feat: unsafe optimization to reduce memory consumption to 8 bytes on …

…64-bit arch; enabled by default

.github/workflows/rust.yml

@@ -13,9 +13,21 @@ jobs:
       run: cargo build --all-targets
     - name: Run tests
       run: cargo test --all-targets
+    - name: Run tests for unsafe configuration (default)
+      run: cargo test --all-targets --features unsafe-opt
+    - name: Run tests for no-unsafe configuration
+      run: cargo test --all-targets --no-default-features
     - name: Clippy
       run: cargo clippy --all-targets -- -D warnings -D clippy::all -D clippy::cargo
     - name: Check for correct formatting
       run: cargo fmt -- --check --files-with-diff
     - name: Cargo audit
       run: bash -c 'which cargo-audit || cargo install cargo-audit; cargo audit --deny-warnings'
+
+    # Ideally we could run the benchmarks here, but that still requires nightly, which
+    # is hard to get on GitHub Actions.
+    #
+    # - name: Run benchmarks for unsafe configuration
+    #   run: cargo +nightly bench --features unsafe-opt,bench --no-default-features --examples
+    # - name: Run benchmarks for no-safe configuration
+    #   run: cargo +nightly bench --features bench --no-default-features --examples

Cargo.toml

@@ -18,15 +18,22 @@ num-bigint = "0.2.6"
 num-traits = "0.2.11"
 either = "1.5.3"
 num-integer = "0.1.42"
+cfg-if = "0.1.10"
 
 [dev-dependencies]
 num-iter = "0.1.40"
 structopt = "0.3.12"
 anyhow = "1.0.35"
 
 [features]
+
+default = ["unsafe-opt"]
+
 # Enable this feature to be able to run the benchmark tests.
 # This flag might go away in the near future when benchmarks
 # are available on cargo stable.
 bench = []
 benchall = []
+
+# An optimization that's unsafe
+unsafe-opt = []

README.md

@@ -3,35 +3,19 @@
 [![Docs.rs link](https://docs.rs/smallbigint/badge.svg)](https://docs.rs/smallbigint)
 [![Commitizen friendly](https://img.shields.io/badge/commitizen-friendly-brightgreen.svg)](http://commitizen.github.io/cz-cli/)
 
-A wrapper around `num_bigint::BigUint` and `num_bigint::BigInt` that
-stays out of the heap for small values.
+Two types, `Uint` and `Int`, like `smallvec` for big integers. Anything that fits in 32 bits stays on the stack. Numbers that don't fit are stored in a `Box<num_bigint::BigUint>` / `Box<num_bigint::BigInt>`.
 
-In the current implementation, we go to the heap for anything that
-doesn't fit in 32 bits.
+On 64-bit architectures, by default we use `unsafe` to compress the types to 8 bytes, exploiting pointer alignment. This behavior is triggered by the `unsafe-opt` feature, which is enabled by default.
 
-This crate already has a lot of relevant methods, but it is not really complete
-yet. Patches are welcome!
+## Implemented traits
 
-## To do, and important:
-
-- Implement `std::fmt::{Binary, LowerHex, Octal, UpperHex}` (easy?)
-- Implement `num_bigint::{ToBigInt, ToBigUint}`
-
-## Other traits and methods still to be implemented:
+Most important numeric traits have been implemented. Here are some that aren't yet; pull requests are welcome!
 
+- `std::fmt::{Binary, LowerHex, Octal, UpperHex}`
 - Bit operations
-- `num_traits::Num` (easy?)
-- `num_traits::Signed`
-- `num_traits::Unsigned`
-- `num_integer::Integer`
-- `num_integer::Roots`
-- `std::iter::Product`
-- `std::iter::Sum`
-- Other methods implemented directly on BigInt, BigUint
-
-## Not done and seems hard:
-
-- `num_traits::pow::Pow`
+- `num_traits::Num`, `num_traits::Signed`, `num_traits::Unsigned`, `num_integer::Integer`, `num_integer::Roots`, `std::iter::Product`, `std::iter::Sum`, `num_traits::pow::Pow`
+- Other methods implemented directly on `BigInt`, `BigUint`
+- Implement `num_bigint::{ToBigInt, ToBigUint}`
 
 # License