);
init_opcode(0x9D, "STA", 3, address_mode_abs_x);
init_opcode(0x99, "STA", 3, address_mode_abs_y);
init_opcode(0x81, "STA", 2, address_mode_ind_x);
init_opcode(0x91, "STA", 2, address_mode_ind_y);
init_opcode(0x86, "STX", 2, address_mode_zp);
init_opcode(0x96, "STX", 2, address_mode_zp_y);
init_opcode(0x8E, "STX", 3, address_mode_abs);
init_opcode(0x84, "STY", 2, address_mode_zp);
init_opcode(0x94, "STY", 2, address_mode_zp_x);
init_opcode(0x8C, "STY", 3, address_mode_abs);
init_opcode(0x10, "BPL", 2, address_mode_rel);
init_opcode(0x30, "BMI", 2, address_mode_rel);
init_opcode(0x50, "BVC", 2, address_mode_rel);
init_opcode(0x70, "BVS", 2, address_mode_rel);
init_opcode(0x90, "BCC", 2, address_mode_rel);
init_opcode(0xB0, "BCS", 2, address_mode_rel);
init_opcode(0xD0, "BNE", 2, address_mode_rel);
init_opcode(0xF0, "BEQ", 2, address_mode_rel);
init_opcode(0xAA, "TAX", 1, address_mode_imp);
init_opcode(0x8A, "TXA", 1, address_mode_imp);
init_opcode(0xCA, "DEX", 1, address_mode_imp);
init_opcode(0xE8, "INX", 1, address_mode_imp);
init_opcode(0xA8, "TAY", 1, address_mode_imp);
init_opcode(0x98, "TYA", 1, address_mode_imp);
init_opcode(0x88, "DEY", 1, address_mode_imp);
init_opcode(0xC8, "INY", 1, address_mode_imp);
init_opcode(0x18, "CLC", 1, address_mode_imp);
init_opcode(0x38, "SEC", 1, address_mode_imp);
init_opcode(0x58, "CLI", 1, address_mode_imp);
init_opcode(0x78, "SEI", 1, address_mode_imp);
init_opcode(0xB8, "CLV", 1, address_mode_imp);
init_opcode(0xD8, "CLD", 1, address_mode_imp);
init_opcode(0xF8, "SED", 1, address_mode_imp);
init_opcode(0x9A, "TXS", 1, address_mode_imp);
init_opcode(0xBA, "TSX", 1, address_mode_imp);
init_opcode(0x48, "PHA", 1, address_mode_imp);
init_opcode(0x68, "PLA", 1, address_mode_imp);
init_opcode(0x08, "PHP", 1, address_mode_imp);
init_opcode(0x28, "PLP", 1, address_mode_imp);
}
void disasm_test()
{
//unsigned char example[] = { 0xa9, 0xc0, 0xaa, 0xe8, 0x69, 0xc4, 0x00 };
//unsigned char example[] = { 0xa9, 0x00, 0x8d, 0x00, 0x02, 0xa9, 0x01, 0x8d, 0x01, 0x02, 0x8d, 0xff, 0x05 };
//unsigned char example[] = { 0xa9, 0x80, 0x85, 0x01, 0x65, 0x01, 0xa9, 0xf1, 0xaa, 0xa9, 0xf2, 0xa8, 0xa9, 0x00, 0x98, 0x8a };
//unsigned char example[] = { 0xa9, 0x03, 0x85, 0x00, 0xa9, 0x09, 0x38, 0xe5, 0x00, 0x85, 0x01 };
//unsigned char example[] = { 0xa2, 0x08, 0xca, 0x8e, 0x00, 0x02, 0xe0, 0x03, 0xf0, 0x03, 0x4c, 0x02, 0x06, 0x8e, 0x01, 0x02 };
//unsigned char example[] = { 0xa2, 0x08, 0xca, 0x8e, 0x00, 0x02, 0xe0, 0x03, 0xd0, 0xf8, 0x8e, 0x01, 0x02, 0x00, 0xff };
//unsigned char example[] = { 0xa2, 0x02, 0x8e, 0x00, 0x02, 0xa9, 0xf0, 0x6d, 0x00, 0x02, 0x90, 0xfb, 0x8e, 0x01, 0x02, 0x00 };
//unsigned char example[] = { 0xa2, 0x00, 0xa0, 0x00, 0x8a, 0x99, 0x00, 0x02, 0x48, 0xe8, 0xc8, 0xc0, 0x10, 0xd0, 0xf5, 0x68, 0x99, 0x00, 0x02, 0xc8, 0xc0, 0x20, 0xd0, 0xf7 };
