char *sqlite3_create_filename( const char *zDatabase, const char *zJournal, const char *zWal, int nParam, const char **azParam ); void sqlite3_free_filename(char*);
These interfces 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:
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 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).
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