Arbitrary Width Integers

This system of crates together forms a kind of big-integer library with separated storage and functional structs, manually controlled bitwidth, and bitwidth dependent operations. Instead of one struct that has all of the allocation and functional capabilities, there are two storage types which manage allocation, InlAwi and ExtAwi, and a common Bits reference type that manages arithmetical functionality. Most operations on Bits are const and have no allocations. Bits backed by InlAwi can perform big-integer arithmetic both at compile time and in a no-std runtime without any allocator at all. Bits backed by ExtAwi can use dynamic bitwidths at runtime. If a function is written purely in terms of Bits, then any mix of InlAwis and ExtAwis can be used as arguments to that function.

A generic FP struct for fixed point numbers is also included, adding more functions for it is currently a WIP.

Bits and InlAwi are provided by the awint_core crate. ExtAwi and FP is provided by the awint_ext crate. The reason for this split is to provide maximum flexibility to no-std and no-alloc use cases. ExtAwi is not within awint_core under a feature flag, because if a no-alloc project depended on both awint_core and awint_macros (which requires ExtAwi), the flag would be activated for the common compilation of awint_core. The awint_macros crate is a proc-macro crate with several construction utilities. The awint_dag crate is a WIP. The awint crate compiles these interfaces together and enables or disables different parts of the system depending on these feature flags:

• "const_support" turns on nightly features that are needed for many functions to be const
• "alloc" turns on parts that require an allocator
• "std" turns on parts that require std
• "rand_support" turns on a dependency to rand_core without its default features
• "serde_support" turns on a dependency to serde without its default features

Note: By default, "const_support" and "std" are turned on, use default-features = false and select specific features to avoid requiring nightly.

NOTE: As of Rust 1.64, if you try to use "const_support" with the macros you may get strange erroneous constant used and deref_mut errors unless you add all of

#![feature(const_trait_impl)]
#![feature(const_mut_refs)]
#![feature(const_option)]

to all of the crate roots where you use the macros in const contexts.

Planned Features

These are currently unimplemented because of other developments and improvements that are being prioritized. Please open an issue or PR if you would like these implemented faster.

• A higher level Awi wrapper around ExtAwi with more traditional big-integer library functions such as a dynamic sign and automatically resizing bitwidth. This higher level wrapper keeps track of leading zeros and ones to speed up operations on very large bitwidth integers with small numerical value.
• Add a const Karatsuba algorithm to multiplication if possible, or add a fast_mul function to awint_ext
• Better string serialization and deserialization performance. Most basic numerical functions are well optimized, but the serialization performance is currently very bad compared to what is possible.
• Add custom allocator parameter to ExtAwi
• Certain formatting and serialization trait impls need more work.
• Make "const_support" compile on stable. Almost every unstable feature used by these crates is some kind of const feature, and will hopefully be stabilized soon.