File system routines

These functions are declared in the main Allegro header file:

 #include <allegro5/allegro.h>

These functions allow access to the filesystem. This can either be the real filesystem like your harddrive, or a virtual filesystem like a .zip archive (or whatever else you or an addon makes it do).

ALLEGRO_FS_ENTRY

typedef struct ALLEGRO_FS_ENTRY ALLEGRO_FS_ENTRY;

Source Code

Opaque filesystem entry object. Represents a file or a directory (check with al_get_fs_entry_mode). There are no user accessible member variables.

ALLEGRO_FILE_MODE

typedef enum ALLEGRO_FILE_MODE

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Filesystem modes/types

ALLEGRO_FILEMODE_READ - Readable
ALLEGRO_FILEMODE_WRITE - Writable
ALLEGRO_FILEMODE_EXECUTE - Executable
ALLEGRO_FILEMODE_HIDDEN - Hidden
ALLEGRO_FILEMODE_ISFILE - Regular file
ALLEGRO_FILEMODE_ISDIR - Directory

al_create_fs_entry

ALLEGRO_FS_ENTRY *al_create_fs_entry(const char *path)

Source Code

Creates an ALLEGRO_FS_ENTRY object pointing to path on the filesystem. ‘path’ can be a file or a directory and must not be NULL.

Examples:

al_destroy_fs_entry

void al_destroy_fs_entry(ALLEGRO_FS_ENTRY *fh)

Source Code

Destroys a fs entry handle. The file or directory represented by it is not destroyed. If the entry was opened, it is closed before being destroyed.

Does nothing if passed NULL.

Examples:

al_get_fs_entry_name

const char *al_get_fs_entry_name(ALLEGRO_FS_ENTRY *e)

Source Code

Returns the entry’s filename path. Note that the filesystem encoding may not be known and the conversion to UTF-8 could in very rare cases cause this to return an invalid path. Therefore it’s always safest to access the file over its ALLEGRO_FS_ENTRY and not the path.

On success returns a read only string which you must not modify or destroy. Returns NULL on failure.

Note: prior to 5.1.5 it was written: “… the path will not be an absolute path if the entry wasn’t created from an absolute path”. This is no longer true.

Examples:

al_update_fs_entry

bool al_update_fs_entry(ALLEGRO_FS_ENTRY *e)

Source Code

Updates file status information for a filesystem entry. File status information is automatically updated when the entry is created, however you may update it again with this function, e.g. in case it changed.

Returns true on success, false on failure. Fills in errno to indicate the error.

al_get_fs_entry_mode

uint32_t al_get_fs_entry_mode(ALLEGRO_FS_ENTRY *e)

Source Code

Returns the entry’s mode flags, i.e. permissions and whether the entry refers to a file or directory.

Examples:

al_get_fs_entry_atime

time_t al_get_fs_entry_atime(ALLEGRO_FS_ENTRY *e)

Source Code

Returns the time in seconds since the epoch since the entry was last accessed.

Warning: some filesystems either don’t support this flag, or people turn it off to increase performance. It may not be valid in all circumstances.

Examples:

al_get_fs_entry_ctime

time_t al_get_fs_entry_ctime(ALLEGRO_FS_ENTRY *e)

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Returns the time in seconds since the epoch this entry was created on the filesystem.

Examples:

al_get_fs_entry_mtime

time_t al_get_fs_entry_mtime(ALLEGRO_FS_ENTRY *e)

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Returns the time in seconds since the epoch since the entry was last modified.

Examples:

al_get_fs_entry_size

off_t al_get_fs_entry_size(ALLEGRO_FS_ENTRY *e)

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Returns the size, in bytes, of the given entry. May not return anything sensible for a directory entry.

al_fs_entry_exists

bool al_fs_entry_exists(ALLEGRO_FS_ENTRY *e)

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Check if the given entry exists on in the filesystem. Returns true if it does exist or false if it doesn’t exist, or an error occurred. Error is indicated in Allegro’s errno.

al_remove_fs_entry

bool al_remove_fs_entry(ALLEGRO_FS_ENTRY *e)

Source Code

Delete this filesystem entry from the filesystem. Only files and empty directories may be deleted.

