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| author | Derek Mauro <dmauro@google.com> | 2023-11-15 18:02:49 -0800 |
|---|---|---|
| committer | Copybara-Service <copybara-worker@google.com> | 2023-11-15 18:03:30 -0800 |
| commit | 3bd86026c93da5a40006fd53403dff9d5f5e30e3 (patch) | |
| tree | 2bb708baea92a1ba2d90e0fcdb388b759aca451e /absl/hash/internal/hash.h | |
| parent | 20f92b10d5ae1dc03592b4b6caafec7b0e161252 (diff) | |
| download | abseil-3bd86026c93da5a40006fd53403dff9d5f5e30e3.tar.gz abseil-3bd86026c93da5a40006fd53403dff9d5f5e30e3.tar.bz2 abseil-3bd86026c93da5a40006fd53403dff9d5f5e30e3.zip | |
Provide AbslHashValue for std::filesystem::path in C++17
This is somewhat tricky to implement because path equality is not
straightforward. See
https://github.com/abseil/abseil-cpp/pull/1560#issuecomment-1799983471
for discussion.
Closes #655
Closes #1560
PiperOrigin-RevId: 582863821
Change-Id: I03517a7f2003614c027c786abbfb91b6571ab662
Diffstat (limited to 'absl/hash/internal/hash.h')
| -rw-r--r-- | absl/hash/internal/hash.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h index e97cb315..003f3dde 100644 --- a/absl/hash/internal/hash.h +++ b/absl/hash/internal/hash.h @@ -56,6 +56,10 @@ #include "absl/types/variant.h" #include "absl/utility/utility.h" +#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L +#include <filesystem> // NOLINT +#endif + #ifdef ABSL_HAVE_STD_STRING_VIEW #include <string_view> #endif @@ -578,6 +582,24 @@ H AbslHashValue(H hash_state, std::basic_string_view<Char> str) { #endif // ABSL_HAVE_STD_STRING_VIEW +#if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L + +// Support std::filesystem::path. The SFINAE is required because some string +// types are implicitly convertible to std::filesystem::path. +template <typename Path, typename H, + typename = absl::enable_if_t< + std::is_same_v<Path, std::filesystem::path>>> +H AbslHashValue(H hash_state, const Path& path) { + // This is implemented by deferring to the standard library to compute the + // hash. The standard library requires that for two paths, `p1 == p2`, then + // `hash_value(p1) == hash_value(p2)`. `AbslHashValue` has the same + // requirement. Since `operator==` does platform specific matching, deferring + // to the standard library is the simplest approach. + return H::combine(std::move(hash_state), std::filesystem::hash_value(path)); +} + +#endif // defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L + // ----------------------------------------------------------------------------- // AbslHashValue for Sequence Containers // ----------------------------------------------------------------------------- |