Pass Node.js Buffer to C++ addon

Question

test.js

buf = new Buffer(100);
for (var i = 0; i < 100; i++) buf[i] = i
addon.myFync(buf);

addon.cpp

Handle<Value> set(const Arguments& args) {
    char *buf = SOMETHING(args[0]);
    return Undefined();
}

How to get the pointer to a data of the buffer inside the C++ function?

What should I write in place of SOMETHING(args[0])?

I have node_buffer.h opened in my editor, but I cannot figure out.

Node version = v0.10.29

score 8 · Accepted Answer · answered Mar 09 '15 at 22:17

8

You can do:

char* buf = node::Buffer::Data(args[0]);

to directly access the bytes of a Buffer.

answered Mar 09 '15 at 22:17

loganfsmyth

Great! I found it also works if you pass typed array, `Uint32Array` for example. – exebook Mar 10 '15 at 11:07
The fact that it works with `Uint32Array` may just be a coincidence, but I'm not as familiar with that so I can't say much more. – loganfsmyth Mar 10 '15 at 17:06
are node::Buffer:Data() or node::Buffer:Length() null terminated? – sgonzalez Jun 30 '20 at 22:19
1

@sgonzalez Seems unlikely but better to post a new question. – loganfsmyth Jun 30 '20 at 23:21
This solution needs an update for the Node Addon API. – Charles Milette Feb 26 '22 at 19:41

score 0 · Answer 2 · answered Mar 09 '15 at 22:12

0

According to the node.js node binding documentation the 'arg[0]' value argument can be accessed as:

String::AsciiValue v(args[0]->ToString());

answered Mar 09 '15 at 22:12

karmasponge

2 Answers2