Struct embly::Comm

pub struct Comm { /* fields omitted */ }

Comm's handle communication between functions or to the function caller

Receive Bytes

When a spark begins execution it can optionally read in any bytes that it might have been sent. Maybe there are bytes ready on startup, maybe it'll receive them later.

Over time, a spark can receive multiple messages. Maybe parts of a request body or various incremental updates. Each separate message will be separated by an io::EOF error.

use embly::Comm;
use std::io;
use std::io::Read;

fn entrypoint(mut comm: Comm) -> io::Result<()> {
    let mut buffer = Vec::new();
    // Comm implements std::io::Read
    comm.read_to_end(&mut buffer)?;

    // a little while later you might get another message
    comm.read_to_end(&mut buffer)?;
    return Ok(())
}

Write Bytes

Writes can be written back. A spark is always executed by something. This could be a command line call, a load balancer or another spark. Writing to a comm will send those bytes back to the spark runner.

use embly::Comm;
use std::io;
use std::io::Write;

fn entrypoint(mut comm: Comm) -> io::Result<()> {
    // you can call write_all to send one message
    comm.write_all("Hello World".as_bytes())?;


    // Or you can make multiple calls with write if you want to construct a
    // message and then flush the response
    comm.write(b"Hello")?;
    comm.write(b"World")?;
    comm.flush()?;
    return Ok(())
}

Trait Implementations

impl Write for Comm

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

Creates a "by reference" adaptor for this instance of Write.

impl Read for Comm

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

unsafe fn initializer(&self) -> Initializer

🔬 This is a nightly-only experimental API. (read_initializer)

Determines if this Reader can work with buffers of uninitialized memory.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Read all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Read all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Read the exact number of bytes required to fill buf.

fn by_ref(&mut self) -> &mut Self

Creates a "by reference" adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>

Transforms this Read instance to an [Iterator] over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R> where
    R: Read, 

Creates an adaptor which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

Creates an adaptor which will read at most limit bytes from it.