在C ++中创建一个简单的配置文件和解析器 [英] Creating a simple configuration file and parser in C++

问题描述

我正在尝试创建一个像这样的简单配置文件

I am trying to create a simple configuration file that looks like this

url = http://mysite.com
file = main.exe
true = 0

希望将配置设置加载到下面列出的程序变量中。

when the program runs, I would like it to load the configuration settings into the programs variables listed below.

string url, file;
bool true_false;

我做了一些研究，这链接似乎有帮助（nucleon的帖子），但我似乎不能得到它的工作，它是太复杂，我不能理解。有一个简单的方法这样做吗？我可以使用 ifstream 加载文件，但这是我自己可以得到的。谢谢！

I have done some research and this link seemed to help (nucleon's post) but I can't seem to get it to work and it is too complicated to understand on my part. Is there a simple way of doing this? I can load the file using ifstream but that is as far as I can get on my own. Thanks!

推荐答案

一般来说，最简单的方法是在两个阶段解析这些典型的配置文件：首先读取行，然后解析

在C ++中，可以使用 std :: getline（）从流中读取行。默认情况下，它会读到下一个'\\\
'（它将消耗，但不返回），你也可以传递一些其他分隔符，使得它成为一个很好的候选人阅读up-to-some-char，如 = 在你的例子中。

In general, it's easiest to parse such typical config files in two stages: first read the lines, and then parse those one by one.
In C++, lines can be read from a stream using std::getline(). While by default it will read up to the next '\n' (which it will consume, but not return), you can pass it some other delimiter, too, which makes it a good candidate for reading up-to-some-char, like = in your example.

为简单起见，以下假设 = 不是由空白包围的 。如果你想在这些位置允许空格，你将战略性地放置是>> std :: ws ，然后从键中删除结尾空格。但是，IMO在语法上增加一点灵活性是不值得配置文件读取器的麻烦。

For simplicity, the following presumes that the = are not surrounded by whitespace. If you want to allow whitespaces at these positions, you will have to strategically place is >> std::ws before reading the value and remove trailing whitespaces from the keys. However, IMO the little added flexibility in the syntax is not worth the hassle for a config file reader.

const char config[] = "url=http://example.com\n"
                      "file=main.exe\n"
                      "true=0";

std::istringstream is_file(config);

std::string line;
while( std::getline(is_file, line) )
{
  std::istringstream is_line(line);
  std::string key;
  if( std::getline(is_line, key, '=') )
  {
    std::string value;
    if( std::getline(is_line, value) ) 
      store_line(key, value);
  }
}

锻炼给读者。）

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