memcpy

node-memcpy

Copies data between node Buffers and/or ArrayBuffers up to ~75 times faster than in pure JS.

Wait, what?

node.js utilizes a non-standard concept of I/O buffers and thus has both its Buffer as well as ArrayBuffer support. While Buffers are nice because they are a lot faster than V8's ArrayBuffers, transferring data between those two types can be ridiculously slow. This is where a node module like memcpy comes into play.

// C++ binding

 i memcpy.100k > cc Buffer -> Buffer: 22.756ms
 i memcpy.100k > cc Buffer -> ArrayBuffer: 23.861ms
 i memcpy.100k > cc Buffer -> Uint8Array: 22.953ms

 i memcpy.100k > cc ArrayBuffer -> Buffer: 22.955ms
 i memcpy.100k > cc ArrayBuffer -> ArrayBuffer: 23.273ms
 i memcpy.100k > cc ArrayBuffer -> Uint8Array: 22.685ms

 i memcpy.100k > cc Uint8Array -> Buffer: 23.472ms
 i memcpy.100k > cc Uint8Array -> ArrayBuffer: 22.975ms
 i memcpy.100k > cc Uint8Array -> Uint8Array: 22.953ms

// Native JS

 i memcpy.100k > js Buffer -> Buffer: 21.617ms
 i memcpy.100k > js Buffer -> ArrayBuffer: 993.361ms
 i memcpy.100k > js Buffer -> Uint8Array: 410.010ms

 i memcpy.100k > js ArrayBuffer -> Buffer: 940.273ms
 i memcpy.100k > js ArrayBuffer -> ArrayBuffer: 1626.182ms
 i memcpy.100k > js ArrayBuffer -> Uint8Array: 1084.790ms

 i memcpy.100k > js Uint8Array -> Buffer: 386.218ms
 i memcpy.100k > js Uint8Array -> ArrayBuffer: 1107.530ms
 i memcpy.100k > js Uint8Array -> Uint8Array: 502.653ms

API

memcpy(target[, targetStart=0], source[, sourceStart=0[, sourceEnd=source.length]):bytesCopied

Argument	Type	Optional	Description
target	Buffer | ArrayBuffer | Uint8Array		Target buffer to copy to
targetStart	number	omittable	Target offset to begin copying to, defaults to 0
source	Buffer | ArrayBuffer | Uint8Array		Source buffer to copy from
sourceStart	number	optional	Source offset to begin copying from, defaults to 0
sourceEnd	number	optional	Source offset to end copying from, defaults ot source.length
@returns	number		Number of bytes copied

Source and target regions may overlap.

Usage

• npm install memcpy

var memcpy = require("memcpy"), // C++ binding if available, else native JS
    memcpy_binding = memcpy.binding, // C++ binding or NULL if not available
    memcpy_native = memcpy.native; // Native JS
...

Please keep in mind that - besides the nice numbers - this is still to be considered experimental. I'd love if you'd review the C++ code to validate that it's safe. I can't yet think of a sane use case, though, as just sticking with Buffers on node.js and ArrayBuffers in the browser should be best practice.

License: Apache License, Version 2.0