process: add `process.hrtime()`

This commit adds a high-resolution timer function.

doc/api/process.markdown

@@ -359,3 +359,25 @@ given, otherwise returns the current mask.
 ## process.uptime()
 
 Number of seconds Node has been running.
+
+
+## process.hrtime()
+
+Returns the current high-resolution real time in a `[seconds, nanoseconds]`
+tuple Array. It is relative to an arbitrary time in the past. It is not
+related to the time of day and therefore not subject to clock drift. The
+primary use is for measuring performance between intervals.
+
+You may pass in the result of a previous call to `process.hrtime()` to get
+a diff reading, useful for benchmarks and measuring intervals:
+
+    var t = process.hrtime();
+    // [ 1800216, 927643717 ]
+
+    setTimeout(function () {
+      t = process.hrtime(t);
+      // [ 1, 6962306 ]
+
+      console.log('benchmark took %d seconds and %d nanoseconds', t[0], t[1]);
+      // benchmark took 1 seconds and 6962306 nanoseconds
+    }, 1000);

src/node.cc

@@ -1571,6 +1571,34 @@ Handle<Value> Kill(const Arguments& args) {
   return Undefined();
 }
 
+// used in Hrtime() below
+#define NANOS_PER_SEC 1000000000
+
+// Hrtime exposes libuv's uv_hrtime() high-resolution timer.
+// The value returned by uv_hrtime() is a 64-bit int representing nanoseconds,
+// so this function instead returns an Array with 2 entries representing seconds
+// and nanoseconds, to avoid any integer overflow possibility.
+// Pass in an Array from a previous hrtime() call to instead get a time diff.
+Handle<Value> Hrtime(const v8::Arguments& args) {
+  HandleScope scope;
+
+  uint64_t t = uv_hrtime();
+
+  if (args.Length() > 0) {
+    // return a time diff tuple
+    Local<Array> inArray = Local<Array>::Cast(args[0]);
+    uint64_t seconds = inArray->Get(0)->Uint32Value();
+    uint64_t nanos = inArray->Get(1)->Uint32Value();
+    t -= (seconds * NANOS_PER_SEC) + nanos;
+  }
+
+  Local<Array> tuple = Array::New(2);
+  tuple->Set(0, Integer::NewFromUnsigned(t / NANOS_PER_SEC));
+  tuple->Set(1, Integer::NewFromUnsigned(t % NANOS_PER_SEC));
+
+  return scope.Close(tuple);
+}
+
 
 typedef void (UV_DYNAMIC* extInit)(Handle<Object> exports);
 
@@ -2150,6 +2178,8 @@ Handle<Object> SetupProcessObject(int argc, char *argv[]) {
   NODE_SET_METHOD(process, "_debugPause", DebugPause);
   NODE_SET_METHOD(process, "_debugEnd", DebugEnd);
 
+  NODE_SET_METHOD(process, "hrtime", Hrtime);
+
   NODE_SET_METHOD(process, "dlopen", DLOpen);
 
   NODE_SET_METHOD(process, "uptime", Uptime);

test/pummel/test-process-hrtime.js

@@ -0,0 +1,40 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// 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.
+
+var common = require('../common');
+var assert = require('assert');
+
+var start = process.hrtime();
+
+// process.hrtime() should return an Array
+assert(Array.isArray(start));
+
+// busy-loop for 2 seconds
+var now = Date.now();
+while (Date.now() - now < 2000);
+
+// get a diff reading
+var diff = process.hrtime(start);
+
+// should be at least 1 second, at most 2 seconds later
+// (the while loop will usually exit a few nanoseconds before 2)
+assert(diff[0] >= 1);
+assert(diff[0] <= 2);