When running in an V8 environment where creating external buffers is not allowed, buffer memory gets corrupted.

Take the following Rust code (lib.rs):

use napi::{Env, JsArrayBuffer};

#[napi_derive::napi]
pub fn create_buffer(env: Env) -> napi::Result<JsArrayBuffer> {
    let data = vec![0xDEu8, 0xAD, 0xBE, 0xEF];
    let v = env.create_arraybuffer_with_data(data)?;

    Ok(v.into_raw())
}

Running this in the NodeJS CLI correctly produces the correct buffer:

> const m = require("/path/to/module-from-above.node");
undefined
> m.createBuffer();
ArrayBuffer { [Uint8Contents]: <de ad be ef>, byteLength: 4 }

Running this in an electron CLI produces a corrupt buffer (electron -i):

> const m = require("/path/to/module-from-above.node");
undefined
> m.createBuffer();
ArrayBuffer { [Uint8Contents]: <de 00 00 00>, byteLength: 4 }
// Content should be <de ad be ef>, only the first byte got copied

This is happening due to a bug here:

More specifically, std::ptr::swap swaps 2 structures from one place to another using their structure size. In this case this means swapping *mut u8, which copies exactly one byte. The correct usage would be std::ptr::copy_nonoverlapping (the swap is not needed because u8 is Copy).

This bug seems to exist in multiple places in different variants (for example, Env::create_arraybuffer_with_borrowed_data completly fails to copy data at all when external buffers are disabled).