145 lines
3.5 KiB
Markdown
145 lines
3.5 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2020 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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# isgzipBuffer
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> Test if a value is a [gzip][gzip-rfc-1952] buffer.
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<section class="usage">
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## Usage
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```javascript
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var isgzipBuffer = require( '@stdlib/assert/is-gzip-buffer' );
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```
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#### isgzipBuffer( value )
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Tests if a value is a [`gzip`][gzip-rfc-1952] buffer.
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```javascript
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var Uint8Array = require( '@stdlib/array/uint8' );
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var buf = new Uint8Array( 20 );
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buf[ 0 ] = 31; // 0x1f => magic number
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buf[ 1 ] = 139; // 0x8b
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buf[ 2 ] = 8; // 0x08 => compression method
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var bool = isgzipBuffer( buf );
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// returns true
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bool = isgzipBuffer( [] );
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// returns false
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- A [gzip][gzip-rfc-1952] buffer is defined as either a Node.js [`Buffer`][@stdlib/buffer/ctor] or [`Uint8Array`][@stdlib/array/uint8] which contains a 10-byte header, a body containing the compressed payload, and an 8-byte footer containing a CRC-32 checksum and the length of the original uncompressed data, modulo `2^32`.
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- This function only examines the 10-byte header to ensure the header includes the expected magic number and compression method. The function does not perform an integrity check.
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</section>
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<!-- /.notes -->
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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 Float32Array = require( '@stdlib/array/float32' );
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var Float64Array = require( '@stdlib/array/float64' );
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var Int8Array = require( '@stdlib/array/int8' );
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var Int16Array = require( '@stdlib/array/int16' );
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var Int32Array = require( '@stdlib/array/int32' );
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var Uint8Array = require( '@stdlib/array/uint8' );
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var Uint8ClampedArray = require( '@stdlib/array/uint8c' );
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var Uint16Array = require( '@stdlib/array/uint16' );
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var Uint32Array = require( '@stdlib/array/uint32' );
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var isgzipBuffer = require( '@stdlib/assert/is-gzip-buffer' );
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var buf = new Uint8Array( 20 );
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buf[ 0 ] = 31; // 0x1f => magic number
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buf[ 1 ] = 139; // 0x8b
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buf[ 2 ] = 8; // 0x08 => compression method
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var bool = isgzipBuffer( buf );
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// returns true
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bool = isgzipBuffer( new Float32Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Int8Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Uint8Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Uint8ClampedArray( 20 ) );
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// returns false
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bool = isgzipBuffer( new Int16Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Uint16Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Int32Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Uint32Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Float64Array( 20 ) );
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// returns false
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bool = isgzipBuffer( new Array( 20 ) );
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// returns false
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bool = isgzipBuffer( {} );
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// returns false
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bool = isgzipBuffer( null );
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// returns false
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[gzip-rfc-1952]: https://tools.ietf.org/html/rfc1952
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[@stdlib/buffer/ctor]: https://www.npmjs.com/package/@stdlib/buffer-ctor
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[@stdlib/array/uint8]: https://www.npmjs.com/package/@stdlib/array-uint8
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</section>
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<!-- /.links -->
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