Create and Destroy VFS Filenames

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## SQLite C Interface

## Create and Destroy VFS Filenames

>     sqlite3_filename sqlite3_create_filename(
>       const char *zDatabase,
>       const char *zJournal,
>       const char *zWal,
>       int nParam,
>       const char **azParam
>     );
>     void sqlite3_free_filename(sqlite3_filename);

These interfaces are provided for use by VFS shim implementations and are not useful outside of that context.

The sqlite3_create_filename(D,J,W,N,P) allocates memory to hold a version of database filename D with corresponding journal file J and WAL file W and with N URI parameters key/values pairs in the array P. The result from sqlite3_create_filename(D,J,W,N,P) is a pointer to a database filename that is safe to pass to routines like:

- sqlite3_uri_parameter(),
- sqlite3_uri_boolean(),
- sqlite3_uri_int64(),
- sqlite3_uri_key(),
- sqlite3_filename_database(),
- sqlite3_filename_journal(), or
- sqlite3_filename_wal().

If a memory allocation error occurs, sqlite3_create_filename() might return a NULL pointer. The memory obtained from sqlite3_create_filename(X) must be released by a corresponding call to sqlite3_free_filename(Y).

The P parameter in sqlite3_create_filename(D,J,W,N,P) should be an array of 2*N pointers to strings. Each pair of pointers in this array corresponds to a key and value for a query parameter. The P parameter may be a NULL pointer if N is zero. None of the 2*N pointers in the P array may be NULL pointers and key pointers should not be empty strings. None of the D, J, or W parameters to sqlite3_create_filename(D,J,W,N,P) may be NULL pointers, though they can be empty strings.

The sqlite3_free_filename(Y) routine releases a memory allocation previously obtained from sqlite3_create_filename(). Invoking sqlite3_free_filename(Y) where Y is a NULL pointer is a harmless no-op.

If the Y parameter to sqlite3_free_filename(Y) is anything other than a NULL pointer or a pointer previously acquired from sqlite3_create_filename(), then bad things such as heap corruption or segfaults may occur. The value Y should not be used again after sqlite3_free_filename(Y) has been called. This means that if the sqlite3_vfs.xOpen() method of a VFS has been called using Y, then the corresponding [sqlite3_module.xClose() method should also be invoked prior to calling sqlite3_free_filename(Y).

See also lists of Objects, Constants, and Functions.