http: move OutgoingMessage into it's own file

3 files changed, 665 insertions, 614 deletions

diff --git a/lib/_http_common.js b/lib/_http_common.js
index 2c6b7d5d3a..40a4b11840 100644
--- a/lib/_http_common.js
+++ b/lib/_http_common.js
@@ -27,6 +27,19 @@ var IncomingMessage = incoming.IncomingMessage;
 var readStart = incoming.readStart;
 var readStop = incoming.readStop;
 
+
+var debug;
+if (process.env.NODE_DEBUG && /http/.test(process.env.NODE_DEBUG)) {
+  debug = function(x) { console.error('HTTP: %s', x); };
+} else {
+  debug = function() { };
+}
+exports.debug = debug;
+
+exports.CRLF = '\r\n';
+exports.chunkExpression = /chunk/i;
+exports.continueExpression = /100-continue/i;
+
 // Only called in the slow case where slow means
 // that the request headers were either fragmented
 // across multiple TCP packets or too large to be
diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
new file mode 100644
index 0000000000..4fe0927cc7
--- /dev/null
+++ b/lib/_http_outgoing.js
@@ -0,0 +1,646 @@
+// 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 assert = require('assert').ok;
+var Stream = require('stream');
+var util = require('util');
+
+var common = require('_http_common');
+
+var CRLF = common.CRLF;
+var chunkExpression = common.chunkExpression;
+var continueExpression = common.continueExpression;
+var debug = common.debug;
+
+
+var connectionExpression = /Connection/i;
+var transferEncodingExpression = /Transfer-Encoding/i;
+var closeExpression = /close/i;
+var contentLengthExpression = /Content-Length/i;
+var dateExpression = /Date/i;
+var expectExpression = /Expect/i;
+
+
+var dateCache;
+function utcDate() {
+  if (!dateCache) {
+    var d = new Date();
+    dateCache = d.toUTCString();
+    setTimeout(function() {
+      dateCache = undefined;
+    }, 1000 - d.getMilliseconds());
+  }
+  return dateCache;
+}
+
+
+function OutgoingMessage() {
+  Stream.call(this);
+
+  this.output = [];
+  this.outputEncodings = [];
+
+  this.writable = true;
+
+  this._last = false;
+  this.chunkedEncoding = false;
+  this.shouldKeepAlive = true;
+  this.useChunkedEncodingByDefault = true;
+  this.sendDate = false;
+
+  this._hasBody = true;
+  this._trailer = '';
+
+  this.finished = false;
+  this._hangupClose = false;
+
+  this.socket = null;
+  this.connection = null;
+}
+util.inherits(OutgoingMessage, Stream);
+
+
+exports.OutgoingMessage = OutgoingMessage;
+
+
+OutgoingMessage.prototype.setTimeout = function(msecs, callback) {
+  if (callback)
+    this.on('timeout', callback);
+  if (!this.socket) {
+    this.once('socket', function(socket) {
+      socket.setTimeout(msecs);
+    });
+  } else
+    this.socket.setTimeout(msecs);
+};
+
+
+OutgoingMessage.prototype.destroy = function(error) {
+  this.socket.destroy(error);
+};
+
+
+// This abstract either writing directly to the socket or buffering it.
+OutgoingMessage.prototype._send = function(data, encoding) {
+  // This is a shameful hack to get the headers and first body chunk onto
+  // the same packet. Future versions of Node are going to take care of
+  // this at a lower level and in a more general way.
+  if (!this._headerSent) {
+    if (typeof data === 'string') {
+      data = this._header + data;
+    } else {
+      this.output.unshift(this._header);
+      this.outputEncodings.unshift('ascii');
+    }
+    this._headerSent = true;
+  }
+  return this._writeRaw(data, encoding);
+};
+
+
+OutgoingMessage.prototype._writeRaw = function(data, encoding) {
+  if (data.length === 0) {
+    return true;
+  }
+
+  if (this.connection &&
+      this.connection._httpMessage === this &&
+      this.connection.writable &&
+      !this.connection.destroyed) {
+    // There might be pending data in the this.output buffer.
+    while (this.output.length) {
+      if (!this.connection.writable) {
+        this._buffer(data, encoding);
+        return false;
+      }
+      var c = this.output.shift();
+      var e = this.outputEncodings.shift();
+      this.connection.write(c, e);
+    }
+
+    // Directly write to socket.
+    return this.connection.write(data, encoding);
+  } else if (this.connection && this.connection.destroyed) {
+    // The socket was destroyed.  If we're still trying to write to it,
+    // then we haven't gotten the 'close' event yet.
+    return false;
+  } else {
+    // buffer, as long as we're not destroyed.
