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dcc6502/dcc6502.c
Nathan Rosenquist 8b01d8b204 Use fread() return value to count bytes 
This commit changes the behavior of dcc6502, so that it consults the
return value of fread(), and then increments the value of byte_count
by the number returned by fread(), rather than implicitly incrementing
it every time.

Previously, a warning occurred during compilation, because the return value
of fread() was ignored. Instead, the number of bytes in the input file were
counted implicitly by incrementing a byte_count variable after every fread()
call.

Additionally, I created a two-byte test input file consisting of the
bytes #$a9ff, which corresponds to LDA #$FF. When dcc6502 tried to
disassemble this input file, it reported that the file had a size of three
bytes. It reported the first two opcodes correctly, but then incorrectly
displayed a BRK as the third opcode.

After this change, the input file now has a reported size of two bytes,
without the phantom BRK opcode at the end.
2018-09-01 20:44:41 -04:00

791 lines
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/**********************************************************************************
* dcc6502.c -> Main module of: *
* Disassembler and Cycle Counter for the 6502 microprocessor *
* *
* This code is offered under the MIT License (MIT) *
* *
* Copyright (c) 1998-2014 Tennessee Carmel-Veilleux <veilleux@tentech.ca> *
* *
* Permission is hereby granted, free of charge, to any person obtaining a copy *
* of this software and associated documentation files (the "Software"), to deal *
* in the Software without restriction, including without limitation the rights *
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell *
* copies of the Software, and to permit persons to whom the Software is *
* furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included in all *
* copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, *
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE *
* SOFTWARE. *
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <ctype.h>
#include <errno.h>
#define VERSION_INFO "v2.1"
#define NUMBER_OPCODES 151
/* Exceptions for cycle counting */
#define CYCLES_CROSS_PAGE_ADDS_ONE (1 << 0)
#define CYCLES_BRANCH_TAKEN_ADDS_ONE (1 << 1)
/* The 6502's 13 addressing modes */
typedef enum {
IMMED = 0, /* Immediate */
ABSOL, /* Absolute */
ZEROP, /* Zero Page */
IMPLI, /* Implied */
INDIA, /* Indirect Absolute */
ABSIX, /* Absolute indexed with X */
ABSIY, /* Absolute indexed with Y */
ZEPIX, /* Zero page indexed with X */
ZEPIY, /* Zero page indexed with Y */
INDIN, /* Indexed indirect (with X) */
ININD, /* Indirect indexed (with Y) */
RELAT, /* Relative */
ACCUM /* Accumulator */
} addressing_mode_e;
/** Some compilers don't have EOK in errno.h */
#ifndef EOK
#define EOK 0
#endif
typedef struct opcode_s {
uint8_t number; /* Number of the opcode */
const char *mnemonic; /* Index in the name table */
addressing_mode_e addressing; /* Addressing mode */
unsigned int cycles; /* Number of cycles */
unsigned int cycles_exceptions; /* Mask of cycle-counting exceptions */
} opcode_t;
typedef struct options_s {
char *filename; /* Input filename */
int nes_mode; /* 1 if NES commenting and warnings are enabled */
int cycle_counting; /* 1 if we want cycle counting */
int hex_output; /* 1 if hex dump output is desired at beginning of line */
unsigned long max_num_bytes;
