binary-layout 3.1.3

The binary-layout library allows type-safe, inplace, zero-copy access to structured binary data. You define a custom data layout and give it a slice of binary data, and it will allow you to read and write the fields defined in the layout from the binary data without having to copy any of the data. It's similar to transmuting to/from a `#[repr(packed)]` struct, but much safer.
Documentation 
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use binary_layout::prelude::*;
use core::any::{Any, TypeId};
use std::convert::TryInto;

mod common;
use common::data_region;

define_layout!(withslice, LittleEndian, {
    first: i8,
    second: i64,
    third: [u8; 5],
    fourth: u16,
    fifth: [u8],
});

#[test]
fn metadata() {
    assert_eq!(0, withslice::first::OFFSET);
    assert_eq!(Some(1), withslice::first::SIZE);
    assert_eq!(1, withslice::second::OFFSET);
    assert_eq!(Some(8), withslice::second::SIZE);
    assert_eq!(9, withslice::third::OFFSET);
    assert_eq!(Some(5), withslice::third::SIZE);
    assert_eq!(14, withslice::fourth::OFFSET);
    assert_eq!(Some(2), withslice::fourth::SIZE);
    assert_eq!(16, withslice::fifth::OFFSET);
    assert_eq!(None, withslice::fifth::SIZE);
}

#[test]
fn types() {
    let storage = data_region(1024, 5);
    let view = withslice::View::new(&storage);

    assert_eq!(
        TypeId::of::<i8>(),
        withslice::first::read(&storage).type_id()
    );
    assert_eq!(
        TypeId::of::<i64>(),
        withslice::second::read(&storage).type_id()
    );
    assert_eq!(
        TypeId::of::<[u8; 5]>(),
        withslice::third::data(&storage).type_id()
    );
    assert_eq!(
        TypeId::of::<u16>(),
        withslice::fourth::read(&storage).type_id()
    );
    assert_eq!(
        TypeId::of::<[u8]>(),
        withslice::fifth::data(&storage).type_id()
    );

    assert_eq!(TypeId::of::<i8>(), view.first().read().type_id());
    assert_eq!(TypeId::of::<i64>(), view.second().read().type_id());
    assert_eq!(TypeId::of::<[u8; 5]>(), view.third().type_id());
    assert_eq!(TypeId::of::<u16>(), view.fourth().read().type_id());
    assert_eq!(TypeId::of::<[u8]>(), view.fifth().type_id());
}

#[test]
fn fields() {
    let mut storage = data_region(1024, 5);

    // Test initial data is read correctly
    assert_eq!(5, withslice::third::data(&storage).len());
    assert_eq!(5, withslice::third::data_mut(&mut storage).len());
    assert_eq!(1024 - 16, withslice::fifth::data(&storage).len());
    assert_eq!(1024 - 16, withslice::fifth::data_mut(&mut storage).len());

    // Test data can be written
    withslice::first::write(&mut storage, 60);
    withslice::second::write(&mut storage, -100_000_000_000);
    withslice::third::data_mut(&mut storage).copy_from_slice(&[10, 20, 30, 40, 50]);
    withslice::fourth::write(&mut storage, 1_000);
    withslice::fifth::data_mut(&mut storage).copy_from_slice(&data_region(1024 - 16, 6));

    // Test reading will return changed data
    assert_eq!(60, withslice::first::read(&storage));
    assert_eq!(-100_000_000_000, withslice::second::read(&storage));
    assert_eq!(&[10, 20, 30, 40, 50], withslice::third::data(&storage));
    assert_eq!(1_000, withslice::fourth::read(&storage));
    assert_eq!(&data_region(1024 - 16, 6), withslice::fifth::data(&storage));
}

#[test]
fn view_readonly() {
    let storage = data_region(1024, 5);
    let view = withslice::View::new(&storage);

    // Test initial data is read correctly
    assert_eq!(
        i8::from_le_bytes((&data_region(1024, 5)[0..1]).try_into().unwrap()),
        view.first().read()
    );
    assert_eq!(
        i64::from_le_bytes((&data_region(1024, 5)[1..9]).try_into().unwrap()),
        view.second().read()
    );
    assert_eq!(&data_region(1024, 5)[9..14], view.third(),);
    assert_eq!(
        u16::from_le_bytes((&data_region(1024, 5)[14..16]).try_into().unwrap()),
        view.fourth().read()
    );
    assert_eq!(&data_region(1024, 5)[16..], view.fifth());

    // Test into_storage will return correct data
    let extracted_storage: &Vec<u8> = view.into_storage();
    assert_eq!(storage, *extracted_storage);
}

#[test]
fn view_readwrite() {
    let mut storage = data_region(1024, 5);
    let mut view = withslice::View::new(&mut storage);

