Decrunches programs crunched with ByteBoozer 1.1

debooze.c

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/stat.h>

#define MEMSIZ 64*1024
#define GETLOC 0x20

uint16_t get, put;
uint8_t cur, mem[MEMSIZ];
uint8_t tab[] = { 4, 2, 2, 2, 5, 2, 2, 3 };

uint8_t nextbit() {
	uint8_t bit = (cur & 0x80) >> 7;
	cur <<= 1;
	if (cur == 0) {
		cur = mem[get++];
		bit = (cur & 0x80) >> 7;
		cur = (cur << 1) | 1;
	}
	return bit;
}

int main(int argc, char *argv[]) {
	if (argc < 3) {
		printf("usage: debooze <input> <output>\n");
		exit(1);
	}

	FILE *fp = fopen(argv[1], "rb");
	if (fp == NULL) {
		printf("error: unable to open %s\n", argv[1]);
		exit(1);
	}
	size_t flen = fread(mem, 1, MEMSIZ, fp);
	printf("read %d bytes from %s\n", flen, argv[1]);
	fclose(fp);

	get = mem[GETLOC] | mem[GETLOC + 1] << 8;

	uint16_t src = flen - 1, dst = MEMSIZ - 1;
	while (dst >= get)
		mem[dst--] = mem[src--];

	cur = mem[get];
	dst = put = mem[get + 1] | mem[get + 2] << 8;
	printf("source: $%04X length: %d bytes\n", get, MEMSIZ - 1 - get);
	get += 3;

	uint8_t copy = nextbit();
	for (;;) {
		uint8_t copylen = 1;
		while (copylen < 0x80 && nextbit() == 1)
			copylen = copylen << 1 | nextbit();
		if (copy == 1) {
			if (copylen == 0xff)
				break;
			copylen++;
			uint8_t tabidx = (copylen >= 3) << 2 | nextbit() << 1 | nextbit();
			uint16_t copysrc = 0;
			do {
				for (int i = 0; i < tab[tabidx]; i++)
					copysrc = copysrc << 1 | nextbit();
				if ((tabidx & 3) == 0)
					break;
				tabidx--;
				copysrc++;
			} while (copysrc != 0);
			copysrc = put - copysrc;
			for (int i = 0; i < copylen; i++)
				mem[put++] = mem[copysrc++];
		} else {
			for (int i = 0; i < copylen; i++)
				mem[put++] = mem[get++];
			if (copylen < 0xff) {
				copy = 1;
				continue;
			}
		}
		copy = nextbit();
	}

	uint16_t dlen = put - dst;
	printf("dest: $%04X length: %d bytes\n", dst, dlen);
	fp = fopen(argv[2], "wb");
	fputc(dst & 0xff, fp);
	fputc((dst & 0xff00) >> 8, fp);
	if ((flen = fwrite(mem + dst, 1, dlen, fp)) != dlen)
		printf("error: unable to write output");
	fclose(fp);
	printf("wrote %d bytes to %s\n", flen, argv[2]);
}