MessagePacker - some Rust in the msgpack protocol

The protocol specification can be found here.

This crate targets simplicity and performance. No dependencies are used, just the standard Rust library.

We have two main structures available:

• Message - Owned parsed values
• MessageRef - Message parsed by reference and bound to the lifetime of the readers source

Example

```rust use msgpacker::prelude::*; use std::io::{Cursor, Seek};

let buffer = vec![0u8; 4096]; let mut cursor = Cursor::new(buffer);

let key = Message::string("some-key"); let value = Message::integer_signed(-15); let entry = MapEntry::new(key, value); let message = Message::map(vec![entry]);

// Write the message to the cursor message.pack(&mut cursor).expect("Message pack failed");

cursor.rewind().expect("Reset the cursor to the beginning");

// Read the message from the cursor let restored = Message::unpack(&mut cursor).expect("Message unpack failed"); let value = restored .asmap() .expect("A map was originally created") .first() .expect("The map contained one entry") .val() .asinteger() .expect("The value was an integer") .as_i64() .expect("The value was a negative integer");

assert_eq!(value, -15);

// Alternatively, we can use the index implementation let value = restored["some-key"] .asinteger() .expect("The value was an integer") .asi64() .expect("The value was a negative number");

assert_eq!(value, -15); ```

Example (by ref)

```rust use msgpacker::prelude::*; use std::io::{Cursor, Seek};

let mut cursor = Cursor::new(vec![0u8; 4096]);

let key = Message::String("some-key".into()); let value = Message::Integer(Integer::signed(-15)); let entry = MapEntry::new(key, value); let message = Message::Map(vec![entry]);

// Write the message to the cursor message.pack(&mut cursor).expect("Message pack failed");

cursor.rewind().expect("Reset the cursor to the beginning");

// The consumer need to guarantee himself the cursor source will live long enough to satisfy the // lifetime of the message reference. // // If this is guaranteed, then the function is safe. let restored = unsafe { MessageRef::unpack(&mut cursor).expect("Message unpack failed") };

// The lifetime of MessageRef is not bound to the Read implementation because the source // might outlive it - as in this example let buffer = cursor.intoinner();

// MessageRef behaves the same as Message, but the runtime cost is cheaper because it will // avoid a couple of unnecessary copies let value = restored .asmap() .expect("A map was originally created") .first() .expect("The map contained one entry") .val() .asinteger() .expect("The value was an integer") .as_i64() .expect("The value was a negative integer");

assert_eq!(value, -15);

// MessageRef also implements Index let value = restored["some-key"] .asinteger() .expect("The value was an integer") .asi64() .expect("The value was a negative number");

assert_eq!(value, -15); ```

Benchmarks

Results obtained with Intel(R) Core(TM) i9-9900X CPU @ 3.50GHz

ignore,no_run $ cargo bench msgpack nil time: [3.3648 ns 3.3783 ns 3.3928 ns] msgunpack nil time: [25.925 ns 26.008 ns 26.097 ns] msgunpack ref nil time: [22.632 ns 22.709 ns 22.789 ns] msgpack int time: [5.9986 ns 6.0216 ns 6.0525 ns] msgunpack int time: [25.481 ns 25.579 ns 25.680 ns] msgunpack ref int time: [22.635 ns 22.727 ns 22.830 ns] msgpack map time: [1.1588 us 1.1626 us 1.1667 us] msgunpack map time: [25.955 ns 26.045 ns 26.141 ns] msgunpack ref map time: [22.626 ns 22.716 ns 22.810 ns]