Hash support for std::wstring_view/u16string_view/u32string_view

PiperOrigin-RevId: 519200954
Change-Id: I349023cacab0ac4cbefb8505efd29a5eda1e9067

absl/hash/hash.h

@@ -113,7 +113,9 @@ ABSL_NAMESPACE_BEGIN
 //     * std::string (as well as any instance of std::basic_string that
 //       uses one of {char, wchar_t, char16_t, char32_t} and its associated
 //       std::char_traits)
-//     * std::string_view
+//     * std::string_view (as well as any instance of std::basic_string_view
+//       that uses one of {char, wchar_t, char16_t, char32_t} and its associated
+//       std::char_traits)
 //  * All the standard sequence containers (provided the elements are hashable)
 //  * All the standard associative containers (provided the elements are
 //    hashable)

absl/hash/hash_test.cc

@@ -53,6 +53,10 @@
 #include "absl/numeric/int128.h"
 #include "absl/strings/cord_test_helpers.h"
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace {
 
 // Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
@@ -488,6 +492,47 @@ TEST(HashValueTest, U32String) {
       std::u32string(U"Iñtërnâtiônàlizætiøn"))));
 }
 
+TEST(HashValueTest, WStringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::wstring_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::wstring_view(), std::wstring_view(L"ABC"), std::wstring_view(L"ABC"),
+      std::wstring_view(L"Some other different string_view"),
+      std::wstring_view(L"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U16StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u16string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u16string_view(), std::u16string_view(u"ABC"),
+                      std::u16string_view(u"ABC"),
+                      std::u16string_view(u"Some other different string_view"),
+                      std::u16string_view(u"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U32StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u32string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u32string_view(), std::u32string_view(U"ABC"),
+                      std::u32string_view(U"ABC"),
+                      std::u32string_view(U"Some other different string_view"),
+                      std::u32string_view(U"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
 TEST(HashValueTest, StdArray) {
   EXPECT_TRUE((is_hashable<std::array<int, 3>>::value));
 

absl/hash/internal/hash.h

@@ -56,6 +56,10 @@
 #include "absl/types/variant.h"
 #include "absl/utility/utility.h"
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
@@ -518,7 +522,8 @@ H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) {
 //  - `absl::Cord`
 //  - `std::string` (and std::basic_string<T, std::char_traits<T>, A> for
 //      any allocator A and any T in {char, wchar_t, char16_t, char32_t})
-//  - `absl::string_view` and `std::string_view`
+//  - `absl::string_view`, `std::string_view`, `std::wstring_view`,
+//    `std::u16string_view`, and `std::u32_string_view`.
 //
 // For simplicity, we currently support only strings built on `char`, `wchar_t`,
 // `char16_t`, or `char32_t`. This support may be broadened, if necessary, but
@@ -544,6 +549,21 @@ H AbslHashValue(
       str.size());
 }
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+// Support std::wstring_view, std::u16string_view and std::u32string_view.
+template <typename Char, typename H,
+          typename = absl::enable_if_t<std::is_same<Char, wchar_t>::value ||
+                                       std::is_same<Char, char16_t>::value ||
+                                       std::is_same<Char, char32_t>::value>>
+H AbslHashValue(H hash_state, std::basic_string_view<Char> str) {
+  return H::combine(
+      H::combine_contiguous(std::move(hash_state), str.data(), str.size()),
+      str.size());
+}
+
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
 // -----------------------------------------------------------------------------
 // AbslHashValue for Sequence Containers
 // -----------------------------------------------------------------------------