Add a function to update the job timestamp

lib/messages.js

@@ -87,3 +87,11 @@ function parseSubmitResult(buffer){
         succeed: succeed
     };
 }
+
+exports.updateJobTimestamp = function(job, newTimestamp) {
+    var headerBlob = job.headerBlob
+    var encodedTsLength = 8
+    var encodedTargetLength = 4
+    var tsOffset = job.headerBlob.length - (encodedTsLength + encodedTargetLength)
+    headerBlob.writeBigUInt64BE(BigInt(newTimestamp), tsOffset)
+}

test/messagesTest.js

@@ -0,0 +1,37 @@
+const { expect } = require('chai');
+const { randomBytes } = require('crypto');
+const constants = require('../lib/constants');
+const { updateJobTimestamp } = require("../lib/messages")
+
+it('should update the job timestamp', function(){
+  function randomHeaderBlob(ts) {
+    var encodedTs = Buffer.alloc(8)
+    encodedTs.writeBigUInt64BE(BigInt(ts))
+    return Buffer.concat([
+      randomBytes(24), // nonce
+      randomBytes(1), // version
+      randomBytes(1 + (2 * constants.GroupSize - 1) * 32), // block deps
+      randomBytes(32), // state hash
+      randomBytes(32), // txs hash
+      encodedTs,
+      randomBytes(4), // target
+    ])
+  }
+
+  for (var i = 1; i <= 10; i += 1) {
+    var now = Date.now() + (i * 60 * 1000)
+    var job = { headerBlob: randomHeaderBlob(now) }
+    var prevHeaderBlob = Buffer.from(job.headerBlob)
+
+    updateJobTimestamp(job, now)
+    expect(job.headerBlob).to.deep.equal(prevHeaderBlob)
+
+    var newTs = now + (i * 60 * 1000)
+    expect(newTs).not.equal(now)
+    updateJobTimestamp(job, newTs)
+    expect(job.headerBlob).to.not.deep.equal(prevHeaderBlob)
+
+    prevHeaderBlob.writeBigUInt64BE(BigInt(newTs), prevHeaderBlob.length - 12)
+    expect(job.headerBlob).to.deep.equal(prevHeaderBlob)
+  }
+})