+    this._buffer(data, encoding);
+    return false;
+  }
+};
+
+
+OutgoingMessage.prototype._buffer = function(data, encoding) {
+  if (data.length === 0) return;
+
+  var length = this.output.length;
+
+  if (length === 0 || typeof data != 'string') {
+    this.output.push(data);
+    this.outputEncodings.push(encoding);
+    return false;
+  }
+
+  var lastEncoding = this.outputEncodings[length - 1];
+  var lastData = this.output[length - 1];
+
+  if ((encoding && lastEncoding === encoding) ||
+      (!encoding && data.constructor === lastData.constructor)) {
+    this.output[length - 1] = lastData + data;
+    return false;
+  }
+
+  this.output.push(data);
+  this.outputEncodings.push(encoding);
+
+  return false;
+};
+
+
+OutgoingMessage.prototype._storeHeader = function(firstLine, headers) {
+  // firstLine in the case of request is: 'GET /index.html HTTP/1.1\r\n'
+  // in the case of response it is: 'HTTP/1.1 200 OK\r\n'
+  var state = {
+    sentConnectionHeader: false,
+    sentContentLengthHeader: false,
+    sentTransferEncodingHeader: false,
+    sentDateHeader: false,
+    sentExpect: false,
+    messageHeader: firstLine
+  };
+
+  var field, value;
+  var self = this;
+
+  if (headers) {
+    var keys = Object.keys(headers);
+    var isArray = (Array.isArray(headers));
+    var field, value;
+
+    for (var i = 0, l = keys.length; i < l; i++) {
+      var key = keys[i];
+      if (isArray) {
+        field = headers[key][0];
+        value = headers[key][1];
+      } else {
+        field = key;
+        value = headers[key];
+      }
+
+      if (Array.isArray(value)) {
+        for (var j = 0; j < value.length; j++) {
+          storeHeader(this, state, field, value[j]);
+        }
+      } else {
+        storeHeader(this, state, field, value);
+      }
+    }
+  }
+
+  // Date header
+  if (this.sendDate == true && state.sentDateHeader == false) {
+    state.messageHeader += 'Date: ' + utcDate() + CRLF;
+  }
+
+  // Force the connection to close when the response is a 204 No Content or
+  // a 304 Not Modified and the user has set a "Transfer-Encoding: chunked"
+  // header.
+  //
+  // RFC 2616 mandates that 204 and 304 responses MUST NOT have a body but
+  // node.js used to send out a zero chunk anyway to accommodate clients
+  // that don't have special handling for those responses.
+  //
+  // It was pointed out that this might confuse reverse proxies to the point
+  // of creating security liabilities, so suppress the zero chunk and force
+  // the connection to close.
+  var statusCode = this.statusCode;
+  if ((statusCode == 204 || statusCode === 304) &&
+      this.chunkedEncoding === true) {
+    debug(statusCode + ' response should not use chunked encoding,' +
+          ' closing connection.');
+    this.chunkedEncoding = false;
+    this.shouldKeepAlive = false;
+  }
+
+  // keep-alive logic
+  if (state.sentConnectionHeader === false) {
+    var shouldSendKeepAlive = this.shouldKeepAlive &&
+        (state.sentContentLengthHeader ||
+         this.useChunkedEncodingByDefault ||
+         this.agent);
+    if (shouldSendKeepAlive) {
+      state.messageHeader += 'Connection: keep-alive\r\n';
+    } else {
+      this._last = true;
+      state.messageHeader += 'Connection: close\r\n';
+    }
+  }
+
+  if (state.sentContentLengthHeader == false &&
+      state.sentTransferEncodingHeader == false) {
+    if (this._hasBody) {
+      if (this.useChunkedEncodingByDefault) {
+        state.messageHeader += 'Transfer-Encoding: chunked\r\n';
+        this.chunkedEncoding = true;
+      } else {
+        this._last = true;
+      }
+    } else {
+      // Make sure we don't end the 0\r\n\r\n at the end of the message.
+      this.chunkedEncoding = false;
+    }
+  }
+
+  this._header = state.messageHeader + CRLF;
+  this._headerSent = false;
+
+  // wait until the first body chunk, or close(), is sent to flush,
+  // UNLESS we're sending Expect: 100-continue.
+  if (state.sentExpect) this._send('');
+};
+
+function storeHeader(self, state, field, value) {
+  // Protect against response splitting. The if statement is there to
+  // minimize the performance impact in the common case.