//unsigned char example[] = { 0x20, 0x09, 0x06, 0x20, 0x0c, 0x06, 0x20, 0x12, 0x06, 0xa2, 0x00, 0x60, 0xe8, 0xe0, 0x05, 0xd0, 0xfb, 0x60, 0x00 };
//unsigned char example[] = { 0x20, 0x06, 0x06, 0x20, 0x38, 0x06, 0x20, 0x0d, 0x06, 0x20, 0x2a, 0x06, 0x60, 0xa9, 0x02, 0x85, 0x02, 0xa9, 0x04, 0x85, 0x03, 0xa9, 0x11, 0x85, 0x10, 0xa9, 0x10, 0x85, 0x12, 0xa9, 0x0f, 0x85, 0x14, 0xa9, 0x04, 0x85, 0x11, 0x85, 0x13, 0x85, 0x15, 0x60, 0xa5, 0xfe, 0x85, 0x00, 0xa5, 0xfe, 0x29, 0x03, 0x18, 0x69, 0x02, 0x85, 0x01, 0x60, 0x20, 0x4d, 0x06, 0x20, 0x8d, 0x06, 0x20, 0xc3, 0x06, 0x20, 0x19, 0x07, 0x20, 0x20, 0x07, 0x20, 0x2d, 0x07, 0x4c, 0x38, 0x06, 0xa5, 0xff, 0xc9, 0x77, 0xf0, 0x0d, 0xc9, 0x64, 0xf0, 0x14, 0xc9, 0x73, 0xf0, 0x1b, 0xc9, 0x61, 0xf0, 0x22, 0x60, 0xa9, 0x04, 0x24, 0x02, 0xd0, 0x26, 0xa9, 0x01, 0x85, 0x02, 0x60, 0xa9, 0x08, 0x24, 0x02, 0xd0, 0x1b, 0xa9, 0x02, 0x85, 0x02, 0x60, 0xa9, 0x01, 0x24, 0x02, 0xd0, 0x10, 0xa9, 0x04, 0x85, 0x02, 0x60, 0xa9, 0x02, 0x24, 0x02, 0xd0, 0x05, 0xa9, 0x08, 0x85, 0x02, 0x60, 0x60, 0x20, 0x94, 0x06, 0x20, 0xa8, 0x06, 0x60, 0xa5, 0x00, 0xc5, 0x10, 0xd0, 0x0d, 0xa5, 0x01, 0xc5, 0x11, 0xd0, 0x07, 0xe6, 0x03, 0xe6, 0x03, 0x20, 0x2a, 0x06, 0x60, 0xa2, 0x02, 0xb5, 0x10, 0xc5, 0x10, 0xd0, 0x06, 0xb5, 0x11, 0xc5, 0x11, 0xf0, 0x09, 0xe8, 0xe8, 0xe4, 0x03, 0xf0, 0x06, 0x4c, 0xaa, 0x06, 0x4c, 0x35, 0x07, 0x60, 0xa6, 0x03, 0xca, 0x8a, 0xb5, 0x10, 0x95, 0x12, 0xca, 0x10, 0xf9, 0xa5, 0x02, 0x4a, 0xb0, 0x09, 0x4a, 0xb0, 0x19, 0x4a, 0xb0, 0x1f, 0x4a, 0xb0, 0x2f, 0xa5, 0x10, 0x38, 0xe9, 0x20, 0x85, 0x10, 0x90, 0x01, 0x60, 0xc6, 0x11, 0xa9, 0x01, 0xc5, 0x11, 0xf0, 0x28, 0x60, 0xe6, 0x10, 0xa9, 0x1f, 0x24, 0x10, 0xf0, 0x1f, 0x60, 0xa5, 0x10, 0x18, 0x69, 0x20, 0x85, 0x10, 0xb0, 0x01, 0x60, 0xe6, 0x11, 0xa9, 0x06, 0xc5, 0x11, 0xf0, 0x0c, 0x60, 0xc6, 0x10, 0xa5, 0x10, 0x29, 0x1f, 0xc9, 0x1f, 0xf0, 0x01, 0x60, 0x4c, 0x35, 0x07, 0xa0, 0x00, 0xa5, 0xfe, 0x91, 0x00, 0x60, 0xa6, 0x03, 0xa9, 0x00, 0x81, 0x10, 0xa2, 0x00, 0xa9, 0x01, 0x81, 0x10, 0x60, 0xa2, 0x00, 0xea, 0xea, 0xca, 0xd0, 0xfb, 0x60 };
unsigned char example[] = { 0x20, 0x06, 0x06, 0x20, 0x37, 0x06, 0x20, 0x0d, 0x06, 0x20, 0x2a, 0x06, 0x60, 0xa9, 0x02, 0x85, 0x02, 0xa9, 0x04, 0x85, 0x03, 0xa9, 0x11, 0x85, 0x10, 0xa9, 0x10, 0x85, 0x12, 0xa9, 0x0f, 0x85, 0x14, 0xa9, 0x04, 0x85, 0x11, 0x85, 0x13, 0x85, 0x15, 0x60, 0xa5, 0xfe, 0x85, 0x00, 0xa5, 0xfe, 0x29, 0x03, 0x18, 0x69, 0x02, 0x85, 0x01, 0x20, 0x57, 0x06, 0x20, 0x43, 0x06, 0x20, 0x4a, 0x06, 0x4c, 0x37, 0x06, 0xa0, 0x00, 0xa5, 0xfe, 0x91, 0x00, 0x60, 0xa6, 0x03, 0xa9, 0x00, 0x81, 0x10, 0xa2, 0x00, 0xa9, 0x01, 0x81, 0x10, 0x60, 0xa6, 0x03, 0xca, 0x8a, 0xb5, 0x10, 0x95, 0x12, 0xca, 0x10, 0xf9, 0xa5, 0x02, 0x4a, 0xb0, 0x09, 0x4a, 0xb0, 0x19, 0x4a, 0xb0, 0x1f, 0x4a, 0xb0, 0x2f, 0xa5, 0x10, 0x38, 0xe9, 0x20, 0x85, 0x10, 0x90, 0x01, 0x60, 0xc6, 0x11, 0xa9, 0x01, 0xc5, 0x11, 0xf0, 0x26, 0x60, 0xe6, 0x10, 0xa9, 0x1f, 0x24, 0x10, 0xf0, 0x1d, 0x60, 0xa5, 0x10, 0x18, 0x69, 0x20, 0x85, 0x10, 0xb0, 0x01, 0x60, 0xe6, 0x11, 0xa9, 0x06, 0xc5, 0x11, 0xf0, 0x0a, 0x60, 0xc6, 0x10, 0xa9, 0x1f, 0x25, 0x10, 0xf0, 0x01, 0x60, 0x4c, 0xab, 0x06 };
