[Buffered Event Hubs Producer] Implements Parition Key to Partition ID mapping

sdk/eventhub/event-hubs/src/impl/partitionAssigner.ts

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 
 import { isDefined } from "../util/typeGuards";
+import { mapPartitionKeyToId } from "./patitionKeyToIdMapper";
 
 /**
  * @internal
@@ -52,17 +53,12 @@ export class PartitionAssigner {
     }
 
     if (isDefined(partitionKey)) {
-      return this._assignPartitionForPartitionKey(partitionKey);
+      return mapPartitionKeyToId(partitionKey, this._partitions.length).toString();
     }
 
     return this._assignRoundRobinPartition();
   }
 
-  private _assignPartitionForPartitionKey(partitionKey: string): string {
-    // TODO: Implement hashing function
-    return partitionKey ? this._partitions[0] : this._partitions[0];
-  }
-
   private _assignRoundRobinPartition(): string {
     const maxPartitionIndex = this._partitions.length - 1;
     const proposedPartitionIndex = this._lastRoundRobinPartitionIndex + 1;

sdk/eventhub/event-hubs/src/impl/patitionKeyToIdMapper.ts

@@ -0,0 +1,130 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+/* eslint-disable no-fallthrough */
+
+import os from "os";
+
+export function mapPartitionKeyToId(partitionKey: string, partitionCount: number): number {
+  const hash = computeHash(Buffer.from(partitionKey, "utf8"));
+  const hashedParitionKey = castToInt16(hash.c ^ hash.b);
+  return Math.abs(hashedParitionKey % partitionCount);
+}
+
+function readUInt32(data: Buffer, offset: number): number {
+  return os.endianness() === "BE" ? data.readUInt32BE(offset) : data.readUInt32LE(offset);
+}
+
+function castToInt16(n: number): number {
+  return new Int16Array([n])[0];
+}
+
+function computeHash(data: Buffer, seed1: number = 0, seed2: number = 0): any {
+  let a: number, b: number, c: number;
+
+  a = b = c = 0xdeadbeef + data.length + seed1;
+  c += seed2;
+
+  let index = 0,
+    size = data.length;
+  while (size > 12) {
+    a += readUInt32(data, index);
+    b += readUInt32(data, index + 4);
+    c += readUInt32(data, index + 8);
+
+    a -= c;
+    a ^= (c << 4) | (c >>> 28);
+    c += b;
+
+    b -= a;
+    b ^= (a << 6) | (a >>> 26);
+    a += c;
+
+    c -= b;
+    c ^= (b << 8) | (b >>> 24);
+    b += a;
+
+    a -= c;
+    a ^= (c << 16) | (c >>> 16);
+    c += b;
+
+    b -= a;
+    b ^= (a << 19) | (a >>> 13);
+    a += c;
+
+    c -= b;
+    c ^= (b << 4) | (b >>> 28);
+    b += a;
+
+    index += 12;
+    size -= 12;
+  }
+
+  let curr = size;
+  switch (curr) {
+    case 12:
+      a += readUInt32(data, index);
+      b += readUInt32(data, index + 4);
+      c += readUInt32(data, index + 8);
+      break;
+    case 11:
+      c += data[index + 10] << 16;
+      curr = 10;
+    case 10:
+      c += data[index + 9] << 8;
+      curr = 9;
+    case 9:
+      c += data[index + 8];
+      curr = 8;
+    case 8:
+      b += readUInt32(data, index + 4);
+      a += readUInt32(data, index);
+      break;
+    case 7:
+      b += data[index + 6] << 16;
+      curr = 6;
+    case 6:
+      b += data[index + 5] << 8;
+      curr = 5;
+    case 5:
+      b += data[index + 4];
+      curr = 4;
+    case 4:
+      a += readUInt32(data, index);
+      break;
+    case 3:
+      a += data[index + 2] << 16;
+      curr = 2;
+    case 2:
+      a += data[index + 1] << 8;
+      curr = 1;
+    case 1:
+      a += data[index];
+      break;
+    case 0:
+      return { b: b >>> 0, c: c >>> 0 };
+  }
+
+  c ^= b;
+  c -= (b << 14) | (b >>> 18);
+
+  a ^= c;
+  a -= (c << 11) | (c >>> 21);
+
+  b ^= a;
+  b -= (a << 25) | (a >>> 7);
+
+  c ^= b;
+  c -= (b << 16) | (b >>> 16);
+
+  a ^= c;
+  a -= (c << 4) | (c >>> 28);
+
+  b ^= a;
+  b -= (a << 14) | (a >>> 18);
+
+  c ^= b;
+  c -= (b << 24) | (b >>> 8);
+
+  return { b: b >>> 0, c: c >>> 0 };
+}

sdk/eventhub/event-hubs/test/internal/impl/mapPartitionKeyToId.spec.ts

@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+import { assert } from "chai";
+import { mapPartitionKeyToId } from "../../../src/impl/patitionKeyToIdMapper";
+
+/**
+ * These unit tests have been created from outputs received from the C# implementation
+ * of Jenkins lookup3 that the Event Hubs service uses.
+ */
+describe("mapPartitionKeyToId", () => {
+  it("short key, small partitions count", () => {
+    assert.equal(mapPartitionKeyToId("alphabet", 3), 0);
+  });
+
+  it("short key, large partitions count", () => {
+    assert.equal(mapPartitionKeyToId("alphabet", 11), 4);
+  });
+
+  it("long key, small partitions count", () => {
+    assert.equal(mapPartitionKeyToId("TheBestParitionEver", 4), 2);
+  });
+
+  it("long key, large partitions count", () => {
+    assert.equal(mapPartitionKeyToId("TheWorstParitionEver", 15), 1);
+  });
+});

sdk/eventhub/event-hubs/tsconfig.json

@@ -4,6 +4,7 @@
     "declarationDir": "./types",
     "outDir": "./dist-esm",
     "downlevelIteration": true,
+    "noFallthroughCasesInSwitch": false,
     "paths": {
       "@azure/event-hubs": ["./src/index"]
     }