#include <stdio.h>
#include <stdlib.h>

/* cc ulzdec.c -o ulzdec && ./ulzdec compressed.bin */

static int
error(const char *name, const char *msg)
{
	fprintf(stderr, "%s: %s\n", name, msg);
	return 0;
}

char *mem, *ptr;

int
decode_ulz(FILE *src)
{
	char c, *copy;
	short i, length;
	ptr = mem = malloc(0x10000);
	while((c = getc(src)) != EOF) {
		if(c & 0x80) { /* DICT */
			if(c & 0x40)
				length = (c & 0x3f) << 8 | getc(src);
			else
				length = c & 0x3f;
			copy = ptr - (getc(src) + 1);
			for(i = 0; i < length + 4; i++)
				*(ptr++) = *(copy++);
		} else /* LIT */
			for(i = 0; i < c + 1; i++)
				*(ptr++) = getc(src);
	}
	return ptr - mem;
}

int
main(int argc, char *argv[])
{
	int res;
	FILE *src, *dst;
	if(argv[1][0] == '-' && argv[1][1] == 'v')
		return !fprintf(stdout, "Ulzdec - ULZ Decoder, 15 Nov 2023.\n");
	if(argc != 3)
		return error("usage", "ulzdec [-v] a.ulz b.bin");
	if(!(src = fopen(argv[1], "rb")))
		return !error("Invalid input file", argv[1]);
	res = decode_ulz(src);
	if(!(dst = fopen(argv[2], "wb")))
		return !error("Invalid output file", argv[1]);
	fwrite(mem, res, 1, dst);
	printf("Decompressed %s -> %s(%d bytes).\n", argv[1], argv[2], res);
	return 0;
}