WT_FILE_SYSTEM Struct Reference

The interface implemented by applications to provide a custom file system implementation. More...

Public Attributes
int(*	fs_directory_list )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *directory, const char *prefix, char ***dirlist, uint32_t *countp)
	Return a list of file names for the named directory. More...
int(*	fs_directory_list_free )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, char **dirlist, uint32_t count)
	Free memory allocated by WT_FILE_SYSTEM::directory_list. More...
int(*	fs_exist )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, bool *existp)
	Return if the named file system object exists. More...
int(*	fs_open_file )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, WT_FS_OPEN_FILE_TYPE file_type, uint32_t flags, WT_FILE_HANDLE **file_handlep)
	Open a handle for a named file system object. More...
int(*	fs_remove )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, uint32_t flags)
	Remove a named file system object. More...
int(*	fs_rename )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *from, const char *to, uint32_t flags)
	Rename a named file system object. More...
int(*	fs_size )(WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, wt_off_t *sizep)
	Return the size of a named file system object. More...
int(*	terminate )(WT_FILE_SYSTEM *file_system, WT_SESSION *session)
	A callback performed when the file system is closed and will no longer be accessed by the WiredTiger database. More...

Detailed Description

The interface implemented by applications to provide a custom file system implementation.

Thread safety: WiredTiger may invoke methods on the WT_FILE_SYSTEM interface from multiple threads concurrently. It is the responsibility of the implementation to protect any shared data.

Applications register implementations with WiredTiger by calling WT_CONNECTION::set_file_system. See Custom File Systems for more information.

    /*
     * Setup a configuration string that will load our custom file system. Use the special local
     * extension to indicate that the entry point is in the same executable. Also enable early load
     * for this extension, since WiredTiger needs to be able to find it before doing any file
     * operations. Finally, pass in two pieces of configuration information to our initialization
     * function as the "config" value.
     */
    open_config =
      "create,log=(enabled=true),extensions=(local={entry=demo_file_system_create,early_load=true,"
      "config={config_string=\"demo-file-system\",config_value=37}})";
    /* Open a connection to the database, creating it if necessary. */
    if ((ret = wiredtiger_open(home, NULL, open_config, &conn)) != 0) {
        fprintf(stderr, "Error connecting to %s: %s\n", home == NULL ? "." : home,
          wiredtiger_strerror(ret));
        return (EXIT_FAILURE);
    }

Examples

ex_file_system.c.

Member Data Documentation

fs_directory_list

int(* WT_FILE_SYSTEM::fs_directory_list) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *directory, const char *prefix, char ***dirlist, uint32_t *countp)

Return a list of file names for the named directory.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

	file_system	the WT_FILE_SYSTEM
	session	the current WiredTiger session
	directory	the name of the directory
	prefix	if not NULL, only files with names matching the prefix are returned
[out]	dirlist	the method returns an allocated array of individually allocated strings, one for each entry in the directory.
[out]	countp	the number of entries returned

Examples

ex_file_system.c.

fs_directory_list_free

int(* WT_FILE_SYSTEM::fs_directory_list_free) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, char **dirlist, uint32_t count)

Free memory allocated by WT_FILE_SYSTEM::directory_list.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

file_system	the WT_FILE_SYSTEM
session	the current WiredTiger session
dirlist	array returned by WT_FILE_SYSTEM::directory_list
count	count returned by WT_FILE_SYSTEM::directory_list

Examples

ex_file_system.c.

fs_exist

int(* WT_FILE_SYSTEM::fs_exist) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, bool *existp)

Return if the named file system object exists.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

	file_system	the WT_FILE_SYSTEM
	session	the current WiredTiger session
	name	the name of the file
[out]	existp	If the named file system object exists

Examples

ex_file_system.c.

fs_open_file

int(* WT_FILE_SYSTEM::fs_open_file) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, WT_FS_OPEN_FILE_TYPE file_type, uint32_t flags, WT_FILE_HANDLE **file_handlep)

Open a handle for a named file system object.

The method should return ENOENT if the file is not being created and does not exist.

The method should return EACCES if the file cannot be opened in the requested mode (for example, a file opened for writing in a readonly file system).

The method should return EBUSY if WT_FS_OPEN_EXCLUSIVE is set and the file is in use.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

	file_system	the WT_FILE_SYSTEM
	session	the current WiredTiger session
	name	the name of the file system object
	file_type	the type of the file The file type is provided to allow optimization for different file access patterns.
	flags	flags indicating how to open the file, one or more of WT_FS_OPEN_CREATE, WT_FS_OPEN_DIRECTIO, WT_FS_OPEN_DURABLE, WT_FS_OPEN_EXCLUSIVE or WT_FS_OPEN_READONLY.
[out]	file_handlep	the handle to the newly opened file. File system implementations must allocate memory for the handle and the WT_FILE_HANDLE::name field, and fill in the WT_FILE_HANDLE:: fields. Applications wanting to associate private information with the WT_FILE_HANDLE:: structure should declare and allocate their own structure as a superset of a WT_FILE_HANDLE:: structure.

Examples

ex_file_system.c.

fs_remove

int(* WT_FILE_SYSTEM::fs_remove) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, uint32_t flags)

Remove a named file system object.

This method is not required for readonly file systems and should be set to NULL when not required by the file system.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

file_system	the WT_FILE_SYSTEM
session	the current WiredTiger session
name	the name of the file system object
flags	0 or WT_FS_DURABLE

Examples

ex_file_system.c.

fs_rename

int(* WT_FILE_SYSTEM::fs_rename) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *from, const char *to, uint32_t flags)

Rename a named file system object.

This method is not required for readonly file systems and should be set to NULL when not required by the file system.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

file_system	the WT_FILE_SYSTEM
session	the current WiredTiger session
from	the original name of the object
to	the new name for the object
flags	0 or WT_FS_DURABLE

Examples

ex_file_system.c.

fs_size

int(* WT_FILE_SYSTEM::fs_size) (WT_FILE_SYSTEM *file_system, WT_SESSION *session, const char *name, wt_off_t *sizep)

Return the size of a named file system object.

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Parameters

	file_system	the WT_FILE_SYSTEM
	session	the current WiredTiger session
	name	the name of the file system object
[out]	sizep	the size of the file system entry

Examples

ex_file_system.c.

terminate

int(* WT_FILE_SYSTEM::terminate) (WT_FILE_SYSTEM *file_system, WT_SESSION *session)

A callback performed when the file system is closed and will no longer be accessed by the WiredTiger database.

This method is not required and should be set to NULL when not required by the file system.

The WT_FILE_SYSTEM::terminate callback is intended to allow cleanup, the handle will not be subsequently accessed by WiredTiger.

Examples

ex_file_system.c.