@stdlib/wasm
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WebAssembly.
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# Memory
> WebAssembly [memory][mdn-webassembly-memory] constructor.
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## Usage
```javascript
var Memory = require( '@stdlib/wasm/memory' );
```
#### Memory( descriptor )
Returns a new WebAssembly [memory][mdn-webassembly-memory] instance.
```javascript
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`.
* * *
<a name="prop-buffer"></a>
#### Memory.prototype.buffer
**Read-only** property which returns the [`ArrayBuffer`][@stdlib/array/buffer] (or [`SharedArrayBuffer`][@stdlib/array/shared-buffer]) referenced by memory instance.
```javascript
var mem = new Memory({
'initial': 0
});
var buf = mem.buffer;
// returns <ArrayBuffer>
```
* * *
### Methods
<a name="method-grow"></a>
#### Memory.prototype.grow( delta )
Increases the size of the memory instance by a specified number of WebAssembly pages (i.e., 64KiB).
```javascript
var mem = new Memory({
'initial': 0
});
// ...
var prevSize = mem.grow( 1 );
```
The method returns the size of the previous [`ArrayBuffer`][@stdlib/array/buffer] (or [`SharedArrayBuffer`][@stdlib/array/shared-buffer]).
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* * *
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## Notes
- Upon increasing the size, the previous [`ArrayBuffer`][@stdlib/array/buffer] is detached, thus invalidating any typed arrays which were views over the previous [`ArrayBuffer`][@stdlib/array/buffer].
- **Detachment** means that the previous [`ArrayBuffer`][@stdlib/array/buffer] byte length becomes zero, and it no longer has bytes accessible to JavaScript.
- When calling `grow`, [`ArrayBuffer`][@stdlib/array/buffer] 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`][@stdlib/array/shared-buffer]) will not become detached and, instead, its length will not be updated.
- Accesses to the `buffer` property after growing a [`SharedArrayBuffer`][@stdlib/array/shared-buffer] will yield a larger [`SharedArrayBuffer`][@stdlib/array/shared-buffer] which may access a larger span of memory than the buffer before growing memory.
- Every [`SharedArrayBuffer`][@stdlib/array/shared-buffer] accessed via the `buffer` property will always refer to the start of the same memory address range and thus manipulate the same data.
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## Examples
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```javascript
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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[mdn-webassembly-memory]: https://developer.mozilla.org/en-US/docs/WebAssembly/JavaScript_interface/Memory
[@stdlib/array/buffer]: https://www.npmjs.com/package/@stdlib/array-buffer
[@stdlib/array/shared-buffer]: https://www.npmjs.com/package/@stdlib/array-shared-buffer
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