79 lines
2.6 KiB
JavaScript
79 lines
2.6 KiB
JavaScript
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function CircularBuffer(capacity){
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if(!(this instanceof CircularBuffer))return new CircularBuffer(capacity);
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if(typeof capacity=="object"&&
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Array.isArray(capacity["_buffer"])&&
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typeof capacity._capacity=="number"&&
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typeof capacity._first=="number"&&
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typeof capacity._size=="number"){
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for(var prop in capacity){
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if(capacity.hasOwnProperty(prop))this[prop]=capacity[prop];
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}
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} else {
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if(typeof capacity!="number"||capacity%1!=0||capacity<1)
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throw new TypeError("Invalid capacity");
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this._buffer=new Array(capacity);
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this._capacity=capacity;
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this._first=0;
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this._size=0;
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}
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}
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CircularBuffer.prototype={
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size:function(){return this._size;},
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capacity:function(){return this._capacity;},
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enq:function(value){
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if(this._first>0)this._first--; else this._first=this._capacity-1;
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this._buffer[this._first]=value;
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if(this._size<this._capacity)this._size++;
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},
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push:function(value){
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if(this._size==this._capacity){
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this._buffer[this._first]=value;
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this._first=(this._first+1)%this._capacity;
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} else {
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this._buffer[(this._first+this._size)%this._capacity]=value;
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this._size++;
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}
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},
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deq:function(){
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if(this._size==0)throw new RangeError("dequeue on empty buffer");
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var value=this._buffer[(this._first+this._size-1)%this._capacity];
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this._size--;
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return value;
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},
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pop:function(){return this.deq();},
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shift:function(){
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if(this._size==0)throw new RangeError("shift on empty buffer");
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var value=this._buffer[this._first];
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if(this._first==this._capacity-1)this._first=0; else this._first++;
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this._size--;
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return value;
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},
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get:function(start,end){
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if(this._size==0&&start==0&&(end==undefined||end==0))return [];
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if(typeof start!="number"||start%1!=0||start<0)throw new TypeError("Invalid start");
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if(start>=this._size)throw new RangeError("Index past end of buffer: "+start);
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if(end==undefined)return this._buffer[(this._first+start)%this._capacity];
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if(typeof end!="number"||end%1!=0||end<0)throw new TypeError("Invalid end");
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if(end>=this._size)throw new RangeError("Index past end of buffer: "+end);
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if(this._first+start>=this._capacity){
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//make sure first+start and first+end are in a normal range
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start-=this._capacity; //becomes a negative number
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end-=this._capacity;
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}
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if(this._first+end<this._capacity)
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return this._buffer.slice(this._first+start,this._first+end+1);
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else
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return this._buffer.slice(this._first+start,this._capacity).concat(this._buffer.slice(0,this._first+end+1-this._capacity));
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},
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toarray:function(){
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if(this._size==0)return [];
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return this.get(0,this._size-1);
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}
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};
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module.exports=CircularBuffer;
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