PSX xosdmain decrypter and decompressor

xosdmain_decomp.cpp

#include <stdio.h>
#include <stdint.h>
#include <elf.h>
#include <string.h>

struct xorInfo
{
	uint8_t *xor_table;
	uint8_t *xor_ptr;
	uint8_t *source;
};

uint8_t xorGetNextByte(xorInfo *info)
{
	uint8_t ret = *info->xor_ptr;
	info->xor_ptr = info->source == info->xor_ptr + 1 ? info->xor_table : info->xor_ptr + 1;
	return ret;
}

void lzDecompress(uint8_t *dest, uint8_t *source, uint8_t *xor_table, uint32_t dest_size)
{
	uint8_t *ptr = dest;
	xorInfo info;
	info.xor_table = xor_table;
	info.xor_ptr = xor_table;
	info.source = source;
	
	uint32_t flag = 0, count = 0, mask = 0, shift = 0;
	while(ptr - dest < dest_size)
	{
		if (count == 0)
		{
			count = 30;
			flag = __builtin_bswap32(*(uint32_t *) source) ^ (xorGetNextByte(&info) << 24 | xorGetNextByte(&info) << 16 | xorGetNextByte(&info) << 8 | xorGetNextByte(&info));
			source += 4;			
			mask = 0x3fff >> (flag & 3);
			shift = 14 - (flag & 3);
		}

		if (flag & 0x80000000)
		{
			uint16_t off_size = __builtin_bswap16(*(uint16_t *) source) ^ (xorGetNextByte(&info) << 8 | xorGetNextByte(&info));
			source += 2;
			uint16_t offset = (off_size & mask) + 1;
			for (uint16_t i = (off_size >> shift) + 3; i > 0; i--)
				*(ptr++) = *(ptr - offset);
		}
		else
			*(ptr++) = *(source++) ^ xorGetNextByte(&info);
		
		count--;
		flag <<= 1;
	}
}

int main(int argc, char ** argv)
{
	if (argc != 3)
	{
		printf("Usage: %s <OSDSYS> <output>\n", argv[0]);
		return -1;
	}
	
	FILE *f = fopen(argv[1], "rb");
	fseek(f, 0, SEEK_END);
	int len = ftell(f);
	fseek(f, 0, SEEK_SET);
	
	uint8_t *buf = new uint8_t[len];
	fread(buf, 1, len, f);
	fclose(f);

	uint8_t *data = buf + 0x380;
	
	uint32_t uncompressed_len = *(uint32_t *) data;
	uint8_t *xor_table = data + 0x10;
	uint32_t xor_table_len = *(uint32_t *) (data + 8);
	
	uint8_t *unpacked = new uint8_t[uncompressed_len];
	lzDecompress(unpacked, &data[0x10 + xor_table_len], xor_table, uncompressed_len);
	delete [] buf;
	
	FILE *fo = fopen(argv[2], "wb");
	fwrite(unpacked, 1, uncompressed_len, fo);
	fclose(fo);

	delete [] unpacked;
	return 0;
}

Similar to OSDSYS compression with an extra xor obfuscation.