memory-helper

#memory-helper

This simple utility class is designed to help manage memory stored in JavaScript TypedArrays. It provides memory addresses (indices) based on past and present requests for arbitrary blocks of memory; these memory locations can subsequently be freed for reuse. The class throws errors if there is not a block of sufficient size remaining; however, it will not prevent developers from writing into adjacent blocks (or, for that matter, any arbitrary indices of their choice). For a solution with much more robust error handling / write protection see: https://github.com/codemix/malloc

The allocation scheme is an approximation of "first-fit". Other schemes may be explored in the future. This utility class was created to provide memory management for genish.js, an audio synthesis library.

##Example

// manage two minutes of stereo audio at 44.1 khz
let helper = MemoryHelper.create( 44100 * 60 * 2 )

// request index to store 1024 samples
let blockSize = 1024,
    idx = helper.alloc( blockSize )

// write noise to memory using index obtained through .alloc()
for( let i = idx; i < idx + blockSize; i++ ) {
  helper.heap[ i ] = Math.random()
}

// free block after use
helper.free( idx )

##API The index.js file exports a factory object, MemoryHelper.

Methods

####.create( numberOfElements, arrayType ) Each MemoryHelper instance contains a single JavaScript TypedArray, with an arbitrary number of elements. By default, the element type is Float32Array and the length of the array is 4096. To create a helper managing an array of sixteen 16-bit integers:

let helper = MemoryHelper.create( 16, Int16Array )

####.alloc( sizeOfMemoryRequest ) Reserve a block of memory and obtain a starting integer index for reading / writing to the block. An error is thrown if insufficient memory is remaining for the allocation request.

####.free( blockIndex ) Free a block beginning at the index blockIndex; this index should have been previously obtained from a call to .alloc(). An error is thrown if a blockIndex is passed that does not have a block index associated with it.

Properties

####.heap The .heap property represents the TypedArray instantiated during a call to MemoryHelper.create(). You can freely read / write to this array; however, the point of the MemoryHelper utility class is to do so using indices obtained from calls to the .malloc() method.

Development and Testing

There's nothing fancy in regards to development... no build script required. For testing simply run npm test (after installing all necessary packages via npm install). Tests use mocha and vanilla assert.