wasmrs 0.17.0

Base host and client implementations of the wasmRS RSocket protocol.
Documentation 
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use std::io::Read;

use bytes::{BufMut, Bytes, BytesMut};

#[must_use]
pub(crate) fn from_u32_bytes(bytes: &[u8]) -> u32 {
  assert!(bytes.len() == 4, "Need 4 bytes to convert to u32");
  let mut num_parts: [u8; 4] = Default::default();

  num_parts[0..4].copy_from_slice(bytes);

  u32::from_be_bytes(num_parts)
}

#[must_use]
pub(crate) fn from_u16_bytes(bytes: &[u8]) -> u16 {
  assert!(bytes.len() == 2, "Need two bytes to convert to u16");
  let mut num_parts: [u8; 2] = Default::default();

  num_parts[0..2].copy_from_slice(bytes);

  u16::from_be_bytes(num_parts)
}

#[must_use]
pub(crate) fn from_u24_bytes(bytes: &[u8]) -> u32 {
  assert!(bytes.len() == 3, "Need three bytes to convert to u24");
  let mut num_parts: [u8; 4] = Default::default();

  num_parts[1..4].copy_from_slice(bytes);

  u32::from_be_bytes(num_parts)
}

#[must_use]
/// Convert a [u32] to a `u24` represented in bytes.
pub fn to_u24_bytes(num: u32) -> Bytes {
  let mut num_parts = BytesMut::with_capacity(3);

  num_parts.put(&num.to_be_bytes()[1..4]);

  num_parts.freeze()
}

/// Read a frame from a buffer.
pub fn read_frame(mut buf: impl Read) -> std::io::Result<Bytes> {
  let mut len_bytes = [0u8; 3];
  buf.read_exact(&mut len_bytes)?;
  let len = from_u24_bytes(&len_bytes);

  let mut frame = vec![0; len as usize];
  buf.read_exact(&mut frame)?;
  Ok(frame.into())
}

#[cfg(test)]
mod test {
  use anyhow::Result;

  use super::read_frame;

  #[test]
  fn test_read_frame() -> Result<()> {
    let mut buf: &[u8] = &[0, 0, 4, 1, 2, 3, 4];
    let frame = read_frame(&mut buf)?;
    assert_eq!(frame, vec![1, 2, 3, 4]);

    Ok(())
  }
}