Most efficient way of copying a "hex array" string to a buffer? - node.js

Question

I'm receiving a high volume of "hex array" strings in the form:
'16 03 03 00 50 40 f2 12 71 0b c0 4f 99 dc 87 6f'
What's the most efficient way of copying them into an existing, larger buffer?
I'm guessing the naive way would be:
var lineBuffer = new Buffer(line.replace(/\s+/g, ''), 'hex');
lineBuffer.copyTo(mainBuffer, offset);
offset += 16;
I'm wary of using line[index] and doing the simple bit shift and sum, because string[index] just resolves to another string.

Answer 1

To move this out of the comments,
The solution you're looking for is probably something like this:
const line = '16 03 03 00 50 40 f2 12 71 0b c0 4f 99 dc 87 6f';
const regex = / /g;
const encoding = 'hex';
const replacement = '';
function getHexString(input) {
return input.replace(regex, replacement);
}
const existingBuffer = Buffer.alloc(1024); // just as an example
const offset = existingBuffer.length; // or wherever you need them to go.
function write(buffer, str, pos) {
const hexString = getHexString(str);
buffer.write(hexString, pos, encoding);
}
write(existingBuffer, line, 0);
I can get about 1,600,000 ops/sec through benchmark.js with () => write(existingBuffer, line, 0). Cheating a bit, since I'm constantly writing to position 0 instead of appending, but it should be close enough to get you an idea. The closest I could come with other combinations I was trying was about 1,200,000 ops/sec.
Also as a side note, I would strongly suggest using Buffer.alloc() wherever you are creating your original buffer, if you aren't. You can also use Buffer.allocUnsafe() which is faster, but that may leave non-zero data in the buffer. Which may be okay, if you know you're going to fill the entire buffer with new data before using it (or are only using known-filled slices). More reading here.