+  if (/[\r\n]/.test(value))
+    value = value.replace(/[\r\n]+[ \t]*/g, '');
+
+  state.messageHeader += field + ': ' + value + CRLF;
+
+  if (connectionExpression.test(field)) {
+    state.sentConnectionHeader = true;
+    if (closeExpression.test(value)) {
+      self._last = true;
+    } else {
+      self.shouldKeepAlive = true;
+    }
+
+  } else if (transferEncodingExpression.test(field)) {
+    state.sentTransferEncodingHeader = true;
+    if (chunkExpression.test(value)) self.chunkedEncoding = true;
+
+  } else if (contentLengthExpression.test(field)) {
+    state.sentContentLengthHeader = true;
+  } else if (dateExpression.test(field)) {
+    state.sentDateHeader = true;
+  } else if (expectExpression.test(field)) {
+    state.sentExpect = true;
+  }
+}
+
+
+OutgoingMessage.prototype.setHeader = function(name, value) {
+  if (arguments.length < 2) {
+    throw new Error('`name` and `value` are required for setHeader().');
+  }
+
+  if (this._header) {
+    throw new Error('Can\'t set headers after they are sent.');
+  }
+
+  var key = name.toLowerCase();
+  this._headers = this._headers || {};
+  this._headerNames = this._headerNames || {};
+  this._headers[key] = value;
+  this._headerNames[key] = name;
+};
+
+
+OutgoingMessage.prototype.getHeader = function(name) {
+  if (arguments.length < 1) {
+    throw new Error('`name` is required for getHeader().');
+  }
+
+  if (!this._headers) return;
+
+  var key = name.toLowerCase();
+  return this._headers[key];
+};
+
+
+OutgoingMessage.prototype.removeHeader = function(name) {
+  if (arguments.length < 1) {
+    throw new Error('`name` is required for removeHeader().');
+  }
+
+  if (this._header) {
+    throw new Error('Can\'t remove headers after they are sent.');
+  }
+
+  if (!this._headers) return;
+
+  var key = name.toLowerCase();
+  delete this._headers[key];
+  delete this._headerNames[key];
+};
+
+
+OutgoingMessage.prototype._renderHeaders = function() {
+  if (this._header) {
+    throw new Error('Can\'t render headers after they are sent to the client.');
+  }
+
+  if (!this._headers) return {};
+
+  var headers = {};
+  var keys = Object.keys(this._headers);
+  for (var i = 0, l = keys.length; i < l; i++) {
+    var key = keys[i];
+    headers[this._headerNames[key]] = this._headers[key];
+  }
+  return headers;
+};
+
+
+Object.defineProperty(OutgoingMessage.prototype, 'headersSent', {
+  configurable: true,
+  enumerable: true,
+  get: function() { return !!this._header; }
+});
+
+
+OutgoingMessage.prototype.write = function(chunk, encoding) {
+  if (!this._header) {
+    this._implicitHeader();
+  }
+
+  if (!this._hasBody) {
+    debug('This type of response MUST NOT have a body. ' +
+          'Ignoring write() calls.');
+    return true;
+  }
+
+  if (typeof chunk !== 'string' && !Buffer.isBuffer(chunk)) {
+    throw new TypeError('first argument must be a string or Buffer');
+  }
+
+  if (chunk.length === 0) return false;
+
+  var len, ret;
+  if (this.chunkedEncoding) {
+    if (typeof(chunk) === 'string' &&
+        encoding !== 'hex' &&
+        encoding !== 'base64' &&
+        encoding !== 'binary') {
+      len = Buffer.byteLength(chunk, encoding);
+      chunk = len.toString(16) + CRLF + chunk + CRLF;
+      ret = this._send(chunk, encoding);
+    } else {
+      // buffer, or a non-toString-friendly encoding
+      len = chunk.length;
+      this._send(len.toString(16) + CRLF);
+      this._send(chunk, encoding);
+      ret = this._send(CRLF);
+    }
+  } else {
+    ret = this._send(chunk, encoding);
+  }
+
+  debug('write ret = ' + ret);
+  return ret;
+};
+
+
+OutgoingMessage.prototype.addTrailers = function(headers) {
+  this._trailer = '';
+  var keys = Object.keys(headers);
+  var isArray = (Array.isArray(headers));
+  var field, value;
+  for (var i = 0, l = keys.length; i < l; i++) {
+    var key = keys[i];
+    if (isArray) {
+      field = headers[key][0];
+      value = headers[key][1];
+    } else {
+      field = key;
+      value = headers[key];
+    }
+
+    this._trailer += field + ': ' + value + CRLF;
+  }
+};
+
+
+var zero_chunk_buf = new Buffer('\r\n0\r\n');
+var crlf_buf = new Buffer('\r\n');
+
+
+OutgoingMessage.prototype.end = function(data, encoding) {
+  if (this.finished) {
+    return false;
+  }
+  if (!this._header) {
+    this._implicitHeader();
+  }
+
+  if (data && !this._hasBody) {
+    debug('This type of response MUST NOT have a body. ' +
+          'Ignoring data passed to end().');
+    data = false;
+  }
+
+  var ret;
+
+  var hot = this._headerSent === false &&
+            (data && data.length > 0) &&
+            this.output.length === 0 &&
+            this.connection &&
+            this.connection.writable &&
+            this.connection._httpMessage === this;
+
+  // The benefits of the hot-path optimization below start to fall
+  // off when the buffer size gets up near 128KB, because the cost
+  // of the copy is more than the cost of the extra write() call.
+  // Switch to the write/end method at that point.  Heuristics and
+  // magic numbers are awful, but slow http responses are worse.
+  if (hot && Buffer.isBuffer(data) && data.length > 120 * 1024)
+    hot = false;
+
+  if (hot) {
+    // Hot path. They're doing
+    //   res.writeHead();
+    //   res.end(blah);
+    // HACKY.
