[AD] ops, forgot attachment

["Angelo Mottola" <a.mottola@xxxxxxxxxx>]

here it is

--
Angelo Mottola
lillo@xxxxxxxxxx

Allegro configuration routines ramblings

Dealing with strings as config keys has some advantages, but also many disadvantages.
If we want to use the config routines for as many purposes as possible, it is necessary
these to be fast. Also, having strings separated by / all over your sources isn't pretty and
asks for troubles when it comes to debugging.
Using integers as keys to the config routines is faster, looks (reads) better and people is
already accustomed to it. To overcome troubles with this and to keep the routines as
general purpose as possible, I've thought about the following structure layout:


typedef struct AL_CONFIG_ENTRY
{
	AL_CONFIG_ENTRY *next;	/* Next element in linked list */
	int key;					/* Key for this element */
	char *name;				/* Key name, if any */
	int type;					/* Key data type */
	union {
		int value;				/* Integer data */
		double fvalue;			/* Floating point data */
		void *ptr;				/* Pointer data */
	} data;
	void (*read_hook)(AL_CONFIG_ENTRY *entry);	/* On-read hook */
	void (*write_hook)(AL_CONFIG_ENTRY *entry);	/* On-write hook */
} AL_CONFIG_ENTRY;


typedef struct AL_CONFIG
{
	struct AL_CONFIG **child;	/* Dynamic array of children */
	char *name;				/* Configuration name */
	int key_min;				/* Minimum key value accepted by this config */
	int key_max;				/* Maximum key value accepted by this config */
	AL_CONFIG_ENTRY **entry;	/* Hash table of stored entries */
	void (*read_hook)(AL_CONFIG_ENTRY *entry);	/* On-read hook */
	void (*write_hook)(AL_CONFIG_ENTRY *entry);	/* On-write hook */
} AL_CONFIG;

An AL_CONFIG has a range of keys; this means that it only accepts keys whose values
and in that range. When accessing data, the user has to specify an AL_CONFIG on
which to work; this can be the private Allegro root config as well as a sub config or a
completely custom config. The data key is compared with the range of the specified
config; if it matches, it looks for the key in the config hash table; if it doesn't match, it
looks for the key in each of its child configs recursively. When (if) the key is found, if the
specified key hooks are set (read or write), they get called. If they're not set, the hooks
of the AL_CONFIG of the found key are checked.
When setting a key, you specify just the AL_CONFIG, the key integer value and the data.
No key name is saved. This means that when saving the config to disk, that key will not
be saved as there's no key name associated with it. If you want the key data to be
written to disk when saving, you have to call

al_set_key_name(AL_CONFIG *config, int key, char *name);

This will set the key name internally, so that when saving the key will be identified by
its name.

/* Create and destroy configs */
AL_CONFIG *al_create_config(AL_CONFIG *parent, char *name, int key_min, int key_max);
void al_destroy_config(AL_CONFIG *config);

/* Data handling */
/* If passed NULL as "config", the private Allegro root config is used */
int al_set_bool(AL_CONFIG *config, int key, int value);
int al_set_int(AL_CONFIG *config, int key, int value);
int al_set_string(AL_CONFIG *config, int key, char *string);
....
int al_get_bool(AL_CONFIG *config, int key);
int al_get_int(AL_CONFIG *config, int key);
char *al_get_string(AL_CONFIG *config, int key);
....

For example you'll have:

(internally in Allegro:)
....
/* the root config doesn't accept any key; it just stores sub configs */
#define AL_CONFIG_KEY_MIN			0
#define AL_CONFIG_KEY_MAX			0
....
#define AL_CONFIG_GFX_KEY_MIN		0x100
#define AL_CONFIG_GFX_KEY_MAX		0x200
....
#define AL_WINDOW_X			AL_CONFIG_GFX_KEY_MIN + 10
....
(during internal Allegro initialization:)
al_root_config = al_create_config(NULL, "Allegro", AL_CONFIG_KEY_MIN, AL_CONFIG_KEY_MAX);
al_create_config(al_root_config, "Graphics", AL_CONFIG_GFX_KEY_MIN, AL_CONFIG_GFX_KEY_MAX);
....
(in your program:)
....
al_set_int(NULL, AL_WINDOW_X, 150); /* This has a write hook that automatically makes the program window to move at x=150 */

Attachment: BeOS Attributes
Description: application/be_attribute