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 {
21 pub fn new(num_bits: usize) -> BitVector {
22 let num_words = u64s(num_bits);
23 BitVector { data: vec![0; num_words] }
27 pub fn clear(&mut self) {
28 for p in &mut self.data {
33 pub fn count(&self) -> usize {
34 self.data.iter().map(|e| e.count_ones() as usize).sum()
38 pub fn contains(&self, bit: usize) -> bool {
39 let (word, mask) = word_mask(bit);
40 (self.data[word] & mask) != 0
43 /// Returns true if the bit has changed.
45 pub fn insert(&mut self, bit: usize) -> bool {
46 let (word, mask) = word_mask(bit);
47 let data = &mut self.data[word];
49 let new_value = value | mask;
55 pub fn insert_all(&mut self, all: &BitVector) -> bool {
56 assert!(self.data.len() == all.data.len());
57 let mut changed = false;
58 for (i, j) in self.data.iter_mut().zip(&all.data) {
69 pub fn grow(&mut self, num_bits: usize) {
70 let num_words = u64s(num_bits);
71 if self.data.len() < num_words {
72 self.data.resize(num_words, 0)
76 /// Iterates over indexes of set bits in a sorted order
78 pub fn iter<'a>(&'a self) -> BitVectorIter<'a> {
80 iter: self.data.iter(),
87 pub struct BitVectorIter<'a> {
88 iter: ::std::slice::Iter<'a, u64>,
93 impl<'a> Iterator for BitVectorIter<'a> {
95 fn next(&mut self) -> Option<usize> {
96 while self.current == 0 {
97 self.current = if let Some(&i) = self.iter.next() {
102 self.idx = u64s(self.idx) * 64;
109 let offset = self.current.trailing_zeros() as usize;
110 self.current >>= offset;
111 self.current >>= 1; // shift otherwise overflows for 0b1000_0000_…_0000
112 self.idx += offset + 1;
113 return Some(self.idx - 1);
117 impl FromIterator<bool> for BitVector {
118 fn from_iter<I>(iter: I) -> BitVector where I: IntoIterator<Item=bool> {
119 let iter = iter.into_iter();
120 let (len, _) = iter.size_hint();
121 // Make the minimum length for the bitvector 64 bits since that's
122 // the smallest non-zero size anyway.
123 let len = if len < 64 { 64 } else { len };
124 let mut bv = BitVector::new(len);
125 for (idx, val) in iter.enumerate() {
138 /// A "bit matrix" is basically a matrix of booleans represented as
139 /// one gigantic bitvector. In other words, it is as if you have
140 /// `rows` bitvectors, each of length `columns`.
142 pub struct BitMatrix {
148 // Create a new `rows x columns` matrix, initially empty.
149 pub fn new(rows: usize, columns: usize) -> BitMatrix {
150 // For every element, we need one bit for every other
151 // element. Round up to an even number of u64s.
152 let u64s_per_row = u64s(columns);
155 vector: vec![0; rows * u64s_per_row],
159 /// The range of bits for a given row.
160 fn range(&self, row: usize) -> (usize, usize) {
161 let u64s_per_row = u64s(self.columns);
162 let start = row * u64s_per_row;
163 (start, start + u64s_per_row)
166 pub fn add(&mut self, source: usize, target: usize) -> bool {
167 let (start, _) = self.range(source);
168 let (word, mask) = word_mask(target);
169 let mut vector = &mut self.vector[..];
170 let v1 = vector[start + word];
172 vector[start + word] = v2;
176 /// Do the bits from `source` contain `target`?
178 /// Put another way, if the matrix represents (transitive)
179 /// reachability, can `source` reach `target`?
180 pub fn contains(&self, source: usize, target: usize) -> bool {
181 let (start, _) = self.range(source);
182 let (word, mask) = word_mask(target);
183 (self.vector[start + word] & mask) != 0
186 /// Returns those indices that are reachable from both `a` and
187 /// `b`. This is an O(n) operation where `n` is the number of
188 /// elements (somewhat independent from the actual size of the
189 /// intersection, in particular).
190 pub fn intersection(&self, a: usize, b: usize) -> Vec<usize> {
191 let (a_start, a_end) = self.range(a);
192 let (b_start, b_end) = self.range(b);
193 let mut result = Vec::with_capacity(self.columns);
194 for (base, (i, j)) in (a_start..a_end).zip(b_start..b_end).enumerate() {
195 let mut v = self.vector[i] & self.vector[j];
201 result.push(base * 64 + bit);
209 /// Add the bits from `read` to the bits from `write`,
210 /// return true if anything changed.