+
+    if (typeof data === 'string') {
+      if (this.chunkedEncoding) {
+        var l = Buffer.byteLength(data, encoding).toString(16);
+        ret = this.connection.write(this._header + l + CRLF +
+                                    data + '\r\n0\r\n' +
+                                    this._trailer + '\r\n', encoding);
+      } else {
+        ret = this.connection.write(this._header + data, encoding);
+      }
+    } else if (Buffer.isBuffer(data)) {
+      if (this.chunkedEncoding) {
+        var chunk_size = data.length.toString(16);
+
+        // Skip expensive Buffer.byteLength() calls; only ISO-8859-1 characters
+        // are allowed in HTTP headers. Therefore:
+        //
+        //   this._header.length == Buffer.byteLength(this._header.length)
+        //   this._trailer.length == Buffer.byteLength(this._trailer.length)
+        //
+        var header_len = this._header.length;
+        var chunk_size_len = chunk_size.length;
+        var data_len = data.length;
+        var trailer_len = this._trailer.length;
+
+        var len = header_len +
+                  chunk_size_len +
+                  2 + // '\r\n'.length
+                  data_len +
+                  5 + // '\r\n0\r\n'.length
+                  trailer_len +
+                  2;  // '\r\n'.length
+
+        var buf = new Buffer(len);
+        var off = 0;
+
+        buf.write(this._header, off, header_len, 'ascii');
+        off += header_len;
+
+        buf.write(chunk_size, off, chunk_size_len, 'ascii');
+        off += chunk_size_len;
+
+        crlf_buf.copy(buf, off);
+        off += 2;
+
+        data.copy(buf, off);
+        off += data_len;
+
+        zero_chunk_buf.copy(buf, off);
+        off += 5;
+
+        if (trailer_len > 0) {
+          buf.write(this._trailer, off, trailer_len, 'ascii');
+          off += trailer_len;
+        }
+
+        crlf_buf.copy(buf, off);
+
+        ret = this.connection.write(buf);
+      } else {
+        var header_len = this._header.length;
+        var buf = new Buffer(header_len + data.length);
+        buf.write(this._header, 0, header_len, 'ascii');
+        data.copy(buf, header_len);
+        ret = this.connection.write(buf);
+      }
+    } else {
+      throw new TypeError('first argument must be a string or Buffer');
+    }
+    this._headerSent = true;
+
+  } else if (data) {
+    // Normal body write.
+    ret = this.write(data, encoding);
+  }
+
+  if (!hot) {
+    if (this.chunkedEncoding) {
+      ret = this._send('0\r\n' + this._trailer + '\r\n'); // Last chunk.
+    } else {
+      // Force a flush, HACK.
+      ret = this._send('');
+    }
+  }
+
+  this.finished = true;
+
+  // There is the first message on the outgoing queue, and we've sent
+  // everything to the socket.
+  debug('outgoing message end.');
+  if (this.output.length === 0 && this.connection._httpMessage === this) {
+    this._finish();
+  }
+
+  return ret;
+};
+
+
+var ServerResponse, ClientRequest;
+
+OutgoingMessage.prototype._finish = function() {
+  assert(this.connection);
+
+  if (!ServerResponse)
+    ServerResponse = require('http').ServerResponse;
+
+  if (!ClientRequest)
+    ClientRequest = require('http').ClientRequest;
+
+  if (this instanceof ServerResponse) {
+    DTRACE_HTTP_SERVER_RESPONSE(this.connection);
+    COUNTER_HTTP_SERVER_RESPONSE();
+  } else {
+    assert(this instanceof ClientRequest);
+    DTRACE_HTTP_CLIENT_REQUEST(this, this.connection);
+    COUNTER_HTTP_CLIENT_REQUEST();
+  }
+  this.emit('finish');
+};
+
+
+OutgoingMessage.prototype._flush = function() {
+  // This logic is probably a bit confusing. Let me explain a bit:
+  //
+  // In both HTTP servers and clients it is possible to queue up several
+  // outgoing messages. This is easiest to imagine in the case of a client.
+  // Take the following situation:
+  //
+  //    req1 = client.request('GET', '/');
+  //    req2 = client.request('POST', '/');
+  //
+  // When the user does
+  //
+  //   req2.write('hello world\n');
+  //
+  // it's possible that the first request has not been completely flushed to
+  // the socket yet. Thus the outgoing messages need to be prepared to queue
+  // up data internally before sending it on further to the socket's queue.
+  //
+  // This function, outgoingFlush(), is called by both the Server and Client
+  // to attempt to flush any pending messages out to the socket.
+
+  if (!this.socket) return;
+
+  var ret;
+  while (this.output.length) {
+
+    if (!this.socket.writable) return; // XXX Necessary?
+
+    var data = this.output.shift();
+    var encoding = this.outputEncodings.shift();
+
+    ret = this.socket.write(data, encoding);
+  }
+
+  if (this.finished) {
+    // This is a queue to the server or client to bring in the next this.