disasm_program(example, sizeof(example), 0x600, stdout);
}
struct parsed_line
{
char label[64];
char op[64];
char args[256];
};
void parse_line(const char *line, int length, parsed_line *parsed)
{
int start, end, pos = 0;
memset(parsed, 0, sizeof(parsed_line));
while ((line[pos] == ' ') || (line[pos] == '\t'))
{
pos++;
}
// special case - set address *=$12AB
if ((line[pos] == '*') && (line[pos + 1] == '='))
{
parsed->op[0] = '*';
pos += 2;
start = pos;
while ((line[pos] != ';') && (line[pos] != '\n') && (line[pos] != '\r') && (line[pos] != 0))
{
pos++;
}
end = pos;
strncpy_s(parsed->args, sizeof(parsed->args), &line[start], end - start);
return;
}
start = pos;
while ((line[pos] == '_') || ((line[pos] >= 'A') && (line[pos] <= 'Z')) || ((line[pos] >= 'a') && (line[pos] <= 'z')) || ((line[pos] >= '0') && (line[pos] <= '9')))
{
pos++;
}
end = pos;
while ((line[pos] == ' ') || (line[pos] == '\t'))
{
pos++;
}
if (line[pos] != ':')
{
strncpy_s(parsed->op, sizeof(parsed->op), &line[start], end - start);
}
else
{
strncpy_s(parsed->label, sizeof(parsed->label), &line[start], end - start);
pos++;
while ((line[pos] == ' ') || (line[pos] == '\t'))
{
pos++;
}
start = pos;
while ((line[pos] == '_') || ((line[pos] >= 'A') && (line[pos] <= 'Z')) || ((line[pos] >= 'a') && (line[pos] <= 'z')) || ((line[pos] >= '0') && (line[pos] <= '9')))
{
pos++;
}
end = pos;
strncpy_s(parsed->op, sizeof(parsed->op), &line[start], end - start);
}
while ((line[pos] == ' ') || (line[pos] == '\t'))
{
pos++;
}
start = pos;
while ((line[pos] != ';') && (line[pos] != '\n') && (line[pos] != '\r') && (line[pos] != 0))
{
pos++;
}
end = pos;
strncpy_s(parsed->args, sizeof(parsed->args), &line[start], end - start);
}
struct symbol
{
char *label;
int offset;
symbol *next;
};
symbol *labels = 0;
symbol *defines = 0;
// TODO: check for duplicate labels
symbol *add_symbol(symbol *list, char *text, int offset)
{
symbol *s = (symbol *)malloc(sizeof(symbol));
size_t size = strlen(text) + 1;
s->label = (char *)malloc(size);
strcpy_s(s->label, size, text);
s->offset = offset;
s->next = list;
return s;
}
#define INVALID_ADDRESS 0xFFFFF
int lookup_symbol(symbol *list, const char *text)
{
for (symbol *s = list; s; s = s->next)
{
if (_stricmp(text, s->label) == 0)
{
return s->offset;
}
}
return INVALID_ADDRESS;
}
void free_symbols(symbol **list)
{
for (symbol *s = *list, *next = 0; s; s = next)
{
next = s->next;
free(s->label);
free(s);
}
*list = 0;
}
int lookup(const char *text)
{
int address = lookup_symbol(defines, text);
if (address == INVALID_ADDRESS)
{
address = lookup_symbol(labels, text);
}
return address;
}
void print_symbols(symbol *list)
