Port FuzzPathop from chromium

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2148023002

Review-Url: https://codereview.chromium.org/2148023002

fuzz/Fuzz.h

@@ -16,6 +16,14 @@ class Fuzz : SkNoncopyable {
 public:
     explicit Fuzz(SkData*);
 
+    // Returns the total number of "random" bytes available.
+    size_t size();
+    // Returns the total number of "random" bytes remaining for randomness.
+    size_t remaining();
+
+    template <typename T>
+    bool next(T* n);
+
     bool nextBool();
     uint8_t  nextB();
     uint32_t nextU();
@@ -43,6 +51,17 @@ private:
     int fNextByte;
 };
 
+template <typename T>
+bool Fuzz::next(T* n) {
+    if (fNextByte + sizeof(T) > fBytes->size()) {
+        return false;
+    }
+
+    memcpy(n, fBytes->bytes() + fNextByte, sizeof(T));
+    fNextByte += sizeof(T);
+    return true;
+}
+
 struct Fuzzable {
     const char* name;
     void (*fn)(Fuzz*);

fuzz/FuzzPathop.cpp

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Fuzz.h"
+#include "SkPath.h"
+#include "SkPathOps.h"
+
+const int kLastOp = SkPathOp::kReverseDifference_SkPathOp;
+
+void BuildPath(Fuzz* fuzz,
+               SkPath* path,
+               int last_verb) {
+  uint8_t operation;
+  SkScalar a, b, c, d, e, f;
+  while (fuzz->next<uint8_t>(&operation)) {
+
+    switch (operation % (last_verb + 1)) {
+      case SkPath::Verb::kMove_Verb:
+        if (!fuzz->next<SkScalar>(&a) || !fuzz->next<SkScalar>(&b))
+          return;
+        path->moveTo(a, b);
+        break;
+
+      case SkPath::Verb::kLine_Verb:
+        if (!fuzz->next<SkScalar>(&a) || !fuzz->next<SkScalar>(&b))
+          return;
+        path->lineTo(a, b);
+        break;
+
+      case SkPath::Verb::kQuad_Verb:
+        if (!fuzz->next<SkScalar>(&a) ||
+            !fuzz->next<SkScalar>(&b) ||
+            !fuzz->next<SkScalar>(&c) ||
+            !fuzz->next<SkScalar>(&d))
+          return;
+        path->quadTo(a, b, c, d);
+        break;
+
+      case SkPath::Verb::kConic_Verb:
+        if (!fuzz->next<SkScalar>(&a) ||
+            !fuzz->next<SkScalar>(&b) ||
+            !fuzz->next<SkScalar>(&c) ||
+            !fuzz->next<SkScalar>(&d) ||
+            !fuzz->next<SkScalar>(&e))
+          return;
+        path->conicTo(a, b, c, d, e);
+        break;
+
+      case SkPath::Verb::kCubic_Verb:
+        if (!fuzz->next<SkScalar>(&a) ||
+            !fuzz->next<SkScalar>(&b) ||
+            !fuzz->next<SkScalar>(&c) ||
+            !fuzz->next<SkScalar>(&d) ||
+            !fuzz->next<SkScalar>(&e) ||
+            !fuzz->next<SkScalar>(&f))
+          return;
+        path->cubicTo(a, b, c, d, e, f);
+        break;
+
+      case SkPath::Verb::kClose_Verb:
+        path->close();
+        break;
+
+      case SkPath::Verb::kDone_Verb:
+        // In this case, simply exit.
+        return;
+    }
+  }
+}
+
+DEF_FUZZ(Pathop, fuzz) {
+    SkOpBuilder builder;
+    while (fuzz->remaining() >= sizeof(uint8_t)) {
+        SkPath path;
+        uint8_t op = fuzz->nextB();
+
+        BuildPath(fuzz, &path, SkPath::Verb::kDone_Verb);
+        builder.add(path, static_cast<SkPathOp>(op % (kLastOp + 1)));
+    }
+
+    SkPath result;
+    builder.resolve(&result);
+}

fuzz/fuzz.cpp

@@ -14,6 +14,8 @@
 #include "SkImageEncoder.h"
 #include "SkMallocPixelRef.h"
 #include "SkPicture.h"
+#include "SkPicture.h"
+#include "SkPicture.h"
 #include "SkStream.h"
 
 #include <cmath>
@@ -404,6 +406,12 @@ Fuzz::Fuzz(SkData* bytes) : fBytes(SkSafeRef(bytes)), fNextByte(0) {}
 void Fuzz::signalBug   () { SkDebugf("Signal bug\n"); raise(SIGSEGV); }
 void Fuzz::signalBoring() { SkDebugf("Signal boring\n"); exit(0); }
 
+size_t Fuzz::size() { return fBytes->size(); }
+
+size_t Fuzz::remaining() {
+    return fBytes->size() - fNextByte;
+}
+
 template <typename T>
 T Fuzz::nextT() {
     if (fNextByte + sizeof(T) > fBytes->size()) {