C ++非空终止字符数组输出 [英] C++ non null terminated char array outputting

问题描述

实际上，我正在接收数据包，然后打印他们的字段。

现在，由于这些字段不是空值终止的，例如，一个大小为512的数据段，但可能或可能不会被完全占用。

当我写这个数据到文件我使用简单的<<重载函数，它不知道任何关于实际数据的事情，只查找数据段的终止。

那么，我怎么能告诉输出函数只写这么多特定字节数？

而不是使用每次调用昂贵的代码：

 在这里输入代码
 
 bytescopied = strncpy（dest，src，maxbytes）; 
 
 if（bytescopied< 0）{//表示没有复制字节，参数错误
 
 throw（fit）; //错误处理程序在这里
 
} else if（bytescopied == maxbytes）{
 
 dest [maxbytes-1] ='\0'; // force null terminator 
 
} 
  

解决方案

如果您想要精确地 maxbytes 字节，请使用写方法

  stream.write（buffer，maxbytes）; 
  

如果你可以在缓冲区中有更少的字节，你怎么知道你的缓冲区包含多少？如果'\0'标记缓冲区结束，您可以写入：

  stream.write（buffer，std :: find（buffer，buffer + maxbytes，'\0'） -  buffer）; 
  

I was trying to output a not null terminated char array to a file.

Actual thing is, I am receiving packets and then printing their fields.

Now as these fields are not null terminated, for example, a data segment which has size of 512 but may or may not be completely occupied.

When I write this data to a file I am using simple << overloaded function which does not know any thing about actual data and only looks for termination of data segment.

So, how can I tell the output function to write only this much specific number of bytes?

Instead of using something like this which is expensive to call each time:

enter code here  

bytescopied = strncpy(dest, src, maxbytes);

if (bytescopied < 0) { // indicates no bytes copied, parameter error

    throw(fit);          // error handler stuff here

 } else if (bytescopied == maxbytes) {

    dest[maxbytes-1] = '\0';   // force null terminator

}

解决方案

If you want to put exactly maxbytes bytes, use write method

stream.write(buffer, maxbytes);

If you can have less bytes in buffer, how do you know how many of them your buffer contains? If '\0' marks buffer end, you can write:

stream.write(buffer, std::find(buffer, buffer+maxbytes, '\0') - buffer);

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