Defer Meshed creation

Refactored Mesh API to defer creation of
SkMesh instances until a GrDirectContext
can be obtained on the RenderThread.
This creates an SkMesh during the prepare
tree step when the UI thread is blocked
to ensure no concurrency issues.

Bug: b/265044322
Test: atest CtsUiRenderingTestCases:MeshTest
Change-Id: Ica8c364b99952e0ee71f7b95b312cf29c51ebc2a

1 files changed, 107 insertions, 0 deletions

diff --git a/libs/hwui/SafeMath.h b/libs/hwui/SafeMath.h
new file mode 100644
index 000000000000..4d6adf55c0cb
--- /dev/null
+++ b/libs/hwui/SafeMath.h
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SkSafeMath_DEFINED
+#define SkSafeMath_DEFINED
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+
+// Copy of Skia's SafeMath API used to validate Mesh parameters to support
+// deferred creation of SkMesh instances on RenderThread.
+// SafeMath always check that a series of operations do not overflow.
+// This must be correct for all platforms, because this is a check for safety at runtime.
+
+class SafeMath {
+public:
+    SafeMath() = default;
+
+    bool ok() const { return fOK; }
+    explicit operator bool() const { return fOK; }
+
+    size_t mul(size_t x, size_t y) {
+        return sizeof(size_t) == sizeof(uint64_t) ? mul64(x, y) : mul32(x, y);
+    }
+
+    size_t add(size_t x, size_t y) {
+        size_t result = x + y;
+        fOK &= result >= x;
+        return result;
+    }
+
+    /**
+     *  Return a + b, unless this result is an overflow/underflow. In those cases, fOK will
+     *  be set to false, and it is undefined what this returns.
+     */
+    int addInt(int a, int b) {
+        if (b < 0 && a < std::numeric_limits<int>::min() - b) {
+            fOK = false;
+            return a;
+        } else if (b > 0 && a > std::numeric_limits<int>::max() - b) {
+            fOK = false;
+            return a;
+        }
+        return a + b;
+    }
+
+    // These saturate to their results
+    static size_t Add(size_t x, size_t y) {
+        SafeMath tmp;
+        size_t sum = tmp.add(x, y);
+        return tmp.ok() ? sum : SIZE_MAX;
+    }
+
+    static size_t Mul(size_t x, size_t y) {
+        SafeMath tmp;
+        size_t prod = tmp.mul(x, y);
+        return tmp.ok() ? prod : SIZE_MAX;
+    }
+
+private:
+    uint32_t mul32(uint32_t x, uint32_t y) {
+        uint64_t bx = x;
+        uint64_t by = y;
+        uint64_t result = bx * by;
+        fOK &= result >> 32 == 0;
+        // Overflow information is capture in fOK. Return the result modulo 2^32.
+        return (uint32_t)result;
+    }
+
+    uint64_t mul64(uint64_t x, uint64_t y) {
+        if (x <= std::numeric_limits<uint64_t>::max() >> 32 &&
+            y <= std::numeric_limits<uint64_t>::max() >> 32) {
+            return x * y;
+        } else {
+            auto hi = [](uint64_t x) { return x >> 32; };
+            auto lo = [](uint64_t x) { return x & 0xFFFFFFFF; };
+
+            uint64_t lx_ly = lo(x) * lo(y);
+            uint64_t hx_ly = hi(x) * lo(y);
+            uint64_t lx_hy = lo(x) * hi(y);
+            uint64_t hx_hy = hi(x) * hi(y);
+            uint64_t result = 0;
+            result = this->add(lx_ly, (hx_ly << 32));
+            result = this->add(result, (lx_hy << 32));
+            fOK &= (hx_hy + (hx_ly >> 32) + (lx_hy >> 32)) == 0;
+
+            return result;
+        }
+    }
+    bool fOK = true;
+};
+
+#endif  // SkSafeMath_DEFINED