C++ 字符串中的字符被忽略

Question

我正在尝试使用 signal11 的 hidapi (here) 写入隐藏设备。在我的故障排除中，我注意到字符串的一部分没有显示到控制台。这是我的代码示例

//device is a hid device and is assigned to in another part of the program.
//dataBuffer is a struct with only a char array called "buffer" and an int which is the size of the array called "size"
void DeviceCommands::Write(hid_device* device, dataBuffer* buf)
{
    std::cout << "Attempting write >> buffer...\n";
    buf->buffer[0] = 0;
    std::cout << "Written to buffer...\n" << "writing buffer to device\n";
    int res = hid_write(device, buf->buffer, sizeof(buf->buffer));
    std::cout << "Write success: "  + '\n';
    std::cout << "Write complete\n";
}

我希望控制台 return 以下内容：

Attempting write >> buffer...
Written to buffer...
writing buffer to device
Write success: (0 if the write succeeds, -1 if it fails)
Write complete

但是，却发生了这种情况：

Attempting write >> buffer...
Written to buffer...
writing buffer to device
ess: Write complete

缺少“Write succ”、结果和换行符，我对 c++ 有点陌生，但我有使用 c# 的经验。我只是很困惑，非常感谢您的帮助，提前致谢并询问您是否需要更多信息！

Answer 1

这一行：

std::cout << "Write success: "  + '\n';

会打印字符串"Write success: "，偏移10个字符，即\n的ascii值。因此你在屏幕上看到 ess。

你可能想要：

std::cout << "Write success: " << res << "\n";

假设 res returns 0 或 -1 根据需要。

Answer 2

不要'add'一个字符到一个字符串。它不会像你期望的那样。

在这里您认为您正在将换行符添加到您的字符串“Write success”，而实际上您是在告诉编译器获取您的常量字符串并且只从第 10 个字符开始流。请记住这里的常量字符串只是一个字符数组，单个字符 '\n' 被转换为数字 10.

您还错过了流式传输的结果。

所以倒数第二行应该是：

std::cout << "Write success: " << res <<  std::endl;

C++ 字符串中的字符被忽略

the characters in a c++ string are being ignored

c++

string

char

hidapi