+    this._finish();
+  } else if (ret) {
+    // This is necessary to prevent https from breaking
+    this.emit('drain');
+  }
+};
diff --git a/lib/http.js b/lib/http.js
index 15fff690bf..e0d3e339eb 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -21,18 +21,11 @@
 
 var util = require('util');
 var net = require('net');
-var Stream = require('stream');
 var url = require('url');
 var EventEmitter = require('events').EventEmitter;
 var HTTPParser = process.binding('http_parser').HTTPParser;
 var assert = require('assert').ok;
 
-var debug;
-if (process.env.NODE_DEBUG && /http/.test(process.env.NODE_DEBUG)) {
-  debug = function(x) { console.error('HTTP: %s', x); };
-} else {
-  debug = function() { };
-}
 
 var incoming = require('_http_incoming');
 var IncomingMessage = exports.IncomingMessage = incoming.IncomingMessage;
@@ -41,9 +34,12 @@ var IncomingMessage = exports.IncomingMessage = incoming.IncomingMessage;
 var common = require('_http_common');
 var parsers = exports.parsers = common.parsers;
 var freeParser = common.freeParser;
+var debug = common.debug;
+var CRLF = common.CRLF;
+var continueExpression = common.continueExpression;
+var chunkExpression = common.chunkExpression;
 
 
-var CRLF = '\r\n';
 var STATUS_CODES = exports.STATUS_CODES = {
   100 : 'Continue',
   101 : 'Switching Protocols',
@@ -104,612 +100,8 @@ var STATUS_CODES = exports.STATUS_CODES = {
 };
 
 
-var connectionExpression = /Connection/i;
-var transferEncodingExpression = /Transfer-Encoding/i;
-var closeExpression = /close/i;
-var chunkExpression = /chunk/i;
-var contentLengthExpression = /Content-Length/i;
-var dateExpression = /Date/i;
-var expectExpression = /Expect/i;
-var continueExpression = /100-continue/i;
-
-var dateCache;
-function utcDate() {
-  if (!dateCache) {
-    var d = new Date();
-    dateCache = d.toUTCString();
-    setTimeout(function() {
-      dateCache = undefined;
-    }, 1000 - d.getMilliseconds());
-  }
-  return dateCache;
-}
-
-
-function OutgoingMessage() {
-  Stream.call(this);
-
-  this.output = [];
-  this.outputEncodings = [];
-
-  this.writable = true;
-
-  this._last = false;
-  this.chunkedEncoding = false;
-  this.shouldKeepAlive = true;
-  this.useChunkedEncodingByDefault = true;
-  this.sendDate = false;
-
-  this._hasBody = true;
-  this._trailer = '';
-
-  this.finished = false;
-  this._hangupClose = false;
-
-  this.socket = null;
-  this.connection = null;
-}
-util.inherits(OutgoingMessage, Stream);
-
-
-exports.OutgoingMessage = OutgoingMessage;
-
-
-OutgoingMessage.prototype.setTimeout = function(msecs, callback) {
-  if (callback)
-    this.on('timeout', callback);
-  if (!this.socket) {
-    this.once('socket', function(socket) {
-      socket.setTimeout(msecs);
-    });
-  } else
-    this.socket.setTimeout(msecs);
-};
-
-
-OutgoingMessage.prototype.destroy = function(error) {
-  this.socket.destroy(error);
-};
-
-
-// This abstract either writing directly to the socket or buffering it.
-OutgoingMessage.prototype._send = function(data, encoding) {
-  // This is a shameful hack to get the headers and first body chunk onto
-  // the same packet. Future versions of Node are going to take care of
-  // this at a lower level and in a more general way.
-  if (!this._headerSent) {
-    if (typeof data === 'string') {
-      data = this._header + data;
-    } else {
-      this.output.unshift(this._header);
-      this.outputEncodings.unshift('ascii');
-    }
-    this._headerSent = true;
-  }
-  return this._writeRaw(data, encoding);
-};
-
-
-OutgoingMessage.prototype._writeRaw = function(data, encoding) {
-  if (data.length === 0) {
-    return true;
-  }
-
-  if (this.connection &&
-      this.connection._httpMessage === this &&
-      this.connection.writable &&
-      !this.connection.destroyed) {
-    // There might be pending data in the this.output buffer.
-    while (this.output.length) {
-      if (!this.connection.writable) {
-        this._buffer(data, encoding);
-        return false;
-      }
-      var c = this.output.shift();
-      var e = this.outputEncodings.shift();
-      this.connection.write(c, e);
-    }
-
-    // Directly write to socket.
-    return this.connection.write(data, encoding);
-  } else if (this.connection && this.connection.destroyed) {
-    // The socket was destroyed.  If we're still trying to write to it,
-    // then we haven't gotten the 'close' event yet.
-    return false;
-  } else {
-    // buffer, as long as we're not destroyed.
