Question

The title is pretty self-explanatory: does anyone know of a (good) properties file reader library for C or, if not, C++?

Edit: To be specific, I want a library which handles the .properties file format used in Java: http://en.wikipedia.org/wiki/.properties

Answer 1

STLSoft‘s 1.10 alpha contains a platformstl::properties_file class. It can be used to read from a file:

using platformstl::properties_file;

properties_file  properties("stuff.properties");

properties_file::value_type  value = properties["name"];

or from memory:

properties_file  properties(
    "name0=value1\n name1 value1 \n name\\ 2 : value\\ 2  ",
    properties_file::contents);

properties_file::value_type  value0 = properties["name0"];

properties_file::value_type  value1 = properties["name1"];

properties_file::value_type  value2 = properties["name 2"];

Looks like the latest 1.10 release has a bunch of comprehensive unit-tests, and that they’ve upgraded the class to handle all the rules and examples given in the Java documentation.

The only apparent rub is that the value_type is an instance of stlsoft::basic_string_view (described in this Dr Dobb’s article), which is somewhat similar to std::string, but doesn’t actually own its memory. Presumably they do this to avoid unneccessary allocations, presumably for performance reasons, which is something the STLSoft design holds dear. But it means that you can’t just write

std::string  value0 = properties["name0"];

You can, however, do this:

std::string  value0 = properties["name0"].c_str();

and this:

std::cout << properties["name0"];

I’m not sure I agree with this design decision, since how likely is it that reading properties – from file or from memory – is going to need the absolute last cycle. I think they should change it to use std::string by default, and then use the “string view” if explicitly required.

Other than that, the properties_file class looks like it does the trick.