Configuration files

These functions are declared in the main Allegro header file:

     #include <allegro5/allegro.h>

Allegro supports reading and writing of configuration files with a simple, INI file-like format.

A configuration file consists of key-value pairs separated by newlines. Keys are separated from values by an equals sign (`=`). All whitespace before the key, after the value and immediately adjacent to the equals sign is ignored. Keys and values may have whitespace characters within them. Keys do not need to be unique, but all but the last one are ignored.

The hash (`#`) character is used a comment when it is the first non-whitespace character on the line. All characters following that character are ignored to the end of the line. The hash character anywhere else on the line has no special significance.

Key-value pairs can be optionally grouped into sections, which are declared by surrounding a section name with square brackets (`[` and `]`) on a single line. Whitespace before the opening bracket is ignored. All characters after the trailing bracket are also ignored.

All key-value pairs that follow a section declaration belong to the last declared section. Key-value pairs that don’t follow any section declarations belong to the global section. Sections do not nest.

Here is an example configuration file:

    #  Monster description
    monster name = Allegro Developer

    [weapon 0]
    damage = 443

    [weapon 1]
    damage = 503

It can then be accessed like this (make sure to check for errors in an actual program):

    ALLEGRO_CONFIG* cfg = al_load_config_file("test.cfg");
    printf("%s\n", al_get_config_value(cfg, "", "monster name")); /* Prints: Allegro Developer */
    printf("%s\n", al_get_config_value(cfg, "weapon 0", "damage")); /* Prints: 443 */
    printf("%s\n", al_get_config_value(cfg, "weapon 1", "damage")); /* Prints: 503 */
    al_destroy_config(cfg);

# ALLEGRO_CONFIG

    typedef struct ALLEGRO_CONFIG ALLEGRO_CONFIG;

Source Code

An abstract configuration structure.

Examples:

- ex_config.c
- ex_vsync.c
- ex_stream_seek.c

# ALLEGRO_CONFIG_SECTION

    typedef struct ALLEGRO_CONFIG_SECTION ALLEGRO_CONFIG_SECTION;

Source Code

An opaque structure used for iterating across sections in a configuration structure.

See also: al_get_first_config_section, al_get_next_config_section

Examples:

- ex_config.c

# ALLEGRO_CONFIG_ENTRY

    typedef struct ALLEGRO_CONFIG_ENTRY ALLEGRO_CONFIG_ENTRY;

Source Code

An opaque structure used for iterating across entries in a configuration section.

See also: al_get_first_config_entry, al_get_next_config_entry

Examples:

- ex_config.c

# al_create_config

    ALLEGRO_CONFIG *al_create_config(void)

Source Code

Create an empty configuration structure.

See also: al_load_config_file, al_destroy_config

Examples:

- ex_vsync.c
- ex_draw.c
- ex_logo.c

# al_destroy_config

    void al_destroy_config(ALLEGRO_CONFIG *config)

Source Code

Free the resources used by a configuration structure. Does nothing if passed NULL.

See also: al_create_config, al_load_config_file

Examples:

- ex_config.c
- ex_vsync.c
- ex_stream_seek.c

# al_load_config_file

    ALLEGRO_CONFIG *al_load_config_file(const char *filename)

Source Code

Read a configuration file from disk. Returns NULL on error. The configuration structure should be destroyed with al_destroy_config.

See also: al_load_config_file_f, al_save_config_file

Examples:

- ex_config.c
- ex_vsync.c
- ex_stream_seek.c

# al_load_config_file_f

    ALLEGRO_CONFIG *al_load_config_file_f(ALLEGRO_FILE *file)

Source Code

Read a configuration file from an already open file.

Returns NULL on error. The configuration structure should be destroyed with al_destroy_config. The file remains open afterwards.

See also: al_load_config_file

# al_save_config_file

    bool al_save_config_file(const char *filename, const ALLEGRO_CONFIG *config)

Source Code

Write out a configuration file to disk. Returns true on success, false on error.

See also: al_save_config_file_f, al_load_config_file

Examples:

- ex_config.c
- ex_vsync.c
- ex_draw.c

# al_save_config_file_f

    bool al_save_config_file_f(ALLEGRO_FILE *file, const ALLEGRO_CONFIG *config)

Source Code

Write out a configuration file to an already open file.

Returns true on success, false on error. The file remains open afterwards.

See also: al_save_config_file

# al_add_config_section

    void al_add_config_section(ALLEGRO_CONFIG *config, const char *name)

Source Code

Add a section to a configuration structure with the given name. If the section already exists then nothing happens.

