1 files changed, 68 insertions, 0 deletions
diff --git a/src/nad_intr.cpp b/src/nad_intr.cpp
new file mode 100644
index 00000000..1f9d1e0c
--- /dev/null
+++ b/src/nad_intr.cpp
@@ -0,0 +1,68 @@
+/* Determine nad table correction value */
+#define PJ_LIB__
+#include "proj_internal.h"
+#include "proj_math.h"
+#include "projects.h"
+
+	LP
+nad_intr(LP t, struct CTABLE *ct) {
+	LP val, frct;
+	ILP indx;
+	double m00, m10, m01, m11;
+	FLP *f00, *f10, *f01, *f11;
+	long index;
+	int in;
+
+	t.lam /= ct->del.lam;
+	indx.lam = isnan(t.lam) ? 0 : (pj_int32)lround(floor(t.lam));
+	t.phi /= ct->del.phi;
+	indx.phi = isnan(t.phi) ? 0 : (pj_int32)lround(floor(t.phi));
+
+	frct.lam = t.lam - indx.lam;
+	frct.phi = t.phi - indx.phi;
+	val.lam = val.phi = HUGE_VAL;
+	if (indx.lam < 0) {
+		if (indx.lam == -1 && frct.lam > 0.99999999999) {
+			++indx.lam;
+			frct.lam = 0.;
+		} else
+			return val;
+	} else if ((in = indx.lam + 1) >= ct->lim.lam) {
+		if (in == ct->lim.lam && frct.lam < 1e-11) {
+			--indx.lam;
+			frct.lam = 1.;
+		} else
+			return val;
+	}
+	if (indx.phi < 0) {
+		if (indx.phi == -1 && frct.phi > 0.99999999999) {
+			++indx.phi;
+			frct.phi = 0.;
+		} else
+			return val;
+	} else if ((in = indx.phi + 1) >= ct->lim.phi) {
+		if (in == ct->lim.phi && frct.phi < 1e-11) {
+			--indx.phi;
+			frct.phi = 1.;
+		} else
+			return val;
+	}
+	index = indx.phi * ct->lim.lam + indx.lam;
+	f00 = ct->cvs + index++;
+	f10 = ct->cvs + index;
+	index += ct->lim.lam;
+	f11 = ct->cvs + index--;
+	f01 = ct->cvs + index;
+	m11 = m10 = frct.lam;
+	m00 = m01 = 1. - frct.lam;
+	m11 *= frct.phi;
+	m01 *= frct.phi;
+	frct.phi = 1. - frct.phi;
+	m00 *= frct.phi;
+	m10 *= frct.phi;
+	val.lam = m00 * f00->lam + m10 * f10->lam +
+			  m01 * f01->lam + m11 * f11->lam;
+	val.phi = m00 * f00->phi + m10 * f10->phi +
+			  m01 * f01->phi + m11 * f11->phi;
+	return val;
+}