212 /// This is used when computing transitive reachability because if
213 /// you have an edge `write -> read`, because in that case
214 /// `write` can reach everything that `read` can (and
215 /// potentially more).
216 pub fn merge(&mut self, read: usize, write: usize) -> bool {
217 let (read_start, read_end) = self.range(read);
218 let (write_start, write_end) = self.range(write);
219 let vector = &mut self.vector[..];
220 let mut changed = false;
221 for (read_index, write_index) in (read_start..read_end).zip(write_start..write_end) {
222 let v1 = vector[write_index];
223 let v2 = v1 | vector[read_index];
224 vector[write_index] = v2;
225 changed = changed | (v1 != v2);
230 pub fn iter<'a>(&'a self, row: usize) -> BitVectorIter<'a> {
231 let (start, end) = self.range(row);
233 iter: self.vector[start..end].iter(),
241 fn u64s(elements: usize) -> usize {
246 fn word_mask(index: usize) -> (usize, u64) {
247 let word = index / 64;
248 let mask = 1 << (index % 64);
253 fn bitvec_iter_works() {
254 let mut bitvec = BitVector::new(100);
264 assert_eq!(bitvec.iter().collect::<Vec<_>>(),
265 [1, 10, 19, 62, 63, 64, 65, 66, 99]);
270 fn bitvec_iter_works_2() {
271 let mut bitvec = BitVector::new(319);
277 assert_eq!(bitvec.iter().collect::<Vec<_>>(), [0, 127, 191, 255, 319]);
281 fn union_two_vecs() {
282 let mut vec1 = BitVector::new(65);
283 let mut vec2 = BitVector::new(65);
284 assert!(vec1.insert(3));
285 assert!(!vec1.insert(3));
286 assert!(vec2.insert(5));
287 assert!(vec2.insert(64));
288 assert!(vec1.insert_all(&vec2));
289 assert!(!vec1.insert_all(&vec2));
290 assert!(vec1.contains(3));
291 assert!(!vec1.contains(4));
292 assert!(vec1.contains(5));
293 assert!(!vec1.contains(63));
294 assert!(vec1.contains(64));
299 let mut vec1 = BitVector::new(65);
300 for index in 0 .. 65 {
301 assert!(vec1.insert(index));
302 assert!(!vec1.insert(index));
306 // Check if the bits set before growing are still set
307 for index in 0 .. 65 {
308 assert!(vec1.contains(index));
311 // Check if the new bits are all un-set
312 for index in 65 .. 128 {
313 assert!(!vec1.contains(index));
316 // Check that we can set all new bits without running out of bounds
317 for index in 65 .. 128 {
318 assert!(vec1.insert(index));
319 assert!(!vec1.insert(index));
324 fn matrix_intersection() {
325 let mut vec1 = BitMatrix::new(200, 200);
327 // (*) Elements reachable from both 2 and 65.
331 vec1.add(2, 10); // (*)
332 vec1.add(2, 64); // (*)
335 vec1.add(2, 160); // (*)
341 vec1.add(65, 10); // (*)
342 vec1.add(65, 64); // (*)
345 vec1.add(65, 160); // (*)
347 let intersection = vec1.intersection(2, 64);
348 assert!(intersection.is_empty());
350 let intersection = vec1.intersection(2, 65);
351 assert_eq!(intersection, &[10, 64, 160]);
356 let mut matrix = BitMatrix::new(64, 100);
364 let mut iter = expected.iter();
365 for i in matrix.iter(2) {
366 let j = *iter.next().unwrap();
369 assert!(iter.next().is_none());
371 let expected = [22, 75];
372 let mut iter = expected.iter();
373 for i in matrix.iter(3) {
374 let j = *iter.next().unwrap();
377 assert!(iter.next().is_none());
380 let mut iter = expected.iter();
381 for i in matrix.iter(4) {
382 let j = *iter.next().unwrap();
385 assert!(iter.next().is_none());
387 let expected = [22, 75];
388 let mut iter = expected.iter();
389 for i in matrix.iter(5) {
390 let j = *iter.next().unwrap();
393 assert!(iter.next().is_none());