uint16_t org; /* Origin of addresses */
long offset; /* File offset to start disassembly from */
} options_t;
/* Opcode table */
static opcode_t g_opcode_table[NUMBER_OPCODES] = {
{0x69, "ADC", IMMED, 2, 0}, /* ADC */
{0x65, "ADC", ZEROP, 3, 0},
{0x75, "ADC", ZEPIX, 4, 0},
{0x6D, "ADC", ABSOL, 4, 0},
{0x7D, "ADC", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x79, "ADC", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x61, "ADC", INDIN, 6, 0},
{0x71, "ADC", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x29, "AND", IMMED, 2, 0}, /* AND */
{0x25, "AND", ZEROP, 3, 0},
{0x35, "AND", ZEPIX, 4, 0},
{0x2D, "AND", ABSOL, 4, 0},
{0x3D, "AND", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x39, "AND", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x21, "AND", INDIN, 6, 0},
{0x31, "AND", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x0A, "ASL", ACCUM, 2, 0}, /* ASL */
{0x06, "ASL", ZEROP, 5, 0},
{0x16, "ASL", ZEPIX, 6, 0},
{0x0E, "ASL", ABSOL, 6, 0},
{0x1E, "ASL", ABSIX, 7, 0},
{0x90, "BCC", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BCC */
{0xB0, "BCS", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BCS */
{0xF0, "BEQ", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BEQ */
{0x24, "BIT", ZEROP, 3, 0}, /* BIT */
{0x2C, "BIT", ABSOL, 4, 0},
{0x30, "BMI", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BMI */
{0xD0, "BNE", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BNE */
{0x10, "BPL", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BPL */
{0x00, "BRK", IMPLI, 7, 0}, /* BRK */
{0x50, "BVC", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BVC */
{0x70, "BVS", RELAT, 2, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BVS */
{0x18, "CLC", IMPLI, 2, 0}, /* CLC */
{0xD8, "CLD", IMPLI, 2, 0}, /* CLD */
{0x58, "CLI", IMPLI, 2, 0}, /* CLI */
{0xB8, "CLV", IMPLI, 2, 0}, /* CLV */
{0xC9, "CMP", IMMED, 2, 0}, /* CMP */
{0xC5, "CMP", ZEROP, 3, 0},
{0xD5, "CMP", ZEPIX, 4, 0},
{0xCD, "CMP", ABSOL, 4, 0},
{0xDD, "CMP", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xD9, "CMP", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xC1, "CMP", INDIN, 6, 0},
{0xD1, "CMP", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xE0, "CPX", IMMED, 2, 0}, /* CPX */
{0xE4, "CPX", ZEROP, 3, 0},
{0xEC, "CPX", ABSOL, 4, 0},
{0xC0, "CPY", IMMED, 2, 0}, /* CPY */
{0xC4, "CPY", ZEROP, 3, 0},
{0xCC, "CPY", ABSOL, 4, 0},
{0xC6, "DEC", ZEROP, 5, 0}, /* DEC */
{0xD6, "DEC", ZEPIX, 6, 0},
{0xCE, "DEC", ABSOL, 6, 0},
{0xDE, "DEC", ABSIX, 7, 0},
{0xCA, "DEX", IMPLI, 2, 0}, /* DEX */
{0x88, "DEY", IMPLI, 2, 0}, /* DEY */
{0x49, "EOR", IMMED, 2, 0}, /* EOR */
{0x45, "EOR", ZEROP, 3, 0},
{0x55, "EOR", ZEPIX, 4, 0},
{0x4D, "EOR", ABSOL, 4, 0},
{0x5D, "EOR", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x59, "EOR", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x41, "EOR", INDIN, 6, 1},
{0x51, "EOR", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xE6, "INC", ZEROP, 5, 0}, /* INC */
{0xF6, "INC", ZEPIX, 6, 0},
{0xEE, "INC", ABSOL, 6, 0},
{0xFE, "INC", ABSIX, 7, 0},
{0xE8, "INX", IMPLI, 2, 0}, /* INX */
{0xC8, "INY", IMPLI, 2, 0}, /* INY */
{0x4C, "JMP", ABSOL, 3, 0}, /* JMP */
{0x6C, "JMP", INDIA, 5, 0},
{0x20, "JSR", ABSOL, 6, 0}, /* JSR */
{0xA9, "LDA", IMMED, 2, 0}, /* LDA */
{0xA5, "LDA", ZEROP, 3, 0},
{0xB5, "LDA", ZEPIX, 4, 0},
{0xAD, "LDA", ABSOL, 4, 0},
{0xBD, "LDA", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xB9, "LDA", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xA1, "LDA", INDIN, 6, 0},
