lib: reintroduce v8 module

I introduced this module over a year ago in a pull request as the v8
module but it was quickly subsumed by the tracing module.

The tracing module was recently removed again and that is why this
commit introduces the v8 module again, including the new features it
picked up commits d23ac0e and f8076c4.

PR-URL: nodejs#131
Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>
Reviewed-By: Christian Tellnes <christian@tellnes.no>
Reviewed-By: Thorsten Lorenz <thlorenz@gmx.de>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

doc/api/_toc.markdown

@@ -34,5 +34,6 @@
 * [UDP/Datagram](dgram.html)
 * [URL](url.html)
 * [Utilities](util.html)
+* [V8](v8.html)
 * [VM](vm.html)
 * [ZLIB](zlib.html)

doc/api/all.markdown

@@ -35,3 +35,4 @@
 @include debugger
 @include cluster
 @include smalloc
+@include v8

doc/api/v8.markdown

@@ -0,0 +1,43 @@
+# V8
+
+    Stability: 1 - Experimental
+
+This module exposes events and interfaces specific to the version of [V8][]
+built with node.  These interfaces are subject to change by upstream and are
+therefore not covered under the stability index.
+
+### getHeapStatistics()
+
+Returns an object with the following properties
+
+```
+{
+  total_heap_size: 7326976,
+  total_heap_size_executable: 4194304,
+  total_physical_size: 7326976,
+  used_heap_size: 3476208,
+  heap_size_limit: 1535115264
+}
+```
+
+### setFlagsFromString()
+
+Set additional V8 command line flags.  Use with care; changing settings
+after the VM has started may result in unpredictable behavior, including
+crashes and data loss.  Or it may simply do nothing.
+
+The V8 options available for a version of node may be determined by running
+`iojs --v8-options`.  An unofficial, community-maintained list of options
+and their effects is available
+[here](https://github.com/thlorenz/v8-flags/blob/master/flags-0.11.md).
+
+Usage:
+
+```
+// Print GC events to stdout for one minute.
+var v8 = require('v8');
+v8.setFlagsFromString('--trace_gc');
+setTimeout(function() { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
+```
+
+[V8]: https://code.google.com/p/v8/

lib/repl.js

@@ -74,7 +74,8 @@ exports.writer = util.inspect;
 exports._builtinLibs = ['assert', 'buffer', 'child_process', 'cluster',
   'crypto', 'dgram', 'dns', 'domain', 'events', 'fs', 'http', 'https', 'net',
   'os', 'path', 'punycode', 'querystring', 'readline', 'stream',
-  'string_decoder', 'tls', 'tty', 'url', 'util', 'vm', 'zlib', 'smalloc'];
+  'string_decoder', 'tls', 'tty', 'url', 'util', 'v8', 'vm', 'zlib',
+  'smalloc'];
 
 
 function REPLServer(prompt, stream, eval_, useGlobal, ignoreUndefined) {

lib/v8.js

@@ -0,0 +1,41 @@
+// Copyright (c) 2014, StrongLoop Inc.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+'use strict';
+
+var EventEmitter = require('events');
+var v8binding = process.binding('v8');
+
+var v8 = module.exports = new EventEmitter();
+v8.getHeapStatistics = v8binding.getHeapStatistics;
+v8.setFlagsFromString = v8binding.setFlagsFromString;
+
+
+function emitGC(before, after) {
+  v8.emit('gc', before, after);
+}
+
+
+v8.on('newListener', function(name) {
+  if (name === 'gc' && EventEmitter.listenerCount(this, name) === 0) {
+    v8binding.startGarbageCollectionTracking(emitGC);
+  }
+});
+
+
+v8.on('removeListener', function(name) {
+  if (name === 'gc' && EventEmitter.listenerCount(this, name) === 0) {
+    v8binding.stopGarbageCollectionTracking();
+  }
+});

node.gyp

@@ -64,6 +64,7 @@
       'lib/tty.js',
       'lib/url.js',
       'lib/util.js',
+      'lib/v8.js',
       'lib/vm.js',
       'lib/zlib.js',
     ],

test/simple/test-v8-flags.js

@@ -0,0 +1,26 @@
+// Copyright (c) 2014, StrongLoop Inc.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var v8 = require('v8');
+var vm = require('vm');
+
+v8.setFlagsFromString('--allow_natives_syntax');
+assert(eval('%_IsSmi(42)'));
+assert(vm.runInThisContext('%_IsSmi(42)'));
+
+v8.setFlagsFromString('--noallow_natives_syntax');
+assert.throws(function() { eval('%_IsSmi(42)') }, SyntaxError);
+assert.throws(function() { vm.runInThisContext('%_IsSmi(42)') }, SyntaxError);

test/simple/test-v8-gc.js

@@ -0,0 +1,46 @@
+// Copyright (c) 2014, StrongLoop Inc.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+// Flags: --expose_gc
+
+var common = require('../common');
+var assert = require('assert');
+var v8 = require('v8');
+
+assert(typeof gc === 'function', 'Run this test with --expose_gc.');
+
+var ncalls = 0;
+var before;
+var after;
+
+function ongc(before_, after_) {
+  // Try very hard to not create garbage because that could kick off another
+  // garbage collection cycle.
+  before = before_;
+  after = after_;
+  ncalls += 1;
+}
+
+gc();
+v8.on('gc', ongc);
+gc();
+v8.removeListener('gc', ongc);
+gc();
+
+assert.equal(ncalls, 1);
+assert.equal(typeof before, 'object');
+assert.equal(typeof after, 'object');
+assert.equal(typeof before.timestamp, 'number');
+assert.equal(typeof after.timestamp, 'number');
+assert.equal(before.timestamp <= after.timestamp, true);

test/simple/test-v8-stats.js

@@ -0,0 +1,29 @@
+// Copyright (c) 2014, StrongLoop Inc.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var v8 = require('v8');
+
+var s = v8.getHeapStatistics();
+var keys = [
+  'heap_size_limit',
+  'total_heap_size',
+  'total_heap_size_executable',
+  'total_physical_size',
+  'used_heap_size'];
+assert.deepEqual(Object.keys(s).sort(), keys);
+keys.forEach(function(key) {
+  assert.equal(typeof s[key], 'number');
+});