Split absl/hash/hash_test.cc into two files

hash_test.cc leans heavily on INSTANTIATE_TYPED_TEST_SUITE_P, which is
quite memory- and CPU-hungry. Split a few heavyweight tests into a new
hash_instantiated_test.cc, reducing peak RAM consumption (or, on
multicore systems, compilation time).

PiperOrigin-RevId: 535305679
Change-Id: Ic204da0a47c749c3f7db5f902ade8d74ed3043bb

1 files changed, 87 insertions, 0 deletions

diff --git a/absl/hash/internal/hash_test.h b/absl/hash/internal/hash_test.h
new file mode 100644
index 00000000..9963dc0b
--- /dev/null
+++ b/absl/hash/internal/hash_test.h
@@ -0,0 +1,87 @@
+// Copyright 2023 The Abseil Authors.
+//
+// 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
+//
+//      https://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.
+
+// Common code shared between absl/hash/hash_test.cc and
+// absl/hash/hash_instantiated_test.cc.
+
+#ifndef ABSL_HASH_INTERNAL_HASH_TEST_H_
+#define ABSL_HASH_INTERNAL_HASH_TEST_H_
+
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/config.h"
+#include "absl/hash/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_test_internal {
+
+// Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
+// mechanism.  `TypeErasedValue<T>` can be constructed with a `T`, and can
+// be compared and hashed.  However, all hashing goes through the hashing
+// type-erasure framework.
+template <typename T>
+class TypeErasedValue {
+ public:
+  TypeErasedValue() = default;
+  TypeErasedValue(const TypeErasedValue&) = default;
+  TypeErasedValue(TypeErasedValue&&) = default;
+  explicit TypeErasedValue(const T& n) : n_(n) {}
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const TypeErasedValue& v) {
+    v.HashValue(absl::HashState::Create(&hash_state));
+    return hash_state;
+  }
+
+  void HashValue(absl::HashState state) const {
+    absl::HashState::combine(std::move(state), n_);
+  }
+
+  bool operator==(const TypeErasedValue& rhs) const { return n_ == rhs.n_; }
+  bool operator!=(const TypeErasedValue& rhs) const { return !(*this == rhs); }
+
+ private:
+  T n_;
+};
+
+// A TypeErasedValue refinement, for containers.  It exposes the wrapped
+// `value_type` and is constructible from an initializer list.
+template <typename T>
+class TypeErasedContainer : public TypeErasedValue<T> {
+ public:
+  using value_type = typename T::value_type;
+  TypeErasedContainer() = default;
+  TypeErasedContainer(const TypeErasedContainer&) = default;
+  TypeErasedContainer(TypeErasedContainer&&) = default;
+  explicit TypeErasedContainer(const T& n) : TypeErasedValue<T>(n) {}
+  TypeErasedContainer(std::initializer_list<value_type> init_list)
+      : TypeErasedContainer(T(init_list.begin(), init_list.end())) {}
+  // one-argument constructor of value type T, to appease older toolchains that
+  // get confused by one-element initializer lists in some contexts
+  explicit TypeErasedContainer(const value_type& v)
+      : TypeErasedContainer(T(&v, &v + 1)) {}
+};
+
+// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
+// detect it.
+template <typename T>
+using is_hashable = std::is_default_constructible<absl::Hash<T>>;
+
+}  // namespace hash_test_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_HASH_TEST_H_