346 lines
11 KiB
JavaScript
346 lines
11 KiB
JavaScript
(function(global) {
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class CBuffer {
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constructor() {
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// handle cases where "new" keyword wasn't used
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if (!(this instanceof CBuffer)) {
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// multiple conditions need to be checked to properly emulate Array
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if (arguments.length > 1 || typeof arguments[0] !== "number") {
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return CBuffer.apply(new CBuffer(arguments.length), arguments);
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} else {
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return new CBuffer(arguments[0]);
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}
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}
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// if no arguments, then nothing needs to be set
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if (arguments.length === 0)
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throw new Error("Missing Argument: You must pass a valid buffer size");
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// this is the same in either scenario
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this.length = this.start = 0;
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// set to callback fn if data is about to be overwritten
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this.overflow = null;
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// emulate Array based on passed arguments
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if (arguments.length > 1 || typeof arguments[0] !== "number") {
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this.data = new Array(arguments.length);
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this.end = (this.size = arguments.length) - 1;
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this.push.apply(this, arguments);
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} else {
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this.data = new Array(arguments[0]);
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this.end = (this.size = arguments[0]) - 1;
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}
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// need to `return this` so `return CBuffer.apply` works
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return this;
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}
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}
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function defaultComparitor(a, b) {
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return a == b ? 0 : a > b ? 1 : -1;
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}
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CBuffer.prototype = {
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// properly set constructor
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constructor: CBuffer,
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/* mutator methods */
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// pop last item
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pop: function() {
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var item;
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if (this.length === 0) return;
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item = this.data[this.end];
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// remove the reference to the object so it can be garbage collected
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delete this.data[this.end];
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this.end = (this.end - 1 + this.size) % this.size;
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this.length--;
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return item;
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},
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// push item to the end
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push: function() {
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var i = 0;
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// check if overflow is set, and if data is about to be overwritten
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if (this.overflow && this.length + arguments.length > this.size) {
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// call overflow function and send data that's about to be overwritten
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for (; i < this.length + arguments.length - this.size; i++) {
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this.overflow(this.data[(this.end + i + 1) % this.size], this);
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}
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}
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// push items to the end, wrapping and erasing existing items
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// using arguments variable directly to reduce gc footprint
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for (i = 0; i < arguments.length; i++) {
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this.data[(this.end + i + 1) % this.size] = arguments[i];
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}
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// recalculate length
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if (this.length < this.size) {
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if (this.length + i > this.size) this.length = this.size;
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else this.length += i;
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}
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// recalculate end
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this.end = (this.end + i) % this.size;
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// recalculate start
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this.start = (this.size + this.end - this.length + 1) % this.size;
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// return number current number of items in CBuffer
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return this.length;
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},
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// reverse order of the buffer
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reverse: function() {
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var i = 0,
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tmp;
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for (; i < ~~(this.length / 2); i++) {
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tmp = this.data[(this.start + i) % this.size];
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this.data[(this.start + i) % this.size] = this.data[
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(this.start + (this.length - i - 1)) % this.size
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];
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this.data[(this.start + (this.length - i - 1)) % this.size] = tmp;
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}
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return this;
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},
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// rotate buffer to the left by cntr, or by 1
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rotateLeft: function(cntr) {
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if (typeof cntr === "undefined") cntr = 1;
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if (typeof cntr !== "number")
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throw new Error("Argument must be a number");
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while (--cntr >= 0) {
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this.push(this.shift());
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}
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return this;
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},
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// rotate buffer to the right by cntr, or by 1
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rotateRight: function(cntr) {
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if (typeof cntr === "undefined") cntr = 1;
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if (typeof cntr !== "number")
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throw new Error("Argument must be a number");
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while (--cntr >= 0) {
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this.unshift(this.pop());
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}
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return this;
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},
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// remove and return first item
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shift: function() {
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var item;
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// check if there are any items in CBuff
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if (this.length === 0) return;
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// store first item for return
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item = this.data[this.start];
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// recalculate start of CBuffer
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this.start = (this.start + 1) % this.size;
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// decrement length
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this.length--;
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return item;
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},
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// sort items
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sort: function(fn) {
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this.data.sort(fn || defaultComparitor);
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this.start = 0;
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this.end = this.length - 1;
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return this;
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},
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// add item to beginning of buffer
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unshift: function() {
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var i = 0;
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// check if overflow is set, and if data is about to be overwritten
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if (this.overflow && this.length + arguments.length > this.size) {
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// call overflow function and send data that's about to be overwritten
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for (; i < this.length + arguments.length - this.size; i++) {
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this.overflow(this.data[this.end - (i % this.size)], this);
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}
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}
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for (i = 0; i < arguments.length; i++) {
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this.data[(this.size + this.start - (i % this.size) - 1) % this.size] =
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arguments[i];
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}
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if (this.size - this.length - i < 0) {
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this.end += this.size - this.length - i;
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if (this.end < 0) this.end = this.size + (this.end % this.size);
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}
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if (this.length < this.size) {
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if (this.length + i > this.size) this.length = this.size;
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else this.length += i;
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}
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this.start -= arguments.length;
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if (this.start < 0) this.start = this.size + (this.start % this.size);
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return this.length;
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},
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/* accessor methods */
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// return index of first matched element
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indexOf: function(arg, idx) {
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if (!idx) idx = 0;
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for (; idx < this.length; idx++) {
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if (this.data[(this.start + idx) % this.size] === arg) return idx;
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}
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return -1;
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},
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// return last index of the first match
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lastIndexOf: function(arg, idx) {
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if (!idx) idx = this.length - 1;
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for (; idx >= 0; idx--) {
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if (this.data[(this.start + idx) % this.size] === arg) return idx;
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}
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return -1;
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},
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// return the index an item would be inserted to if this
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// is a sorted circular buffer
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sortedIndex: function(value, comparitor, context) {
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comparitor = comparitor || defaultComparitor;
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var isFull = this.length === this.size,
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low = this.start,
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high = isFull ? this.length - 1 : this.length;
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// Tricky part is finding if its before or after the pivot
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// we can get this info by checking if the target is less than
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// the last item. After that it's just a typical binary search.
