Note: This readme is auto generated. Please refer to the docs.

Lexerus

Lexerus is a lexer dinosaur that consumes a [Buffer] constructed from [str] and spits out a structure through the lexer::Lexer::lex call.

This library uses the lexerus_derive::Token and lexerus_derive::Lexer macros to decorate a structure for automatic parsing. See those macros for additional options.

This library was developed in conjunction with SPEW and examples on actual implementation can be found there.

An annotated struct will act as an AND and all tokens must be matched before Lexer::lex returns a valid Result::Ok An annotated enum acts as an OR and any of the match arms must be met in order for the Lexer::lex to return a valid Result::Ok

Example

// Create and decorate a struct
#[derive(Lexer, Token, Debug)]
enum Trex<'code> {
    Trex(#[pattern = "rawr"] Buffer<'code>),
    Other(#[pattern = "meow"] Buffer<'code>),
};

// Create a raw buffe
let mut buffer = Buffer::from("rawr");

// Attempt to parse the trex
let trex_calling = Trex::lex(&mut buffer).unwrap();

if let Trex::Trex(trex_calling) = trex_calling {
    assert_eq!(trex_calling.to_string(), "rawr");
}
else {
    panic!("expected trex");
}

// Create and decorate a struct
#[derive(Lexer, Token, Debug)]
struct Trex<'code>(#[pattern = "trex::"] Buffer<'code>);

#[derive(Lexer, Token, Debug)]
struct TrexCall<'code>(
    #[pattern = "RAWR"] Buffer<'code>,
);

#[derive(Lexer, Token, Debug)]
struct Call<'code> {
    rex: Trex<'code>,
    call: TrexCall<'code>,
}

// Create a raw buffe
let mut buffer = Buffer::from("trex::RAWR");

// Attempt to parse the trex
let trex_calling = Call::lex(&mut buffer).unwrap();

// Extract the buffer from trex
let trex = trex_calling.rex.buffer().unwrap();
let trex_calling = trex_calling.buffer().unwrap();

// Buffer should contain the exact matched string
assert_eq!(trex_calling.to_string(), "trex::RAWR");
assert_eq!(trex.to_string(), "trex::");

Goals

• No heap allocations when parsing. However be aware that certain [helpers] may use heap allocations if required.
• Heap allocations only occur when calling Token::buffer on non-contigous sections of text or_repeated_ sections of text. This is inevitable beause different sections of [str] have to be stitched together and the only way to do so is with a heap allocation.
• Proper debuggable information, i.e. the [Buffer] retains information about its source and theexact range on the source. The [Error] which Lexer::lex generates contains a clone of the unparsed [Buffer] so that the program can debug where the Lexer::lex failed.