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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 ArrayBuffer -> Buffer: 22.955ms
 i memcpy.100k > cc ArrayBuffer -> ArrayBuffer: 23.273ms
// Native JS
 i memcpy.100k > js Buffer -> Buffer: 21.617ms
 i memcpy.100k > js Buffer -> ArrayBuffer: 993.361ms
 i memcpy.100k > js ArrayBuffer -> Buffer: 940.273ms
 i memcpy.100k > js ArrayBuffer -> ArrayBuffer: 1626.182ms


memcpy(target[, targetStart=0], source[, sourceStart=0[, sourceEnd=source.length]):bytesCopied
Argument Type Optional Description
target Buffer | ArrayBuffer Target buffer to copy to
targetStart number omittable Target offset to begin copying to, defaults to 0
source Buffer | ArrayBuffer 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.


  • 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.


Denys Khanzhiyev (node 0.11.13+ support with nan)

License: Apache License, Version 2.0