最近项目中要用到socket通讯，由于涉及到组包问题，所以需要数据类型之间的来回转换，现在分享出来
如果想要请教Socket的问题请留言，我会随时回答的
1. int类型转16进制hexstring
//int 转16进制
- (NSString *)hexFromInt:(NSInteger)val {
    return [NSString stringWithFormat:@"%X", val];
2.16进制转换为NSData
+ (NSData *)dataFromHexString:(NSString *)hexString
    NSAssert((hexString.length > 0) && (hexString.length % 2 == 0), @"hexString.length mod 2 != 0");
    NSMutableData *data = [[NSMutableData alloc] init];
    for (NSUInteger i=0; i<hexString.length; i+=2) {
        NSRange tempRange = NSMakeRange(i, 2);
        NSString *tempStr = [hexString substringWithRange:tempRange];
        NSScanner *scanner = [NSScanner scannerWithString:tempStr];
        unsigned int tempIntValue;
        [scanner scanHexInt:&tempIntValue];
        [data appendBytes:&tempIntValue length:1];
    return data;
3.NSData转16进制
+ (NSString *)hexStringFromData:(NSData *)data
    NSAssert(data.length > 0, @"data.length <= 0");
    NSMutableString *hexString = [[NSMutableString alloc] init];
    const Byte *bytes = data.bytes;
    for (NSUInteger i=0; i<data.length; i++) {
        Byte value = bytes[i];
        Byte high = (value & 0xf0) >> 4;
        Byte low = value & 0xf;
        [hexString appendFormat:@"%x%x", high, low];
    }//for
    return hexString;
4.NSString转int类型
int a = [aStrinng  intValue];
5.uint8转NSData(占两位)
+ (NSData *)byteFromUInt8:(uint8_t)val
    NSMutableData *valData = [[NSMutableData alloc] init];
    unsigned char valChar[1];
    valChar[0] = 0xff & val;
    [valData appendBytes:valChar length:1];
    return [self dataWithReverse:valData];
6.uint16 转NSData（占四位）
+ (NSData *)bytesFromUInt16:(uint16_t)val
    NSMutableData *valData = [[NSMutableData alloc] init];
    unsigned char valChar[2];
    valChar[0] = 0xff & val;
    valChar[1] = (0xff00 & val) >> 8;
    [valData appendBytes:valChar length:2];
    return [self dataWithReverse:valData];
7.Uint32 转NSData（占八位）
+ (NSData *)bytesFromUInt32:(uint32_t)val
    NSMutableData *valData = [[NSMutableData alloc] init];
    unsigned char valChar[4];
    valChar[0] = 0xff & val;
    valChar[1] = (0xff00 & val) >> 8;
    valChar[2] = (0xff0000 & val) >> 16;
    valChar[3] = (0xff000000 & val) >> 24;
    [valData appendBytes:valChar length:4];
    return [self dataWithReverse:valData];
8.NSString 转NSData
NSData *data = [aString  dataUsingEncoding:NSUTF8StringEncoding];// 通过utf-8转为data
9.NSData转Uint8
+ (uint8_t)uint8FromBytes:(NSData *)fData
    NSAssert(fData.length == 1, @"uint8FromBytes: (data length != 1)");
    NSData *data = fData;
    uint8_t val = 0;
    [data getBytes:&val length:1];
    return val;
10.NSData转Uint16
+ (uint16_t)uint16FromBytes:(NSData *)fData
    NSAssert(fData.length == 2, @"uint16FromBytes: (data length != 2)");
    NSData *data = [self dataWithReverse:fData];;
    uint16_t val0 = 0;
    uint16_t val1 = 0;
    [data getBytes:&val0 range:NSMakeRange(0, 1)];
    [data getBytes:&val1 range:NSMakeRange(1, 1)];
    uint16_t dstVal = (val0 & 0xff) + ((val1 << 8) & 0xff00);
    return dstVal;
11.NSData转Uint32
+ (uint32_t)uint32FromBytes:(NSData *)fData
    NSAssert(fData.length == 4, @"uint32FromBytes: (data length != 4)");
    NSData *data = [self dataWithReverse:fData];
    uint32_t val0 = 0;
    uint32_t val1 = 0;
    uint32_t val2 = 0;
    uint32_t val3 = 0;
    [data getBytes:&val0 range:NSMakeRange(0, 1)];
    [data getBytes:&val1 range:NSMakeRange(1, 1)];
    [data getBytes:&val2 range:NSMakeRange(2, 1)];
    [data getBytes:&val3 range:NSMakeRange(3, 1)];
    uint32_t dstVal = (val0 & 0xff) + ((val1 << 8) & 0xff00) + ((val2 << 16) & 0xff0000) + ((val3 << 24) & 0xff000000);
    return dstVal;
12.NSData转Byte
   uint8_t byteArray[[data length]];
    [data getBytes:&byteArray length:[data length]];
    for (int i = 0; i < [data length] ; i++ ) {
        Byte byte = byteArray[i];
        NSLog(@"--byte%x",byte);
13.NSData的拼接
[data1 appendData:data2];
14.NSData转int (用CFSwapInt32BigToHost)
NSData *data4 = [completeData subdataWithRange:NSMakeRange(0, 4)];
int value = CFSwapInt32BigToHost(*(int*)([data4 bytes]));
以上可能会用到的反转字节序列代码
+ (NSData *)dataWithReverse:(NSData *)srcData
    //    NSMutableData *dstData = [[NSMutableData alloc] init];
    //    for (NSUInteger i=0; i<srcData.length; i++) {
    //        [dstData appendData:[srcData subdataWithRange:NSMakeRange(srcData.length-1-i, 1)]];
    //    }//for
    NSUInteger byteCount = srcData.length;
    NSMutableData *dstData = [[NSMutableData alloc] initWithData:srcData];
    NSUInteger halfLength = byteCount / 2;
    for (NSUInteger i=0; i<halfLength; i++) {
        NSRange begin = NSMakeRange(i, 1);
        NSRange end = NSMakeRange(byteCount - i - 1, 1);
        NSData *beginData = [srcData subdataWithRange:begin];
        NSData *endData = [srcData subdataWithRange:end];
        [dstData replaceBytesInRange:begin withBytes:endData.bytes];
        [dstData replaceBytesInRange:end withBytes:beginData.bytes];
    }//for
    return dstData;
————————————————
                            
2022-07-30：以下go语言代码输出什么？A：[]byte{} []byte；B：[]byte{} []uint8；C：[]uint8{} []byte；D：[]uin8{} []uint8。
                            
这是一个bug，说正确答案应该是[]uint8{}[]uint8才对，因为byten8{}[]uint8。有人说是网络层，也有人说是数据链路层。...