Index: src/os_win.c
==================================================================
--- src/os_win.c
+++ src/os_win.c
@@ -313,26 +313,10 @@
  */
 #ifndef SQLITE_WIN32_DBG_BUF_SIZE
 #  define SQLITE_WIN32_DBG_BUF_SIZE   ((int)(4096-sizeof(DWORD)))
 #endif
 
-/*
- * The value used with sqlite3_win32_set_directory() to specify that
- * the data directory should be changed.
- */
-#ifndef SQLITE_WIN32_DATA_DIRECTORY_TYPE
-#  define SQLITE_WIN32_DATA_DIRECTORY_TYPE (1)
-#endif
-
-/*
- * The value used with sqlite3_win32_set_directory() to specify that
- * the temporary directory should be changed.
- */
-#ifndef SQLITE_WIN32_TEMP_DIRECTORY_TYPE
-#  define SQLITE_WIN32_TEMP_DIRECTORY_TYPE (2)
-#endif
-
 /*
  * If compiled with SQLITE_WIN32_MALLOC on Windows, we will use the
  * various Win32 API heap functions instead of our own.
  */
 #ifdef SQLITE_WIN32_MALLOC
@@ -1931,11 +1915,14 @@
 ** the provided arguments.  The type argument must be 1 in order to set the
 ** data directory or 2 in order to set the temporary directory.  The zValue
 ** argument is the name of the directory to use.  The return value will be
 ** SQLITE_OK if successful.
 */
-int sqlite3_win32_set_directory(DWORD type, LPCWSTR zValue){
+int sqlite3_win32_set_directory(
+  unsigned long type, /* Identifier for directory being set or reset */
+  void *zValue        /* New value for directory being set or reset */
+){
   char **ppDirectory = 0;
 #ifndef SQLITE_OMIT_AUTOINIT
   int rc = sqlite3_initialize();
   if( rc ) return rc;
 #endif
@@ -1947,13 +1934,14 @@
   assert( !ppDirectory || type==SQLITE_WIN32_DATA_DIRECTORY_TYPE
           || type==SQLITE_WIN32_TEMP_DIRECTORY_TYPE
   );
   assert( !ppDirectory || sqlite3MemdebugHasType(*ppDirectory, MEMTYPE_HEAP) );
   if( ppDirectory ){
+    LPCWSTR zStrValue = zValue;
     char *zValueUtf8 = 0;
-    if( zValue && zValue[0] ){
-      zValueUtf8 = winUnicodeToUtf8(zValue);
+    if( zStrValue && zStrValue[0] ){
+      zValueUtf8 = winUnicodeToUtf8(zStrValue);
       if ( zValueUtf8==0 ){
         return SQLITE_NOMEM_BKPT;
       }
     }
     sqlite3_free(*ppDirectory);

Index: src/sqlite.h.in
==================================================================
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -5507,10 +5507,40 @@
 ** made NULL or made to point to memory obtained from [sqlite3_malloc]
 ** or else the use of the [data_store_directory pragma] should be avoided.
 */
 SQLITE_EXTERN char *sqlite3_data_directory;
 
+/*
+** CAPI3REF: Win32 Specific Interface
+**
+** These interfaces are available only on Windows.  The
+** [sqlite3_win32_set_directory] interface is used to set the value associated
+** with the [sqlite3_temp_directory] or [sqlite3_data_directory] variable, to
+** zValue, depending on the value of the type parameter.  The zValue parameter
+** should be NULL to cause the previous value to be freed via [sqlite3_free];
+** a non-NULL value will be copied into memory obtained from [sqlite3_malloc]
+** prior to being used.  The [sqlite3_win32_set_directory] interface returns
+** [SQLITE_OK] to indicate success, [SQLITE_ERROR] if the type is unsupported,
+** or [SQLITE_NOMEM] if memory could not be allocated.  The value of the
+** [sqlite3_data_directory] variable is intended to act as a replacement for
+** the current directory on the sub-platforms of Win32 where that concept is
+** not present, e.g. WinRT and UWP.
+*/
+int sqlite3_win32_set_directory(
+  unsigned long type, /* Identifier for directory being set or reset */
+  void *zValue        /* New value for directory being set or reset */
+);
+
+/*
+** CAPI3REF: Win32 Directory Types
+**
+** These macros are only available on Windows.  They define the allowed values
+** for the type argument to the [sqlite3_win32_set_directory] interface.
+*/
+#define SQLITE_WIN32_DATA_DIRECTORY_TYPE  1
+#define SQLITE_WIN32_TEMP_DIRECTORY_TYPE  2
+
 /*
 ** CAPI3REF: Test For Auto-Commit Mode
 ** KEYWORDS: {autocommit mode}
 ** METHOD: sqlite3
 **