Crossbeam Receiver to BufRead? - rust

Question

I receive a long string (several gigabytes) as chunks of [u8]s in a Crossbeam channel. I want to break it down to lines. How do I turn these chunks into a BufRead?
fn foo(recv: crossbeam_channel::Receiver<Vec<u8>>) {
let mut buf_read: dyn std::io::BufRead = WHAT_COMES_HERE(recv); // <----
for line in buf_read.lines() {
// ...
}
}
I make these chunks on another thread since they are CPU-intensive to make. I could use something else than Vec<u8> if it makes more sense.

Answer 1

I don't think there is anything builtin, but it shouldn't be too difficult to write yourself. For example something like this:
use crossbeam_channel; // 0.5.4
use std::cmp::min;
use std::io::BufRead;
struct CrossbeamReader {
recv: crossbeam_channel::Receiver<Vec<u8>>,
offset: usize,
buffer: Vec<u8>,
}
impl CrossbeamReader {
fn new (recv: crossbeam_channel::Receiver<Vec<u8>>) -> Self
{
CrossbeamReader { recv, offset: 0, buffer: vec![], }
}
}
impl std::io::Read for CrossbeamReader {
fn read (&mut self, buf: &mut [u8]) -> std::io::Result<usize>
{
while self.offset >= self.buffer.len() {
self.buffer = match self.recv.recv() {
Ok (v) => v,
Err (_) => return Ok (0), // TODO: error handling
};
self.offset = 0;
}
let size = min (buf.len(), self.buffer.len() - self.offset);
buf[..size].copy_from_slice (&self.buffer[self.offset .. self.offset + size]);
self.offset += size;
Ok (size)
}
}
pub fn foo(recv: crossbeam_channel::Receiver<Vec<u8>>) {
let buf_read = std::io::BufReader::new (CrossbeamReader::new (recv));
for _line in buf_read.lines() {
// ...
}
}
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