{
for (symbol *s = list; s; s = s->next)
{
printf("%04x %s\n", s->offset, s->label);
}
}
int parse_value(const char *text)
{
int value = 0;
if (*text == '$')
{
text++; // skip hex prefix
for (;;)
{
if ((*text >= '0') && (*text <= '9'))
{
value = value * 16 + (*text - '0');
text++;
}
else if ((*text >= 'A') && (*text <= 'F'))
{
value = value * 16 + (*text - 'A' + 10);
text++;
}
else if ((*text >= 'a') && (*text <= 'f'))
{
value = value * 16 + (*text - 'a' + 10);
text++;
}
else
{
break;
}
}
}
else
{
for (;;)
{
if ((*text >= '0') && (*text <= '9'))
{
value = value * 10 + (*text - '0');
text++;
}
else
{
break;
}
}
}
return value;
}
address_mode get_address_mode(const char *args, int *ptr_address)
{
address_mode mode = address_mode_undef;
int address = 0;
const char *c = args;
#define _skip_spaces while ((*c == ' ') || (*c == '\t')) {c++;}
_skip_spaces;
if (*c == 0)
{
mode = address_mode_imp;
}
else if (((c[0] == 'A') || (c[0] == 'a')) && c[1] == 0)
{
mode = address_mode_acc;
c++;
}
else if (*c == '#')
{
mode = address_mode_imm;
c++;
}
else if (*c == '(')
{
mode = address_mode_ind;
c++;
}
else
{
mode = address_mode_abs;
}
_skip_spaces;
if (*c == '$')
{
address = parse_value(c);
*c++;
while (((*c >= '0') && (*c <= '9')) || ((*c >= 'A') && (*c <= 'F')) || ((*c >= 'a') && (*c <= 'f')))
{
c++;
}
}
else if ((*c >= '0') && (*c <= '9'))
{
address = parse_value(c);
while ((*c >= '0') && (*c <= '9'))
{
c++;
}
}
else
{
bool label_lo = false;
bool label_hi = false;
if (*c == '<')
{
label_lo = true;
c++;
}
else if (*c == '>')
{
label_hi = true;
c++;
}
char lookup_str[64];
int lookup_len = 0;
while ((lookup_len < 63) && (*c == '_') || ((*c >= 'A') && (*c <= 'Z')) || ((*c >= 'a') && (*c <= 'z')) || ((*c >= '0') && (*c <= '9')))
{
lookup_str[lookup_len++] = *c++;
}
lookup_str[lookup_len] = 0;
if (lookup_len)
{
address = lookup(lookup_str);
if (label_lo)
{
address = address & 0xFF;
}
else if (label_hi)
{
address = (address >> 8) & 0xFF;
}
}
}
_skip_spaces;
if (*c == ')')
{
c++;
_skip_spaces;
if (*c == ',')
{
c++;
_skip_spaces;
if ((*c == 'y') || (*c == 'Y'))
{
mode = address_mode_ind_y;
*c++;
}
}
}
if (*c == ',')
{
c++;
_skip_spaces;
if (((*c == 'x') || (*c == 'X')) && (mode == address_mode_ind))
{
mode = address_mode_ind_x;
c++;
_skip_spaces;
assert(*c == ')');
c++;
}
else if (((*c == 'x') || (*c == 'X')) && (mode == address_mode_abs))
{
mode = address_mode_abs_x;
c++;
}
else if (((*c == 'y') || (*c == 'Y')) && (mode == address_mode_abs))
{
mode = address_mode_abs_y;
c++;
}
else
{
assert(!"invalid mode");
}
}
_skip_spaces;
assert(*c == 0);
assert(mode != address_mode_undef);
if (ptr_address)
{
*ptr_address = address;
}
return mode;
}
int translate_dcb(const char *args, unsigned char *out)
{
int pos = 0;
int length = 0;
for (;;)
{
while ((args[pos] == ' ') || (args[pos] == '\t'))
{
pos++;
}
if (args[pos] != 0)
