path: root/cart2xex.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <string.h>
#include <errno.h>

#include "cart.h"
#include "get_address.h"
#include "loadscreen_bin.h"

/*
	cart2xex 20061018 bkw
	updated 20070524 bkw
	added atari800 CART format 20071227 bkw

	Quick & dirty utility to convert Atari 8-bit cartridge images
	to Atari DOS binary load files (suitable for use with DOS the 2.0S
	"L" command, or your favorite 3-sector loader, etc).

	Works on non-bankswitched 8K or 16K cart images. Output is:
	- Segment containing code that prints LOADING (suppress with -n)
	- 6-byte Atari binary load header
	- The entire input
	- 4-byte header, followed by the init address (total 6 bytes)
	- 4-byte header, followed by the run address (total 6 bytes)

	Without the LOADING screen, the resulting binary is 18 bytes
	larger than the input.

	If the cart image isn't exactly 8192 or 16384 bytes long, an error
	is printed, and the program exits with status 1. Otherwise, exit
	status is 0 (success).

	Future options (stuff I might add, if there's any interest):

	- ATR image output support (image would consist of a 3-sector
	  loader plus the binary)... not really necessary: can use "makeatr"
	  to make a k-file if you really want.

	- Simple algorithm to detect STA/STX/STY instructions that write
	  to the ROM address space. If I were going to copy-protect a cart,
	  to keep people from dumping it to a bin, I'd write to what's supposed
	  to be ROM, then read it back. If I got back what I wrote there, it
	  means the "ROM" is actually RAM, so I'd refuse to play the game.
	  Parker Bros. Frogger does this.
	  The trouble is, a *simple* algorithm will probably fail. Several
	  self-destructing carts I've dealt with use STA ($00),Y to write to
	  ROM... meaning I basically need a complete emulator. Atari++ has a
	  nice debugger with conditional breakpoints, maybe there's a way to
	  hook into that?

	- Documentation for all this crap, if I really add it :)
*/

#ifndef VERSION
#define VERSION "???"
#endif

#define SELF "cart2xex"

#define BANNER \
	SELF " v" VERSION " - by B. Watson (WTFPL)\n"

#define MAX_CART_SIZE (16384 + 16)

char *usage =
	"\nUsage: " SELF " [-cdhilnprR] [-t title] infile.rom [outfile.xex]\n"
	"  -c        Check only; do not create xex file\n"
	"  -d        Don't include code to reboot the Atari when RESET is pressed\n"
	"  -h        Print this help\n"
	"  -i addr   Force init address to addr (0 = no init address)\n"
	"  -r addr   Force run address to addr (0 = no run address)\n"
	"  -l addr   Force load address to addr\n"
	"  -R        ROM is right cartridge image (same as -l0x8000)\n"
	"  -p pages  Reserve # of pages below RAMTOP\n"
	"  -n        Do not include code for LOADING screen\n"
	"  -t title  Set title for LOADING screen (default: outfile)\n";

int loadscreen = 1; /* true if we're going to prepend a title screen */
int checkonly  = 0; /* true if we're not writing an output file */
int reserve_pages = 0; /* number of extra pages of RAM to reserve */
int reboot_reset = 1; /* true if RESET key causes a reboot */

/* buffer[] will contain the cart image after it's loaded, which may
	or may not include a 16-byte CART header. rom will point to the start
	of the actual ROM data (buffer or buffer+16) */
unsigned char buffer[MAX_CART_SIZE];
unsigned char *rom;

/* warn() and die() are like the Perl functions of the same names, kind of */
void warn(char *msg) {
	if(msg) fprintf(stderr, "%s\n", msg);
}

void die(char *msg) {
	warn(msg);
	exit(1);
}

/* cart_image_valid() looks at an atari800-style CART header and returns
	true if the cartridge type is 8K or 16K non-bankswitched */
int cart_image_valid(unsigned char *cart) {
	int cart_type;

	cart_dump_header(cart, 0);

	cart_type = get_cart_type(cart);

	/* magic numbers: types 1 and 2 are "Standard 8K" and "Standard 16K",
		type 21 is "Standard 8K right slot", which are the only types we
		can support. */
	if(cart_type != 1 && cart_type != 2 && cart_type != 21)
		return 0;

