introduce fnv1a hashing function (#39515)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39515

changelog: [internal]

Implements FNV hashing algorithm: http://www.isthe.com/chongo/tech/comp/fnv/

Reviewed By: javache

Differential Revision: D49358327

fbshipit-source-id: b211da89ca7b6bea6ed1b0732e639bbc2de210f7

packages/react-native/ReactCommon/react/renderer/core/PropsMacros.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <react/renderer/core/RawPropsPrimitives.h>
+#include <react/utils/fnv1a.h>
 #include <functional>
 
 // We need to use clang pragmas inside of a macro below,
@@ -23,7 +24,7 @@
   ([]() constexpr->RawPropsPropNameHash {                 \
     CLANG_PRAGMA("clang diagnostic push")                 \
     CLANG_PRAGMA("clang diagnostic ignored \"-Wshadow\"") \
-    return folly::hash::fnv32_buf(s, sizeof(s) - 1);      \
+    return facebook::react::fnv1a(s);                     \
     CLANG_PRAGMA("clang diagnostic pop")                  \
   }())
 

packages/react-native/ReactCommon/react/utils/fnv1a.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+namespace facebook::react {
+
+/**
+ * FNV-1a hash function implementation.
+ * Implemented as described in http://www.isthe.com/chongo/tech/comp/fnv/.
+ *
+ * Please use std::hash if possible. `fnv1a` should only be used in cases
+ * when std::hash does not provide the needed functionality. For example,
+ * constexpr.
+ */
+constexpr uint32_t fnv1a(std::string_view string) noexcept {
+  constexpr uint32_t offset_basis = 2166136261;
+
+  uint32_t hash = offset_basis;
+
+  for (auto const& c : string) {
+    hash ^= static_cast<int8_t>(c);
+    // Using shifts and adds instead of multiplication with a prime number.
+    // This is faster when compiled with optimizations.
+    hash +=
+        (hash << 1) + (hash << 4) + (hash << 7) + (hash << 8) + (hash << 24);
+  }
+
+  return hash;
+}
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/utils/tests/fnv1aTests.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+#include <react/utils/fnv1a.h>
+
+namespace facebook::react {
+
+TEST(fnv1aTests, testBasicHashing) {
+  EXPECT_EQ(fnv1a("react"), fnv1a("react"));
+
+  EXPECT_NE(fnv1a("react"), fnv1a("tceat"));
+
+  auto string1 = "case 1";
+  auto string2 = "different string";
+  EXPECT_EQ(fnv1a(string1), fnv1a(string1));
+  EXPECT_NE(fnv1a(string1), fnv1a(string2));
+}
+
+} // namespace facebook::react