# Configuration files

These functions are declared in the main Allegro header file:

~~~~c
 #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:

~~~~ini
# 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):

~~~~c
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);
~~~~

## API: ALLEGRO_CONFIG

An abstract configuration structure.

## API: ALLEGRO_CONFIG_SECTION

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

See also: [al_get_first_config_section], [al_get_next_config_section]

## API: ALLEGRO_CONFIG_ENTRY

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

See also: [al_get_first_config_entry], [al_get_next_config_entry]

## API: al_create_config

Create an empty configuration structure.

See also: [al_load_config_file], [al_destroy_config]

## API: al_destroy_config

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

See also: [al_create_config], [al_load_config_file]

## API: al_load_config_file

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]

## API: al_load_config_file_f

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]

## API: al_save_config_file

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]

## API: al_save_config_file_f

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]

## API: al_add_config_section

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

## API: al_add_config_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.

See also: [al_add_config_section]

## API: al_get_config_value

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]

## API: al_set_config_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.

See also: [al_get_config_value]

## API: al_get_first_config_section

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.

See also: [al_get_next_config_section]

## API: al_get_next_config_section

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]

## API: al_get_first_config_entry

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]

## API: al_get_next_config_entry

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].

## API: al_merge_config

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]

## API: al_merge_config_into

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]

