Simple-Config

A parser for a simple configuration file format.

To use this library you just need to add config.c and config.h to your project.

Example

# A sample config file for a generic text editor
font: "JetBrainsMono Nerd Font"
font.size: 14
zoom: 1.5
line_numbers: true
bg.color: rgba(255, 255, 255, 1)

int
main(void)
{
    CfgError err;
    CfgEntry *entries = malloc(64 * sizeof(CfgEntry));
    Cfg cfg = {.entries = entries, .capacity = 64};

    int res = cfg_parse_file("sample.cfg", &cfg, &err);

    if (res != 0) {
        cfg_fprint_error(stderr, &err);
        free(entries);
        return 1;
    }

    // Default value         --------------------+
    // (if key is not found)                     |
    //                                           v
    char* font = cfg_get_string(&cfg, "font", "Noto Sans Mono");
    int font_size = cfg_get_int(&cfg, "font.size", 12);
    float zoom = cfg_get_float(&cfg, "zoom", 1.0);
    bool line_num = cfg_get_bool(&cfg, "line_numbers", true);
    CfgColor bg = cfg_get_color(&cfg, "bg.color",
                                      (CfgColor){
                                          .r = 255,
                                          .g = 255,
                                          .b = 255,
                                          .a = 1,
                                      });

    free(entries);
    return 0;
}

A fully working example can be found in example.c, to build it just run make.

Implementations

The program has two implementations:

• The first one uses static arrays to store keys and strings. For this reason, a maximum length must be defined at compile time.

• The second one uses a memory arena to address this limitation.

Another viable strategy might be to represent keys and strings as pointers to "slices" within the source string.

Specification

• A config file must have the .cfg file extension

• A config file consists of zero or more lines

• A line is composed of a key, a colon (:), a value, and a newline (\n)

• A key is a sequence of one or more alphabetic characters, dots (.) or underscores (_)

• A value can be one of the following types: string, boolean, integer, float, or color

• A comment starts with a # and can placed on its own line or at the end of an entry

Data types

• String: A string is enclosed within double quotes (") and can contain alphabetic characters, punctuation, digits, and blanks (spaces or tabs). Double quotes are not allowed inside a string.

• Boolean: A boolean is either true or false

• Integer: An integer is a sequence of digits, which may be preceded by a hyphen (-) to indicate a negative value

• Float: A floating-point number consists of a sequence of digits with a decimal point (.), which may be preceded by a hyphen (-) to indicate a negative value

• Color: A color is defined in the rgba(R, G, B, A) format, where R, G, and B are integers between 0 and 255, and A is a floating-point number between 0 and 1

EBNF grammar

cfg    ::= line*
line   ::= key ':' val '\n'
key    ::= (alpha | '.' | '_')+
val    ::= string | bool | int | float | color

string ::= '"' (alpha | punct | digit | blank)+ '"'
alpha  ::= 'a' ... 'z' | 'A' ... 'Z'
punct  ::= '.' | ':' | '~' | '!' | ...
blank  ::= ' ' | '\t'

bool   ::= true | false

int    ::= '-'? digit+
float  ::= '-'? digit+ '.' digit+
digit  ::= '0' ... '9'

color  ::= 'rgba(' digit+ ',' digit+ ',' digit+ ',' digit+ ')'

Acknowledgements

This project was built as a collaborative work by Haru and Cozis.

License

This project uses the GPLv3 license.