{0xB1, "LDA", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xA2, "LDX", IMMED, 2, 0}, /* LDX */
{0xA6, "LDX", ZEROP, 3, 0},
{0xB6, "LDX", ZEPIY, 4, 0},
{0xAE, "LDX", ABSOL, 4, 0},
{0xBE, "LDX", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xA0, "LDY", IMMED, 2, 0}, /* LDY */
{0xA4, "LDY", ZEROP, 3, 0},
{0xB4, "LDY", ZEPIX, 4, 0},
{0xAC, "LDY", ABSOL, 4, 0},
{0xBC, "LDY", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x4A, "LSR", ACCUM, 2, 0}, /* LSR */
{0x46, "LSR", ZEROP, 5, 0},
{0x56, "LSR", ZEPIX, 6, 0},
{0x4E, "LSR", ABSOL, 6, 0},
{0x5E, "LSR", ABSIX, 7, 0},
{0xEA, "NOP", IMPLI, 2, 0}, /* NOP */
{0x09, "ORA", IMMED, 2, 0}, /* ORA */
{0x05, "ORA", ZEROP, 3, 0},
{0x15, "ORA", ZEPIX, 4, 0},
{0x0D, "ORA", ABSOL, 4, 0},
{0x1D, "ORA", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x19, "ORA", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x01, "ORA", INDIN, 6, 0},
{0x11, "ORA", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x48, "PHA", IMPLI, 3, 0}, /* PHA */
{0x08, "PHP", IMPLI, 3, 0}, /* PHP */
{0x68, "PLA", IMPLI, 4, 0}, /* PLA */
{0x28, "PLP", IMPLI, 4, 0}, /* PLP */
{0x2A, "ROL", ACCUM, 2, 0}, /* ROL */
{0x26, "ROL", ZEROP, 5, 0},
{0x36, "ROL", ZEPIX, 6, 0},
{0x2E, "ROL", ABSOL, 6, 0},
{0x3E, "ROL", ABSIX, 7, 0},
{0x6A, "ROR", ACCUM, 2, 0}, /* ROR */
{0x66, "ROR", ZEROP, 5, 0},
{0x76, "ROR", ZEPIX, 6, 0},
{0x6E, "ROR", ABSOL, 6, 0},
{0x7E, "ROR", ABSIX, 7, 0},
{0x40, "RTI", IMPLI, 6, 0}, /* RTI */
{0x60, "RTS", IMPLI, 6, 0}, /* RTS */
{0xE9, "SBC", IMMED, 2, 0}, /* SBC */
{0xE5, "SBC", ZEROP, 3, 0},
{0xF5, "SBC", ZEPIX, 4, 0},
{0xED, "SBC", ABSOL, 4, 0},
{0xFD, "SBC", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xF9, "SBC", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0xE1, "SBC", INDIN, 6, 0},
{0xF1, "SBC", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x38, "SEC", IMPLI, 2, 0}, /* SEC */
{0xF8, "SED", IMPLI, 2, 0}, /* SED */
{0x78, "SEI", IMPLI, 2, 0}, /* SEI */
{0x85, "STA", ZEROP, 3, 0}, /* STA */
{0x95, "STA", ZEPIX, 4, 0},
{0x8D, "STA", ABSOL, 4, 0},
{0x9D, "STA", ABSIX, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x99, "STA", ABSIY, 4, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x81, "STA", INDIN, 6, 0},
{0x91, "STA", ININD, 5, CYCLES_CROSS_PAGE_ADDS_ONE},
{0x86, "STX", ZEROP, 3, 0}, /* STX */
{0x96, "STX", ZEPIY, 4, 0},
{0x8E, "STX", ABSOL, 4, 0},
{0x84, "STY", ZEROP, 3, 0}, /* STY */
{0x94, "STY", ZEPIX, 4, 0},
{0x8C, "STY", ABSOL, 4, 0},
{0xAA, "TAX", IMPLI, 2, 0}, /* TAX */
{0xA8, "TAY", IMPLI, 2, 0}, /* TAY */
{0xBA, "TSX", IMPLI, 2, 0}, /* TSX */
{0x8A, "TXA", IMPLI, 2, 0}, /* TXA */
{0x9A, "TXS", IMPLI, 2, 0}, /* TXS */
{0x98, "TYA", IMPLI, 2, 0} /* TYA */
};
/* This function emits a comment header with information about the file
being disassembled */
static void emit_header(options_t *options, int fsize) {
fprintf(stdout, "; Source generated by DCC6502 version %s\n", VERSION_INFO);
fprintf(stdout, "; For more info about DCC6502, see https://github.com/tcarmelveilleux/dcc6502\n");
fprintf(stdout, "; FILENAME: %s, File Size: %d, ORG: $%04X\n", options->filename, fsize, options->org);
if (options->hex_output) fprintf(stdout, "; -> Hex output enabled\n");
if (options->cycle_counting) fprintf(stdout, "; -> Cycle counting enabled\n");
if (options->nes_mode) fprintf(stdout, "; -> NES mode enabled\n");
fprintf(stdout, ";---------------------------------------------------------------------------\n");
