1 files changed, 121 insertions, 0 deletions
diff --git a/js/src/vm/Uint8Clamped.h b/js/src/vm/Uint8Clamped.h
new file mode 100644
index 0000000000..5cc391f4b7
--- /dev/null
+++ b/js/src/vm/Uint8Clamped.h
@@ -0,0 +1,121 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_Uint8Clamped_h
+#define vm_Uint8Clamped_h
+
+#include <stdint.h>
+
+namespace js {
+
+extern uint32_t ClampDoubleToUint8(const double x);
+
+struct uint8_clamped {
+  uint8_t val;
+
+  uint8_clamped() = default;
+  uint8_clamped(const uint8_clamped& other) = default;
+
+  // invoke our assignment helpers for constructor conversion
+  explicit uint8_clamped(uint8_t x) { *this = x; }
+  explicit uint8_clamped(uint16_t x) { *this = x; }
+  explicit uint8_clamped(uint32_t x) { *this = x; }
+  explicit uint8_clamped(uint64_t x) { *this = x; }
+  explicit uint8_clamped(int8_t x) { *this = x; }
+  explicit uint8_clamped(int16_t x) { *this = x; }
+  explicit uint8_clamped(int32_t x) { *this = x; }
+  explicit uint8_clamped(int64_t x) { *this = x; }
+  explicit uint8_clamped(double x) { *this = x; }
+
+  uint8_clamped& operator=(const uint8_clamped& x) = default;
+
+  uint8_clamped& operator=(uint8_t x) {
+    val = x;
+    return *this;
+  }
+
+  uint8_clamped& operator=(uint16_t x) {
+    val = (x > 255) ? 255 : uint8_t(x);
+    return *this;
+  }
+
+  uint8_clamped& operator=(uint32_t x) {
+    val = (x > 255) ? 255 : uint8_t(x);
+    return *this;
+  }
+
+  uint8_clamped& operator=(uint64_t x) {
+    val = (x > 255) ? 255 : uint8_t(x);
+    return *this;
+  }
+
+  uint8_clamped& operator=(int8_t x) {
+    val = (x >= 0) ? uint8_t(x) : 0;
+    return *this;
+  }
+
+  uint8_clamped& operator=(int16_t x) {
+    val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
+    return *this;
+  }
+
+  uint8_clamped& operator=(int32_t x) {
+    val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
+    return *this;
+  }
+
+  uint8_clamped& operator=(int64_t x) {
+    val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
+    return *this;
+  }
+
+  uint8_clamped& operator=(const double x) {
+    val = uint8_t(ClampDoubleToUint8(x));
+    return *this;
+  }
+
+  operator uint8_t() const { return val; }
+
+  void staticAsserts() {
+    static_assert(sizeof(uint8_clamped) == 1,
+                  "uint8_clamped must be layout-compatible with uint8_t");
+  }
+};
+
+/* Note that we can't use std::numeric_limits here due to uint8_clamped. */
+template <typename T>
+inline constexpr bool TypeIsFloatingPoint() {
+  return false;
+}
+template <>
+inline constexpr bool TypeIsFloatingPoint<float>() {
+  return true;
+}
+template <>
+inline constexpr bool TypeIsFloatingPoint<double>() {
+  return true;
+}
+
+template <typename T>
+inline constexpr bool TypeIsUnsigned() {
+  return false;
+}
+template <>
+inline constexpr bool TypeIsUnsigned<uint8_t>() {
+  return true;
+}
+template <>
+inline constexpr bool TypeIsUnsigned<uint16_t>() {
+  return true;
+}
+template <>
+inline constexpr bool TypeIsUnsigned<uint32_t>() {
+  return true;
+}
+
+}  // namespace js
+
+#endif  // vm_Uint8Clamped_h