1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use std::iter::FromIterator;
13 /// A very simple BitVector type.
14 #[derive(Clone, Debug, PartialEq)]
15 pub struct BitVector {
20 pub fn new(num_bits: usize) -> BitVector {
21 let num_words = u64s(num_bits);
22 BitVector { data: vec![0; num_words] }
25 pub fn clear(&mut self) {
26 for p in &mut self.data {
31 pub fn contains(&self, bit: usize) -> bool {
32 let (word, mask) = word_mask(bit);
33 (self.data[word] & mask) != 0
36 /// Returns true if the bit has changed.
37 pub fn insert(&mut self, bit: usize) -> bool {
38 let (word, mask) = word_mask(bit);
39 let data = &mut self.data[word];
41 let new_value = value | mask;
46 pub fn insert_all(&mut self, all: &BitVector) -> bool {
47 assert!(self.data.len() == all.data.len());
48 let mut changed = false;
49 for (i, j) in self.data.iter_mut().zip(&all.data) {
59 pub fn grow(&mut self, num_bits: usize) {
60 let num_words = u64s(num_bits);
61 if self.data.len() < num_words {
62 self.data.resize(num_words, 0)
66 /// Iterates over indexes of set bits in a sorted order
67 pub fn iter<'a>(&'a self) -> BitVectorIter<'a> {
69 iter: self.data.iter(),
76 pub struct BitVectorIter<'a> {
77 iter: ::std::slice::Iter<'a, u64>,
82 impl<'a> Iterator for BitVectorIter<'a> {
84 fn next(&mut self) -> Option<usize> {
85 while self.current == 0 {
86 self.current = if let Some(&i) = self.iter.next() {
91 self.idx = u64s(self.idx) * 64;
98 let offset = self.current.trailing_zeros() as usize;
99 self.current >>= offset;
100 self.current >>= 1; // shift otherwise overflows for 0b1000_0000_…_0000
101 self.idx += offset + 1;
102 return Some(self.idx - 1);
106 impl FromIterator<bool> for BitVector {
107 fn from_iter<I>(iter: I) -> BitVector where I: IntoIterator<Item=bool> {
108 let iter = iter.into_iter();
109 let (len, _) = iter.size_hint();
110 // Make the minimum length for the bitvector 64 bits since that's
111 // the smallest non-zero size anyway.
112 let len = if len < 64 { 64 } else { len };
113 let mut bv = BitVector::new(len);
114 for (idx, val) in iter.enumerate() {
127 /// A "bit matrix" is basically a matrix of booleans represented as
128 /// one gigantic bitvector. In other words, it is as if you have
129 /// `rows` bitvectors, each of length `columns`.
131 pub struct BitMatrix {
137 // Create a new `rows x columns` matrix, initially empty.
138 pub fn new(rows: usize, columns: usize) -> BitMatrix {
139 // For every element, we need one bit for every other
140 // element. Round up to an even number of u64s.
141 let u64s_per_row = u64s(columns);
144 vector: vec![0; rows * u64s_per_row],
148 /// The range of bits for a given row.
149 fn range(&self, row: usize) -> (usize, usize) {
150 let u64s_per_row = u64s(self.columns);
151 let start = row * u64s_per_row;
152 (start, start + u64s_per_row)
155 pub fn add(&mut self, source: usize, target: usize) -> bool {
156 let (start, _) = self.range(source);
157 let (word, mask) = word_mask(target);
158 let mut vector = &mut self.vector[..];
159 let v1 = vector[start + word];
161 vector[start + word] = v2;
165 /// Do the bits from `source` contain `target`?
167 /// Put another way, if the matrix represents (transitive)
168 /// reachability, can `source` reach `target`?
169 pub fn contains(&self, source: usize, target: usize) -> bool {
170 let (start, _) = self.range(source);
171 let (word, mask) = word_mask(target);
172 (self.vector[start + word] & mask) != 0
175 /// Returns those indices that are reachable from both `a` and
176 /// `b`. This is an O(n) operation where `n` is the number of
177 /// elements (somewhat independent from the actual size of the
178 /// intersection, in particular).
179 pub fn intersection(&self, a: usize, b: usize) -> Vec<usize> {
180 let (a_start, a_end) = self.range(a);
181 let (b_start, b_end) = self.range(b);
182 let mut result = Vec::with_capacity(self.columns);
183 for (base, (i, j)) in (a_start..a_end).zip(b_start..b_end).enumerate() {
184 let mut v = self.vector[i] & self.vector[j];
190 result.push(base * 64 + bit);
198 /// Add the bits from `read` to the bits from `write`,
199 /// return true if anything changed.