}
/* This function appends cycle counting to the comment block. See following
* for methods used:
* "Nick Bensema's Guide to Cycle Counting on the Atari 2600"
* http://www.alienbill.com/2600/cookbook/cycles/nickb.txt
*/
static char *append_cycle(char *input, uint8_t entry, uint16_t pc, uint16_t new_pc) {
char tmpstr[256];
int cycles = g_opcode_table[entry].cycles;
int exceptions = g_opcode_table[entry].cycles_exceptions;
int crosses_page = ((pc & 0xff00u) != (new_pc & 0xff00u)) ? 1 : 0;
// On some exceptional conditions, instruction will take an extra cycle, or even two
if (exceptions != 0) {
if ((exceptions & CYCLES_BRANCH_TAKEN_ADDS_ONE) && (exceptions & CYCLES_CROSS_PAGE_ADDS_ONE)) {
/* Branch case: check for page crossing, since it can be determined
* statically from the relative offset and current PC.
*/
if (crosses_page) {
/* Crosses page, always at least 1 extra cycle, two times */
sprintf(tmpstr, " Cycles: %d/%d", cycles + 1, cycles + 2);
} else {
/* Does not cross page, maybe one extra cycle if branch taken */
sprintf(tmpstr, " Cycles: %d/%d", cycles, cycles + 1);
}
} else {
/* One exception: two times, can't tell in advance whether page crossing occurs */
sprintf(tmpstr, " Cycles: %d/%d", cycles, cycles + 1);
}
} else {
/* No exceptions, no extra time */
sprintf(tmpstr, " Cycles: %d", cycles);
}
strcat(input, tmpstr);
return (input + strlen(input));
}
static void add_nes_str(char *instr, char *instr2) {
strcat(instr, " [NES] ");
strcat(instr, instr2);
}
/* This function put NES-specific info in the comment block */
static void append_nes(char *input, uint16_t arg) {
switch(arg) {
case 0x2000: add_nes_str(input, "PPU setup #1"); break;
case 0x2001: add_nes_str(input, "PPU setup #2"); break;
case 0x2002: add_nes_str(input, "PPU status"); break;
case 0x2003: add_nes_str(input, "SPR-RAM address select"); break;
case 0x2004: add_nes_str(input, "SPR-RAM data"); break;
case 0x2005: add_nes_str(input, "PPU scroll"); break;
case 0x2006: add_nes_str(input, "VRAM address select"); break;
case 0x2007: add_nes_str(input, "VRAM data"); break;
case 0x4000: add_nes_str(input, "Audio -> Square 1"); break;
case 0x4001: add_nes_str(input, "Audio -> Square 1"); break;
case 0x4002: add_nes_str(input, "Audio -> Square 1"); break;
case 0x4003: add_nes_str(input, "Audio -> Square 1"); break;
case 0x4004: add_nes_str(input, "Audio -> Square 2"); break;
case 0x4005: add_nes_str(input, "Audio -> Square 2"); break;
case 0x4006: add_nes_str(input, "Audio -> Square 2"); break;
case 0x4007: add_nes_str(input, "Audio -> Square 2"); break;
case 0x4008: add_nes_str(input, "Audio -> Triangle"); break;
case 0x4009: add_nes_str(input, "Audio -> Triangle"); break;
case 0x400a: add_nes_str(input, "Audio -> Triangle"); break;
case 0x400b: add_nes_str(input, "Audio -> Triangle"); break;
case 0x400c: add_nes_str(input, "Audio -> Noise control reg"); break;
case 0x400e: add_nes_str(input, "Audio -> Noise Frequency reg #1"); break;
case 0x400f: add_nes_str(input, "Audio -> Noise Frequency reg #2"); break;
case 0x4010: add_nes_str(input, "Audio -> DPCM control"); break;
case 0x4011: add_nes_str(input, "Audio -> DPCM D/A data"); break;
case 0x4012: add_nes_str(input, "Audio -> DPCM address"); break;
case 0x4013: add_nes_str(input, "Audio -> DPCM data length"); break;
case 0x4014: add_nes_str(input, "Sprite DMA trigger"); break;
case 0x4015: add_nes_str(input, "IRQ status / Sound enable"); break;