# al_remove_config_section

    bool al_remove_config_section(ALLEGRO_CONFIG *config, char const *section)

Source Code

Remove a section of a configuration.

Returns true if the section was removed, or false if the section did not exist.

Since: 5.1.5

Examples:

- ex_config.c

# al_add_config_comment

    void al_add_config_comment(ALLEGRO_CONFIG *config,
       const char *section, const char *comment)

Source Code

Add a comment in a section of a configuration. If the section doesn’t yet exist, it will be created. The section can be NULL or “” for the global section.

The comment may or may not begin with a hash character. Any newlines in the comment string will be replaced by space characters.

See also: al_add_config_section

# al_get_config_value

    const char *al_get_config_value(const ALLEGRO_CONFIG *config,
       const char *section, const char *key)

Source Code

Gets a pointer to an internal character buffer that will only remain valid as long as the ALLEGRO_CONFIG structure is not destroyed. Copy the value if you need a copy. The section can be NULL or “” for the global section. Returns NULL if the section or key do not exist.

See also: al_set_config_value

Examples:

- ex_config.c
- ex_vsync.c
- ex_stream_seek.c

# al_set_config_value

    void al_set_config_value(ALLEGRO_CONFIG *config,
       const char *section, const char *key, const char *value)

Source Code

Set a value in a section of a configuration. If the section doesn’t yet exist, it will be created. If a value already existed for the given key, it will be overwritten. The section can be NULL or “” for the global section.

For consistency with the on-disk format of config files, any leading and trailing whitespace will be stripped from the value. If you have significant whitespace you wish to preserve, you should add your own quote characters and remove them when reading the values back in.

See also: al_get_config_value

Examples:

- ex_config.c
- ex_resize2.c
- ex_vsync.c

# al_remove_config_key

    bool al_remove_config_key(ALLEGRO_CONFIG *config, char const *section,
       char const *key)

Source Code

Remove a key and its associated value in a section of a configuration.

Returns true if the entry was removed, or false if the entry did not exist.

Since: 5.1.5

Examples:

- ex_config.c

# al_get_first_config_section

    char const *al_get_first_config_section(ALLEGRO_CONFIG const *config,
       ALLEGRO_CONFIG_SECTION **iterator)

Source Code

Returns the name of the first section in the given config file. Usually this will return an empty string for the global section, even it contains no values. The `iterator` parameter will receive an opaque iterator which is used by al_get_next_config_section to iterate over the remaining sections.

The returned string and the iterator are only valid as long as no change is made to the passed ALLEGRO_CONFIG.

See also: al_get_next_config_section

Examples:

- ex_config.c

# al_get_next_config_section

    char const *al_get_next_config_section(ALLEGRO_CONFIG_SECTION **iterator)

Source Code

Returns the name of the next section in the given config file or NULL if there are no more sections. The `iterator` must have been obtained with al_get_first_config_section first.

See also: al_get_first_config_section

Examples:

- ex_config.c

# al_get_first_config_entry

    char const *al_get_first_config_entry(ALLEGRO_CONFIG const *config,
       char const *section, ALLEGRO_CONFIG_ENTRY **iterator)

Source Code

Returns the name of the first key in the given section in the given config or NULL if the section is empty. The `iterator` works like the one for al_get_first_config_section.

The returned string and the iterator are only valid as long as no change is made to the passed ALLEGRO_CONFIG.

See also: al_get_next_config_entry

Examples:

- ex_config.c

# al_get_next_config_entry

    char const *al_get_next_config_entry(ALLEGRO_CONFIG_ENTRY **iterator)

Source Code

Returns the next key for the iterator obtained by al_get_first_config_entry. The `iterator` works like the one for al_get_next_config_section.

Examples:

- ex_config.c

# al_merge_config

    ALLEGRO_CONFIG *al_merge_config(const ALLEGRO_CONFIG *cfg1,
        const ALLEGRO_CONFIG *cfg2)

Source Code

Merge two configuration structures, and return the result as a new configuration. Values in configuration ‘cfg2’ override those in ‘cfg1’. Neither of the input configuration structures are modified. Comments from ‘cfg2’ are not retained.

See also: al_merge_config_into

# al_merge_config_into

    void al_merge_config_into(ALLEGRO_CONFIG *master, const ALLEGRO_CONFIG *add)

Source Code

Merge one configuration structure into another. Values in configuration ‘add’ override those in ‘master’. ‘master’ is modified. Comments from ‘add’ are not retained.

See also: al_merge_config

Allegro version 5.2.10 - Last updated: 2024-12-29 03:54:49 UTC