toad-msg
Low-level representation of CoAP messages.
The most notable item in toad_msg
is Message
;
a CoAP message very close to the actual byte layout.
Allocation
CoAP messages have some attributes whose size is dynamic:
- The message payload (in http terms: the request/response body)
- the number of options (in http terms: headers)
- the value of an option (in http terms: header value)
Message
does not require an allocator and has no opinions about what kind of collection
it uses internally to store these values.
It solves this problem by being generic over the collections it needs and uses an Array
trait
to capture its idea of what makes a collection useful.
This means that you may use a provided implementation (for Vec
or tinyvec::ArrayVec
)
or provide your own collection (see the custom collections example)
//! Note: both of these type aliases are exported by `toad_msg` for convenience.
use ArrayVec;
use ;
// Message Payload byte buffer
// |
// | Array of options in the message
// vvvvvvv vvvvvvvvvvvvvvvvv
type VecMessage = ;
// Used like: `ArrayVecMessage<1024, 256, 16>`; a message that can store a payload up to 1024 bytes, and up to 16 options each with up to a 256 byte value.
type ArrayVecMessage<
const PAYLOAD_SIZE: usize,
const OPT_SIZE: usize,
const NUM_OPTS: usize,
> = ;
It may look a little ugly, but a core goal of toad
is to be platform- and alloc-agnostic.
Performance
This crate uses criterion
to measure performance of the heaped & heapless implementations in this crate as well as coap_lite::Packet
.
In general, toad_msg::VecMessage
performs identically to coap_lite (+/- 5%), and both are much faster than toad_msg::ArrayVecMessage
.
Benchmarks:
Serializing to bytes
Click to expand chart
Deserializing from bytes
Click to expand chart
License
Licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.