case 0x4016: add_nes_str(input, "Joypad & I/O port for port #1"); break;
case 0x4017: add_nes_str(input, "Joypad & I/O port for port #2"); break;
}
}
/* Helper macros for disassemble() function */
#define DUMP_FORMAT (options->hex_output ? "%-16s%-16s;" : "%-8s%-16s;")
#define HIGH_PART(val) (((val) >> 8) & 0xFFu)
#define LOW_PART(val) ((val) & 0xFFu)
#define LOAD_WORD(buffer, current_pc) ((uint16_t)buffer[(current_pc) + 1] | (((uint16_t)buffer[(current_pc) + 2]) << 8))
/* This function disassembles the opcode at the PC and outputs it in *output */
static void disassemble(char *output, uint8_t *buffer, options_t *options, uint16_t *pc) {
char opcode_repr[256], hex_dump[256];
int opcode_idx;
int len = 0;
int entry = 0;
int found = 0;
uint8_t byte_operand;
uint16_t word_operand = 0;
uint16_t current_addr = *pc;
uint8_t opcode = buffer[current_addr];
const char *mnemonic;
opcode_repr[0] = '\0';
hex_dump[0] = '\0';
// Linear search for opcode
for (opcode_idx = 0; opcode_idx < NUMBER_OPCODES; opcode_idx++) {
if (opcode == g_opcode_table[opcode_idx].number) {
/* Found the opcode, record its table index */
found = 1;
entry = opcode_idx;
}
}
// For opcode not found, terminate early
if (!found) {
sprintf(opcode_repr, ".byte $%02X", opcode);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X:", current_addr, opcode);
sprintf(output, "%-16s%-16s; INVALID OPCODE !!!\n", hex_dump, opcode_repr);
} else {
sprintf(hex_dump, "$%04X", current_addr);
sprintf(output, "%-8s%-16s; INVALID OPCODE !!!\n", hex_dump, opcode_repr);
}
return;
}
// Opcode found in table: disassemble properly according to addressing mode
mnemonic = g_opcode_table[entry].mnemonic;
// Set hex dump to default single address format. Will be overwritten
// by more complex output in case of hex dump mode enabled
sprintf(hex_dump, "$%04X", current_addr);
switch (g_opcode_table[entry].addressing) {
case IMMED:
/* Get immediate value operand */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s #$%02X", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case ABSOL:
/* Get absolute address operand */
word_operand = LOAD_WORD(buffer, *pc);
*pc += 2;
sprintf(opcode_repr, "%s $%02X%02X", mnemonic, HIGH_PART(word_operand), LOW_PART(word_operand));
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X%02X:", current_addr, opcode, LOW_PART(word_operand), HIGH_PART(word_operand));
}
break;
case ZEROP:
/* Get zero page address */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s $%02X", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case IMPLI:
sprintf(opcode_repr, "%s", mnemonic);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X:", current_addr, opcode);
}
break;
case INDIA:
/* Get indirection address */
word_operand = LOAD_WORD(buffer, *pc);
*pc += 2;
sprintf(opcode_repr, "%s ($%02X%02X)", mnemonic, HIGH_PART(word_operand), LOW_PART(word_operand));
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X%02X:", current_addr, opcode, LOW_PART(word_operand), HIGH_PART(word_operand));
}
break;
case ABSIX:
/* Get base address */
word_operand = LOAD_WORD(buffer, *pc);
*pc += 2;
sprintf(opcode_repr, "%s $%02X%02X,X", mnemonic, HIGH_PART(word_operand), LOW_PART(word_operand));
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X%02X:", current_addr, opcode, LOW_PART(word_operand), HIGH_PART(word_operand));
}
break;
case ABSIY:
/* Get baser address */
word_operand = LOAD_WORD(buffer, *pc);
*pc += 2;
