Use MurmurHash3 when native hashing function is not available

packages/react-dom-bindings/src/server/ReactDOMLegacyServerStreamConfig.js

@@ -77,6 +77,4 @@ export function closeWithError(destination: Destination, error: mixed): void {
   destination.destroy(error);
 }
 
-export function createFastHash(input: string): string | number {
-  return input;
-}
+export {createFastHashJS as createFastHash} from 'react-server/src/createFastHashJS';

packages/react-server-dom-fb/src/ReactServerStreamConfigFB.js

@@ -84,6 +84,4 @@ export function closeWithError(destination: Destination, error: mixed): void {
   destination.error = error;
 }
 
-export function createFastHash(input: string): string | number {
-  return input;
-}
+export {createFastHashJS as createFastHash} from 'react-server/src/createFastHashJS';

packages/react-server/src/ReactServerStreamConfigBrowser.js

@@ -183,6 +183,4 @@ export function closeWithError(destination: Destination, error: mixed): void {
   }
 }
 
-export function createFastHash(input: string): string | number {
-  return input;
-}
+export {createFastHashJS as createFastHash} from 'react-server/src/createFastHashJS';

packages/react-server/src/ReactServerStreamConfigEdge.js

@@ -183,6 +183,4 @@ export function closeWithError(destination: Destination, error: mixed): void {
   }
 }
 
-export function createFastHash(input: string): string | number {
-  return input;
-}
+export {createFastHashJS as createFastHash} from 'react-server/src/createFastHashJS';

packages/react-server/src/createFastHashJS.js

@@ -0,0 +1,122 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+// A pure JS implementation of a string hashing function. We do not use it for
+// security or obfuscation purposes, only to create compact hashes. So we
+// prioritize speed over collision avoidance. For example, we use this to hash
+// the component key path used by useFormState for MPA-style submissions.
+//
+// In environments where built-in hashing functions are available, we prefer
+// those instead. Like Node's crypto module, or Bun.hash. Unfortunately this
+// does not include the web standard crypto API because those methods are all
+// async. For our purposes, we need it to be sync because the cost of context
+// switching is too high to be worth it.
+//
+// The most popular hashing algorithm that meets these requirements in the JS
+// ecosystem is MurmurHash3, and almost all implementations I could find used
+// some version of the implementation by Gary Court inlined below.
+
+export function createFastHashJS(key: string): number {
+  return murmurhash3_32_gc(key, 0);
+}
+
+/* eslint-disable prefer-const, no-fallthrough */
+
+/**
+ * @license
+ *
+ * JS Implementation of MurmurHash3 (r136) (as of May 20, 2011)
+ *
+ * Copyright (c) 2011 Gary Court
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+function murmurhash3_32_gc(key: string, seed: number): number {
+  let remainder, bytes, h1, h1b, c1, c2, k1, i;
+
+  remainder = key.length & 3; // key.length % 4
+  bytes = key.length - remainder;
+  h1 = seed;
+  c1 = 0xcc9e2d51;
+  c2 = 0x1b873593;
+  i = 0;
+
+  while (i < bytes) {
+    k1 =
+      (key.charCodeAt(i) & 0xff) |
+      ((key.charCodeAt(++i) & 0xff) << 8) |
+      ((key.charCodeAt(++i) & 0xff) << 16) |
+      ((key.charCodeAt(++i) & 0xff) << 24);
+    ++i;
+
+    k1 =
+      ((k1 & 0xffff) * c1 + ((((k1 >>> 16) * c1) & 0xffff) << 16)) & 0xffffffff;
+    k1 = (k1 << 15) | (k1 >>> 17);
+    k1 =
+      ((k1 & 0xffff) * c2 + ((((k1 >>> 16) * c2) & 0xffff) << 16)) & 0xffffffff;
+
+    h1 ^= k1;
+    h1 = (h1 << 13) | (h1 >>> 19);
+    h1b =
+      ((h1 & 0xffff) * 5 + ((((h1 >>> 16) * 5) & 0xffff) << 16)) & 0xffffffff;
+    h1 = (h1b & 0xffff) + 0x6b64 + ((((h1b >>> 16) + 0xe654) & 0xffff) << 16);
+  }
+
+  k1 = 0;
+
+  switch (remainder) {
+    case 3:
+      k1 ^= (key.charCodeAt(i + 2) & 0xff) << 16;
+    case 2:
+      k1 ^= (key.charCodeAt(i + 1) & 0xff) << 8;
+    case 1:
+      k1 ^= key.charCodeAt(i) & 0xff;
+
+      k1 =
+        ((k1 & 0xffff) * c1 + ((((k1 >>> 16) * c1) & 0xffff) << 16)) &
+        0xffffffff;
+      k1 = (k1 << 15) | (k1 >>> 17);
+      k1 =
+        ((k1 & 0xffff) * c2 + ((((k1 >>> 16) * c2) & 0xffff) << 16)) &
+        0xffffffff;
+      h1 ^= k1;
+  }
+
+  h1 ^= key.length;
+
+  h1 ^= h1 >>> 16;
+  h1 =
+    ((h1 & 0xffff) * 0x85ebca6b +
+      ((((h1 >>> 16) * 0x85ebca6b) & 0xffff) << 16)) &
+    0xffffffff;
+  h1 ^= h1 >>> 13;
+  h1 =
+    ((h1 & 0xffff) * 0xc2b2ae35 +
+      ((((h1 >>> 16) * 0xc2b2ae35) & 0xffff) << 16)) &
+    0xffffffff;
+  h1 ^= h1 >>> 16;
+
+  return h1 >>> 0;
+}