Support hashing of base::GUID

Implement a custom hasher for base::GUID so it may be used in standard
hash containers.

Bug: 1026195
Change-Id: I4a6315b21543e374b7eb6e8863b0afc3ff57f334
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2533644
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827073}

base/guid.h

@@ -11,6 +11,7 @@
 #include <string>
 
 #include "base/base_export.h"
+#include "base/hash/hash.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
 
@@ -82,6 +83,16 @@ class BASE_EXPORT GUID {
   std::string lowercase_;
 };
 
+// For runtime usage only. Do not store the result of this hash, as it may
+// change in future Chromium revisions.
+struct BASE_EXPORT GUIDHash {
+  size_t operator()(const GUID& guid) const {
+    // TODO(crbug.com/1026195): Avoid converting to string to take the hash when
+    // the internal type is migrated to a non-string type.
+    return FastHash(guid.AsLowercaseString());
+  }
+};
+
 // Stream operator so GUID objects can be used in logging statements.
 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const GUID& guid);
 

base/guid_unittest.cc

@@ -7,6 +7,7 @@
 #include <stdint.h>
 
 #include <limits>
+#include <unordered_set>
 
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
@@ -147,4 +148,20 @@ TEST(GUIDTest, Equality) {
   EXPECT_EQ(GUID(), GUID());
 }
 
+TEST(GUIDTest, UnorderedSet) {
+  std::unordered_set<GUID, GUIDHash> guid_set;
+
+  static constexpr char kGUID1[] = "01234567-89ab-cdef-fedc-ba9876543210";
+  guid_set.insert(GUID::ParseCaseInsensitive(ToLowerASCII(kGUID1)));
+  EXPECT_EQ(1u, guid_set.size());
+  guid_set.insert(GUID::ParseCaseInsensitive(ToUpperASCII(kGUID1)));
+  EXPECT_EQ(1u, guid_set.size());
+
+  static constexpr char kGUID2[] = "deadbeef-dead-beef-dead-beefdeadbeef";
+  guid_set.insert(GUID::ParseCaseInsensitive(ToLowerASCII(kGUID2)));
+  EXPECT_EQ(2u, guid_set.size());
+  guid_set.insert(GUID::ParseCaseInsensitive(ToUpperASCII(kGUID2)));
+  EXPECT_EQ(2u, guid_set.size());
+}
+
 }  // namespace base