Crate minivec

A space-optimized version of alloc::vec::Vec that’s only the size of a single pointer! Ideal for low-level APIs where ABI calling conventions will typically require most structs be spilled onto the stack and copied instead of being passed solely in registers.

For example, in the x64 msvc ABI:

There’s a strict one-to-one correspondence between a function call’s arguments and the registers used for those arguments. Any argument that doesn’t fit in 8 bytes, or isn’t 1, 2, 4, or 8 bytes, must be passed by reference. A single argument is never spread across multiple registers.

In addition, its single word size makes it ideal for use as a struct member where multiple inclusions of Vec as a field can balloon the size.

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In general, MiniVec aims to be API compatible with what’s currently stable in the stdlib so some Nightly features are not supported.

MiniVec has stable implementations of the following nightly-only associated functions on Vec:

• into_raw_parts
• shrink_to
• spare_capacity_mut
• drain_filter
• split_at_spare_mut
• extend_from_within

MiniVec has the following associated functions not found in Vec:

• from_raw_part
• drain_vec
• assume_minivec_init

MiniVec has the following extensions to the existing Vec API:

• push returns a mutable reference to the newly created element

MiniVec is #![no_std]-compliant.

MiniVec does not support zero-sized types.

Eventual TODO’s:

• add myriad specializations to associated functions such as FromIterator once stable
• add Allocator support once stable
  • Because MiniVec is only a single pointer, MiniVec::new_in() will be forced to allocate when using a stateful Allocator. A theoretical implementation of MiniVec might be able to avoid an allocation here in the case of a custom zero-sized Allocator but that has not been implemented.

Macros

mini_vec

mini_vec! is a macro similar in spirit to the stdlib’s vec!.

Structs

Drain

Drain is an iterator that removes the selected sub-range from the MiniVec and returns the removed elements to the caller lazily.

DrainFilter

DrainFilter is a version of Drain that uses the supplied predicate to determine when an element should be removed from the MiniVec and returned to the user.

IntoIter

IntoIter is an iterator type that consumes the MiniVec and transfers ownership of the contained elements to the caller when iterated.

MiniVec

MiniVec is a space-optimized implementation of alloc::vec::Vec that is only the size of a single pointer and also extends portions of its API. MiniVec also aims to bring as many Nightly features from Vec to stable toolchains as is possible. In many cases, it is a drop-in replacement for Vec.

Splice

Splice is an iterator that removes a sub-section of the backing MiniVec and then replaces it with the contents of another iterator. The removed sub-section and the iterator used to replace it can have independent lengths.

TryReserveError

TryReserveError is the error type returned from the try_reserve family of functions.

Enums

LayoutErr

LayoutErr is the error type returned by the alignment-based associated functions for MiniVec

TryReserveErrorKind

TryReserveErrorKind is a variant encompassing the various types of allocation failures that can occur.