+ (NSData *)hexToBytes:(NSString *)str {

NSMutableData *data = [NSMutableData data];

int idx;

for (idx = 0; idx+2 <= str.length; idx+=2) {

NSRange range = NSMakeRange(idx, 2);

NSString* hexStr = [str substringWithRange:range];

NSScanner* scanner = [NSScanner scannerWithString:hexStr];

unsigned int intValue;

[scanner scanHexInt:&intValue];

[data appendBytes:&intValue length:1];

}

return data;

//? ? 8afb0a3df680e1e1c0c3407e47f6c548? NSString

//? ? <8afb0a3d f680e1e1 c0c3407e 47f6c548>? NSData

}