Configuration files

ALLEGRO_CONFIG
al_create_config
al_destroy_config
al_load_config_file
al_load_config_file_f
al_save_config_file
al_save_config_file_f
al_add_config_section
al_add_config_comment
al_get_config_value
al_set_config_value
al_get_first_config_section
al_get_next_config_section
al_get_first_config_entry
al_get_next_config_entry
al_merge_config
al_merge_config_into

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;

An abstract configuration structure.

al_create_config

ALLEGRO_CONFIG *al_create_config(void)

Create an empty configuration structure.

al_destroy_config

void al_destroy_config(ALLEGRO_CONFIG *config)

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

al_load_config_file

ALLEGRO_CONFIG *al_load_config_file(const char *filename)

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

al_load_config_file_f

ALLEGRO_CONFIG *al_load_config_file_f(ALLEGRO_FILE *file)

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.

al_save_config_file

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

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

al_save_config_file_f

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

Write out a configuration file to an already open file.

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

al_add_config_section

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

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

al_add_config_comment

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

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.

al_get_config_value

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

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.

al_set_config_value

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

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.

al_get_first_config_section

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

Returns the name of the first section in the given config file. Usually this will return an empty string for the global section. 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.

al_get_next_config_section

char const *al_get_next_config_section(ALLEGRO_CONFIG_SECTION **iterator)

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.

al_get_first_config_entry

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

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.

al_get_next_config_entry

char const *al_get_next_config_entry(ALLEGRO_CONFIG_ENTRY **iterator)

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.

al_merge_config

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

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.

al_merge_config_into

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

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