Returns true on success, and false on failure, error is indicated in Allegro’s errno.

al_filename_exists

bool al_filename_exists(const char *path)

Source Code

Check if the path exists on the filesystem, without creating an ALLEGRO_FS_ENTRY object explicitly.

al_remove_filename

bool al_remove_filename(const char *path)

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Delete the given path from the filesystem, which may be a file or an empty directory. This is the same as al_remove_fs_entry, except it expects the path as a string.

Returns true on success, and false on failure. Allegro’s errno is filled in to indicate the error.

Directory functions

al_open_directory

bool al_open_directory(ALLEGRO_FS_ENTRY *e)

Source Code

Opens a directory entry object. You must call this before using al_read_directory on an entry and you must call al_close_directory when you no longer need it.

Returns true on success.

Examples:

al_read_directory

ALLEGRO_FS_ENTRY *al_read_directory(ALLEGRO_FS_ENTRY *e)

Source Code

Reads the next directory item and returns a filesystem entry for it.

Returns NULL if there are no more entries or if an error occurs. Call al_destroy_fs_entry on the returned entry when you are done with it.

This function will ignore any files or directories named . or .. which may exist on certain platforms and may signify the current and the parent directory.

Examples:

al_close_directory

bool al_close_directory(ALLEGRO_FS_ENTRY *e)

Source Code

Closes a previously opened directory entry object.

Returns true on success, false on failure and fills in Allegro’s errno to indicate the error.

Examples:

al_get_current_directory

char *al_get_current_directory(void)

Source Code

Returns the path to the current working directory, or NULL on failure. The returned path is dynamically allocated and must be destroyed with al_free.

Allegro’s errno is filled in to indicate the error if there is a failure. This function may not be implemented on some (virtual) filesystems.

al_change_directory

bool al_change_directory(const char *path)

Source Code

Changes the current working directory to ‘path’.

Returns true on success, false on error.

al_make_directory

bool al_make_directory(const char *path)

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Creates a new directory on the filesystem. This function also creates any parent directories as needed.

Returns true on success (including if the directory already exists), otherwise returns false on error. Fills in Allegro’s errno to indicate the error.

al_open_fs_entry

ALLEGRO_FILE *al_open_fs_entry(ALLEGRO_FS_ENTRY *e, const char *mode)

Source Code

Open an ALLEGRO_FILE handle to a filesystem entry, for the given access mode. This is like calling al_fopen with the name of the filesystem entry, but uses the appropriate file interface, not whatever was set with the latest call to al_set_new_file_interface.

Returns the handle on success, NULL on error.

ALLEGRO_FOR_EACH_FS_ENTRY_RESULT

typedef enum ALLEGRO_FOR_EACH_FS_ENTRY_RESULT {

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Return values for the callbacks of al_for_each_fs_entry and for that function itself.

ALLEGRO_FOR_EACH_FS_ENTRY_ERROR - An error ocurred.
ALLEGRO_FOR_EACH_FS_ENTRY_OK - Continue normally and recurse into directories.
ALLEGRO_FOR_EACH_FS_ENTRY_SKIP - Continue but do NOT recusively descend.
ALLEGRO_FOR_EACH_FS_ENTRY_STOP - Stop iterating and return.

al_for_each_fs_entry

int al_for_each_fs_entry(ALLEGRO_FS_ENTRY *dir,
                         int (*callback)(ALLEGRO_FS_ENTRY *dir, void *extra),
                         void *extra)

Source Code

This function takes the ALLEGRO_FS_ENTRY dir, which should represent a directory, and looks for any other file system entries that are in it. This function will then call the callback function callback once for every filesystem entry in the directory dir.

The callback callback must be of type int callback(ALLEGRO_FS_ENTRY * entry, void * extra). The callback will be called with a pointer to an ALLEGRO_FS_ENTRY that matches one file or directory in dir, and the pointer passed in the extra parameter to al_for_each_fs_entry.

