Merge pull request #6 from saxbophone/develop

Version 0.5.8

Author: saxbophone

Makefile

@@ -5,7 +5,9 @@ CC=gcc
 STANDARD=-std=c99
 OPTIMISE=-O0
 DEBUG=-g
-CFLAGS=$(STANDARD) $(OPTIMISE) $(DEBUG)
+INCLUDES=
+CFLAGS=$(STANDARD) $(OPTIMISE) $(DEBUG) $(INCLUDES)
+LIBPNG=-lpng
 LIB=saxbospiral.h
 
 saxbospiral.o: saxbospiral.c $(LIB)
@@ -33,7 +35,7 @@ render.o: $(LIB) render.c
 	$(CC) $(CFLAGS) -c render.c
 
 render: saxbospiral.o render.o
-	$(CC) $(CFLAGS) -o render saxbospiral.o render.o -lpng
+	$(CC) $(CFLAGS) -o render saxbospiral.o render.o $(LIBPNG)
 
 test-unit: tests
 	./tests

saxbospiral.c

@@ -11,7 +11,7 @@ extern "C"{
 #endif
 
 const version_t VERSION = {
-    .major = 0, .minor = 5, .patch = 7,
+    .major = 0, .minor = 5, .patch = 8,
 };
 
 const size_t FILE_HEADER_SIZE = 25;
@@ -202,35 +202,40 @@ spiral_collides(spiral_t spiral) {
 
 // private function, given a spiral struct, the index of one of it's lines and
 // a target length to set that line to, attempt to set the target line to that
-// length, recursively calling self to resize the previous line if that is not
-// possible.
+// length, back-tacking to resize the previous line if it collides.
 static spiral_t
 resize_spiral(spiral_t spiral, size_t index, uint32_t length) {
-    // first, set the target line to the target length
-    spiral.lines[index].length = length;
-    // also, set cache validity to this index so we invalidate any invalid
-    // entries in the co-ord cache
-    spiral.co_ord_cache.validity = (
-        index < spiral.co_ord_cache.validity
-    ) ? index : spiral.co_ord_cache.validity;
-    // update the spiral's co-ord cache
-    cache_spiral_points(&spiral, index + 1);
-    // now, check for collisions
-    if(spiral_collides(spiral)) {
-        // there were collisions, so reset the target line to 1
-        spiral.lines[index].length = 1;
-        do {
-            // recursively call resize_spiral(), increasing the size of the
-            // previous line until we get something that doesn't collide
-            spiral = resize_spiral(
-                spiral, index - 1, spiral.lines[index - 1].length + 1
-            );
-            // update the spiral's co-ord cache
-            cache_spiral_points(&spiral, index + 1);
-            // check if it still collides
-        } while(spiral_collides(spiral));
+    // setup state variables, these are used in place of recursion for managing
+    // state of which line is being resized, and what size it should be.
+    size_t current_index = index;
+    size_t current_length = length;
+    while(true) {
+        // set the target line to the target length
+        spiral.lines[current_index].length = current_length;
+        // also, set cache validity to this index so we invalidate any invalid
+        // entries in the co-ord cache
+        spiral.co_ord_cache.validity = (
+            current_index < spiral.co_ord_cache.validity
+        ) ? current_index : spiral.co_ord_cache.validity;
+        // update the spiral's co-ord cache
+        cache_spiral_points(&spiral, current_index + 1);
+        if(spiral_collides(spiral)) {
+            // if we've caused a collision, we should back-track
+            // and increase the size of the previous line segment
+            current_index--;
+            current_length = spiral.lines[current_index].length + 1;
+        } else if(current_index != index) {
+            // if we didn't cause a collision but we're not on the top-most
+            // line, then we've just resolved a collision situation.
+            // we now need to work on the next line and start by setting to 1.
+            current_index++;
+            current_length = 1;
+        } else {
+            // if we're on the top-most line and there's no collision
+            // this means we've finished! Return result.
+            return spiral;
+        }
     }
-    return spiral;
 }
 
 // given a spiral for which the length of all its lines are not yet known,