C++：当我将值赋给缓冲区时，它不起作用

好的，所以我有一段代码。这会将标题的内容插入缓冲区中：C++：当我将值赋给缓冲区时，它不起作用

buffer = (uint8_t*)malloc(totalSize); 
buffer[0] = ((header.sequenceNumber >> 24) & 0xFF); 
buffer[1] = ((header.sequenceNumber >> 16) & 0xFF); 
buffer[2] = ((header.sequenceNumber >> 8) & 0xFF); 
buffer[3] = (header.sequenceNumber & 0xFF); 
buffer[4] = ((header.ackNumber >> 24) & 0xFF); 
buffer[5] = ((header.ackNumber >> 16) & 0xFF); 
buffer[6] = ((header.ackNumber >> 8) & 0xFF); 
buffer[7] = (header.ackNumber & 0xFF); 
buffer[8] = ((header.connectionId >> 8) & 0xFF); 
buffer[9] = (header.connectionId & 0xFF); 
buffer[10] = (0 & 0xFF); 
unsigned i = (((unsigned)header.ack) << 2) + (((unsigned)header.syn) << 1) + (unsigned)header.fin; 
buffer[11] = (i & 0xFF);

，并且缓冲区内容完全错误。我试图通过添加这一段代码调试：

std::cerr << "DEBUG: Values are: " 
    << ((header.sequenceNumber >> 24) & 0xFF) << ", " 
    << ((header.sequenceNumber >> 16) & 0xF) << ", " 
    << ((header.sequenceNumber >> 8) & 0xFF) << ", " 
    << (header.sequenceNumber & 0xFF) << ", " 
    << ((header.ackNumber >> 24) & 0xFF) << ", " 
    << ((header.ackNumber >> 16) & 0xFF) << ", " 
    << ((header.ackNumber >> 8) & 0xFF) << ", " 
    << (header.ackNumber & 0xFF) << ", " 
    << ((header.connectionId >> 8) & 0xFF) << ", " 
    << (header.connectionId & 0xFF) << ", " 
    << (0 & 0xFF) << ", " 
    << (i & 0xFF) << endl; 

std::cerr << "DEBUG: Buffer header is: " 
    << buffer[0] << ", " << buffer[1] << ", " << buffer[2] << ", " 
    << buffer[3] << ", " << buffer[4] << ", " << buffer[5] << ", " 
    << buffer[6] << ", " << buffer[7] << ", " << buffer[8] << ", " 
    << buffer[9] << ", " << buffer[10] << ", " << buffer[11] << endl; 

std::cerr << "DEBUG: getBuffer ends. The size is " << totalSize 
    << ". The buffer is " << buffer << endl;

而这被示出在控制台：

DEBUG: Values are: 0, 0, 48, 57, 0, 0, 0, 0, 0, 0, 0, 2 
DEBUG: Buffer header is: , , 0, 9, , , , , , , , 
DEBUG: getBuffer ends. The size is 12. The buffer is

的12个值是正确的。但缓冲区的12个元素是完全错误的。

来源

2017-05-17 NormalGuy

malloc？你正在编写C++。使用std :: vector。 –

我认为缓冲区内容是正确的，但是您将其报告给stderr的方式失败。

std::cerr << "DEBUG: Buffer header is: " 
      << buffer[0];

写入uint8_t到stderr（如果buffer是uint8_t*类型的），但是这只是一个unsigned char因此使用ASCII编码。要获得正确的整数值，请使用

std::cerr << "DEBUG: Buffer header is: " 
      << int(buffer[0]);

来源

2017-05-17 09:35:07 Walter

太好了。我改变了一点，到（int）缓冲区[0]，它的工作原理。 – NormalGuy

@NormalGuy很高兴帮助。 Btw，'int（buffer [0]）'是C++风格，'（int）buffer [0]'是古老的C风格并且不推荐（但是你似乎是C黑客，因为你使用malloc ）'）。 – Walter

C++：当我将值赋给缓冲区时，它不起作用

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