streams: add cork option to pipe

doc/api/stream.markdown

@@ -333,6 +333,8 @@ readable.isPaused() // === false
 * `destination` {[Writable][] Stream} The destination for writing data
 * `options` {Object} Pipe options
  * `end` {Boolean} End the writer when the reader ends. Default = `true`
+ * `cork` {Boolean} Before each write, cork the stream and then uncork it on the
+ next tick in order to consolidate writes. Default = `false`
 
 This method pulls all the data out of a readable stream, and writes it
 to the supplied destination, automatically managing the flow so that
@@ -1315,7 +1317,7 @@ for examples and testing, but there are occasionally use cases where
 it can come in handy as a building block for novel sorts of streams.
 
 
-## Simplified Constructor API
+## Simplified Constructor API
 
 <!--type=misc-->
 

lib/_stream_readable.js

@@ -467,6 +467,9 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
  dest !== process.stdout &&
  dest !== process.stderr;
 
+ var autoCork = pipeOpts && pipeOpts.cork && (typeof dest.cork === 'function');
+ var corked = false;
+
  var endFn = doEnd ? onend : cleanup;
  if (state.endEmitted)
  process.nextTick(endFn);
@@ -515,9 +518,26 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
  ondrain();
  }
 
+ function maybeCork() {
+ if (!autoCork || corked) {
+ debug('already corked');
+ return;
+ }
+ debug('corking');
+ corked = true;
+ dest.cork();
+ process.nextTick(uncork);
+ }
+ function uncork() {
+ debug('uncorking');
+ corked = false;
+ dest.uncork();
+ }
  src.on('data', ondata);
  function ondata(chunk) {
  debug('ondata');
+ maybeCork();
+ debug('corks=%d', dest._writableState.corked);
  var ret = dest.write(chunk);
  if (false === ret) {
  debug('false write response, pause',

test/parallel/test-stream-pipe-cork.js

@@ -0,0 +1,176 @@
+'use strict';
+var common = require('../common');
+var assert = require('assert');
+
+var stream = require('stream');
+// tiny node-tap lookalike.
+var tests = [];
+var count = 0;
+
+function test(name, fn) {
+ count++;
+ tests.push([name, fn]);
+}
+
+function run() {
+ var next = tests.shift();
+ if (!next)
+ return console.error('ok');
+
+ var name = next[0];
+ var fn = next[1];
+ console.log('# %s', name);
+ fn({
+ same: assert.deepEqual,
+ equal: assert.equal,
+ end: function() {
+ count--;
+ run();
+ }
+ });
+}
+
+// ensure all tests have run
+process.on('exit', function() {
+ assert.equal(count, 0);
+});
+
+process.nextTick(run);
+test('all sync', function (t) {
+ var counter = 0;
+ var expectCount = 0;
+ function cnt(msg) {
+ expectCount++;
+ var expect = expectCount;
+ var called = false;
+ return function(er) {
+ if (er)
+ throw er;
+ called = true;
+ counter++;
+ t.equal(counter, expect);
+ };
+ }
+ var p = new stream.PassThrough();
+ var w = new stream.Writable();
+ w._write = function(chunk, e, cb) {
+ assert(false, 'Should not call _write');
+ };
+ p.pipe(w, {
+ cork: true
+ });
+ var expectChunks =
+ [
+ { encoding: 'buffer',
+ chunk: [104, 101, 108, 108, 111, 44, 32] },
+ { encoding: 'buffer',
+ chunk: [119, 111, 114, 108, 100] },
+ { encoding: 'buffer',
+ chunk: [33] },
+ { encoding: 'buffer',
+ chunk: [10, 97, 110, 100, 32, 116, 104, 101, 110, 46, 46, 46] },
+ { encoding: 'buffer',
+ chunk: [250, 206, 190, 167, 222, 173, 190, 239, 222, 202, 251, 173]}
+ ];
+
+ var actualChunks;
+ w._writev = function(chunks, cb) {
+ actualChunks = chunks.map(function(chunk) {
+ return {
+ encoding: chunk.encoding,
+ chunk: Buffer.isBuffer(chunk.chunk) ?
+ Array.prototype.slice.call(chunk.chunk) : chunk.chunk
+ };
+ });
+ cb();
+ };
+ p.write('hello, ', 'ascii', cnt('hello'));
+ p.write('world', 'utf8', cnt('world'));
+
+ p.write(new Buffer('!'), 'buffer', cnt('!'));
+
+ p.write('\nand then...', 'binary', cnt('and then'));
+ p.write('facebea7deadbeefdecafbad', 'hex', cnt('hex'));
+
+ p.end(cnt('end'));
+
+
+ w.on('finish', function() {
+ // make sure finish comes after all the write cb
+ cnt('finish')();
+ t.same(expectChunks, actualChunks);
+ t.end();
+ });
+});
+test('2 groups', function (t) {
+ var counter = 0;
+ var expectCount = 0;
+ function cnt(msg) {
+ expectCount++;
+ var expect = expectCount;
+ var called = false;
+ return function(er) {
+ if (er)
+ throw er;
+ called = true;
+ counter++;
+ t.equal(counter, expect);
+ };
+ }
+ var p = new stream.PassThrough();
+ var w = new stream.Writable();
+ w._write = function(chunk, e, cb) {
+ assert(false, 'Should not call _write');
+ };
+ p.pipe(w, {
+ cork: true
+ });
+ var expectChunks = [
+ [
+ { encoding: 'buffer',
+ chunk: [104, 101, 108, 108, 111, 44, 32] },
+ { encoding: 'buffer',
+ chunk: [119, 111, 114, 108, 100] }
+ ],[
+ { encoding: 'buffer',
+ chunk: [33] },
+ { encoding: 'buffer',
+ chunk: [10, 97, 110, 100, 32, 116, 104, 101, 110, 46, 46, 46] },
+ { encoding: 'buffer',
+ chunk: [250, 206, 190, 167, 222, 173, 190, 239, 222, 202, 251, 173]}
+ ]];
+
+ var actualChunks = [];
+ var called = 0;
+ w._writev = function(chunks, cb) {
+ actualChunks.push(chunks.map(function(chunk) {
+ return {
+ encoding: chunk.encoding,
+ chunk: Buffer.isBuffer(chunk.chunk) ?
+ Array.prototype.slice.call(chunk.chunk) : chunk.chunk
+ };
+ }));
+ cb();
+ };
+ p.write('hello, ', 'ascii', cnt('hello'));
+ p.write('world', 'utf8', cnt('world'));
+ process.nextTick(function () {
+ p.write(new Buffer('!'), 'buffer', cnt('!'));
+
+ p.write('\nand then...', 'binary', cnt('and then'));
+ p.write('facebea7deadbeefdecafbad', 'hex', cnt('hex'));
+
+ p.end(cnt('end'));
+ });
+
+ w.on('finish', function() {
+ // make sure finish comes after all the write cb
+ cnt('finish')();
+ console.log('expected');
+ console.log(expectChunks);
+ console.log('actual');
+ console.log(actualChunks);
+ t.same(expectChunks, actualChunks);
+ t.end();
+ });
+});