//
//  j2b.c
//  Dumb J2B Archive parser
//
//  Created by Christopher Snowhill on 10/4/13.
//  Copyright 2013 __NoWork, Inc__. All rights reserved.
//

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

#include "j2b.h"

void * unpackJ2b( const void * in, long * size )
{
    uint32_t fileLength;
    uint32_t checksum;
    uint32_t lenCompressed;
    uint32_t lenUncompressed;
    const uint8_t * in8 = ( const uint8_t * ) in;
    Bytef * uncompressedData;
    int zErr;
    uLong dataUncompressed;
    
    if ( *size < 8 )
        return 0;
    
    if ( in8[0] != 'M' || in8[1] != 'U' || in8[2] != 'S' || in8[3] != 'E' ||
        in8[4] != 0xDE || in8[5] != 0xAD ||
        ( ( in8[6] != 0xBE || in8[7] != 0xAF ) && ( in8[6] != 0xBA || in8[7] != 0xBE ) ) )
    {
        return 0;
    }
    
    if ( *size < 12 )
        return 0;
    
    fileLength = in8[8] | (in8[9] << 8) | (in8[10] << 16) | (in8[11] << 24);
    
    if ( fileLength < 12 || fileLength + 12 > *size )
        return 0;
    
    checksum = in8[12] | (in8[13] << 8) | (in8[14] << 16) | (in8[15] << 24);
    lenCompressed = in8[16] | (in8[17] << 8) | (in8[18] << 16) | (in8[19] << 24);
    lenUncompressed = in8[20] | (in8[21] << 8) | (in8[22] << 16) | (in8[23] << 24);
    
    if ( lenCompressed + 12 > fileLength )
        return 0;
    
    if ( crc32( 0, in8 + 24, lenCompressed) != checksum )
        return 0;
    
    uncompressedData = (Bytef *) malloc( lenUncompressed );
    
    if ( !uncompressedData )
        return 0;
    
    dataUncompressed = lenUncompressed;
    
    zErr = uncompress( uncompressedData, &dataUncompressed, in8 + 24, lenCompressed );
    if ( zErr != Z_OK )
    {
        free( uncompressedData );
        return 0;
    }
    
    *size = dataUncompressed;
    
    return uncompressedData;
}