Nodes: deduplicate ping pong math operation

The formula did not change. The only side effect of this change should be
that the compositor node now does not divide by zero in some cases.

source/blender/blenlib/intern/math_base_inline.c

@@ -387,6 +387,14 @@ MINLINE float wrapf(float value, float max, float min)
   return (range != 0.0f) ? value - (range * floorf((value - min) / range)) : min;
 }
 
+MINLINE float pingpongf(float value, float scale)
+{
+  if (scale == 0.0f) {
+    return 0.0f;
+  }
+  return fabsf(fractf((value - scale) / (scale * 2.0f)) * scale * 2.0f - scale);
+}
+
 // Square.
 
 MINLINE int square_s(short a)

source/blender/compositor/operations/COM_MathBaseOperation.cpp

@@ -671,9 +671,7 @@ void MathPingpongOperation::executePixelSampled(float output[4],
   this->m_inputValue1Operation->readSampled(inputValue1, x, y, sampler);
   this->m_inputValue2Operation->readSampled(inputValue2, x, y, sampler);
 
-  output[0] = fabsf(fractf((inputValue1[0] - inputValue2[0]) / (inputValue2[0] * 2.0f)) *
-                        inputValue2[0] * 2.0f -
-                    inputValue2[0]);
+  output[0] = pingpongf(inputValue1[0], inputValue2[0]);
 
   clampIfNeeded(output);
 }

source/blender/nodes/texture/nodes/node_texture_math.c

@@ -282,12 +282,7 @@ static void valuefn(float *out, TexParams *p, bNode *node, bNodeStack **in, shor
     }
 
     case NODE_MATH_PINGPONG: {
-      if (in1 == 0.0f) {
-        *out = 0.0f;
-      }
-      else {
-        *out = fabsf(fractf((in0 - in1) / (in1 * 2.0f)) * in1 * 2.0f - in1);
-      }
+      *out = pingpongf(in0, in1);
       break;
     }