/*
 * uncompress.c
 *
 * Piotr Fusik, 18.11.2001
 */

#include <zlib.h>

int uncompress (char* dest, unsigned* destLen,
                const char* source, unsigned sourceLen)
{
	unsigned len;
	unsigned char* ptr;
	unsigned long csum;
	/* source[0]: Compression method and flags
	    bits 0 to 3: Compression method (must be Z_DEFLATED)
	    bits 4 to 7: Compression info (must be <= 7)
	   source[1]: Flags
	    bits 0 to 4: Check bits
	    bit 5:       Preset dictionary (not supported, sorry)
	    bits 6 to 7: Compression level
	*/
	if ((source[0] & 0x8f) != Z_DEFLATED || source[1] & 0x20)
		return Z_DATA_ERROR;
	if ((((unsigned) source[0] << 8) | (unsigned char) source[1]) % 31)
		return Z_DATA_ERROR;
	*destLen = len = inflatemem(dest, source + 2);
	ptr = (unsigned char*) source + sourceLen - 4;
	csum = adler32(adler32(0L, Z_NULL, 0), dest, len);
	if ((unsigned char) csum != ptr[3]
	 || (unsigned char) (csum >> 8) != ptr[2]
	 || (unsigned char) (csum >> 16) != ptr[1]
	 || (unsigned char) (csum >> 24) != ptr[0])
		return Z_DATA_ERROR;
	return Z_OK;
}