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