aaac7fed
 liuqimichale
add
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'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;
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