	/* bad cksum is not a fatal error */
	if(cart_checksum_ok(cart))
		fprintf(stderr, "CART checksum:  0x%08x (OK)\n", get_cart_checksum(cart));
	else
		warn("Warning: CART checksum invalid, file may be corrupt");

	return 1;
}

/* For now, all the work is done in main() */
int main(int argc, char **argv) {
	int maxres, c, size = 0;
	unsigned char init_lo, init_hi, run_lo, run_hi, option, present, ramtop_adj;
	int runadr, initadr;
	int force_init = -1, force_run = -1, force_load = -1;
	char *infile = "-", outfile[4096] = "-";
	FILE *in = stdin, *out = stdout;
	char *title = NULL;

	puts(BANNER);

	argc--; argv++;

	while(argc && *argv[0] == '-') {
		switch(argv[0][1]) {
			case 't':
				if(argv[0][2]) {
					title = &argv[0][2];
				} else {
					argc--; argv++;
					if(argc) {
						title = &argv[0][0];
					} else {
						die(usage);
					}
				}
				break;

			case 'p':
				if(argv[0][2]) {
					reserve_pages = get_address(NULL, &argv[0][2]);
				} else {
					argc--; argv++;
					if(argc) {
						reserve_pages = get_address(NULL, argv[0]);
					} else {
						die(usage);
					}
				}
				if(reserve_pages < 0)
					exit(1);
				break;

			case 'R':
				force_load = 0x8000;
				break;

			case 'l':
				if(argv[0][2]) {
					force_load = get_address(NULL, &argv[0][2]);
				} else {
					argc--; argv++;
					if(argc) {
						force_load = get_address(NULL, argv[0]);
					} else {
						die(usage);
					}
				}
				if(force_load < 0)
					exit(1);
				break;

			case 'i':
				if(argv[0][2]) {
					force_init = get_address(NULL, &argv[0][2]);
				} else {
					argc--; argv++;
					if(argc) {
						force_init = get_address(NULL, argv[0]);
					} else {
						die(usage);
					}
				}
				if(force_init < 0)
					exit(1);
				break;

			case 'r':
				if(argv[0][2]) {
					force_run = get_address(NULL, &argv[0][2]);
				} else {
					argc--; argv++;
					if(argc) {
						force_run = get_address(NULL, argv[0]);
					} else {
						die(usage);
					}
				}
				if(force_run < 0)
					exit(1);
				break;

			case 'c':
				checkonly = 1;
				break;

			case 'n':
				loadscreen = 0;
				break;

			case 'd':
				reboot_reset = 0;
				break;

			case 'h':
				printf(usage);
				exit(0);
				break;

			default:
				fprintf(stderr, "Unrecognized option '-%c'\n", argv[0][1]);
				die(usage);
				break;
		}

		argc--; argv++;
	}

	if(argc) {
		infile = *argv;
		argc--; argv++;
	}

	if(argc) {
		strcpy(outfile, *argv);
		argc--; argv++;
	} else if(!checkonly && strcmp(infile, "-") != 0) {
		char *p;

		strcpy(outfile, infile);
		p = strrchr(outfile, '.');
		if(!p) p = outfile + strlen(outfile);
		*p = '\0';
		strcat(outfile, ".xex");
		fprintf(stderr, "- Output is '%s'\n", outfile);

		if(strcmp(infile, outfile) == 0)
			die("Input and output filenames are the same, aborting!\n");
	}

	if(argc)
		die(usage);

	if(strcmp(infile, "-") != 0) {
		if( !(in = fopen(infile, "rb")) ) {
			perror(infile);
			exit(1);
		}
	}

	while( (c = getc(in)) != EOF && size < MAX_CART_SIZE) {
		buffer[size++] = c;
	}

	if(has_cart_signature(buffer)) {
		int header_size;

		warn("Image type:     Atari800 CART format");
		if(!cart_image_valid(buffer))
			die("Unsupported/invalid CART image\n"
					"(only 8K/16K non-banked images are supported)");

		if(get_cart_type(buffer) == 21) {
			/* right cartridge */
			force_load = 0x8000;
			warn("Forcing load address to $8000 for right-slot cartridge");
		}

		header_size = get_cart_size(buffer);
		rom = buffer + 16;
		size -= 16;

		if(size != header_size)
			die("CART header says image should be %d bytes, but only %d bytes "
					"are in the image! Corrupt/damaged CART image?");
	} else {
		warn("Image type:     Raw dump");
		rom = buffer;
	}

	if( !(c == EOF && (size == 8192 || size == 16384)) ) {
		if(rom[0] == 0xff && rom[1] == 0xff) {
			warn("This looks like an Atari binary load file!");
		} else if(rom[0] == 0x00 && rom[1] == 0x00) {
			warn("This looks like an Atari BASIC program!");
		}

		die("Cartridge size must be 8192 or 16384 bytes\n"
				"(Are you sure this is a valid Atari 8-bit cartridge image?)");
	}

