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 (this instanceof BufferPool === false) {
11    throw new TypeError("Classes can't be function-called");
12  }
13
14  if (typeof initialSize === 'function') {
15    shrinkStrategy = growStrategy;
16    growStrategy = initialSize;
17    initialSize = 0;
18  }
19  else if (typeof initialSize === 'undefined') {
20    initialSize = 0;
21  }
22  this._growStrategy = (growStrategy || function(db, size) {
23    return db.used + size;
24  }).bind(null, this);
25  this._shrinkStrategy = (shrinkStrategy || function(db) {
26    return initialSize;
27  }).bind(null, this);
28  this._buffer = initialSize ? new Buffer(initialSize) : null;
29  this._offset = 0;
30  this._used = 0;
31  this._changeFactor = 0;
32  this.__defineGetter__('size', function(){
33    return this._buffer == null ? 0 : this._buffer.length;
34  });
35  this.__defineGetter__('used', function(){
36    return this._used;
37  });
38}
39
40BufferPool.prototype.get = function(length) {
41  if (this._buffer == null || this._offset + length > this._buffer.length) {
42    var newBuf = new Buffer(this._growStrategy(length));
43    this._buffer = newBuf;
44    this._offset = 0;
45  }
46  this._used += length;
47  var buf = this._buffer.slice(this._offset, this._offset + length);
48  this._offset += length;
49  return buf;
50}
51
52BufferPool.prototype.reset = function(forceNewBuffer) {
53  var len = this._shrinkStrategy();
54  if (len < this.size) this._changeFactor -= 1;
55  if (forceNewBuffer || this._changeFactor < -2) {
56    this._changeFactor = 0;
57    this._buffer = len ? new Buffer(len) : null;
58  }
59  this._offset = 0;
60  this._used = 0;
61}
62
63module.exports = BufferPool;