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f5e8a90
docs: added feature descriptions to README
alejandro-vaz Sep 5, 2026
873eb81
fix: style formatting
alejandro-vaz Sep 5, 2026
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7 changes: 4 additions & 3 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -19,11 +19,12 @@ debug = false
strip = true

[features]
std = []
specialization = []
internals = []
may_dangle = []
rayon = ["std", "dep:rayon"]
serde = ["dep:serde_core"]
internals = []
specialization = []
std = []

[dependencies]
arbitrary = { version = "1.4", optional = true, default-features = false }
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24 changes: 23 additions & 1 deletion README.md
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Expand Up @@ -21,7 +21,10 @@

[Release notes](https://github.com/servo/rust-smallvec/releases)

"Small vector" optimization for Rust: store up to a small number of items on the stack
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.

## Example

Expand All @@ -40,3 +43,22 @@ v.push(5);
v[0] = v[1] + v[2];
v.sort();
```

## Feature List

By default, SmallVec does not make use of any feature. SmallVec without any features enabled does not make use of the standard library.

- `arbitrary`: implements `Arbitrary` for any `SmallVec` storing elements that implement `Arbitrary`
- `borsh`: implements `BorshSerialize`, `BorshDeserialize` and `BorshSchema`
- `bytes`: implements `BufMut` for SmallVec
- `defmt`: implements `defmt::Format` for SmallVec
- `encase`: implements encasing as a runtime-sized array
- `internals`: exports through the public API `TaggedLen` and `RawSmallVec`
- `malloc_size_of`: implements `MallocSizeOf` and `MallocShallowSizeOf`
- `may_dangle` (nightly): enables the eyepatch optimization for dropping
- `rayon`: implements parallel iteration
- `serde`: implements serde's serialization and deserialization
- `specialization` (nightly): enables specialization, improving performance on some cases
- `std`: implements the `std::io::Write` type for `SmallVec<u8, N>`

> The `rayon` feature implicitly requires `std`.
57 changes: 1 addition & 56 deletions src/lib.rs
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Expand Up @@ -4,69 +4,14 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! 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
//!
//! ### `std`
//!
//! When this feature is enabled, traits available from `std` are implemented:
//!
//! * `SmallVec<u8, _>` implements the [`std::io::Write`] trait.
//! * [`CollectionAllocErr`] implements [`std::error::Error`].
//!
//! This feature is not compatible with `#![no_std]` programs.
//!
//! ### `serde`
//!
//! When this optional dependency is enabled, `SmallVec` implements the
//! `serde::Serialize` and `serde::Deserialize` traits.
//!
//! ### `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](https://github.com/rust-lang/rust/issues/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](https://doc.rust-lang.org/1.42.0/nomicon/dropck.html#an-escape-hatch).
//!
//! Tracking issue: [rust-lang/rust#34761](https://github.com/rust-lang/rust/issues/34761)
//!
//! ### `encase`
//!
//! When this optional dependency is enabled, `SmallVec` implements `encase`'s
//! traits.

#![doc = include_str!("../README.md")]
#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![cfg_attr(feature = "specialization", allow(incomplete_features))]
#![cfg_attr(feature = "specialization", feature(specialization, trusted_len))]
#![cfg_attr(feature = "may_dangle", feature(dropck_eyepatch))]

#[doc(hidden)]
extern crate alloc;

#[cfg(feature = "std")]
extern crate std;

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