	/* All this info comes from Mapping the Atari, originally by
		Ian Chadwick, now available for free at
		http://www.atariarchives.org/mapping/
	*/

	/* Assume we're using a Left Cartridge. Not many Right Cartridges
		were ever made... */
	run_lo  = rom[size-6]; /* $BFFA */
	run_hi  = rom[size-5]; /* $BFFB */
	present = rom[size-4]; /* $BFFC */
	option  = rom[size-3]; /* $BFFD */
	init_lo = rom[size-2]; /* $BFFE */
	init_hi = rom[size-1]; /* $BFFF */

	/* Some helpful messages... decode the cart options */
	if(present) { /* $BFFC */
		fprintf(stderr,
				"Hmm, this cart image has $%02X in the \"cartridge present\" "
				"byte at $BFFC\n"
				"(should be $00). "
				"Are you sure it's really a valid image?\n",
				present);
	}

	fprintf(stderr, "Image size:     %dK (addresses $%04X - $%04X)\n",
			size/1024, 49152-size, 49152-1);
	fprintf(stderr, "Run address:    $%02X%02X\n", run_hi, run_lo);
	fprintf(stderr, "Init address:   $%02X%02X\n", init_hi, init_lo);
	fprintf(stderr, "Option byte:    $%02X\n", option);

	/* $BFFD, bits 0, 2, 7 */
	fprintf(stderr, "- Cartridge does %sallow disk boot\n",
			(option & 1) ? "" : "NOT ");

	fprintf(stderr, "- Cartridge gets initialized, %s\n",
			(option & 4) ?
				"then started normally" :
				"but NOT started (weird)");

	fprintf(stderr, "Cartridge type:  %s\n",
			(option & 128) ?
				"diagnostic (output binary may not run correctly!)" :
				"normal (non-diagnostic)");

	if(checkonly)
		exit(0);

	if(force_load >= 0) {
		fprintf(stderr, "-l option: Load address forced to $%04X\n", force_load);
	}

	if(force_init >= 0) {
		init_lo = rom[size-2] = force_init & 0xff;
		init_hi = rom[size-1] = (force_init >> 8) & 0xff;
		fprintf(stderr, "-i option: Init address forced to $%04X\n", force_init);
	}

	if(force_run >= 0) {
		run_lo = rom[size-6] = force_run & 0xff;
		run_hi = rom[size-5] = (force_run >> 8) & 0xff;
		fprintf(stderr, "-r option: Run address forced to $%04X\n", force_run);
	}

	runadr = run_lo + (run_hi << 8);
	if(runadr && (runadr < 49152-size || runadr >= 49152))
		warn("Warning: Run address not in cartridge address range");

	initadr = init_lo + (init_hi << 8);
	if(initadr && (initadr < 49152-size || initadr >= 49152))
		warn("Warning: Init address not in cartridge address range");

	if(size == 8192 && force_load < 0) {
		if(runadr >= 0x8000 && runadr < 0xa000)
			warn("This may be a \"right cartridge\" ROM, try -R?");
	}

	/* Whew! Finally all checks are done, we can open the output file */
	if(strcmp(outfile, "-") != 0) {
		if( !(out = fopen(outfile, "wb")) ) {
			perror(outfile);
			fclose(in);
			exit(1);
		}

		if(!title) {
			char *p;

			title = outfile;

			/* remove directory if present */
			p = strrchr(title, '/');
			if(p) title = p + 1;

			/* remove extension if present */
			p = strrchr(title, '.');
			if(p) *p = '\0';
		}

	}

	if(isatty(fileno(out))) {
		warn("\nStandard output is a terminal, not writing binary data.\n"
				"Either redirect to a file or set the output filename.");
		die(usage);
	}

	maxres = ((0xc000 - size) - 0x7000) >> 8;
	if(reserve_pages > maxres) {
		fprintf(stderr, "Can't reserve %d pages below RAMTOP. Maximum "
				"reserved pages is %d for a %dK ROM.\n",
				reserve_pages, maxres, size/1024);
		exit(1);
	}

	if(reserve_pages) {
		fprintf(stderr, "Reserving %d pages below RAMTOP\n", reserve_pages);
	}

	ramtop_adj = (size >> 8) + reserve_pages;

