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streams2: Add high water mark for Readable

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Also, organize the numeric settings a bit on the ReadableState class
This commit is contained in:
isaacs
2012-11-12 23:31:25 -08:00
parent 63ac07b32b
commit f20fd22abd
2 changed files with 33 additions and 5 deletions
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36
lib/_stream_readable.js
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@@ -32,13 +32,34 @@ util.inherits(Readable, Stream);
function ReadableState(options, stream) {
options = options || {};
this.bufferSize = options.bufferSize || 16 * 1024;
assert(typeof this.bufferSize === 'number');
// cast to an int
this.bufferSize = ~~this.bufferSize;
// the argument passed to this._read(n,cb)
this.bufferSize = options.hasOwnProperty('bufferSize') ?
options.bufferSize : 16 * 1024;
// the point at which it stops calling _read() to fill the buffer
this.highWaterMark = options.hasOwnProperty('highWaterMark') ?
options.highWaterMark : 16 * 1024;
// the minimum number of bytes to buffer before emitting 'readable'
// default to pushing everything out as fast as possible.
this.lowWaterMark = options.hasOwnProperty('lowWaterMark') ?
options.lowWaterMark : 1024;
// cast to ints.
assert(typeof this.bufferSize === 'number');
assert(typeof this.lowWaterMark === 'number');
assert(typeof this.highWaterMark === 'number');
this.bufferSize = ~~this.bufferSize;
this.lowWaterMark = ~~this.lowWaterMark;
this.highWaterMark = ~~this.highWaterMark;
assert(this.bufferSize >= 0);
assert(this.lowWaterMark >= 0);
assert(this.highWaterMark >= this.lowWaterMark,
this.highWaterMark + '>=' + this.lowWaterMark);
this.buffer = [];
this.length = 0;
this.pipes = [];
@@ -136,9 +157,16 @@ Readable.prototype.read = function(n) {
// if we need a readable event, then we need to do some reading.
var doRead = state.needReadable;
// if we currently have less than the lowWaterMark, then also read some
if (state.length - n <= state.lowWaterMark)
// if we currently have less than the highWaterMark, then also read some
if (state.length - n <= state.highWaterMark)
doRead = true;
// if we currently have *nothing*, then always try to get *something*
// no matter what the high water mark says.
if (state.length === 0)
doRead = true;
// however, if we've ended, then there's no point, and if we're already
// reading, then it's unnecessary.
if (state.ended || state.reading)

2
lib/_stream_transform.js
View File

@@ -130,7 +130,7 @@ Transform.prototype._write = function(chunk, cb) {
// if we weren't waiting for it, but nothing is queued up, then
// still kick off a transform, just so it's there when the user asks.
var doRead = rs.needReadable || rs.length <= rs.lowWaterMark;
var doRead = rs.needReadable || rs.length <= rs.highWaterMark;
if (doRead && !rs.reading) {
var ret = this.read(0);
if (ret !== null)