    // Test initial data is read correctly
    assert_eq!(
        i8::from_le_bytes((&data_region(1024, 5)[0..1]).try_into().unwrap()),
        view.first().read()
    );
    assert_eq!(
        i64::from_le_bytes((&data_region(1024, 5)[1..9]).try_into().unwrap()),
        view.second().read()
    );
    assert_eq!(&data_region(1024, 5)[9..14], view.third(),);
    assert_eq!(
        u16::from_le_bytes((&data_region(1024, 5)[14..16]).try_into().unwrap()),
        view.fourth().read()
    );
    assert_eq!(&data_region(1024, 5)[16..], view.fifth());

    // Test data can be written
    view.first_mut().write(50);
    view.second_mut().write(10i64.pow(15));
    view.third_mut().copy_from_slice(&[10, 20, 30, 40, 50]);
    view.fourth_mut().write(1000);
    view.fifth_mut()
        .copy_from_slice(&data_region(1024, 6)[16..]);

    // Test reading will return changed data
    assert_eq!(50, view.first().read());
    assert_eq!(10i64.pow(15), view.second().read());
    assert_eq!(&[10, 20, 30, 40, 50], view.third());
    assert_eq!(1000, view.fourth().read());
    assert_eq!(&data_region(1024, 6)[16..], view.fifth());

    // Test into_storage will return correct data
    let extracted_storage = view.into_storage().to_vec();
    assert_eq!(&storage, &extracted_storage);

    // Test storage is actually changed
    assert_eq!(50, i8::from_le_bytes((&storage[0..1]).try_into().unwrap()));
    assert_eq!(
        10i64.pow(15),
        i64::from_le_bytes((&storage[1..9]).try_into().unwrap())
    );
    assert_eq!(&[10, 20, 30, 40, 50], &storage[9..14]);
    assert_eq!(
        1000,
        u16::from_le_bytes((&storage[14..16]).try_into().unwrap())
    );
    assert_eq!(&data_region(1024, 6)[16..], &storage[16..]);
}

#[test]
fn view_vec_readonly() {
    let view = withslice::View::new(data_region(1024, 5));

    // Test initial data is read correctly
    assert_eq!(
        i8::from_le_bytes((&data_region(1024, 5)[0..1]).try_into().unwrap()),
        view.first().read()
    );
    assert_eq!(
        i64::from_le_bytes((&data_region(1024, 5)[1..9]).try_into().unwrap()),
        view.second().read()
    );
    assert_eq!(&data_region(1024, 5)[9..14], view.third(),);
    assert_eq!(
        u16::from_le_bytes((&data_region(1024, 5)[14..16]).try_into().unwrap()),
        view.fourth().read()
    );
    assert_eq!(&data_region(1024, 5)[16..], view.fifth());

    // Test into_storage will return correct data
    let extracted_storage: Vec<u8> = view.into_storage();
    assert_eq!(&data_region(1024, 5), &*extracted_storage);
}

#[test]
fn view_vec_readwrite() {
    let mut view = withslice::View::new(data_region(1024, 5));

    // Test initial data is read correctly
    assert_eq!(
        i8::from_le_bytes((&data_region(1024, 5)[0..1]).try_into().unwrap()),
        view.first().read()
    );
    assert_eq!(
        i64::from_le_bytes((&data_region(1024, 5)[1..9]).try_into().unwrap()),
        view.second().read()
    );
    assert_eq!(&data_region(1024, 5)[9..14], view.third(),);
    assert_eq!(
        u16::from_le_bytes((&data_region(1024, 5)[14..16]).try_into().unwrap()),
        view.fourth().read()
    );
    assert_eq!(&data_region(1024, 5)[16..], view.fifth());

    // Test data can be written
    view.first_mut().write(50);
    view.second_mut().write(10i64.pow(15));
    view.third_mut().copy_from_slice(&[10, 20, 30, 40, 50]);
    view.fourth_mut().write(1000);
    view.fifth_mut()
        .copy_from_slice(&data_region(1024, 6)[16..]);

    // Test reading will return changed data
    assert_eq!(50, view.first().read());
    assert_eq!(10i64.pow(15), view.second().read());
    assert_eq!(&[10, 20, 30, 40, 50], view.third());
    assert_eq!(1000, view.fourth().read());
    assert_eq!(&data_region(1024, 6)[16..], view.fifth());

    // Test into_storage will return correct data
    let extracted_storage = view.into_storage();
    assert_eq!(
        50,
        i8::from_le_bytes((&extracted_storage[0..1]).try_into().unwrap())
    );
    assert_eq!(
        10i64.pow(15),
        i64::from_le_bytes((&extracted_storage[1..9]).try_into().unwrap())
    );
    assert_eq!(&[10, 20, 30, 40, 50], &extracted_storage[9..14]);
    assert_eq!(
        1000,
        u16::from_le_bytes((&extracted_storage[14..16]).try_into().unwrap())
    );
    assert_eq!(&data_region(1024, 6)[16..], &extracted_storage[16..]);
}