child_process: fix sending utf-8 to child process

In process#send() and child_process.ChildProcess#send(), use 'utf8' as
the encoding instead of 'ascii' because 'ascii' mutilates non-ASCII
input. Correctly handle partial character sequences by introducing
a StringDecoder.

Sending over UTF-8 no longer works in v0.10 because the high bit of
each byte is now cleared when converting a Buffer to ASCII. See
commit 96a314b for details.

Fixes #4999 and #5011.

lib/child_process.js

@@ -19,6 +19,7 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+var StringDecoder = require('string_decoder').StringDecoder;
 var EventEmitter = require('events').EventEmitter;
 var net = require('net');
 var dgram = require('dgram');
@@ -321,11 +322,12 @@ function handleMessage(target, message, handle) {
 function setupChannel(target, channel) {
   target._channel = channel;
 
+  var decoder = new StringDecoder('utf8');
   var jsonBuffer = '';
   channel.buffering = false;
   channel.onread = function(pool, offset, length, recvHandle) {
     if (pool) {
-      jsonBuffer += pool.toString('ascii', offset, offset + length);
+      jsonBuffer += decoder.write(pool.slice(offset, offset + length));
 
       var i, start = 0;
 

test/simple/test-child-process-send-utf8.js

@@ -0,0 +1,34 @@
+// 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 fork = require('child_process').fork;
+
+var expected = Array(1e5).join('ßßßß');
+if (process.argv[2] === 'child') {
+  process.send(expected);
+} else {
+  var child = fork(process.argv[1], ['child']);
+  child.on('message', common.mustCall(function(actual) {
+    assert.equal(actual, expected);
+  }));
+}