	/* Write the loading screen object code, unless suppressed */
	if(loadscreen) {
		int i;
		char c, d;

		/* loadscreen.bin adjusts RAMTOP to make room for the cart image,
			so it needs to know the size. */
		loadscreen_bin[6] = ramtop_adj;

		if(title) {
			/* WARNING: magic number here! */
			/* Look for "Title offset: loadscreen_bin_len - $xx"
				in dasm output. */
			int offset = loadscreen_bin_len - 27;
			int len = strlen(title);

			if(len > 20) {
				fprintf(stderr, "Title > 20 characters, truncating\n");
				len = 20;
			}
			offset += 10-len/2;

			fprintf(stderr, "- Setting title to \"");
			for(i=0; i<len; i++) {
				c = title[i];

				c = tolower(c);
				d = c;

				if(c >= 33 && c <= 63) {
					c -= 32;
				} else if(c >= 64 && c <= 95) {
					c += 32;
				} else if(!isalnum(c)) {
					d = c = 32;
				}
				fputc(d, stderr);

				loadscreen_bin[offset+i] = c;
			}

			fputc('"', stderr);
			fputc('\n', stderr);
		} else {
			fprintf(stderr,
					"No -t and no output filename, not setting load screen title\n");
		}

		/* loadscreen_bin already includes $FF, $FF header */
		for(i=0; i<loadscreen_bin_len; i++)
			putc(loadscreen_bin[i], out);
	} else {
		/* $FF, $FF binary load header. All Atari executables must have this. */
		putc(0xff, out);
		putc(0xff, out);

		/* Without the title screen, we still need to set RAMTOP. Do it
			by loading a 1-byte segment at $6A. */
		putc(0x6a, out);
		putc(0x00, out);
		putc(0x6a, out);
		putc(0x00, out);
		putc(0xc0 - ramtop_adj, out); /* assume RAMTOP is 48K */
	}

	if(reboot_reset) {
		/* make the Atari reboot when user presses RESET (POKE 580,1) */
		putc(0x44, out); /* start addr LSB */
		putc(0x02, out); /* start addr MSB */
		putc(0x44, out); /* end addr LSB */
		putc(0x02, out); /* end addr MSB */
		putc(0x01, out); /* one byte of data */
	}

	/* Now write the Atari binary load file... Remember, the 6502 expects
		addresses to be little-endian (LSB, then MSB) */

	/* First segment: the code. */
	/* Load address (LSB first). $8000 for a 16K cart, or $A000 for 8K,
		or force_load if user used it */
	if(force_load >= 0) {
		putc(force_load & 0xff, out);
		putc(force_load >> 8, out);
		force_load += (size - 1);
		putc(force_load & 0xff, out);
		putc(force_load >> 8, out);
	} else {
		putc(0, out);
		putc(size == 16384 ? 0x80 : 0xa0, out);
		/* End address (LSB first). Always $BFFF */
		putc(0xff, out);
		putc(0xbf, out);
	}

	/* Image data */
	for(c=0; c<size; c++)
		putc(rom[c], out);

	/* Only write init address if it's not 0 */
	if(init_hi || init_lo) {
		/* Next segment loads at INITAD ($2E2), contains the cart's init addr */
		putc(0xe2, out);
		putc(0x02, out);

		/* Segment length is 2 bytes (ends at $2E3) */
		putc(0xe3, out);
		putc(0x02, out);

		/* Init address will get loaded at $2E2 and $2E3 */
		putc(init_lo, out);
		putc(init_hi, out);
	}

	/* Only write run address if it's not 0 */
	/* Next segment loads at RUNAD ($2E0), contains the cart's run address */
	if(run_hi || run_lo) {
		putc(0xe0, out);
		putc(0x02, out);

		/* Segment length is 2 bytes (ends at $2E1) */
		putc(0xe1, out);
		putc(0x02, out);

		/* Run address will get loaded at $2E0 and $2E1 */
		putc(run_lo, out);
		putc(run_hi, out);
	}

	/* Check for I/O errors before closing files */
	c = 0;
	if(ferror(in)) {
		fprintf(stderr, "%s: %s\n", infile, strerror(errno));
		c = 1;
	}

	if(ferror(out)) {
		fprintf(stderr, "%s: %s\n", outfile, strerror(errno));
		c = 1;
	}

	/* Close 'em, we're done */
	fclose(in);
	fclose(out);

	/* That's all, folks! */
	exit(c);
}