11 releases (5 breaking)

0.6.3 Mar 18, 2021
0.6.1 Dec 29, 2020
0.4.1 Nov 12, 2020
0.2.0 Jun 24, 2020

32 downloads per month

MIT/Apache

85KB
1.5K SLoC

simple_parse

crates.io mio Lines of Code

simple_parse is a declarative binary stream parser that aims to generate the most efficient parsing code possible for your custom types while remaining safe.

Features Description
Fast The generated parsing code is often faster than "idiomatic" C implementations
No copy Able to return references into byte slices
Built-in endianness support Annotating structs/fields with endian gives control over how numbers will be parsed
Convert back to bytes In addition to parsing arbitrary bytes, simple_parse also allows dumping structs back into binary form

If simple_parse is unable to describe your complex/non-standard binary formats, take a look at deku.

Usage

Snippets taken from examples/struct.rs

use ::simple_parse::{SpRead, SpWrite};

#[derive(SpRead, SpWrite)]
pub struct SomeStruct {
    pub some_field: u8,
    #[sp(endian="big")]
    pub items: Vec<u32>,
}

// Emulate data coming from a socket
let mut srv_sock: &[u8] = &[
    1,                      // some_field
    0,0,0,2,                // items.len()
    0xDE,0xAD,0xBE,0xEF,    // items[0]
    0xBA,0xDC,0x0F,0xFE     // items[1]
];

// Parse incoming bytes into SomeStruct
let mut my_struct = SomeStruct::from_reader(&mut srv_sock)?;

/// Modify the struct
my_struct.items.push(0xFFFFFFFF);

/// Encode our struct back into bytes
let mut cli_sock: Vec<u8> = Vec::new();
my_struct.to_writer(&mut cli_sock)?;
//dst_buf == [1, 0, 0, 0, 3, DE, AD, BE, EF, BA, DC, F, FE, FF, FF, FF, FF]

For complete examples see : examples

Project Goals

In vague order of priority, simple_parse aims to provide :

  1. Safety
  2. Performance
  3. Ease of use
  4. Adaptability

In other words, simple_parse will try to generate the most performant code while never compromising on safety.

Secondly, priority will be given to ease of use by providing default implementations that work well in most cases while also allowing some customisation to accomodate for binary formats we cannot control (see the bmp image parsing example).

Advanced Usage

simple_parse provides a few ways to enhance the generate parsing code. See attributes.rs for an exhaustive list of options.

Validation

It is possible to insert validation "hooks" at any point in the parsing/writing process.

For example, BMP image headers must always start with the two first bytes being 'BM' :

#[derive(SpRead, SpWrite)]
struct BmpHeader {
    #[sp(validate = "validate_header")]
    magic: u16,
    size: u32,
    reserved1: u16,
    reserved2: u16,
    pixel_array_offset: u32,
    // ...

(Taken from bmp example)

This tells simple_parse to insert a call to validate_header(magic: &u16, ctx: &mut SpCtx) directly after having populated the u16 when reading and before dumping the struct as bytes when writing.

Custom Length (for TLV style)

simple_parse provides default implementations for dynamically sized types by simply prepending the number of elements (count) followed by the elements.

i.e. A Vec with three values turns into :

// [count] | [count] * [elements]
[3u32][val1][val2][val3]

When parsing binary formats that dont follow this layout, you can annotate your dynamically sized field with count :

pub struct File {
    pub content_len: u16,
    pub filename: String, // Use the default prepended count
    #[sp(count="content_len")]
    pub contents: Vec<u8>, // Use an existing field as the count

The content_len field will be used to populate contents and contents.len() will be written at that offset when writing.

Custom Read/Write

When simple_parse's default reading and writing implementations are not well suited for your formats, you can override them with the reader and writer attributes.

struct BmpHeader {
    comp_bitmask: u32,
    #[sp(
        reader="BmpComp::read, comp_bitmask",
        writer="BmpComp::write",
    )]
    compression_info: BmpComp,
    //...

When reading, this will generate code like :

compression_info = BmpComp::read(comp_bitmask: &u32, src: &mut Read, ctx: &mut SpCtx)?;

And when writing :

written_sz += BmpComp::write(&self.compression_info, ctx: &mut SpCtx, dst: &mut Write)?;

Note : Using reader will generate suboptimal parsing code as simple_parse cannot make any assumptions about the custom reader's impact on the input bytes.

License

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.

Dependencies

~0.5–1MB
~22K SLoC