sprintf(opcode_repr, "%s $%02X%02X,Y", mnemonic, HIGH_PART(word_operand), LOW_PART(word_operand));
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X%02X:", current_addr, opcode, LOW_PART(word_operand), HIGH_PART(word_operand));
}
break;
case ZEPIX:
/* Get zero-page base address */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s $%02X,X", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case ZEPIY:
/* Get zero-page base address */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s $%02X,Y", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case INDIN:
/* Get zero-page base address */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s ($%02X,X)", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case ININD:
/* Get zero-page base address */
byte_operand = buffer[*pc + 1];
*pc += 1;
sprintf(opcode_repr, "%s ($%02X),Y", mnemonic, byte_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case RELAT:
/* Get relative modifier */
byte_operand = buffer[*pc + 1];
*pc += 1;
// Compute displacement from first byte after full instruction.
word_operand = current_addr + 2;
if (byte_operand > 0x7Fu) {
word_operand -= ((~byte_operand & 0x7Fu) + 1);
} else {
word_operand += byte_operand & 0x7Fu;
}
sprintf(opcode_repr, "%s $%04X", mnemonic, word_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case ACCUM:
sprintf(opcode_repr, "%s A", mnemonic);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X:", current_addr, opcode);
}
break;
default:
// Will not happen since each entry in opcode_table has address mode set
break;
}
// Emit disassembly line content, prior to annotation comments
len = sprintf(output, DUMP_FORMAT, hex_dump, opcode_repr);
output += len;
/* Add cycle count if necessary */
if (options->cycle_counting) {
output = append_cycle(output, entry, *pc + 1, word_operand);
}
/* Add NES port info if necessary */
switch (g_opcode_table[entry].addressing) {
case ABSOL:
case ABSIX:
case ABSIY:
if (options->nes_mode) {
append_nes(output, word_operand);
}
break;
default:
/* Other addressing modes: not enough info to add NES register annotation */
break;
}
}
static void version(void) {
fprintf(stderr, "DCC6502 %s (C)1998-2014 Tennessee Carmel-Veilleux <veilleux@tentech.ca>\n", VERSION_INFO);
fprintf(stderr, "This software is licensed under the MIT license. See the LICENSE file.\n");
fprintf(stderr, "See source on github: https://github.com/tcarmelveilleux/dcc6502.\n");
}
static void usage(void) {
fprintf(stderr, "\nUsage: dcc6502 [options] FILENAME\n");
fprintf(stderr, " -?/-h : Show this help message\n");
fprintf(stderr, " -o ORIGIN : Set the origin (base address of disassembly) [default: 0x8000]\n");
fprintf(stderr, " -m NUM_BYTES : Only disassemble the first NUM_BYTES bytes\n");
fprintf(stderr, " -s NUM_BYTES : Disassemble after skipping NUM_BYTES from start of input file\n");
fprintf(stderr, " -d : Enable hex dump within disassembly\n");
fprintf(stderr, " -n : Enable NES register annotations\n");
fprintf(stderr, " -v : Get only version information\n");
fprintf(stderr, " -c : Enable cycle counting annotations\n");
fprintf(stderr, "\n");
}
static int str_arg_to_ulong(char *str, unsigned long *value) {
uint32_t tmp = 0;
char *endptr;
errno = EOK;
tmp = strtoul(str, &endptr, 0);
/* In case of conversion error, return error indication */
if ((EOK != errno) || (*endptr != '\0')) {
return 0;
} else {
*value = tmp;
return 1;
}
}
static void usage_and_exit(int exit_code, const char *message) {
version();
usage();