-    this._buffer(data, encoding);
-    return false;
-  }
-};
-
-
-OutgoingMessage.prototype._buffer = function(data, encoding) {
-  if (data.length === 0) return;
-
-  var length = this.output.length;
-
-  if (length === 0 || typeof data != 'string') {
-    this.output.push(data);
-    this.outputEncodings.push(encoding);
-    return false;
-  }
-
-  var lastEncoding = this.outputEncodings[length - 1];
-  var lastData = this.output[length - 1];
-
-  if ((encoding && lastEncoding === encoding) ||
-      (!encoding && data.constructor === lastData.constructor)) {
-    this.output[length - 1] = lastData + data;
-    return false;
-  }
-
-  this.output.push(data);
-  this.outputEncodings.push(encoding);
-
-  return false;
-};
-
-
-OutgoingMessage.prototype._storeHeader = function(firstLine, headers) {
-  // firstLine in the case of request is: 'GET /index.html HTTP/1.1\r\n'
-  // in the case of response it is: 'HTTP/1.1 200 OK\r\n'
-  var state = {
-    sentConnectionHeader: false,
-    sentContentLengthHeader: false,
-    sentTransferEncodingHeader: false,
-    sentDateHeader: false,
-    sentExpect: false,
-    messageHeader: firstLine
-  };
-
-  var field, value;
-  var self = this;
-
-  if (headers) {
-    var keys = Object.keys(headers);
-    var isArray = (Array.isArray(headers));
-    var field, value;
-
-    for (var i = 0, l = keys.length; i < l; i++) {
-      var key = keys[i];
-      if (isArray) {
-        field = headers[key][0];
-        value = headers[key][1];
-      } else {
-        field = key;
-        value = headers[key];
-      }
-
-      if (Array.isArray(value)) {
-        for (var j = 0; j < value.length; j++) {
-          storeHeader(this, state, field, value[j]);
-        }
-      } else {
-        storeHeader(this, state, field, value);
-      }
-    }
-  }
-
-  // Date header
-  if (this.sendDate == true && state.sentDateHeader == false) {
-    state.messageHeader += 'Date: ' + utcDate() + CRLF;
-  }
-
-  // Force the connection to close when the response is a 204 No Content or
-  // a 304 Not Modified and the user has set a "Transfer-Encoding: chunked"
-  // header.
-  //
-  // RFC 2616 mandates that 204 and 304 responses MUST NOT have a body but
-  // node.js used to send out a zero chunk anyway to accommodate clients
-  // that don't have special handling for those responses.
-  //
-  // It was pointed out that this might confuse reverse proxies to the point
-  // of creating security liabilities, so suppress the zero chunk and force
-  // the connection to close.
-  var statusCode = this.statusCode;
-  if ((statusCode == 204 || statusCode === 304) &&
-      this.chunkedEncoding === true) {
-    debug(statusCode + ' response should not use chunked encoding,' +
-          ' closing connection.');
-    this.chunkedEncoding = false;
-    this.shouldKeepAlive = false;
-  }
-
-  // keep-alive logic
-  if (state.sentConnectionHeader === false) {
-    var shouldSendKeepAlive = this.shouldKeepAlive &&
-        (state.sentContentLengthHeader ||
-         this.useChunkedEncodingByDefault ||
-         this.agent);
-    if (shouldSendKeepAlive) {
-      state.messageHeader += 'Connection: keep-alive\r\n';
-    } else {
-      this._last = true;
-      state.messageHeader += 'Connection: close\r\n';
-    }
-  }
-
-  if (state.sentContentLengthHeader == false &&
-      state.sentTransferEncodingHeader == false) {
-    if (this._hasBody) {
-      if (this.useChunkedEncodingByDefault) {
-        state.messageHeader += 'Transfer-Encoding: chunked\r\n';
-        this.chunkedEncoding = true;
-      } else {
-        this._last = true;
-      }
-    } else {
-      // Make sure we don't end the 0\r\n\r\n at the end of the message.
-      this.chunkedEncoding = false;
-    }
-  }
-
-  this._header = state.messageHeader + CRLF;
-  this._headerSent = false;
-
-  // wait until the first body chunk, or close(), is sent to flush,
-  // UNLESS we're sending Expect: 100-continue.
-  if (state.sentExpect) this._send('');
-};
-
-function storeHeader(self, state, field, value) {
-  // Protect against response splitting. The if statement is there to
-  // minimize the performance impact in the common case.