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if (low && comparitor.call(context, value, this.data[high]) > 0) {
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(low = 0), (high = this.end);
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}
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while (low < high) {
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var mid = (low + high) >>> 1;
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if (comparitor.call(context, value, this.data[mid]) > 0) low = mid + 1;
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else high = mid;
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}
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return !isFull
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? low
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: // http://stackoverflow.com/a/18618273/1517919
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(((low - this.start) % this.length) + this.length) % this.length;
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},
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/* iteration methods */
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// check every item in the array against a test
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every: function(callback, context) {
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var i = 0;
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for (; i < this.length; i++) {
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if (
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!callback.call(
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context,
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this.data[(this.start + i) % this.size],
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i,
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this
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)
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)
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return false;
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}
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return true;
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},
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// loop through each item in buffer
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// TODO: figure out how to emulate Array use better
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forEach: function(callback, context) {
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var i = 0;
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for (; i < this.length; i++) {
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callback.call(
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context,
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this.data[(this.start + i) % this.size],
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i,
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this
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);
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}
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},
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// check items agains test until one returns true
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// TODO: figure out how to emuldate Array use better
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some: function(callback, context) {
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var i = 0;
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for (; i < this.length; i++) {
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if (
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callback.call(
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context,
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this.data[(this.start + i) % this.size],
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i,
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this
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)
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)
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return true;
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}
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return false;
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},
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// calculate the average value of a circular buffer
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avg: function() {
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return this.length == 0 ? 0 : this.sum() / this.length;
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},
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// loop through each item in buffer and calculate sum
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sum: function() {
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var index = this.length;
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var s = 0;
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while (index--) s += this.data[index];
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return s;
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},
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// loop through each item in buffer and calculate median
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median: function() {
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if (this.length === 0) return 0;
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var values = this.slice().sort(defaultComparitor);
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var half = Math.floor(values.length / 2);
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if (values.length % 2) return values[half];
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else return (values[half - 1] + values[half]) / 2.0;
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},
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/* utility methods */
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// reset pointers to buffer with zero items
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// note: this will not remove values in cbuffer, so if for security values
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// need to be overwritten, run `.fill(null).empty()`
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empty: function() {
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//var i = 0;
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this.length = this.start = 0;
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this.end = this.size - 1;
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return this;
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},
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// fill all places with passed value or function
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fill: function(arg) {
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var i = 0;
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if (typeof arg === "function") {
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while (((this.data[i] = arg()), ++i < this.size));
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} else {
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while (((this.data[i] = arg), ++i < this.size));
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}
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// reposition start/end
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this.start = 0;
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this.end = this.size - 1;
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this.length = this.size;
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return this;
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},
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// return first item in buffer
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first: function() {
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return this.data[this.start];
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},
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// return last item in buffer
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last: function() {
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return this.data[this.end];
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},
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// return specific index in buffer
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get: function(arg) {
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return this.data[(this.start + arg) % this.size];
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},
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isFull: function() {
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return this.size === this.length;
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},
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// set value at specified index
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set: function(idx, arg) {
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return (this.data[(this.start + idx) % this.size] = arg);
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},
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// return clean array of values
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toArray: function() {
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return this.slice();
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},
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// slice the buffer to an arraay
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slice: function(start, end) {
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var size = this.length;
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start = +start || 0;
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if (start < 0) {
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if (start >= end) return [];
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start = -start > size ? 0 : size + start;
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}
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if (end == null || end > size) end = size;
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else if (end < 0) end += size;
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else end = +end || 0;
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size = start < end ? end - start : 0;
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var result = Array(size);
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for (var index = 0; index < size; index++) {
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result[index] = this.data[(this.start + start + index) % this.size];
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}
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return result;
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}
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};
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if (typeof module === "object" && module.exports) module.exports = CBuffer;
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else global.CBuffer = CBuffer;
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})(this);
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