201 /// This is used when computing transitive reachability because if
202 /// you have an edge `write -> read`, because in that case
203 /// `write` can reach everything that `read` can (and
204 /// potentially more).
205 pub fn merge(&mut self, read: usize, write: usize) -> bool {
206 let (read_start, read_end) = self.range(read);
207 let (write_start, write_end) = self.range(write);
208 let vector = &mut self.vector[..];
209 let mut changed = false;
210 for (read_index, write_index) in (read_start..read_end).zip(write_start..write_end) {
211 let v1 = vector[write_index];
212 let v2 = v1 | vector[read_index];
213 vector[write_index] = v2;
214 changed = changed | (v1 != v2);
219 pub fn iter<'a>(&'a self, row: usize) -> BitVectorIter<'a> {
220 let (start, end) = self.range(row);
222 iter: self.vector[start..end].iter(),
229 fn u64s(elements: usize) -> usize {
233 fn word_mask(index: usize) -> (usize, u64) {
234 let word = index / 64;
235 let mask = 1 << (index % 64);
240 fn bitvec_iter_works() {
241 let mut bitvec = BitVector::new(100);
251 assert_eq!(bitvec.iter().collect::<Vec<_>>(),
252 [1, 10, 19, 62, 63, 64, 65, 66, 99]);
257 fn bitvec_iter_works_2() {
258 let mut bitvec = BitVector::new(319);
264 assert_eq!(bitvec.iter().collect::<Vec<_>>(), [0, 127, 191, 255, 319]);
268 fn union_two_vecs() {
269 let mut vec1 = BitVector::new(65);
270 let mut vec2 = BitVector::new(65);
271 assert!(vec1.insert(3));
272 assert!(!vec1.insert(3));
273 assert!(vec2.insert(5));
274 assert!(vec2.insert(64));
275 assert!(vec1.insert_all(&vec2));
276 assert!(!vec1.insert_all(&vec2));
277 assert!(vec1.contains(3));
278 assert!(!vec1.contains(4));
279 assert!(vec1.contains(5));
280 assert!(!vec1.contains(63));
281 assert!(vec1.contains(64));
286 let mut vec1 = BitVector::new(65);
287 for index in 0 .. 65 {
288 assert!(vec1.insert(index));
289 assert!(!vec1.insert(index));
293 // Check if the bits set before growing are still set
294 for index in 0 .. 65 {
295 assert!(vec1.contains(index));
298 // Check if the new bits are all un-set
299 for index in 65 .. 128 {
300 assert!(!vec1.contains(index));
303 // Check that we can set all new bits without running out of bounds
304 for index in 65 .. 128 {
305 assert!(vec1.insert(index));
306 assert!(!vec1.insert(index));
311 fn matrix_intersection() {
312 let mut vec1 = BitMatrix::new(200, 200);
314 // (*) Elements reachable from both 2 and 65.
318 vec1.add(2, 10); // (*)
319 vec1.add(2, 64); // (*)
322 vec1.add(2, 160); // (*)
328 vec1.add(65, 10); // (*)
329 vec1.add(65, 64); // (*)
332 vec1.add(65, 160); // (*)
334 let intersection = vec1.intersection(2, 64);
335 assert!(intersection.is_empty());
337 let intersection = vec1.intersection(2, 65);
338 assert_eq!(intersection, &[10, 64, 160]);
343 let mut matrix = BitMatrix::new(64, 100);
351 let mut iter = expected.iter();
352 for i in matrix.iter(2) {
353 let j = *iter.next().unwrap();
356 assert!(iter.next().is_none());
358 let expected = [22, 75];
359 let mut iter = expected.iter();
360 for i in matrix.iter(3) {
361 let j = *iter.next().unwrap();
364 assert!(iter.next().is_none());
367 let mut iter = expected.iter();
368 for i in matrix.iter(4) {
369 let j = *iter.next().unwrap();
372 assert!(iter.next().is_none());
374 let expected = [22, 75];
375 let mut iter = expected.iter();
376 for i in matrix.iter(5) {
377 let j = *iter.next().unwrap();
380 assert!(iter.next().is_none());