star-cpr

commit aa2327408636298b2ff7e4a61b4f8e6b159be44f
parent 58b26eeea2b9f865a10b67e9500e8c18f46be5c7
Author: Christophe Coustet <christophe.coustet@meso-star.com>
Date:   Fri,  3 Mar 2023 16:40:21 +0100

Fix integer arithmetic for intersection computations

Diffstat:
M
src/scpr_intersector.c
 | 
67
+++++++++++++++++++++++++++++++++----------------------------------

1 file changed, 33 insertions(+), 34 deletions(-)
diff --git a/src/scpr_intersector.c b/src/scpr_intersector.c
@@ -454,12 +454,11 @@ safe_mul
    int64_t b,
    int* ovflw)
 {
-  if(*ovflw) return 0;
-  if(b != 0 && abs(a) > 1 + (INT64_MAX / abs(b))) goto error;
-  return a * b;
-error:
-    *ovflw = 1;
-    return 0;
+  int64_t r;
+  if(b == 0) return 0;
+  r = a * b;
+  if (r / b != a) *ovflw = 1;
+  return r;
 }
 
 /* Check if a triangle is CCW (>0), CW (<0), or flat (=0) */
@@ -534,38 +533,38 @@ check_two_segments_intersection
   }
   else if(ccw1 == 0 && ccw2 == 0 && ccw3 == 0 && ccw4 == 0) {
     /* collinear segments */
-    struct scpr_callback_segment arg1, arg2;
-    arg1.polygon = polygon1;
-    arg1.component = comp_idx1;
-    arg1.first_vertex = r11;
-    arg1.last_vertex = r12;
-    arg2.polygon = polygon2;
-    arg2.component = comp_idx2;
-    arg2.first_vertex = r21;
-    arg2.last_vertex = r22;
-    if(callbacks->collinear_segments
-        && callbacks->collinear_segments(&arg1, &arg2, data))
-    {
-      res = RES_BAD_ARG;
-      goto error;
+    if(callbacks->collinear_segments) {
+      struct scpr_callback_segment arg1, arg2;
+      arg1.polygon = polygon1;
+      arg1.component = comp_idx1;
+      arg1.first_vertex = r11;
+      arg1.last_vertex = r12;
+      arg2.polygon = polygon2;
+      arg2.component = comp_idx2;
+      arg2.first_vertex = r21;
+      arg2.last_vertex = r22;
+      if(callbacks->collinear_segments(&arg1, &arg2, data)) {
+        res = RES_BAD_ARG;
+        goto error;
+      }
     }
   }
   else if(ccw1 * ccw2 < 0 && ccw3 * ccw4 < 0) {
     /* Basic segment intersection */
-    struct scpr_callback_segment arg1, arg2;
-    arg1.polygon = polygon1;
-    arg1.component = comp_idx1;
-    arg1.first_vertex = r11;
-    arg1.last_vertex = r12;
-    arg2.polygon = polygon2;
-    arg2.component = comp_idx2;
-    arg2.first_vertex = r21;
-    arg2.last_vertex = r22;
-    if(callbacks->simple_intersection
-        && callbacks->simple_intersection(&arg1, &arg2, data))
-    {
-      res = RES_BAD_ARG;
-      goto error;
+    if(callbacks->simple_intersection) {
+      struct scpr_callback_segment arg1, arg2;
+      arg1.polygon = polygon1;
+      arg1.component = comp_idx1;
+      arg1.first_vertex = r11;
+      arg1.last_vertex = r12;
+      arg2.polygon = polygon2;
+      arg2.component = comp_idx2;
+      arg2.first_vertex = r21;
+      arg2.last_vertex = r22;
+      if(callbacks->simple_intersection(&arg1, &arg2, data)) {
+        res = RES_BAD_ARG;
+        goto error;
+      }
     }
 }