Crate cap_vec 

A heap-backed vector with fixed maximum capacity for no_std environments.

CapVec<T, N> stores up to N values of type T contiguously in a backing buffer. Unlike alloc::vec::Vec, its maximum capacity is fixed at compile time and never grows after construction. Its logical length can still change dynamically from 0 to N.

This is useful when a fixed upper bound is part of the program design, but a stack-allocated [T; N] would be too large or too inflexible. The crate uses alloc and is compatible with #![no_std] targets that provide a global allocator.

Allocation model

CapVec::new creates an empty vector without allocating. The backing buffer is created on the first successful push, insert, extend, or when constructing from a full array. For non-zero-sized buffers this allocates heap storage for exactly N elements; zero-sized buffers use a dangling non-null sentinel. The buffer is reused by operations such as clear. Use shrink_to_fit on an empty vector to drop the backing buffer.

Capacity

Maximum capacity is encoded in the const generic parameter N. The capacity method returns the currently-created backing buffer size: 0 before the buffer is created, otherwise N. Use max_capacity to get the fixed upper bound and spare_capacity to get the remaining room before the vector is full. Operations that would exceed the maximum capacity return the provided element instead of reallocating. CapVec<T, 0> is valid and can never hold an element.

use cap_vec::CapVec;

let mut v = CapVec::<i32, 4>::new();
assert!(v.is_empty());

v.push(10).unwrap();
v.push(20).unwrap();
v.push(30).unwrap();
assert_eq!(v.len(), 3);

assert_eq!(v.first(), Some(&10));
assert_eq!(v.get(1), Some(&20));
assert_eq!(v.last(), Some(&30));

assert_eq!(&v[..], &[10, 20, 30]);
assert_eq!(v.remove(1), Some(20));
assert_eq!(v.pop(), Some(30));
assert_eq!(v.pop(), Some(10));

Structs

CapVec

A heap-backed vector with compile-time fixed maximum capacity.

Drain

An iterator over elements removed by CapVec::drain.

IntoIter

A consuming iterator over a CapVec.