Module icu_locid::shortvec

This module includes variable-length data types that are const-constructible for single values and overflow to the heap.

Why?

This module is far from the first stack-or-heap vector in the Rust ecosystem. It was created with the following value proposition:

1. Enable safe const construction of stack collections.
2. Avoid stack size penalties common with stack-or-heap collections.

As of this writing, heapless and tinyvec don’t support const construction except for empty vectors, and smallvec supports it on unstable.

Additionally, ShortBoxSlice has a smaller stack size than any of these:

use core::mem::size_of;

// NonZeroU64 has a niche that this module utilizes
use core::num::NonZeroU64;

// ShortBoxSlice is the same size as `Box<[]>` for small or nichey values
assert_eq!(16, size_of::<shortvec::ShortBoxSlice::<NonZeroU64>>());

// Note: SmallVec supports pushing and therefore has a capacity field
assert_eq!(24, size_of::<smallvec::SmallVec::<[NonZeroU64; 1]>>());

// Note: heapless doesn't support spilling to the heap
assert_eq!(16, size_of::<heapless::Vec::<NonZeroU64, 1>>());

// Note: TinyVec only supports types that implement `Default`
assert_eq!(24, size_of::<tinyvec::TinyVec::<[u64; 1]>>());

The module is no_std with alloc.

Modules

• litemap 🔒

Structs

• ShortBoxSlice 🔒
  A boxed slice that supports no-allocation, constant values if length 0 or 1.
• ShortBoxSliceIntoIter
  An iterator that yields elements from a ShortBoxSlice.

Enums

• ShortBoxSliceInner 🔒
  A boxed slice that supports no-allocation, constant values if length 0 or 1. Using ZeroOne(Option) saves 8 bytes in ShortBoxSlice via niche optimization.
• ShortBoxSliceIntoIterInner 🔒