iOS BCD码、数据流、字节和MD5计算

一、各个之间的相互转换

1、字符串转数据流NSData

    NSString *str = @"abc123";

    NSData *dd = [str dataUsingEncoding:NSUTF8StringEncoding];

    NSLog(@"%@",dd); // dd = <61626331 3233>

通过打印转换后的数据流可以看到，数据流里是两位一个字节存储字符串ASCII码的十六进制，a = 97 = 0x61,  1 = 49 = 0x31

2、字节与数据流转换

    Byte bb[] = {,,,,,};

    NSData *dd = [[NSData alloc]initWithBytes:bb length:];

    NSLog(@"%@",dd);  // dd = <61626331 3233>　　　打印的结果和字符串转换是一样的

    //数据流转字节
    Byte *bb = (Byte *)[dd bytes];

3、根据需要直接变成NSData，倒过来同理NSData转字符串也是先变成字节在转字符串

    NSString *bcdstr = @"";

    int leng = (int)bcdstr.length/;

    if (bcdstr.length% == ) //判断奇偶数

    {

        leng +=;

    }

    Byte bbte[leng];

    for (int i = ; i<leng-; i++)

    {

        bbte[i] = (int)strtoul([[bcdstr substringWithRange:NSMakeRange(i*, )]UTF8String], , );

    }

    if (bcdstr.length% == )

    {

        bbte[leng-] = (int)strtoul([[bcdstr substringWithRange:NSMakeRange((leng - )*, )]UTF8String], , ) *;

    }else

    {

        bbte[leng-] = (int)strtoul([[bcdstr substringWithRange:NSMakeRange((leng - )*, )]UTF8String], , );

    }

    NSData *de = [[NSData alloc]initWithBytes:bbte length:leng];

    NSLog(@"%@",de); //<61626331 3233>

4、十六进制转成ASCII

//十六进制转ASCII  31 = 1  44 = D

-(NSString *)stringFromHexString:(NSString *)hexString

{

    char *myBuffer = (char *)malloc((int)[hexString length] /  + );

    bzero(myBuffer, [hexString length] /  + );

    for (int i = ; i < [hexString length] - ; i += ) {

        unsigned int anInt;

        NSString * hexCharStr = [hexString substringWithRange:NSMakeRange(i, )];

        NSScanner * scanner = [[NSScanner alloc] initWithString:hexCharStr] ;

        [scanner scanHexInt:&anInt];

        myBuffer[i / ] = (char)anInt;

    }

    NSString *unicodeString = [NSString stringWithCString:myBuffer encoding:];

    return unicodeString;

}

二、MD5计算

1、字符串的MD5计算

+(NSString *)md5HexDigest:(NSString *)str

{

    const char *original_str = [str UTF8String];

    unsigned char result[CC_MD5_DIGEST_LENGTH]; //16

    CC_MD5(original_str, (int)strlen(original_str), result);

    NSMutableString *hash = [NSMutableString string];

    for (int i = ; i < ; i++)

    {

        [hash appendFormat:@"%02x", result[i]];//两位表示 不足两位补0

    }

    return [hash lowercaseString];

}

2、字符串的MD5计算

+(NSString*)getMD5WithData:(NSData *)data

{

    //不要把数据流先转成char，不然如果遇到00字节就不会计算00后面数据

    unsigned char result[];

    CC_MD5([data bytes], (int)[data length], result);

    NSMutableString *hash = [NSMutableString string];

    for (int i = ; i < ; i++)

    {

        [hash appendFormat:@"%02x", result[i]];//x就是小写的字母，X就是大写的字母，2个字节不足补0

    }

    return hash;

}

三、CRC16验证计算（需要一个头文件）

+(NSData *)crc16Digest:(NSData *)data

{

    Byte *bs = (Byte *)[data bytes];

    int len = (int)data.length;

    unsigned char acc[len];

    for (int i = ; i<len; i++)

    {

        acc[i] =bs[i];

    }

    unsigned short intup = CRC16(acc, len); //调用这个要导入1个头文件

    NSString *str = [[NSString alloc]initWithFormat:@"%x",intup];

    int b = -(int)str.length;

    NSString *ss=[NSString new];

    for (int i =; i<b; i++){

        ss = [NSString stringWithFormat:@"0%@",ss];

    }

    ss = [NSString stringWithFormat:@"%@%@",ss,str];

    //高低位转换

    NSString *stra = [ss substringToIndex:];

    NSString *end = [ss substringFromIndex:];

    NSString *yy = [NSString stringWithFormat:@"%@%@",end,stra];

    NSData *rrdata = [SingMent transcodebcd:yy];

    return rrdata;

}

iOS BCD码、数据流、字节和MD5计算的相关教程结束。