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 {
34 pub fn contains(&self, bit: usize) -> bool {
35 let (word, mask) = word_mask(bit);
36 (self.data[word] & mask) != 0
39 /// Returns true if the bit has changed.
41 pub fn insert(&mut self, bit: usize) -> bool {
42 let (word, mask) = word_mask(bit);
43 let data = &mut self.data[word];
45 let new_value = value | mask;
51 pub fn insert_all(&mut self, all: &BitVector) -> bool {
52 assert!(self.data.len() == all.data.len());
53 let mut changed = false;
54 for (i, j) in self.data.iter_mut().zip(&all.data) {
65 pub fn grow(&mut self, num_bits: usize) {
66 let num_words = u64s(num_bits);
67 if self.data.len() < num_words {
68 self.data.resize(num_words, 0)
72 /// Iterates over indexes of set bits in a sorted order
74 pub fn iter<'a>(&'a self) -> BitVectorIter<'a> {
76 iter: self.data.iter(),
83 pub struct BitVectorIter<'a> {
84 iter: ::std::slice::Iter<'a, u64>,
89 impl<'a> Iterator for BitVectorIter<'a> {
91 fn next(&mut self) -> Option<usize> {
92 while self.current == 0 {
93 self.current = if let Some(&i) = self.iter.next() {
98 self.idx = u64s(self.idx) * 64;
105 let offset = self.current.trailing_zeros() as usize;
106 self.current >>= offset;
107 self.current >>= 1; // shift otherwise overflows for 0b1000_0000_…_0000
108 self.idx += offset + 1;
109 return Some(self.idx - 1);
113 impl FromIterator<bool> for BitVector {
114 fn from_iter<I>(iter: I) -> BitVector where I: IntoIterator<Item=bool> {
115 let iter = iter.into_iter();
116 let (len, _) = iter.size_hint();
117 // Make the minimum length for the bitvector 64 bits since that's
118 // the smallest non-zero size anyway.
119 let len = if len < 64 { 64 } else { len };
120 let mut bv = BitVector::new(len);
121 for (idx, val) in iter.enumerate() {
134 /// A "bit matrix" is basically a matrix of booleans represented as
135 /// one gigantic bitvector. In other words, it is as if you have
136 /// `rows` bitvectors, each of length `columns`.
138 pub struct BitMatrix {
144 // Create a new `rows x columns` matrix, initially empty.
145 pub fn new(rows: usize, columns: usize) -> BitMatrix {
146 // For every element, we need one bit for every other
147 // element. Round up to an even number of u64s.
148 let u64s_per_row = u64s(columns);
151 vector: vec![0; rows * u64s_per_row],
155 /// The range of bits for a given row.
156 fn range(&self, row: usize) -> (usize, usize) {
157 let u64s_per_row = u64s(self.columns);
158 let start = row * u64s_per_row;
159 (start, start + u64s_per_row)
162 pub fn add(&mut self, source: usize, target: usize) -> bool {
163 let (start, _) = self.range(source);
164 let (word, mask) = word_mask(target);
165 let mut vector = &mut self.vector[..];
166 let v1 = vector[start + word];
168 vector[start + word] = v2;
172 /// Do the bits from `source` contain `target`?
174 /// Put another way, if the matrix represents (transitive)
175 /// reachability, can `source` reach `target`?
176 pub fn contains(&self, source: usize, target: usize) -> bool {
177 let (start, _) = self.range(source);
178 let (word, mask) = word_mask(target);
179 (self.vector[start + word] & mask) != 0
182 /// Returns those indices that are reachable from both `a` and
183 /// `b`. This is an O(n) operation where `n` is the number of
184 /// elements (somewhat independent from the actual size of the
185 /// intersection, in particular).
186 pub fn intersection(&self, a: usize, b: usize) -> Vec<usize> {
187 let (a_start, a_end) = self.range(a);
188 let (b_start, b_end) = self.range(b);
189 let mut result = Vec::with_capacity(self.columns);
190 for (base, (i, j)) in (a_start..a_end).zip(b_start..b_end).enumerate() {
191 let mut v = self.vector[i] & self.vector[j];
197 result.push(base * 64 + bit);
205 /// Add the bits from `read` to the bits from `write`,
206 /// return true if anything changed.
