Redis Protocol

A Rust implementation of the Redis protocol.

Features

• Owned and zero-copy Bytes-based parsing interfaces.
• Supports RESP2 and RESP3 frames, including streaming frames.
• Publish-subscribe message utilities.
• A cluster hash slot interface.
• RESP2 and RESP3 codec interfaces.
• Utility functions for converting from RESP2 to RESP3.
• Traits for converting frames into other types.

Examples

use redis_protocol::resp2::{
  decode::decode,
  encode::encode,
  types::{OwnedFrame as Frame, Resp2Frame}
};

fn main() {
  let frame = Frame::BulkString("foobar".into());
  let mut buf = vec![0; frame.encode_len(false)];

  let len = encode(&mut buf, &frame, false).expect("Error encoding frame");
  println!("Encoded {} bytes into buffer with contents {:?}", len, buf);

  // ["Foo", nil, "Bar"]
  let buf: &[u8] = b"*3\r\n$3\r\nFoo\r\n$-1\r\n$3\r\nBar\r\n";
  match decode(&buf).unwrap() {
    Some((frame, amt)) => println!("Parsed {:?} and read {} bytes", frame, amt),
    None => println!("Incomplete frame."),
  };
}

Build Features

no_std

no_std builds are supported by disabling the std feature. However, a few optional dependencies must be activated as a substitute.

redis-protocol = { version = "X.X.X", default-features = false, features = ["libm", "hashbrown", "alloc"] }

Decoding

Both RESP2 and RESP3 interfaces support 3 different Frame interfaces. These interfaces are designed to support different use cases:

• OwnedFrame types use core container types to implement owned frame variants. This is the easiest frame interface to use, but often requires moving or copying the underlying buffer contents when decoding.
• BytesFrame types use Bytes as the backing container. The bytes feature flag enables this frame type and a set of associated functions that avoid moving or copying BytesMut contents.
• RangeFrame types represent ranges into an associated buffer and are typically used to implement forms of zero-copy parsing. This is the lowest level interface.

RESP2 OwnedFrame Decoding Example

Simple array decoding example adapted from the tests

use redis_protocol::resp2::{
  decode::decode,
  types::{OwnedFrame, Resp2Frame}
};

fn should_decode_array() {
  // ["Foo", nil, "Bar"]
  let buf: &[u8] = b"*3\r\n$3\r\nFoo\r\n$-1\r\n$3\r\nBar\r\n";

  let (frame, amt) = decode(&buf).unwrap().unwrap();
  assert_eq!(frame, OwnedFrame::Array(vec![
    OwnedFrame::BulkString("Foo".into()),
    OwnedFrame::Null,
    OwnedFrame::BulkString("Bar".into())
  ]));
  assert_eq!(amt, buf.len());
}

RESP2 BytesFrame Decoding Example

Array decoding example adapted from the tests

use redis_protocol::resp2::{
  decode::decode_bytes_mut,
  types::{BytesFrame, Resp2Frame}
};
use bytes::BytesMut;

fn should_decode_array_no_nulls() {
  let expected = (
    BytesFrame::Array(vec![
      BytesFrame::SimpleString("Foo".into()),
      BytesFrame::SimpleString("Bar".into()),
    ]),
    16,
  );
  let mut bytes: BytesMut = "*2\r\n+Foo\r\n+Bar\r\n".into();
  let total_len = bytes.len();

  let (frame, amt, buf) = match decode_bytes_mut(&mut bytes) {
    Ok(Some(result)) => result,
    Ok(None) => panic!("Expected complete frame"),
    Err(e) => panic!("{:?}", e)
  };

  assert_eq!(frame, expected.0, "decoded frame matched");
  assert_eq!(amt, expected.1, "decoded frame len matched");
  assert_eq!(buf.len(), expected.1, "output buffer len matched");
  assert_eq!(buf.len() + bytes.len(), total_len, "total len matched");
}

RESP2 RangeFrame Decoding Example

Implement a custom borrowed frame type that can only represent BulkString and SimpleString

use redis_protocol::resp2::{
  decode::decode_range,
  types::RangeFrame
};
use std::str;

enum MyBorrowedFrame<'a> {
  BulkString(&'a [u8]),
  SimpleString(&'a str),
}

fn decode_borrowed(buf: &[u8]) -> Option<MyBorrowedFrame> {
  match decode_range(buf).ok()? {
    Some((RangeFrame::BulkString((i, j)), _)) => {
      Some(MyBorrowedFrame::BulkString(&buf[i..j]))
    }
    Some((RangeFrame::SimpleString((i, j)), _)) => {
      let parsed = str::from_utf8(&buf[i..j]).ok()?;
      Some(MyBorrowedFrame::SimpleString(parsed))
    }
    _ => None,
  }
}

Encoding

Similar to the decoding interface, there are 3 frame types available to callers for encoding use cases.

• OwnedFrame - See above. Callers that use this interface often have to allocate additional containers on the heap, and often have to move or copy the contents into these frame types from other types, such as RedisValue in fred.
• BytesFrame - See above. This frame type often avoids the need to copy or move the contents from upstream types such as RedisValue, but still requires callers to allocate containers on the heap (i.e. the Vec in the Array variant).
• BorrowedFrame - This frame type serves a similar purpose to the RangeFrame type in the decoding interface in that it can be used when callers want to entirely avoid heap allocations. In practice this often requires the caller to create some intermediate reference-based types, but significantly outperforms other approaches that require allocations.

Options

All encoding interfaces expose an additional parameter, int_as_bulkstring for RESP2 or int_as_blobstring for RESP3, that can be used to encode integers as BulkString or BlobString using a more optimized code path that avoids heap allocations.

In practice Redis expects all incoming frames to be an array of blob or bulk strings. This option can be used to automatically convert integers to byte arrays without additional allocations.

Buffer Management

In some cases this library can automatically extend buffers while encoding. The extend_encode_* family of functions operate on BytesMut types and can automatically resize buffers while encoding, whereas the encode_* family of functions require the caller to allocate the correct amount beforehand.

use redis_protocol::resp2::{
  encode,
  types::{OwnedFrame, BytesFrame, BorrowedFrame, Resp2Frame}
};
use bytes::BytesMut;

fn main() {
  // using OwnedFrame variants, manually allocating the buffer
  let frame = OwnedFrame::BulkString("foobar".into());
  let mut buf = vec![0; frame.encode_len(false)];
  let len = encode::encode(&mut buf, &frame, false).expect("Error encoding frame");
  println!("Encoded {} bytes into buffer with contents {:?}", len, buf);

  // using BytesFrame variants
  let frame = BytesFrame::BulkString("foobar".into());
  let mut buf = BytesMut::new();
  let len = encode::extend_encode(&mut buf, &frame, false).expect("Error encoding frame");
  println!("Encoded {} bytes into buffer with contents {:?}", len, buf);

  // using BorrowedFrame variants
  let value: String = "foobar".into();
  let frame = BorrowedFrame::BulkString(value.as_bytes());
  let mut buf = BytesMut::new();
  let len = encode::extend_encode_borrowed(&mut buf, &frame, false).expect("Error encoding frame");
  println!("Encoded {} bytes into buffer with contents {:?}", len, buf);
}