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stream: don't create unnecessary buffers in Readable

If there is an encoding, and we do 'stream.push(chunk, enc)', and the
encoding argument matches the stated encoding, then we're converting from
a string, to a buffer, and then back to a string.  Of course, this is a
completely pointless bit of work, so it's best to avoid it when we know
that we can do so safely.
v0.10.6-release
isaacs 12 years ago
parent
commit
bdb78b9945
  1. 6
      doc/api/stream.markdown
  2. 25
      lib/_stream_readable.js
  3. 4
      lib/_stream_transform.js

6
doc/api/stream.markdown

@ -131,13 +131,15 @@ TLS, may ignore this argument, and simply provide data whenever it
becomes available. There is no need, for example to "wait" until
`size` bytes are available before calling `stream.push(chunk)`.
### readable.push(chunk)
### readable.push(chunk, [encoding])
* `chunk` {Buffer | null | String} Chunk of data to push into the read queue
* `encoding` {String} Encoding of String chunks. Must be a valid
Buffer encoding, such as `'utf8'` or `'ascii'`
* return {Boolean} Whether or not more pushes should be performed
Note: **This function should be called by Readable implementors, NOT
by consumers of Readable subclasses.** The `_read()` function will not
by consumers of Readable streams.** The `_read()` function will not
be called again until at least one `push(chunk)` call is made. If no
data is available, then you MAY call `push('')` (an empty string) to
allow a future `_read` call, without adding any data to the queue.

25
lib/_stream_readable.js

@ -83,10 +83,12 @@ function ReadableState(options, stream) {
this.readingMore = false;
this.decoder = null;
this.encoding = null;
if (options.encoding) {
if (!StringDecoder)
StringDecoder = require('string_decoder').StringDecoder;
this.decoder = new StringDecoder(options.encoding);
this.encoding = options.encoding;
}
}
@ -106,19 +108,27 @@ function Readable(options) {
// This returns true if the highWaterMark has not been hit yet,
// similar to how Writable.write() returns true if you should
// write() some more.
Readable.prototype.push = function(chunk) {
Readable.prototype.push = function(chunk, encoding) {
var state = this._readableState;
if (typeof chunk === 'string' && !state.objectMode)
chunk = new Buffer(chunk, arguments[1]);
return readableAddChunk(this, state, chunk, false);
if (typeof chunk === 'string' && !state.objectMode) {
encoding = encoding || 'utf8';
if (encoding !== state.encoding) {
chunk = new Buffer(chunk, encoding);
encoding = '';
}
}
return readableAddChunk(this, state, chunk, encoding, false);
};
// Unshift should *always* be something directly out of read()
Readable.prototype.unshift = function(chunk) {
var state = this._readableState;
return readableAddChunk(this, state, chunk, true);
return readableAddChunk(this, state, chunk, '', true);
};
function readableAddChunk(stream, state, chunk, addToFront) {
function readableAddChunk(stream, state, chunk, encoding, addToFront) {
var er = chunkInvalid(state, chunk);
if (er) {
stream.emit('error', er);
@ -134,7 +144,7 @@ function readableAddChunk(stream, state, chunk, addToFront) {
var e = new Error('stream.unshift() after end event');
stream.emit('error', e);
} else {
if (state.decoder && !addToFront)
if (state.decoder && !addToFront && !encoding)
chunk = state.decoder.write(chunk);
// update the buffer info.
@ -179,6 +189,7 @@ Readable.prototype.setEncoding = function(enc) {
if (!StringDecoder)
StringDecoder = require('string_decoder').StringDecoder;
this._readableState.decoder = new StringDecoder(enc);
this._readableState.encoding = enc;
};
// Don't raise the hwm > 128MB

4
lib/_stream_transform.js

@ -135,9 +135,9 @@ function Transform(options) {
});
}
Transform.prototype.push = function(chunk) {
Transform.prototype.push = function(chunk, encoding) {
this._transformState.needTransform = false;
return Duplex.prototype.push.call(this, chunk);
return Duplex.prototype.push.call(this, chunk, encoding);
};
// This is the part where you do stuff!

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