Add file sqlite3rtree.h.

FossilOrigin-Name: e1d9ffce0f84469eeb926f50030cb772de98a652

ext/rtree/sqlite3rtree.h

@@ -0,0 +1,26 @@
+
+#include <sqlite3.h>
+
+typedef struct RtreeGeometry RtreeGeometry;
+
+struct RtreeGeometry {
+  void *pContext;                 /* Copy of pContext passed to s_r_g_c() */
+  int nParam;                     /* Size of array aParam[] */
+  double *aParam;                 /* Parameters passed to SQL geom function */
+  void *pUser;                    /* Callback implementation user data */
+  void (*xDelUser)(void *);       /* Called by SQLite to clean up pUser */
+};
+
+/*
+** Register a geometry callback named zGeom that can be used as part of an
+** R-Tree geometry query as follows:
+**
+**   SELECT ... FROM <rtree> WHERE <rtree> MATCH $zGeom(... params ...)
+*/
+int sqlite3_rtree_geometry_callback(
+  sqlite3 *db,
+  const char *zGeom,
+  int (*xGeom)(RtreeGeometry *, int nCoord, double *aCoord, int *piResOut),
+  void *pContext
+);
+