{
out[length++] = parse_value(args + pos);
}
while ((args[pos] != ',') && (args[pos] != '\n') && (args[pos] != 0))
{
pos++;
}
if ((args[pos] == '\n') || (args[pos] == 0))
{
break;
}
else if (args[pos] == ',')
{
pos++;
}
}
return length;
}
int translate_instruction(const char *op, address_mode mode, int current_address, int parsed_address, unsigned char *out)
{
for (int pass = 0; pass < 2; pass++)
{
for (int id = 0; id < 256; id++)
{
if (_stricmp(opcodes[id].mnemonic, op) == 0)
{
address_mode test_mode = mode;
// special case: branch instructions have relative addressing
if ((opcodes[id].mode == address_mode_rel) && (mode == address_mode_abs))
{
test_mode = address_mode_rel;
parsed_address = parsed_address - current_address - 2;
}
else if ((opcodes[id].mode == address_mode_acc) && (mode == address_mode_imp))
{
test_mode = address_mode_acc;
}
else if ((pass == 0) && (parsed_address <= 0xFF))
{
// check for zp addressing only on first pass
if (mode == address_mode_abs)
{
test_mode = address_mode_zp;
}
else if (mode == address_mode_abs_x)
{
test_mode = address_mode_zp_x;
}
else if (mode == address_mode_abs_y)
{
test_mode = address_mode_zp_y;
}
}
if (opcodes[id].mode == test_mode)
{
out[0] = id;
if (opcodes[id].length == 2)
{
out[1] = parsed_address & 0xFF;
}
else if (opcodes[id].length == 3)
{
out[1] = parsed_address & 0xFF;
out[2] = (parsed_address >> 8) & 0xFF;
}
return opcodes[id].length;
}
}
}
}
assert(!"invalid op/mode");
}
int translate_program(const char *program, unsigned char *bytes, int size, int base_address)
{
// do 2 passes:
// 1) index labels
// 2) actually do translation
int offset = 0;
for (int pass = 0; pass < 2; pass++)
{
const char *c = program;
const char *end = program + size - 1;
const char *line = c;
parsed_line parsed;
int length = 0;
offset = base_address;
while (c <= end)
{
if ((*c == '\n') || (*c == '\r') || (*c == 0) || (c == end))
{
if (length > 0)
{
parse_line(line, length, &parsed);
if (strlen(parsed.label) > 0)
{
if (pass == 0)
{
labels = add_symbol(labels, parsed.label, offset);
}
}
if (_stricmp(parsed.op, "DEFINE") == 0)
{
if (pass == 0)
{
// special case, split symbol and value
int pos = 0;
int len = strlen(parsed.args);
for (int i = 0; i < len; i++)
{
if ((parsed.args[i] == ' ') || (parsed.args[i] == '\t'))
{
pos = i;
break;
}
}
parsed.args[pos] = 0;
pos++;
while ((parsed.args[pos] == ' ') || (parsed.args[pos] == '\t'))
{
pos++;
}
int value = parse_value(parsed.args + pos);
defines = add_symbol(defines, parsed.args, value);
}
}
else if (parsed.op[0])
{
if (_stricmp(parsed.op, "DCB") == 0)
{
// TODO: implement
offset += translate_dcb(parsed.args, bytes + offset);
}
else if (parsed.op[0] == '*')
{
offset = parse_value(parsed.args);
}
else
{
int address = 0;
address_mode mode = get_address_mode(parsed.args, &address);
offset += translate_instruction(parsed.op, mode, offset, address, bytes + offset);
