340 lines
6.9 KiB
Markdown
340 lines
6.9 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Circular Buffer
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> Circular buffer constructor.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var circularBuffer = require( '@stdlib/utils/circular-buffer' );
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```
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#### circularBuffer( buffer )
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Returns a new circular buffer instance.
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```javascript
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var buf = circularBuffer( 3 );
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// returns <CircularBuffer>
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```
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The `buffer` argument may either be a integer which specifies the buffer size or an array-like object to use as the underlying buffer.
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```javascript
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var Float64Array = require( '@stdlib/array/float64' );
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// Use a typed array as the underlying buffer:
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var buf = circularBuffer( new Float64Array( 3 ) );
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// returns <CircularBuffer>
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```
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##### buf.clear()
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Clears a buffer.
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```javascript
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var buf = circularBuffer( 3 );
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// returns <CircularBuffer>
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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buf.push( 'beep' );
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// Get the number of elements currently in the buffer:
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var n = buf.count;
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// returns 3
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// Clear all buffer items:
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buf.clear();
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// Get the number of elements in the buffer:
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n = buf.count;
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// returns 0
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```
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##### buf.count
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Returns the number of elements currently in the buffer.
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```javascript
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var buf = circularBuffer( 3 );
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// returns <CircularBuffer>
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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// Determine how many elements are in the buffer:
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var n = buf.count;
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// returns 2
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```
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##### buf.full
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Returns a `boolean` indicating if a buffer is full.
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```javascript
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var buf = circularBuffer( 3 );
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// returns <CircularBuffer>
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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// Determine if the buffer is full:
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var bool = buf.full;
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// returns false
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// Add another value to the buffer:
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buf.push( 'beep' );
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// Determine if the buffer is full:
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bool = buf.full;
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// returns true
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```
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##### buf.iterator( \[niters] )
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Returns an iterator for iterating over a buffer. If an environment supports `Symbol.iterator`, the returned iterator is iterable.
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```javascript
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var buf = circularBuffer( 2 );
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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buf.push( 'beep' );
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buf.push( 'boop' );
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// Create an iterator:
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var it = buf.iterator();
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// Iterate over the buffer...
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var v = it.next().value;
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// returns 'beep'
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v = it.next().value;
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// returns 'boop'
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v = it.next().value;
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// returns 'beep'
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v = it.next().value;
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// returns 'boop'
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v = it.next().value;
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// returns 'beep'
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```
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By default, provided a buffer is **full**, the method returns an infinite iterator. To limit the number of iterations, provide an `niters` argument.
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```javascript
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var buf = circularBuffer( 2 );
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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buf.push( 'beep' );
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buf.push( 'boop' );
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// Create an iterator:
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var it = buf.iterator( buf.length );
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// Iterate over the buffer...
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var v = it.next().value;
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// returns 'beep'
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v = it.next().value;
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// returns 'boop'
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var bool = it.next().done;
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// returns true
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```
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A returned iterator does **not** iterate over partially full circular buffers.
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```javascript
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var buf = circularBuffer( 5 );
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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// Create an iterator:
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var it = buf.iterator();
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// Determine if the buffer is full:
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var bool = buf.full;
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// returns false
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// Iterate over the buffer...
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bool = it.next().done;
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// returns true
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```
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If iterating over a partially full circular buffer is necessary, use `buf.toArray()` and iterate over the returned array.
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##### buf.length
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Buffer length (capacity).
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```javascript
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var buf = circularBuffer( new Array( 3 ) );
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// Get the buffer length:
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var len = buf.length;
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// returns 3
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```
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##### buf.push( value )
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Adds a value to the buffer.
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```javascript
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var buf = circularBuffer( 3 );
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// Fill the buffer...
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var v = buf.push( 'foo' );
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// returns undefined
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v = buf.push( 'bar' );
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// returns undefined
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v = buf.push( 'beep' );
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// returns undefined
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// Now that the buffer is full, each push will cause a value to be removed:
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v = buf.push( 'boop' );
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// returns 'foo'
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```
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When a circular buffer is empty or partially full, this method returns `undefined`. Once a circular buffer is **full**, the method returns removed values.
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##### buf.toArray()
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Returns an array of buffer values.
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```javascript
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var buf = circularBuffer( 3 );
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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buf.push( 'beep' );
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buf.push( 'boop' );
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// Get an array of buffer values:
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var vals = buf.toArray();
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// returns [ 'bar', 'beep', 'boop' ]
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```
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##### buf.toJSON()
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Serializes a circular buffer as JSON.
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```javascript
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var buf = circularBuffer( 3 );
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// Add values to the buffer:
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buf.push( 'foo' );
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buf.push( 'bar' );
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buf.push( 'beep' );
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buf.push( 'boop' );
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// Serialize to JSON:
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var o = buf.toJSON();
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// returns { 'type': 'circular-buffer', 'length': 3, 'data': [ 'bar', 'beep', 'boop' ] }
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```
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**Note**: `JSON.stringify()` implicitly calls this method when stringifying a circular buffer instance.
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var circularBuffer = require( '@stdlib/utils/circular-buffer' );
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var buf;
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var v;
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var i;
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// Create a circular buffer capable of holding 5 elements:
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buf = circularBuffer( 5 );
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console.log( 'Buffer length: %s', buf.length );
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// Continuously add values to the buffer...
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for ( i = 0; i < 100; i++ ) {
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v = buf.push( i );
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console.log( 'Count: %d. Added value: %s. Removed value: %s.', buf.count, i, ( v === void 0 ) ? '(none)' : v );
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}
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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</section>
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<!-- /.links -->
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