Convert the string to hexadecimal string and display it

Convert the string to 16 Hexadecimal string and display

Barrage agreement I

// -  Bytes sent 
5d0000005d000000b1020000xxxxxxx00
5d000000 :  Send content length  ( The length of the content  = (5d000000  The length of the content  4 byte ) + (b1020000  Version information length  4 byte )  (xxxxxxx) The length of  + (00  Message tail  1 byte )  )
5d000000 :  Length of content sent  ( The length of the content  = (5d000000  The length of the content  4 byte ) + (b1020000  Version information length  4 byte )  (xxxxxxx) The length of  + (00  Message tail  1 byte )  )
b1020000 :  Version information characters  (b1020000 4 byte )
xxxxxxx :  Sent content ;
00 :  Fixed characters at the end 

// -  String rotation data
NSData *data = [self.msgContent dataUsingEncoding:NSUTF8StringEncoding];
NSMutableString *content = [NSMutableString string];

// -  Fixed characters inside 
char tail = 0x00;
int version = 0x000002b1;
int length = (int)(sizeof(length) +  sizeof(version) + data.length + sizeof(tail));

// -  Byte order conversion 
tail = CFSwapInt32(tail);
version = CFSwapInt32(version);
length = CFSwapInt32(length);

// -  Concatenate numbers into strings ( With 16 The form of base , %08x  If the number is  0x08,  Just change it to  0x00000008)
NSString *header = [NSString stringWithFormat:@"%08x%08x%08x", length, length, version];

// -  take bytes Each character in is spliced into a string ( With 16 The form of base , %08x  If the number is  0x08,  Just change it to  0x00000008)
// -  The use here is  unsigned char  without  char  There is a reason   for example , " I " The code of is  E6 88 91,  Use char  Will turn into  FFFFFFE6 FFFFFF88 FFFFFF91,  While using  unsigned char  Will turn into  E68891  [ Data address ](https://www.geek-share.com/detail/2764755658.html)
for (int i = 0; i < data.length; i++) {
    unsigned char va = *(char *)(data.bytes + i);
    [content appendFormat:@"%02x", va];
}
// -  Stitching result string 
NSString *result = [NSString stringWithFormat:@"%@%@%02x", header, content, tail];
return result;

Barrage agreement II

    NSDictionary *contentDic = [self.msgContent toDictionary];
    if (!contentDic) return nil;
    
    NSData *data = [NSJSONSerialization dataWithJSONObject:contentDic options:NSJSONWritingPrettyPrinted error:nil];
    NSMutableString *content = [NSMutableString string];
    int headerLenth = 16;
    int contentLen = CFSwapInt32LittleToHost((int)(data.length + headerLenth));
    short headerLen = CFSwapInt16LittleToHost(headerLenth);
    short version = CFSwapInt16LittleToHost(1);
    int operation = CFSwapInt32LittleToHost(self.operationCode);
    int seq = CFSwapInt32LittleToHost(0);
    NSString *header = [NSString stringWithFormat:@"%08x%04x%04x%08x%08x", contentLen, headerLen, version, operation, seq];

    for (int i = 0; i < data.length; i++) {
        unsigned char va = *(char *)(data.bytes + i);
        [content appendFormat:@"%02x", va];
    }
    NSString *result = [NSString stringWithFormat:@"%@%@", header, content];
    return  result;