Expand description
Small vectors in various sizes. These store a certain number of elements inline, and fall back to the heap for larger allocations. This can be a useful optimization for improving cache locality and reducing allocator traffic for workloads that fit within the inline buffer.
no_std support
By default, smallvec does not depend on std. However, the optional
write feature implements the std::io::Write trait for vectors of u8.
When this feature is enabled, smallvec depends on std.
Optional features
serde
When this optional dependency is enabled, SmallVec implements the serde::Serialize and
serde::Deserialize traits.
write
When this feature is enabled, SmallVec<[u8; _]> implements the std::io::Write trait.
This feature is not compatible with #![no_std] programs.
union
This feature requires Rust 1.49.
When the union feature is enabled smallvec will track its state (inline or spilled)
without the use of an enum tag, reducing the size of the smallvec by one machine word.
This means that there is potentially no space overhead compared to Vec.
Note that smallvec can still be larger than Vec if the inline buffer is larger than two
machine words.
To use this feature add features = ["union"] in the smallvec section of Cargo.toml.
Note that this feature requires Rust 1.49.
Tracking issue: rust-lang/rust#55149
const_generics
This feature requires Rust 1.51.
When this feature is enabled, SmallVec works with any arrays of any size, not just a fixed
list of sizes.
const_new
This feature requires Rust 1.51.
This feature exposes the functions SmallVec::new_const, SmallVec::from_const, and smallvec_inline which enables the SmallVec to be initialized from a const context.
For details, see the
Rust Reference.
drain_filter
This feature is unstable. It may change to match the unstable drain_filter method in libstd.
Enables the drain_filter method, which produces an iterator that calls a user-provided
closure to determine which elements of the vector to remove and yield from the iterator.
drain_keep_rest
This feature is unstable. It may change to match the unstable drain_keep_rest method in libstd.
Enables the DrainFilter::keep_rest method.
specialization
This feature is unstable and requires a nightly build of the Rust toolchain.
When this feature is enabled, SmallVec::from(slice) has improved performance for slices
of Copy types. (Without this feature, you can use SmallVec::from_slice to get optimal
performance for Copy types.)
Tracking issue: rust-lang/rust#31844
may_dangle
This feature is unstable and requires a nightly build of the Rust toolchain.
This feature makes the Rust compiler less strict about use of vectors that contain borrowed references. For details, see the Rustonomicon.
Tracking issue: rust-lang/rust#34761
Macros
- Creates a
SmallVeccontaining the arguments. - Creates an inline
SmallVeccontaining the arguments. This macro is enabled by the featureconst_new.
Structs
- An iterator that removes the items from a
SmallVecand yields them by value. - An iterator that consumes a
SmallVecand yields its items by value. - A
Vec-like container that can store a small number of elements inline.
Enums
- Error type for APIs with fallible heap allocation
Traits
- Types that can be used as the backing store for a
SmallVec. - Convenience trait for constructing a
SmallVec