jagged_array

This crate provides a jagged array, i.e. a type that is semantically equivalent to Box<[Box<[T]>]>, but implemented with better memory locality and fewer heap allocations.

Example

extern crate jagged_array;
extern crate streaming_iterator;
use std::iter::FromIterator;
use jagged_array::{Jagged2, Jagged2Builder};
use streaming_iterator::StreamingIterator;

// Create a builder object for the array, and append some data.
// Each `extend` call builds another row.
let mut builder = Jagged2Builder::new();
builder.extend(&[1, 2, 3]); // row 0 = [1, 2, 3]
builder.extend(vec![4]);    // row 1 = [4]
builder.extend(&[]);        // row 2 = []
builder.extend(5..7);       // row 3 = [5, 6]

// Finalize the builder into a non-resizable jagged array.
let mut a: Jagged2<u32> = builder.into();
// Alternatively, we could have created the same array from a Vec<Vec<T>> type:
let alt_form = Jagged2::from_iter(vec![
    vec![1, 2, 3],
    vec![4],
    vec![],
    vec![5, 6],
]);
assert_eq!(a, alt_form);

// Indexing is done in [row, column] form and supports `get` and `get_mut` variants.
assert_eq!(a[[1, 0]], 4);
*a.get_mut([1, 0]).unwrap() = 11;
assert_eq!(a.get([1, 0]), Some(&11));

// Whole rows can also be accessed and modified
assert_eq!(a.get_row(3), Some(&[5, 6][..]));
a.get_row_mut(3).unwrap()[1] = 11;
// Note that although elements are modifiable, the structure is not;
// items cannot be inserted into rows, nor can new rows be added.

// Iteration via `StreamingIterator`s. See the docs for more detail.
let mut iter = a.stream();
while let Some(row) = iter.next() {
    println!("row: {:?}", row);
}

Documentation

Documentation can be found on docs.rs

Benchmarks

$ cargo bench
test bench_access_jag   ... bench:         109 ns/iter (+/- 4)
test bench_access_vec   ... bench:         122 ns/iter (+/- 4)
test bench_collect_jag  ... bench:       2,619 ns/iter (+/- 177)
test bench_collect_vec  ... bench:       3,638 ns/iter (+/- 854)
test bench_flat_len_jag ... bench:           0 ns/iter (+/- 0)
test bench_flat_len_vec ... bench:          50 ns/iter (+/- 5)
test bench_serde_jag    ... bench:     343,839 ns/iter (+/- 36,172)
test bench_serde_vec    ... bench:     378,089 ns/iter (+/- 37,954)

*_jag indicates runtime for the Jagged2<u32> implementation, *_vec indicates runtime for Vec<Vec<u32>>. See benches/jagged2.rs for more details.

License

The code in this repository is licensed under either of

• Apache License, Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this repository by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.