iOS NSData 和十六进制字符串之间的相互转换

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本文记录的是使用OC进行NSData和十六进制字符串之间的相互转换。其中将十六进制字符串转换成NSData的代码如下:

- (NSData *)convertHexStrToData:(NSString *)str {
    if (!str || [str length] == 0) {
        return nil;
    }

    NSMutableData *hexData = [[NSMutableData alloc] initWithCapacity:8];
    NSRange range;
    if ([str length] % 2 == 0) {
        range = NSMakeRange(0, 2);
    } else {
        range = NSMakeRange(0, 1);
    }
    for (NSInteger i = range.location; i < [str length]; i += 2) {
        unsigned int anInt;
        NSString *hexCharStr = [str substringWithRange:range];
        NSScanner *scanner = [[NSScanner alloc] initWithString:hexCharStr];

        [scanner scanHexInt:&anInt];
        NSData *entity = [[NSData alloc] initWithBytes:&anInt length:1];
        [hexData appendData:entity];

        range.location += range.length;
        range.length = 2;
    }

    LEDEBUG(@"hexdata: %@", hexData);
    return hexData;
}

如果传入参数 str 为 1ff, 则hexdata打印出:hexdata: <01ff>

将NSData转换成十六进制的字符串则可使用如下方式:

- (NSString *)convertDataToHexStr:(NSData *)data {
    if (!data || [data length] == 0) {
        return @"";
    }
    NSMutableString *string = [[NSMutableString alloc] initWithCapacity:[data length]];

    [data enumerateByteRangesUsingBlock:^(const void *bytes, NSRange byteRange, BOOL *stop) {
        unsigned char *dataBytes = (unsigned char*)bytes;
        for (NSInteger i = 0; i < byteRange.length; i++) {
            NSString *hexStr = [NSString stringWithFormat:@"%x", (dataBytes[i]) & 0xff];
            if ([hexStr length] == 2) {
                [string appendString:hexStr];
            } else {
                [string appendFormat:@"0%@", hexStr];
            }
        }
    }];

    return string;
}

将第一个例子中生成的NSData当做入参，则返回的string为01ff

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