Rust lense macro

Borrow based by-ref reader allowing the consumer to peek into [u8] streams assuming given types. The consumer experience is almost identical to that of using any normal struct.

TODO

• [ ] Variable length types
• [ ] Syntax extension
  • [ ] Automate ordering (C style)
  • [ ] Lint manually ordered fields
  • [ ] #[derive(..)] attribute

Usage

rust // Manual creation make_lense!{Alice, AliceWriter, a: u8, b: u16, c: u32, d: u64, } //// Syntax extension // #[derive(lense)] // struct Alice { // a: u8, // b: u16, // c: u32, // d: u64, // } ```rust let mut a = vec![0x00, // a[0].a 0x01, 0x02, // a[0].b 0x03, 0x04, 0x05, 0x06, // a[0].c 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, // a[0].d 0x00, // ... 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, ];

let mut a_ = Alice::writer(); { // construct a new Alice and populate the fields let mut al = a.borrowlense(); *al.a = 0; *al.b = 513; *al.c = 100992003; *a_l.d = 1012478732780767239; }

// Check that the manually populated Alice is equal to the buffer a assert!(a.asbytes() == &a[0..Alice::size()]);

// Format: [(size, chunk); n] where n is number of chunks // size only present for variable length fields let mut pos = 0; loop { // iterate over each Alice in our buffer a let (, mut a) = a.splitatmut(pos); match Alice::frombuf(&mut a) { Ok((mut a, size)) => { *a.a += pos as u8; pos += size; println!("a: {}; b: {}; c: {}; d: {}", *a.a, *a.b, *a.c, *a.d); }, Err(LenseError::NothingToParse) => break, // no more to process :) Err(LenseError::UnexpectedSize) => break, // Invalid chunk Err(LenseError::Incomplete) => break, // Incomplete }; };

println!("Mutated result: {:?}", &*a); Output altered for viewing a: 0; b: 513; c: 100992003; d: 1012478732780767239 a: 15; b: 513; c: 100992003; d: 1012478732780767239 a: 30; b: 513; c: 100992003; d: 1012478732780767239 Mutated result: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 30, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]

```

Benchmarks

Linux livecd 3.18.9-hardened #1 SMP x86_64 Intel(R) Atom(TM) CPU N450 @ 1.66GHz GenuineIntel GNU/Linux

test alice_writer_init ... bench: 170 ns/iter (+/- 3) = 88 MB/s test alice_writer_uninit ... bench: 169 ns/iter (+/- 65) = 88 MB/s test alice_x3_reader ... bench: 2 ns/iter (+/- 0) = 22500 MB/s test u64x2_reader ... bench: 1 ns/iter (+/- 0) = 16000 MB/s test u64x2_writer_init ... bench: 123 ns/iter (+/- 35) = 130 MB/s test u64x2_writer_uninit ... bench: 123 ns/iter (+/- 5) = 130 MB/s test u64x31_reader ... bench: 18 ns/iter (+/- 0) = 13777 MB/s test u64x31_writer_init ... bench: 185 ns/iter (+/- 11) = 1340 MB/s test u64x31_writer_uninit ... bench: 141 ns/iter (+/- 11) = 1758 MB/s Macbook Pro 2014, i7? (Thanks frankmcsherry) test alice_writer_init ... bench: 29 ns/iter (+/- 14) = 517 MB/s test alice_writer_uninit ... bench: 29 ns/iter (+/- 9) = 517 MB/s test alice_x3_reader ... bench: 1 ns/iter (+/- 1) = 45000 MB/s test u64x2_reader ... bench: 0 ns/iter (+/- 0) = 16000 MB/s test u64x2_writer_init ... bench: 20 ns/iter (+/- 8) = 800 MB/s test u64x2_writer_uninit ... bench: 21 ns/iter (+/- 9) = 761 MB/s test u64x31_reader ... bench: 2 ns/iter (+/- 0) = 124000 MB/s test u64x31_writer_init ... bench: 29 ns/iter (+/- 4) = 8551 MB/s test u64x31_writer_uninit ... bench: 26 ns/iter (+/- 6) = 9538 MB/s