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Memory

WebAssembly memory constructor.

Installation

npm install @stdlib/wasm-memory

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var Memory = require( '@stdlib/wasm-memory' );

Memory( descriptor )

Returns a new WebAssembly memory instance.

var mem = new Memory({
    'initial': 0
});
// returns <Memory>

The descriptor argument is an object which supports the following properties:

• initial: (required) initial memory size in units of WebAssembly pages (i.e., 64KiB).
• maximum: maximum memory size in units of WebAssembly pages (i.e., 64KiB).
• shared: boolean indicating whether the memory is shared. Default: false.

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Memory.prototype.buffer

Read-only property which returns the ArrayBuffer (or SharedArrayBuffer) referenced by memory instance.

var mem = new Memory({
    'initial': 0
});

var buf = mem.buffer;
// returns <ArrayBuffer>

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Methods

Memory.prototype.grow( delta )

Increases the size of the memory instance by a specified number of WebAssembly pages (i.e., 64KiB).

var mem = new Memory({
    'initial': 0
});

// ...

var prevSize = mem.grow( 1 );

The method returns the size of the previous ArrayBuffer (or SharedArrayBuffer).

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Notes

• Upon increasing the size, the previous ArrayBuffer is detached, thus invalidating any typed arrays which were views over the previous ArrayBuffer.
• Detachment means that the previous ArrayBuffer byte length becomes zero, and it no longer has bytes accessible to JavaScript.
• When calling grow, ArrayBuffer detachment applies even when delta is zero.
• Detachment only applies for non-shared memory instances. For a shared memory instance, the initial buffer (which is a SharedArrayBuffer) will not become detached and, instead, its length will not be updated.
• Accesses to the buffer property after growing a SharedArrayBuffer will yield a larger SharedArrayBuffer which may access a larger span of memory than the buffer before growing memory.
• Every SharedArrayBuffer accessed via the buffer property will always refer to the start of the same memory address range and thus manipulate the same data.

Examples

var hasWebAssemblySupport = require( '@stdlib/assert-has-wasm-support' );
var DataView = require( '@stdlib/array-dataview' );
var Memory = require( '@stdlib/wasm-memory' );

function main() {
    var view;
    var mem;
    var v;
    if ( !hasWebAssemblySupport() ) {
        console.error( 'Environment does not support WebAssembly.' );
        return;
    }
    mem = new Memory({
        'initial': 1
    });
    view = new DataView( mem.buffer );

    view.setFloat64( 0, 3.14 );

    // ...

    v = view.getFloat64( 0 );
    console.log( v );
    // => 3.14
}

main();

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.