jsnanigans · April 17, 2023 09:39 · Apr 17, 2023
diff --git a/hashText.ts b/hashText.ts
@@ -0,0 +1,5 @@
+function hashText(text: string, seed = 42): number {
+  const encoder = new TextEncoder();
+  const inputUint8Array = encoder.encode(text);
+  return murmur3_32(inputUint8Array, inputUint8Array.length, seed);
+}
diff --git a/murmur3_32.ts b/murmur3_32.ts
@@ -0,0 +1,53 @@
+function murmur3_32(key: Uint8Array, len: number, seed: number): number {
+  const c1 = 0xcc9e2d51;
+  const c2 = 0x1b873593;
+  const r1 = 15;
+  const r2 = 13;
+  const m = 5;
+  const n = 0xe6546b64;
+
+  let hash = seed;
+
+  function rol(value: number, shift: number): number {
+    return (value << shift) | (value >>> (32 - shift));
+  }
+
+  for (let i = 0; i < len - (len % 4); i += 4) {
+    let k =
+      key[i] | (key[i + 1] << 8) | (key[i + 2] << 16) | (key[i + 3] << 24);
+
+    k = (k * c1) | 0;
+    k = rol(k, r1);
+    k = (k * c2) | 0;
+
+    hash ^= k;
+    hash = rol(hash, r2);
+    hash = (hash * m + n) | 0;
+  }
+
+  let remainingBytes = 0;
+  switch (len % 4) {
+    case 3:
+      remainingBytes ^= key[len - 3] << 16;
+      break;
+    case 2:
+      remainingBytes ^= key[len - 2] << 8;
+      break;
+    case 1:
+      remainingBytes ^= key[len - 1];
+      remainingBytes = (remainingBytes * c1) | 0;
+      remainingBytes = rol(remainingBytes, r1);
+      remainingBytes = (remainingBytes * c2) | 0;
+      hash ^= remainingBytes;
+  }
+
+  hash ^= len;
+
+  hash ^= hash >>> 16;
+  hash = (hash * 0x85ebca6b) | 0;
+  hash ^= hash >>> 13;
+  hash = (hash * 0xc2b2ae35) | 0;
+  hash ^= hash >>> 16;
+
+  return hash >>> 0;
+}
diff --git a/test.ts b/test.ts
@@ -0,0 +1,42 @@
+import hashText from "src/lib/hashText";
+
+// mock "new TextEncoder()" and set it on the global.TextEncoder is not defined
+class TextEncoder {
+  encode(input: string): Uint8Array {
+    return new Uint8Array(input.split("").map((char) => char.charCodeAt(0)));
+  }
+}
+
+(globalThis as any).TextEncoder = TextEncoder;
+
+describe('hashText', () => {
+  it('should return the same hash for the same input and seed', () => {
+    const input = 'Hello, world!';
+
+    const hash1 = hashText(input);
+    const hash2 = hashText(input);
+
+    expect(hash1).toStrictEqual(hash2);
+  });
+
+  it('should return different hashes for different inputs with the same seed', () => {
+    const input1 = 'Hello, world!';
+    const input2 = 'Second String';
+
+    const hash1 = hashText(input1);
+    const hash2 = hashText(input2);
+
+    expect(hash1).not.toStrictEqual(hash2);
+  });
+
+  it('should return different hashes for the same input with different seeds', () => {
+    const input = 'Hello, world!';
+    const seed1 = 42;
+    const seed2 = 84;
+
+    const hash1 = hashText(input, seed1);
+    const hash2 = hashText(input, seed2);
+
+    expect(hash1).not.toStrictEqual(hash2);
+  });
+});
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