1/*!
 2 * ws: a node.js websocket client
 3 * Copyright(c) 2011 Einar Otto Stangvik <einaros@gmail.com>
 4 * MIT Licensed
 5 */
 6
 7var util = require('util');
 8
 9function BufferPool(initialSize, growStrategy, shrinkStrategy) {
10  if (typeof initialSize === 'function') {
11    shrinkStrategy = growStrategy;
12    growStrategy = initialSize;
13    initialSize = 0;
14  }
15  else if (typeof initialSize === 'undefined') {
16    initialSize = 0;
17  }
18  this._growStrategy = (growStrategy || function(db, size) {
19    return db.used + size;
20  }).bind(null, this);
21  this._shrinkStrategy = (shrinkStrategy || function(db) {
22    return initialSize;
23  }).bind(null, this);
24  this._buffer = initialSize ? new Buffer(initialSize) : null;
25  this._offset = 0;
26  this._used = 0;
27  this._changeFactor = 0;
28  this.__defineGetter__('size', function(){
29    return this._buffer == null ? 0 : this._buffer.length;
30  });
31  this.__defineGetter__('used', function(){
32    return this._used;
33  });
34}
35
36BufferPool.prototype.get = function(length) {
37  if (this._buffer == null || this._offset + length > this._buffer.length) {
38    var newBuf = new Buffer(this._growStrategy(length));
39    this._buffer = newBuf;
40    this._offset = 0;
41  }
42  this._used += length;
43  var buf = this._buffer.slice(this._offset, this._offset + length);
44  this._offset += length;
45  return buf;
46}
47
48BufferPool.prototype.reset = function(forceNewBuffer) {
49  var len = this._shrinkStrategy();
50  if (len < this.size) this._changeFactor -= 1;
51  if (forceNewBuffer || this._changeFactor < -2) {
52    this._changeFactor = 0;
53    this._buffer = len ? new Buffer(len) : null;
54  }
55  this._offset = 0;
56  this._used = 0;
57}
58
59module.exports = BufferPool;