avoid divide by zero

R=kjlubick@google.com
Bug: skia:7623
Change-Id: Ia9fb31201a39a4540d94f97e8d2f06eb290ab6e5
Reviewed-on: https://skia-review.googlesource.com/114082
Commit-Queue: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>

1 files changed, 14 insertions, 8 deletions

diff --git a/src/pathops/SkPathOpsQuad.cpp b/src/pathops/SkPathOpsQuad.cpp
index f410ea3737..9a104bfe2b 100644
--- a/src/pathops/SkPathOpsQuad.cpp
+++ b/src/pathops/SkPathOpsQuad.cpp
@@ -141,6 +141,15 @@ int SkDQuad::RootsValidT(double A, double B, double C, double t[2]) {
     return foundRoots;
 }
 
+static int handle_zero(const double B, const double C, double s[2]) {
+    if (approximately_zero(B)) {
+        s[0] = 0;
+        return C == 0;
+    }
+    s[0] = -C / B;
+    return 1;
+}
+
 /*
 Numeric Solutions (5.6) suggests to solve the quadratic by computing
        Q = -1/2(B + sgn(B)Sqrt(B^2 - 4 A C))
@@ -150,16 +159,13 @@ and using the roots
 */
 // this does not discard real roots <= 0 or >= 1
 int SkDQuad::RootsReal(const double A, const double B, const double C, double s[2]) {
+    if (!A) {
+        return handle_zero(B, C, s);
+    }
     const double p = B / (2 * A);
     const double q = C / A;
-    if (!A || (approximately_zero(A) && (approximately_zero_inverse(p)
-            || approximately_zero_inverse(q)))) {
-        if (approximately_zero(B)) {
-            s[0] = 0;
-            return C == 0;
-        }
-        s[0] = -C / B;
-        return 1;
+    if (approximately_zero(A) && (approximately_zero_inverse(p) || approximately_zero_inverse(q))) {
+        return handle_zero(B, C, s);
     }
     /* normal form: x^2 + px + q = 0 */
     const double p2 = p * p;