feat(ObjectID): use FNV-1a hash for objectId

Uses a hash of the hostname in the object id. Hashing algorithm
is FNV-1a, 24-bit, using xor-folding.

Fixes NODE-1484

Author: daprahamian

lib/bson/fnv1a.js

@@ -0,0 +1,36 @@
+'use strict';
+
+const Long = require('./long');
+
+const MASK_8 = 0xff;
+const MASK_24 = 0xffffff;
+const MASK_32 = 0xffffffff;
+
+// See http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param for the definition of these parameters;
+const FNV_PRIME = new Long(16777619, 0);
+const OFFSET_BASIS = new Long(2166136261, 0);
+const FNV_MASK = new Long(MASK_32, 0);
+
+function fnv1a32(input, encoding) {
+  encoding = encoding || 'utf8';
+  const octets = Buffer.from(input, encoding);
+
+  let hash = OFFSET_BASIS;
+  for (let i = 0; i < octets.length; i += 1) {
+    hash = hash.xor(new Long(octets[i], 0));
+    hash = hash.multiply(FNV_PRIME);
+    hash = hash.and(FNV_MASK);
+  }
+  return hash.getLowBitsUnsigned();
+}
+
+function fnv1a24(input, encoding) {
+  const _32bit = fnv1a32(input, encoding);
+  const base = _32bit & MASK_24;
+  const top = (_32bit >>> 24) & MASK_8;
+  const final = (base ^ top) & MASK_24;
+
+  return final;
+}
+
+module.exports = { fnv1a24, fnv1a32 };

lib/bson/objectid.js

@@ -1,4 +1,8 @@
 'use strict';
+
+const hostname = require('os').hostname;
+const fnv1a24 = require('./fnv1a').fnv1a24;
+
 /**
  * Machine id.
  *
@@ -7,7 +11,7 @@
  * that would mean an asyc call to gethostname, so we don't bother.
  * @ignore
  */
-var MACHINE_ID = parseInt(Math.random() * 0xffffff, 10);
+const MACHINE_ID = fnv1a24(hostname);
 
 // Regular expression that checks for hex value
 var checkForHexRegExp = new RegExp('^[0-9a-fA-F]{24}$');

test/node/fnv1a.js

@@ -0,0 +1,26 @@
+'use strict';
+
+const fnv1a = require('../../lib/bson/fnv1a');
+const fnv1a24 = fnv1a.fnv1a24;
+const expect = require('chai').expect;
+describe('fnv1a', function() {
+  require('./specs/object-id/vectors.json').vectors.forEach(testCase => {
+    const hash = testCase.hash;
+
+    let vector;
+    let encoding;
+    if (typeof testCase.vector === 'string') {
+      vector = testCase.vector;
+      encoding = 'utf8';
+    } else if (typeof testCase.vectorHex === 'string') {
+      vector = testCase.vectorHex;
+      encoding = 'hex';
+    }
+
+    it(`should properly hash the string "${vector}" with a 24 bit FNV-1a`, function() {
+      const hashed = fnv1a24(vector, encoding);
+      const buff = Buffer.from([(hashed >>> 16) & 0xff, (hashed >>> 8) & 0xff, hashed & 0xff]);
+      expect(buff.toString('hex')).to.equal(hash);
+    });
+  });
+});