When callback returns ALLEGRO_FOR_EACH_FS_ENTRY_STOP or ALLEGRO_FOR_EACH_FS_ENTRY_ERROR, iteration will stop immediately and al_for_each_fs_entry will return the value the callback returned.

When callback returns ALLEGRO_FOR_EACH_FS_ENTRY_OK iteration will continue normally, and if the ALLEGRO_FS_ENTRY parameter of callback is a directory, al_for_each_fs_entry will call itself on that directory. Therefore the function will recusively descend into that directory.

However, when callback returns ALLEGRO_FOR_EACH_FS_ENTRY_SKIP iteration will continue, but al_for_each_fs_entry will NOT recurse into the ALLEGRO_FS_ENTRY parameter of callback even if it is a directory.

This function will skip any files or directories named . or .. which may exist on certain platforms and may signify the current and the parent directory. The callback will not be called for files or directories with such a name.

Returns ALLEGRO_FOR_EACH_FS_ENTRY_OK if successful, or ALLEGRO_FOR_EACH_FS_ENTRY_ERROR if something went wrong in processing the directory. In that case it will use al_set_errno to indicate the type of error which occurred. This function returns ALLEGRO_FOR_EACH_FS_ENTRY_STOP in case iteration was stopped by making callback return that value. In this case, al_set_errno will not be used.

Since: 5.1.9

Examples:

ex_dir.c

Alternative filesystem functions

By default, Allegro uses platform specific filesystem functions for things like directory access. However if for example the files of your game are not in the local filesystem but inside some file archive, you can provide your own set of functions (or use an addon which does this for you, for example our physfs addon allows access to the most common archive formats).

ALLEGRO_FS_INTERFACE

typedef struct ALLEGRO_FS_INTERFACE ALLEGRO_FS_INTERFACE;

Source Code

The available functions you can provide for a filesystem. They are:

   ALLEGRO_FS_ENTRY *  fs_create_entry   (const char *path);
   void                fs_destroy_entry  (ALLEGRO_FS_ENTRY *e);
   const char *        fs_entry_name     (ALLEGRO_FS_ENTRY *e);
   bool                fs_update_entry   (ALLEGRO_FS_ENTRY *e);
   uint32_t            fs_entry_mode     (ALLEGRO_FS_ENTRY *e);
   time_t              fs_entry_atime    (ALLEGRO_FS_ENTRY *e);
   time_t              fs_entry_mtime    (ALLEGRO_FS_ENTRY *e);
   time_t              fs_entry_ctime    (ALLEGRO_FS_ENTRY *e);
   off_t               fs_entry_size     (ALLEGRO_FS_ENTRY *e);
   bool                fs_entry_exists   (ALLEGRO_FS_ENTRY *e);
   bool                fs_remove_entry   (ALLEGRO_FS_ENTRY *e);

   bool                fs_open_directory (ALLEGRO_FS_ENTRY *e);
   ALLEGRO_FS_ENTRY *  fs_read_directory (ALLEGRO_FS_ENTRY *e);
   bool                fs_close_directory(ALLEGRO_FS_ENTRY *e);

   bool                fs_filename_exists(const char *path);
   bool                fs_remove_filename(const char *path);
   char *              fs_get_current_directory(void);
   bool                fs_change_directory(const char *path);
   bool                fs_make_directory(const char *path);

   ALLEGRO_FILE *      fs_open_file(ALLEGRO_FS_ENTRY *e);

al_set_fs_interface

void al_set_fs_interface(const ALLEGRO_FS_INTERFACE *fs_interface)

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Set the ALLEGRO_FS_INTERFACE table for the calling thread.

al_set_standard_fs_interface

void al_set_standard_fs_interface(void)

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Return the ALLEGRO_FS_INTERFACE table to the default, for the calling thread.

al_get_fs_interface

const ALLEGRO_FS_INTERFACE *al_get_fs_interface(void)

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Return a pointer to the ALLEGRO_FS_INTERFACE table in effect for the calling thread.

See also: al_store_state, al_restore_state.

Allegro version 5.2.8 - Last updated: 2022-06-06 01:17:43 UTC