NSData category that determines whether data is ZIP format

NSData+ZipFile.m

@implementation NSData (ZipFile)

- (BOOL)isZipFormatData {
    // Zip files start with the bytes { 50, 4b, 03, 04 }
    
    if (self.length < 4)
        return NO;
    
    unsigned char signature[4];
    [self getBytes:signature length:sizeof(signature)];
    
    return (signature[0] == 0x50) &&
           (signature[1] == 0x4b) &&
           (signature[2] == 0x03) &&
           (signature[3] == 0x04);
}

@end