208 /// This is used when computing transitive reachability because if
209 /// you have an edge `write -> read`, because in that case
210 /// `write` can reach everything that `read` can (and
211 /// potentially more).
212 pub fn merge(&mut self, read: usize, write: usize) -> bool {
213 let (read_start, read_end) = self.range(read);
214 let (write_start, write_end) = self.range(write);
215 let vector = &mut self.vector[..];
216 let mut changed = false;
217 for (read_index, write_index) in (read_start..read_end).zip(write_start..write_end) {
218 let v1 = vector[write_index];
219 let v2 = v1 | vector[read_index];
220 vector[write_index] = v2;
221 changed = changed | (v1 != v2);
226 pub fn iter<'a>(&'a self, row: usize) -> BitVectorIter<'a> {
227 let (start, end) = self.range(row);
229 iter: self.vector[start..end].iter(),
237 fn u64s(elements: usize) -> usize {
242 fn word_mask(index: usize) -> (usize, u64) {
243 let word = index / 64;
244 let mask = 1 << (index % 64);
249 fn bitvec_iter_works() {
250 let mut bitvec = BitVector::new(100);
260 assert_eq!(bitvec.iter().collect::<Vec<_>>(),
261 [1, 10, 19, 62, 63, 64, 65, 66, 99]);
266 fn bitvec_iter_works_2() {
267 let mut bitvec = BitVector::new(319);
273 assert_eq!(bitvec.iter().collect::<Vec<_>>(), [0, 127, 191, 255, 319]);
277 fn union_two_vecs() {
278 let mut vec1 = BitVector::new(65);
279 let mut vec2 = BitVector::new(65);
280 assert!(vec1.insert(3));
281 assert!(!vec1.insert(3));
282 assert!(vec2.insert(5));
283 assert!(vec2.insert(64));
284 assert!(vec1.insert_all(&vec2));
285 assert!(!vec1.insert_all(&vec2));
286 assert!(vec1.contains(3));
287 assert!(!vec1.contains(4));
288 assert!(vec1.contains(5));
289 assert!(!vec1.contains(63));
290 assert!(vec1.contains(64));
295 let mut vec1 = BitVector::new(65);
296 for index in 0 .. 65 {
297 assert!(vec1.insert(index));
298 assert!(!vec1.insert(index));
302 // Check if the bits set before growing are still set
303 for index in 0 .. 65 {
304 assert!(vec1.contains(index));
307 // Check if the new bits are all un-set
308 for index in 65 .. 128 {
309 assert!(!vec1.contains(index));
312 // Check that we can set all new bits without running out of bounds
313 for index in 65 .. 128 {
314 assert!(vec1.insert(index));
315 assert!(!vec1.insert(index));
320 fn matrix_intersection() {
321 let mut vec1 = BitMatrix::new(200, 200);
323 // (*) Elements reachable from both 2 and 65.
327 vec1.add(2, 10); // (*)
328 vec1.add(2, 64); // (*)
331 vec1.add(2, 160); // (*)
337 vec1.add(65, 10); // (*)
338 vec1.add(65, 64); // (*)
341 vec1.add(65, 160); // (*)
343 let intersection = vec1.intersection(2, 64);
344 assert!(intersection.is_empty());
346 let intersection = vec1.intersection(2, 65);
347 assert_eq!(intersection, &[10, 64, 160]);
352 let mut matrix = BitMatrix::new(64, 100);
360 let mut iter = expected.iter();
361 for i in matrix.iter(2) {
362 let j = *iter.next().unwrap();
365 assert!(iter.next().is_none());
367 let expected = [22, 75];
368 let mut iter = expected.iter();
369 for i in matrix.iter(3) {
370 let j = *iter.next().unwrap();
373 assert!(iter.next().is_none());
376 let mut iter = expected.iter();
377 for i in matrix.iter(4) {
378 let j = *iter.next().unwrap();
381 assert!(iter.next().is_none());
383 let expected = [22, 75];
384 let mut iter = expected.iter();
385 for i in matrix.iter(5) {
386 let j = *iter.next().unwrap();
389 assert!(iter.next().is_none());