-  if (/[\r\n]/.test(value))
-    value = value.replace(/[\r\n]+[ \t]*/g, '');
-
-  state.messageHeader += field + ': ' + value + CRLF;
-
-  if (connectionExpression.test(field)) {
-    state.sentConnectionHeader = true;
-    if (closeExpression.test(value)) {
-      self._last = true;
-    } else {
-      self.shouldKeepAlive = true;
-    }
-
-  } else if (transferEncodingExpression.test(field)) {
-    state.sentTransferEncodingHeader = true;
-    if (chunkExpression.test(value)) self.chunkedEncoding = true;
-
-  } else if (contentLengthExpression.test(field)) {
-    state.sentContentLengthHeader = true;
-  } else if (dateExpression.test(field)) {
-    state.sentDateHeader = true;
-  } else if (expectExpression.test(field)) {
-    state.sentExpect = true;
-  }
-}
-
-
-OutgoingMessage.prototype.setHeader = function(name, value) {
-  if (arguments.length < 2) {
-    throw new Error('`name` and `value` are required for setHeader().');
-  }
-
-  if (this._header) {
-    throw new Error('Can\'t set headers after they are sent.');
-  }
-
-  var key = name.toLowerCase();
-  this._headers = this._headers || {};
-  this._headerNames = this._headerNames || {};
-  this._headers[key] = value;
-  this._headerNames[key] = name;
-};
-
-
-OutgoingMessage.prototype.getHeader = function(name) {
-  if (arguments.length < 1) {
-    throw new Error('`name` is required for getHeader().');
-  }
-
-  if (!this._headers) return;
-
-  var key = name.toLowerCase();
-  return this._headers[key];
-};
-
-
-OutgoingMessage.prototype.removeHeader = function(name) {
-  if (arguments.length < 1) {
-    throw new Error('`name` is required for removeHeader().');
-  }
-
-  if (this._header) {
-    throw new Error('Can\'t remove headers after they are sent.');
-  }
-
-  if (!this._headers) return;
-
-  var key = name.toLowerCase();
-  delete this._headers[key];
-  delete this._headerNames[key];
-};
-
-
-OutgoingMessage.prototype._renderHeaders = function() {
-  if (this._header) {
-    throw new Error('Can\'t render headers after they are sent to the client.');
-  }
-
-  if (!this._headers) return {};
-
-  var headers = {};
-  var keys = Object.keys(this._headers);
-  for (var i = 0, l = keys.length; i < l; i++) {
-    var key = keys[i];
-    headers[this._headerNames[key]] = this._headers[key];
-  }
-  return headers;
-};
-
-
-Object.defineProperty(OutgoingMessage.prototype, 'headersSent', {
-  configurable: true,
-  enumerable: true,
-  get: function() { return !!this._header; }
-});
-
-
-OutgoingMessage.prototype.write = function(chunk, encoding) {
-  if (!this._header) {
-    this._implicitHeader();
-  }
-
-  if (!this._hasBody) {
-    debug('This type of response MUST NOT have a body. ' +
-          'Ignoring write() calls.');
-    return true;
-  }
-
-  if (typeof chunk !== 'string' && !Buffer.isBuffer(chunk)) {
-    throw new TypeError('first argument must be a string or Buffer');
-  }
-
-  if (chunk.length === 0) return false;
-
-  var len, ret;
-  if (this.chunkedEncoding) {
-    if (typeof(chunk) === 'string' &&
-        encoding !== 'hex' &&
-        encoding !== 'base64' &&
-        encoding !== 'binary') {
-      len = Buffer.byteLength(chunk, encoding);
-      chunk = len.toString(16) + CRLF + chunk + CRLF;
-      ret = this._send(chunk, encoding);
-    } else {
-      // buffer, or a non-toString-friendly encoding
-      len = chunk.length;
-      this._send(len.toString(16) + CRLF);
-      this._send(chunk, encoding);
-      ret = this._send(CRLF);
-    }
-  } else {
-    ret = this._send(chunk, encoding);
-  }
-
-  debug('write ret = ' + ret);
-  return ret;
-};
-
-
-OutgoingMessage.prototype.addTrailers = function(headers) {
-  this._trailer = '';
-  var keys = Object.keys(headers);
-  var isArray = (Array.isArray(headers));
-  var field, value;
-  for (var i = 0, l = keys.length; i < l; i++) {
-    var key = keys[i];
-    if (isArray) {
-      field = headers[key][0];
-      value = headers[key][1];
-    } else {
-      field = key;
-      value = headers[key];
-    }
-
-    this._trailer += field + ': ' + value + CRLF;
-  }
-};
-
-
-var zero_chunk_buf = new Buffer('\r\n0\r\n');
-var crlf_buf = new Buffer('\r\n');
-
-
-OutgoingMessage.prototype.end = function(data, encoding) {
-  if (this.finished) {
-    return false;
-  }
-  if (!this._header) {
-    this._implicitHeader();
-  }
-
-  if (data && !this._hasBody) {
-    debug('This type of response MUST NOT have a body. ' +
-          'Ignoring data passed to end().');
-    data = false;
-  }
-
-  var ret;
-
-  var hot = this._headerSent === false &&
-            (data && data.length > 0) &&
-            this.output.length === 0 &&
-            this.connection &&
-            this.connection.writable &&
-            this.connection._httpMessage === this;
-
-  // The benefits of the hot-path optimization below start to fall
-  // off when the buffer size gets up near 128KB, because the cost
-  // of the copy is more than the cost of the extra write() call.
-  // Switch to the write/end method at that point.  Heuristics and
-  // magic numbers are awful, but slow http responses are worse.
-  if (hot && Buffer.isBuffer(data) && data.length > 120 * 1024)
-    hot = false;
-
-  if (hot) {
-    // Hot path. They're doing
-    //   res.writeHead();
-    //   res.end(blah);
-    // HACKY.
