Scans through a ROM and decompresses all Yay0 data found inside.

yay0dump.c

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

#ifdef _MSC_VER
#define __builtin_bswap32(x) _byteswap_ulong(x)
#endif

typedef struct
{
	uint32_t magic;
	uint32_t uncompressedLength;
	uint32_t opPtr;
	uint32_t dataPtr;
} Yay0Header;

uint32_t Yay0Uncompress(uint8_t *src, uint8_t **dst)
{
	uint8_t  byte = 0, mask = 0;
	uint8_t *ctrl, *ops, *data, *dstPtr;
	uint16_t copy, op;
	uint32_t written = 0, length;
	Yay0Header *hdr;
	
	hdr = (Yay0Header *)src;

	length = __builtin_bswap32(hdr->uncompressedLength);
	dstPtr = *dst = malloc(length);

	ctrl = src + sizeof(Yay0Header);
	ops  = src + __builtin_bswap32(hdr->opPtr);
	data = src + __builtin_bswap32(hdr->dataPtr);
	
	while (written < length)
	{
		if ((mask >>= 1) == 0)
		{
			byte = *ctrl++;
			mask = 0x80;
		}

		if (byte & mask)
		{
			*dstPtr++ = *data++;
			written++;
		}
		else
		{
			op = (ops[0] << 8) | ops[1];
			ops += 2;		
			
			written += copy = (op >> 12) ? (2 + (op >> 12)) : (18 + *data++);

			while (copy--)
				*dstPtr++ = dstPtr[-(op & 0xfff) - 1];
		}	
	}

	return written;
}

int main(int argc, char **argv)
{
	char     fn[256];
	uint8_t *inBuf, *inStart, *inEnd, *outBuf;
	FILE    *in, *out;
	long     inLen, bufLen;
	
	if (argc != 2)
	{
		printf("Usage: %s ROM\n", argv[0]);
		return 0;
	}
	
	if ((in = fopen(argv[1], "rb")) == NULL)
	{
		perror("Error opening ROM");
		return 1;
	}
	
	fseek(in, 0, SEEK_END);
	inLen   = ftell(in);
	inStart = inBuf = malloc(inLen);
	rewind(in);
	fread(inBuf, 1, inLen, in);
	fclose(in);
	
	inEnd = inBuf + inLen;
	
	while (inBuf < inEnd)
	{
		if (*(uint32_t *)inBuf == 0x30796159)
		{
			sprintf(fn, "%08x.bin", (uint32_t)(inBuf - inStart));
			out = fopen(fn, "wb");
			
			printf("Extracting %s...\n", fn);
			
			bufLen = Yay0Uncompress(inBuf, &outBuf);
			fwrite(outBuf, 1, bufLen, out);
			
			fclose(out);
			free(outBuf);
		}
		
		inBuf++;
	}
	
	free(inStart);
	
	puts("\nDone!");
	
	return 0;
}

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