if (NULL != message) {
fprintf(stderr, "%s\n", message);
}
exit(exit_code);
}
static void parse_args(int argc, char *argv[], options_t *options) {
int arg_idx = 1;
unsigned long tmp_value;
options->cycle_counting = 0;
options->hex_output = 0;
options->nes_mode = 0;
options->org = 0x8000;
options->max_num_bytes = 65536;
options->offset = 0;
while (arg_idx < argc) {
/* First non-dash-starting argument is assumed to be filename */
if (argv[arg_idx][0] != '-') {
break;
}
/* Got a switch, process it */
switch (argv[arg_idx][1]) {
case 'h':
case '?':
usage_and_exit(0, NULL);
break;
case 'n':
options->nes_mode = 1;
break;
case 'c':
options->cycle_counting = 1;
break;
case 'd':
options->hex_output = 1;
break;
case 'v':
version();
exit(0);
break;
case 'o':
if ((arg_idx == (argc - 1)) || (argv[arg_idx + 1][0] == '-')) {
usage_and_exit(1, "Missing argument to -o switch");
}
/* Get argument and parse it */
arg_idx++;
if (!str_arg_to_ulong(argv[arg_idx], &tmp_value)) {
usage_and_exit(1, "Invalid argument to -o switch");
}
options->org = (uint16_t)(tmp_value & 0xFFFFu);
break;
case 'm':
if ((arg_idx == (argc - 1)) || (argv[arg_idx + 1][0] == '-')) {
usage_and_exit(1, "Missing argument to -m switch");
}
/* Get argument and parse it */
arg_idx++;
if (!str_arg_to_ulong(argv[arg_idx], &tmp_value)) {
usage_and_exit(1, "Invalid argument to -m switch");
}
options->max_num_bytes = tmp_value;
break;
case 's':
if ((arg_idx == (argc - 1)) || (argv[arg_idx + 1][0] == '-')) {
usage_and_exit(1, "Missing argument to -s switch");
}
/* Get argument and parse it */
arg_idx++;
if (!str_arg_to_ulong(argv[arg_idx], &tmp_value)) {
usage_and_exit(1, "Invalid argument to -s switch");
}
options->offset = (long)tmp_value;
break;
default:
version();
usage();
fprintf(stderr, "Unrecognized switch: %s\n", argv[arg_idx]);
exit(1);
}
arg_idx++;
}
/* Make sure we have a filename left to take after we stopped parsing switches */
if (arg_idx >= argc) {
usage_and_exit(1, "Missing filename from command line");
}
options->filename = argv[arg_idx];
}
int main(int argc, char *argv[]) {
int byte_count = 0;
char tmpstr[512];
uint8_t *buffer; /* Memory buffer */
FILE *input_file; /* Input file */
uint16_t pc; /* Program counter */
options_t options; /* Command-line options parsing results */
int result = 0;
parse_args(argc, argv, &options);
buffer = calloc(1, 65536);
if (NULL == buffer) {
usage_and_exit(3, "Could not allocate disassembly memory buffer.");
}
/* Read file into memory buffer */
input_file = fopen(options.filename, "rb");
if (NULL == input_file) {
version();
fprintf(stderr, "File not found or invalid filename : %s\n", options.filename);
exit(2);
}
if (options.offset) {
result = fseek(input_file, options.offset, SEEK_SET);
if (result < 0) {
fprintf(stderr, "fseek(%s, %ld, SEEK_SET) failed: %s (%d)\n", options.filename, options.offset, strerror(errno), result);
exit(2);
}
}
byte_count = 0;
while(!feof(input_file) && ((options.org + byte_count) <= 0xFFFFu) && (byte_count < options.max_num_bytes)) {
size_t bytes_read = fread(&buffer[options.org + byte_count], 1, 1, input_file);
byte_count += bytes_read;
}
fclose(input_file);
/* Disassemble contents of buffer */
emit_header(&options, byte_count);
pc = options.org;
while((pc <= 0xFFFFu) && ((pc - options.org) < byte_count)) {
disassemble(tmpstr, buffer, &options, &pc);
fprintf(stdout, "%s\n", tmpstr);
pc++;
}
free(buffer);
return 0;
}
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