66 lines
1.6 KiB
JavaScript
66 lines
1.6 KiB
JavaScript
'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;
|