}
}
}
if (*c == 0)
{
break;
}
line = c + 1;
length = 0;
}
else
{
length++;
}
c++;
}
}
return offset - base_address;
}
int asm_program(const char *program, unsigned char *bytes, int size, int base_address)
{
int byte_size = translate_program(program, bytes, size, base_address);
#if 0
printf("\nDEFINES\n=======\n");
print_symbols(defines);
printf("\nLABELS\n=======\n");
print_symbols(labels);
#endif
return byte_size;
}
void asm_test()
{
#if 1
const char *program =
"; static noise\n"
"\n"
"define symbol 123\n"
"start: ldy #$ff\n\r"
" ldx\t#$0\n"
"loop: lda $fe\n"
" \t sta $200 , x\n"
" and #$7\n"
"define another $123\n"
" sta $300, x\r"
" and #$3\n"
" sta $400 ,x\n"
" and #$1\n"
" sta $500,x\n"
" inx\n"
" dey\n"
" bne loop\n"
" rts\n"
"*=512\n"
"offset512:"
"*=$400\n"
"offsetx400:"
//"label: dcb 12,34,56"
;
#else
const char *program =
"XXX #$FFFF\n"
"XXX #9999\n"
"XXX #<label\n"
"XXX #>label\n"
"XXX #symbol\n"
"XXX $FFFF\n"
"XXX $0,x \n"
"XXX $FFFF ,x\n"
"XXX $FFFF,y\n"
"XXX ($0 ),y\n"
"XXX ($0,x)\n"
"XXX (label ) , y\n"
"XXX (label , x)\n"
"XXX 9999\n"
"XXX label\n"
"XXX label,x\n"
"XXX label,y\n"
"XXX a\n";
#endif
unsigned char *bytes = (unsigned char *)malloc(0x10000);
int size = asm_program(program, bytes, sizeof(program) - 1, 0x600);
disasm_program(bytes, size, 0x600, stdout);
}
int main(int argc, char *argv[])
{
bool disasm = false;
int base_address = 0x600;
init();
int out_buffer_size = 0x10000;
unsigned char *out_data = (unsigned char *)malloc(out_buffer_size);
for (int i = 1; i < argc; i++)
{
if (argv[i][0] == '-' && argv[i][1] == 'd')
{
disasm = true;
}
else if (argv[i][0] == '-' && argv[i][1] == 'b')
{
base_address = parse_value(&argv[i][2]);
}
else
{
FILE *f_in;
fopen_s(&f_in, argv[i], "rb");
if (f_in)
{
printf("Processing file: %s\n", argv[i]);
free_symbols(&labels);
free_symbols(&defines);
assert(labels == 0);
assert(defines == 0);
fseek(f_in, 0, SEEK_END);
int input_size = ftell(f_in);
unsigned char *input_data = (unsigned char *)malloc(input_size);
fseek(f_in, 0, SEEK_SET);
fread((void *)input_data, input_size, 1, f_in);
fclose(f_in);
if (!disasm)
{
memset(out_data, 0, out_buffer_size);
int out_size = asm_program((const char *)input_data, out_data, input_size, base_address);
FILE *f_out;
char outname[100] = "../disasm/";
strcat_s(outname, argv[i]);
int len = strnlen_s(outname, sizeof(outname));
outname[len - 3] = 0;
strcat_s(outname, "disasm");
printf("Writing to file: %s\n", outname);
fopen_s(&f_out, outname, "wb");
if (f_out)
{
disasm_program(out_data, out_size, base_address, f_out);
fclose(f_out);
}
else
{
printf("Error opening output file: %s\n", outname);
}
}
else
{
disasm_program(input_data, input_size, base_address, stdout);
}
free(input_data);
}
else
{
printf("Error opening input file: %s\n", argv[i]);
}
}
}
system("pause");
return 0;
}