-
-    if (typeof data === 'string') {
-      if (this.chunkedEncoding) {
-        var l = Buffer.byteLength(data, encoding).toString(16);
-        ret = this.connection.write(this._header + l + CRLF +
-                                    data + '\r\n0\r\n' +
-                                    this._trailer + '\r\n', encoding);
-      } else {
-        ret = this.connection.write(this._header + data, encoding);
-      }
-    } else if (Buffer.isBuffer(data)) {
-      if (this.chunkedEncoding) {
-        var chunk_size = data.length.toString(16);
-
-        // Skip expensive Buffer.byteLength() calls; only ISO-8859-1 characters
-        // are allowed in HTTP headers. Therefore:
-        //
-        //   this._header.length == Buffer.byteLength(this._header.length)
-        //   this._trailer.length == Buffer.byteLength(this._trailer.length)
-        //
-        var header_len = this._header.length;
-        var chunk_size_len = chunk_size.length;
-        var data_len = data.length;
-        var trailer_len = this._trailer.length;
-
-        var len = header_len +
-                  chunk_size_len +
-                  2 + // '\r\n'.length
-                  data_len +
-                  5 + // '\r\n0\r\n'.length
-                  trailer_len +
-                  2;  // '\r\n'.length
-
-        var buf = new Buffer(len);
-        var off = 0;
-
-        buf.write(this._header, off, header_len, 'ascii');
-        off += header_len;
-
-        buf.write(chunk_size, off, chunk_size_len, 'ascii');
-        off += chunk_size_len;
-
-        crlf_buf.copy(buf, off);
-        off += 2;
-
-        data.copy(buf, off);
-        off += data_len;
-
-        zero_chunk_buf.copy(buf, off);
-        off += 5;
-
-        if (trailer_len > 0) {
-          buf.write(this._trailer, off, trailer_len, 'ascii');
-          off += trailer_len;
-        }
-
-        crlf_buf.copy(buf, off);
-
-        ret = this.connection.write(buf);
-      } else {
-        var header_len = this._header.length;
-        var buf = new Buffer(header_len + data.length);
-        buf.write(this._header, 0, header_len, 'ascii');
-        data.copy(buf, header_len);
-        ret = this.connection.write(buf);
-      }
-    } else {
-      throw new TypeError('first argument must be a string or Buffer');
-    }
-    this._headerSent = true;
-
-  } else if (data) {
-    // Normal body write.
-    ret = this.write(data, encoding);
-  }
-
-  if (!hot) {
-    if (this.chunkedEncoding) {
-      ret = this._send('0\r\n' + this._trailer + '\r\n'); // Last chunk.
-    } else {
-      // Force a flush, HACK.
-      ret = this._send('');
-    }
-  }
-
-  this.finished = true;
-
-  // There is the first message on the outgoing queue, and we've sent
-  // everything to the socket.
-  debug('outgoing message end.');
-  if (this.output.length === 0 && this.connection._httpMessage === this) {
-    this._finish();
-  }
-
-  return ret;
-};
-
-
-OutgoingMessage.prototype._finish = function() {
-  assert(this.connection);
-  if (this instanceof ServerResponse) {
-    DTRACE_HTTP_SERVER_RESPONSE(this.connection);
-    COUNTER_HTTP_SERVER_RESPONSE();
-  } else {
-    assert(this instanceof ClientRequest);
-    DTRACE_HTTP_CLIENT_REQUEST(this, this.connection);
-    COUNTER_HTTP_CLIENT_REQUEST();
-  }
-  this.emit('finish');
-};
-
-
-OutgoingMessage.prototype._flush = function() {
-  // This logic is probably a bit confusing. Let me explain a bit:
-  //
-  // In both HTTP servers and clients it is possible to queue up several
-  // outgoing messages. This is easiest to imagine in the case of a client.
-  // Take the following situation:
-  //
-  //    req1 = client.request('GET', '/');
-  //    req2 = client.request('POST', '/');
-  //
-  // When the user does
-  //
-  //   req2.write('hello world\n');
-  //
-  // it's possible that the first request has not been completely flushed to
-  // the socket yet. Thus the outgoing messages need to be prepared to queue
-  // up data internally before sending it on further to the socket's queue.
-  //
-  // This function, outgoingFlush(), is called by both the Server and Client
-  // to attempt to flush any pending messages out to the socket.
-
-  if (!this.socket) return;
-
-  var ret;
-  while (this.output.length) {
-
-    if (!this.socket.writable) return; // XXX Necessary?
-
-    var data = this.output.shift();
-    var encoding = this.outputEncodings.shift();
-
-    ret = this.socket.write(data, encoding);
-  }
-
-  if (this.finished) {
-    // This is a queue to the server or client to bring in the next this.
-    this._finish();
-  } else if (ret) {
-    // This is necessary to prevent https from breaking
-    this.emit('drain');
-  }
-};
-
+var outgoing = require('_http_outgoing');
+var OutgoingMessage = exports.OutgoingMessage = outgoing.OutgoingMessage;