| 'use strict'; |
| |
| var RingBuffer = function(bufferSize) { |
| this._bufferSize = bufferSize; |
| this.clear(); |
| }; |
| |
| RingBuffer.prototype.clear = function() { |
| this._buffer = new Array(this._bufferSize); |
| this._ringOffset = 0; |
| this._ringSize = this._bufferSize; |
| this._head = 0; |
| this._tail = 0; |
| this.length = 0; |
| }; |
| |
| RingBuffer.prototype.push = function(value) { |
| var expandBuffer = false, |
| expandRing = false; |
| |
| if (this._ringSize < this._bufferSize) { |
| expandBuffer = (this._tail === 0); |
| } else if (this._ringOffset === this._ringSize) { |
| expandBuffer = true; |
| expandRing = (this._tail === 0); |
| } |
| |
| if (expandBuffer) { |
| this._tail = this._bufferSize; |
| this._buffer = this._buffer.concat(new Array(this._bufferSize)); |
| this._bufferSize = this._buffer.length; |
| |
| if (expandRing) |
| this._ringSize = this._bufferSize; |
| } |
| |
| this._buffer[this._tail] = value; |
| this.length += 1; |
| if (this._tail < this._ringSize) this._ringOffset += 1; |
| this._tail = (this._tail + 1) % this._bufferSize; |
| }; |
| |
| RingBuffer.prototype.peek = function() { |
| if (this.length === 0) return void 0; |
| return this._buffer[this._head]; |
| }; |
| |
| RingBuffer.prototype.shift = function() { |
| if (this.length === 0) return void 0; |
| |
| var value = this._buffer[this._head]; |
| this._buffer[this._head] = void 0; |
| this.length -= 1; |
| this._ringOffset -= 1; |
| |
| if (this._ringOffset === 0 && this.length > 0) { |
| this._head = this._ringSize; |
| this._ringOffset = this.length; |
| this._ringSize = this._bufferSize; |
| } else { |
| this._head = (this._head + 1) % this._ringSize; |
| } |
| return value; |
| }; |
| |
| module.exports = RingBuffer; |