Crate compactvec 

compact-vec

A CompactVec is a Vec<u32>-compatible container that automatically stores unsigned integers in the smallest possible byte width (1, 2, 3, or 4 bytes per element), upgrading in place when a newly pushed value exceeds the current maximum representable value.

Quick example

use compact_vec::CompactVec;

let mut cv = CompactVec::new();
cv.push(0);          // stored as u8  – 1 byte
cv.push(255);        // stored as u8  – 1 byte
cv.push(256);        // triggers upgrade: all elements re-encoded as u16
assert_eq!(cv.width_bits(), 16);
assert_eq!(cv.get(0), Some(0));
assert_eq!(cv.get(2), Some(256));

Memory savings

Value range	Width	Savings vs Vec<u32>
0 – 255	8 bit	75 %
256 – 65 535	16 bit	50 %
65 536 – 16 M	24 bit	25 %
16 M – 4 G	32 bit	0 %

Feature flags

Flag	Effect
serde	Implements Serialize / Deserialize

Structs

CompactVec

A Vec<u32>-compatible container that packs integers into the smallest possible byte width, upgrading automatically when a new value demands more space.

IntoIter

Consuming iterator over a CompactVec, produced by CompactVec::into_iter.

Iter

Borrowing iterator over a CompactVec.

Enums

BitWidth

Discriminant for the current per-element storage width of a CompactVec.