Split edge stepping into its own function

1 files changed, 69 insertions, 62 deletions

diff --git a/dda.c b/dda.c
index 8446293..420aeed 100644
--- a/dda.c
+++ b/dda.c
@@ -102,84 +102,91 @@ edge_init (edge_t *edge, double x0, double y0, double x1, double y1)
 }
 
 static void
+edge_step (edge_t *edge, test_data_t *testdata, int i)
+{
+    if (edge->dx_positive)
+    {
+	while (edge->e <= 0)
+	{
+	    if ((edge->xi & 0xff) == N_GRID_X - 1)
+	    {
+		edge->e += edge->delta_e_big_x;
+		edge->xi += (1 << 8);
+		edge->xi &= 0xffffff00;
+	    }
+	    else
+	    {
+		edge->e += edge->delta_e_small_x;
+		edge->xi++;
+	    }
+	}
+    }
+    else
+    {
+    begin:
+	if ((edge->xi & 0xff) == 0)
+	{
+	    if (edge->e > edge->delta_e_big_x)
+	    {
+		edge->e -= edge->delta_e_big_x;
+		edge->xi -= (1 << 8);
+		edge->xi |= (N_GRID_X - 1);
+		goto small;
+	    }
+	}
+	else
+	{
+	small:
+	    if (edge->e > edge->delta_e_small_x)
+	    {
+		edge->e -= edge->delta_e_small_x;
+		edge->xi--;
+		goto begin;
+	    }
+	}
+    }
+
+    if (testdata->points[i++] != sample_to_pos (edge->xi)		||
+	testdata->points[i++] != sample_to_pos (edge->yi))
+    {
+	printf ("%d error %f %f\n", i, testdata->points[i - 1],
+		sample_to_pos (edge->xi));
+	exit (-1);
+    }
+
+    if ((edge->yi & 0xff) == (N_GRID_Y - 1))
+    {
+	edge->e -= edge->delta_e_big_y;
+	edge->yi += (1 << 8);
+	edge->yi &= 0xffffff00;
+    }
+    else
+    {
+	edge->e -= edge->delta_e_small_y;
+	edge->yi++;
+    }
+}
+
+static void
 dda (test_data_t *testdata)
 {
     double x0 = testdata->segment.x0;
     double y0 = testdata->segment.y0;
     double x1 = testdata->segment.x1;
     double y1 = testdata->segment.y1;
-    int i = 0;
-
 #if 0
     printf ("= = = = %f %f %f %f = = = = \n", x0, y0, x1, y1);
 #endif
     edge_t edge;
+    int i = 0;
 
     edge_init (&edge, x0, y0, x1, y1);
 
     while (edge.yi < edge.bottom)
     {
-	if (edge.dx_positive)
-	{
-	    while (edge.e <= 0)
-	    {
-		if ((edge.xi & 0xff) == N_GRID_X - 1)
-		{
-		    edge.e += edge.delta_e_big_x;
-		    edge.xi += (1 << 8);
-		    edge.xi &= 0xffffff00;
-		}
-		else
-		{
-		    edge.e += edge.delta_e_small_x;
-		    edge.xi++;
-		}
-	    }
-	}
-	else
-	{
-	begin:
-	    if ((edge.xi & 0xff) == 0)
-	    {
-		if (edge.e > edge.delta_e_big_x)
-		{
-		    edge.e -= edge.delta_e_big_x;
-		    edge.xi -= (1 << 8);
-		    edge.xi |= (N_GRID_X - 1);
-		    goto small;
-		}
-	    }
-	    else
-	    {
-	    small:
-		if (edge.e > edge.delta_e_small_x)
-		{
-		    edge.e -= edge.delta_e_small_x;
-		    edge.xi--;
-		    goto begin;
-		}
-	    }
-	}
-
-	if (testdata->points[i++] != sample_to_pos (edge.xi)		||
-	    testdata->points[i++] != sample_to_pos (edge.yi))
-	{
-	    printf ("%d error %f %f\n", i, testdata->points[i - 1],
-		    sample_to_pos (edge.xi));
-	    exit (-1);
-	}
+	edge_step (&edge, testdata, i);
 
-	if ((edge.yi & 0xff) == (N_GRID_Y - 1))
-	{
-	    edge.e -= edge.delta_e_big_y;
-	    edge.yi += (1 << 8);
-	    edge.yi &= 0xffffff00;
-	}
-	else
-	{
-	    edge.e -= edge.delta_e_small_y;
-	    edge.yi++;
-	}
+	i += 2;
     }
 }