Merge pull request #132 from contain-rs/fereidani

Fereidani's first contribution

Author: pczarn

.github/workflows/rust.yml

@@ -54,7 +54,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [1.67.0, 1.68.0]
+        rust: [1.82.0, 1.83.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v5

Cargo.toml

@@ -10,7 +10,7 @@ documentation = "https://docs.rs/bit-vec/"
 keywords = ["data-structures", "bitvec", "bitmask", "bitmap", "bit"]
 readme = "README.md"
 edition = "2021"
-rust-version = "1.67"
+rust-version = "1.82"
 
 [dependencies]
 borsh = { version = "1.5.5", default-features = false, features = ["derive"], optional = true }

README.md

@@ -8,7 +8,7 @@
 [![crates.io][crates.io shield]][crates.io link]
 [![Documentation][docs.rs badge]][docs.rs link]
 ![Rust CI][github ci badge]
-![MSRV][rustc 1.67+]
+![MSRV][rustc 1.82+]
 <br />
 <br />
 [![Dependency Status][deps.rs status]][deps.rs link]
@@ -21,8 +21,8 @@
 [crates.io link]: https://crates.io/crates/bit-vec
 [docs.rs badge]: https://docs.rs/bit-vec/badge.svg?version=0.8.0
 [docs.rs link]: https://docs.rs/bit-vec/0.8.0/bit_vec/
-[github ci badge]: https://github.com/contain-rs/bit-vec/workflows/Rust/badge.svg?branch=master
-[rustc 1.67+]: https://img.shields.io/badge/rustc-1.67%2B-blue.svg
+[github ci badge]: https://github.com/contain-rs/bit-vec/actions/workflows/rust.yml/badge.svg
+[rustc 1.82+]: https://img.shields.io/badge/rustc-1.82%2B-blue.svg
 [deps.rs status]: https://deps.rs/crate/bit-vec/0.8.0/status.svg
 [deps.rs link]: https://deps.rs/crate/bit-vec/0.8.0
 [shields.io download count]: https://img.shields.io/crates/d/bit-vec.svg

benches/bench.rs

@@ -42,6 +42,18 @@ fn bench_usize_small(b: &mut Bencher) {
     });
 }
 
+#[bench]
+fn bench_to_bytes(b: &mut Bencher) {
+    let mut bit_vec = BitVec::from_elem(BENCH_BITS, false);
+    let mut r = small_rng();
+    for _ in 0..BENCH_BITS / 10 {
+        bit_vec.set((r.next_u32() as usize) % BENCH_BITS, true);
+    }
+    b.iter(|| {
+        black_box(bit_vec.to_bytes());
+    });
+}
+
 #[bench]
 fn bench_bit_set_big_fixed(b: &mut Bencher) {
     let mut r = small_rng();

src/lib.rs

@@ -826,7 +826,7 @@ impl<B: BitBlock> BitVec<B> {
     pub fn or(&mut self, other: &Self) -> bool {
         self.ensure_invariant();
         debug_assert!(other.is_last_block_fixed());
-        self.process(other, |w1, w2| (w1 | w2))
+        self.process(other, |w1, w2| w1 | w2)
     }
 
     /// Calculates the bitwise `and` of two bitvectors.
@@ -857,7 +857,7 @@ impl<B: BitBlock> BitVec<B> {
     pub fn and(&mut self, other: &Self) -> bool {
         self.ensure_invariant();
         debug_assert!(other.is_last_block_fixed());
-        self.process(other, |w1, w2| (w1 & w2))
+        self.process(other, |w1, w2| w1 & w2)
     }
 
     /// Calculates the difference between two bitvectors.
@@ -896,7 +896,7 @@ impl<B: BitBlock> BitVec<B> {
     pub fn difference(&mut self, other: &Self) -> bool {
         self.ensure_invariant();
         debug_assert!(other.is_last_block_fixed());
-        self.process(other, |w1, w2| (w1 & !w2))
+        self.process(other, |w1, w2| w1 & !w2)
     }
 
     /// Calculates the xor of two bitvectors.
@@ -927,7 +927,7 @@ impl<B: BitBlock> BitVec<B> {
     pub fn xor(&mut self, other: &Self) -> bool {
         self.ensure_invariant();
         debug_assert!(other.is_last_block_fixed());
-        self.process(other, |w1, w2| (w1 ^ w2))
+        self.process(other, |w1, w2| w1 ^ w2)
     }
 
     /// Calculates the nand of two bitvectors.
@@ -1322,30 +1322,35 @@ impl<B: BitBlock> BitVec<B> {
     /// assert_eq!(bv.to_bytes(), [0b00100000, 0b10000000]);
     /// ```
     pub fn to_bytes(&self) -> Vec<u8> {
+        static REVERSE_TABLE: [u8; 256] = {
+            let mut tbl = [0u8; 256];
+            let mut i: u8 = 0;
+            loop {
+                tbl[i as usize] = i.reverse_bits();
+                if i == 255 {
+                    break;
+                }
+                i += 1;
+            }
+            tbl
+        };
         self.ensure_invariant();
-        // Oh lord, we're mapping this to bytes bit-by-bit!
-        fn bit<B: BitBlock>(bit_vec: &BitVec<B>, byte: usize, bit: usize) -> u8 {
-            let offset = byte * 8 + bit;
-            if offset >= bit_vec.nbits {
-                0
-            } else {
-                (bit_vec[offset] as u8) << (7 - bit)
+
+        let len = self.nbits / 8 + if self.nbits % 8 == 0 { 0 } else { 1 };
+        let mut result = Vec::with_capacity(len);
+
+        for byte_idx in 0..len {
+            let mut byte = 0u8;
+            for bit_idx in 0..8 {
+                let offset = byte_idx * 8 + bit_idx;
+                if offset < self.nbits && self[offset] {
+                    byte |= 1 << bit_idx;
+                }
             }
+            result.push(REVERSE_TABLE[byte as usize]);
         }
 
-        let len = self.nbits / 8 + if self.nbits % 8 == 0 { 0 } else { 1 };
-        (0..len)
-            .map(|i| {
-                bit(self, i, 0)
-                    | bit(self, i, 1)
-                    | bit(self, i, 2)
-                    | bit(self, i, 3)
-                    | bit(self, i, 4)
-                    | bit(self, i, 5)
-                    | bit(self, i, 6)
-                    | bit(self, i, 7)
-            })
-            .collect()
+        result
     }
 
     /// Compares a `BitVec` to a slice of `bool`s.