1 files changed, 75 insertions, 0 deletions
diff --git a/mfbt/PairHash.h b/mfbt/PairHash.h
new file mode 100644
index 0000000000..100832dc12
--- /dev/null
+++ b/mfbt/PairHash.h
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+/* -*- 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/. */
+
+/* Utilities for hashing pairs. */
+
+#ifndef mozilla_PairHash_h
+#define mozilla_PairHash_h
+
+#include "mozilla/CompactPair.h"
+#include "mozilla/HashFunctions.h"
+
+#include <utility>  // std::pair
+
+namespace mozilla {
+
+/**
+ * The HashPair overloads below do just what you'd expect.
+ *
+ * These functions support hash of std::pair<T,U> and mozilla::CompactPair<T,u>
+ * where type T and U both support AddToHash.
+ */
+template <typename U, typename V>
+[[nodiscard]] inline HashNumber HashPair(const std::pair<U, V>& pair) {
+  // Pair hash combines the hash of each member
+  return HashGeneric(pair.first, pair.second);
+}
+
+template <typename U, typename V>
+[[nodiscard]] inline HashNumber HashCompactPair(const CompactPair<U, V>& pair) {
+  // Pair hash combines the hash of each member
+  return HashGeneric(pair.first(), pair.second());
+}
+
+/**
+ * Hash policy for std::pair compatible with HashTable
+ */
+template <typename T, typename U>
+struct PairHasher {
+  using Key = std::pair<T, U>;
+  using Lookup = Key;
+
+  static HashNumber hash(const Lookup& aLookup) { return HashPair(aLookup); }
+
+  static bool match(const Key& aKey, const Lookup& aLookup) {
+    return aKey == aLookup;
+  }
+
+  static void rekey(Key& aKey, const Key& aNewKey) { aKey = aNewKey; }
+};
+
+/**
+ * Hash policy for mozilla::CompactPair compatible with HashTable
+ */
+template <typename T, typename U>
+struct CompactPairHasher {
+  using Key = CompactPair<T, U>;
+  using Lookup = Key;
+
+  static HashNumber hash(const Lookup& aLookup) {
+    return HashCompactPair(aLookup);
+  }
+
+  static bool match(const Key& aKey, const Lookup& aLookup) {
+    return aKey == aLookup;
+  }
+
+  static void rekey(Key& aKey, const Key& aNewKey) { aKey = aNewKey; }
+};
+
+}  // namespace mozilla
+
+#endif /* mozilla_PairHash_h */