feat: added client data pointer for caller convenience

src/common/interp2d.c

@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: interp2d.c,v 2.14 2014/06/06 00:56:42 greg Exp $";
+static const char RCSid[] = "$Id: interp2d.c,v 2.15 2021/02/13 16:49:18 greg Exp $";
 #endif
 /*
  * General interpolation method for unstructured values on 2-D plane.
@@ -70,6 +70,7 @@ interp2_alloc(int nsamps)
 	nip->ns = nsamps;
 	nip->dmin = 1;		/* default minimum diameter */
 	nip->smf = NI2DSMF;	/* default smoothing factor */
+	nip->c_data = NULL;
 	nip->da = NULL;
 				/* caller must assign spt[] array */
 	return(nip);

src/common/interp2d.h

@@ -1,4 +1,4 @@
-/* RCSid $Id: interp2d.h,v 2.9 2013/02/15 19:15:16 greg Exp $ */
+/* RCSid $Id: interp2d.h,v 2.10 2021/02/13 16:49:18 greg Exp $ */
 /*
  * Header for interpolation of anisotropic samples on 2-D plane.
  *
@@ -25,6 +25,7 @@ typedef struct {
 	float		smin[2];	/* sample minima */
 	float		smax[2];	/* sample maxima */
 	float		grid2;		/* grid diameter squared */
+	void		*c_data;	/* client data pointer */
 	struct interp2_samp {
 		unsigned short	dia[NI2DIR];
 		unsigned short	infl[NI2DIM];