1 files changed, 88 insertions, 0 deletions
diff --git a/mfbt/IntegerTypeTraits.h b/mfbt/IntegerTypeTraits.h
new file mode 100644
index 0000000000..57c5c4103c
--- /dev/null
+++ b/mfbt/IntegerTypeTraits.h
@@ -0,0 +1,88 @@
+/* -*- 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/. */
+
+/* Helpers to manipulate integer types that don't fit in TypeTraits.h */
+
+#ifndef mozilla_IntegerTypeTraits_h
+#define mozilla_IntegerTypeTraits_h
+
+#include <stddef.h>
+#include <stdint.h>
+#include <type_traits>
+
+namespace mozilla {
+
+namespace detail {
+
+/**
+ * StdintTypeForSizeAndSignedness returns the stdint integer type
+ * of given size (can be 1, 2, 4 or 8) and given signedness
+ * (false means unsigned, true means signed).
+ */
+template <size_t Size, bool Signedness>
+struct StdintTypeForSizeAndSignedness;
+
+template <>
+struct StdintTypeForSizeAndSignedness<1, true> {
+  typedef int8_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<1, false> {
+  typedef uint8_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<2, true> {
+  typedef int16_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<2, false> {
+  typedef uint16_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<4, true> {
+  typedef int32_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<4, false> {
+  typedef uint32_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<8, true> {
+  typedef int64_t Type;
+};
+
+template <>
+struct StdintTypeForSizeAndSignedness<8, false> {
+  typedef uint64_t Type;
+};
+
+}  // namespace detail
+
+template <size_t Size>
+struct UnsignedStdintTypeForSize
+    : detail::StdintTypeForSizeAndSignedness<Size, false> {};
+
+template <size_t Size>
+struct SignedStdintTypeForSize
+    : detail::StdintTypeForSizeAndSignedness<Size, true> {};
+
+template <typename IntegerType>
+struct PositionOfSignBit {
+  static_assert(std::is_integral_v<IntegerType>,
+                "PositionOfSignBit is only for integral types");
+  // 8 here should be CHAR_BIT from limits.h, but the world has moved on.
+  static const size_t value = 8 * sizeof(IntegerType) - 1;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_IntegerTypeTraits_h