Filesystem

Collaboration diagram for Filesystem:

Functions
std::string	Utopia::DataIO::expanduser (const std::string &path)
	Expands a path with a leading ~ character into an absolute path.
std::string	Utopia::DataIO::get_abs_filepath (const Config &cfg)
	Extracts an absolute file path from a configuration.

Detailed Description

Filesystem tools

The Filesystem module contains tools that make interacting with the filesystem more convenient, e.g. to generate file paths from the configuration.

Function Documentation

expanduser()

std::string Utopia::DataIO::expanduser

(

const std::string &

path

)

Expands a path with a leading ~ character into an absolute path.

This function uses the environment variable HOME and replaces a leading ~ character with that path. If there was no leading ~ character, the given path is returned.

Parameters

path	The path to expand

Exceptions

If	the given path needs expansion but no HOME environment variable was set.

                                             {
    using namespace std::string_literals;
 
    if (path.empty() or path.substr(0, 1) != "~"s) {
        return path;
    }
 
    const std::string HOME = std::getenv("HOME");
    if (HOME.empty()) {
        throw std::invalid_argument(
            "Cannot expand path because the environment variable 'HOME' was "
            "not set! Use an absolute path to specify the given path: "
            + path
        );
    }
    return HOME + path.substr(1, std::string::npos);
}

get_abs_filepath()

std::string Utopia::DataIO::get_abs_filepath

(

const Config &

cfg

)

Extracts an absolute file path from a configuration.

Expected keys: filename, base_dir (optional). If no base_dir key is present, will prepend the current working directory.

If the base directory or the filename specify a relative directory, the resulting absolute path will start from the current working directory.

Furthermore, this function will call expanduser to allow using the ~ character to refer to the home directory.

Parameters

cfg	The configuration node with required key filename and optional key base_dir.

                                               {
    using std::filesystem::path;
    using std::filesystem::current_path;
 
    const path filename = expanduser(get_as<std::string>("filename", cfg));
 
    path p = current_path();
    if (cfg["base_dir"]) {
        // By using append, we ensure that p remains an absolute path:
        //  - if base_dir is relative, will append, making it absolute
        //  - if base_dir is absolute, will overwrite current_path
        p.append(expanduser(get_as<std::string>("base_dir", cfg)));
    }
    p /= filename;
    return expanduser(p);
}