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//===-- sanitizer_bvgraph.h -------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of Sanitizer runtime.
// BVGraph -- a directed graph.
//
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_BVGRAPH_H
#define SANITIZER_BVGRAPH_H
#include "sanitizer_common.h"
#include "sanitizer_bitvector.h"
namespace __sanitizer {
// Directed graph of fixed size implemented as an array of bit vectors.
// Not thread-safe, all accesses should be protected by an external lock.
template<class BV>
class BVGraph {
public:
enum SizeEnum : uptr { kSize = BV::kSize };
uptr size() const { return kSize; }
// No CTOR.
void clear() {
for (uptr i = 0; i < size(); i++)
v[i].clear();
}
bool empty() const {
for (uptr i = 0; i < size(); i++)
if (!v[i].empty())
return false;
return true;
}
// Returns true if a new edge was added.
bool addEdge(uptr from, uptr to) {
check(from, to);
return v[from].setBit(to);
}
// Returns true if at least one new edge was added.
uptr addEdges(const BV &from, uptr to, uptr added_edges[],
uptr max_added_edges) {
uptr res = 0;
t1.copyFrom(from);
while (!t1.empty()) {
uptr node = t1.getAndClearFirstOne();
if (v[node].setBit(to))
if (res < max_added_edges)
added_edges[res++] = node;
}
return res;
}
// *EXPERIMENTAL*
// Returns true if an edge from=>to exist.
// This function does not use any global state except for 'this' itself,
// and thus can be called from different threads w/o locking.
// This would be racy.
// FIXME: investigate how much we can prove about this race being "benign".
bool hasEdge(uptr from, uptr to) { return v[from].getBit(to); }
// Returns true if the edge from=>to was removed.
bool removeEdge(uptr from, uptr to) {
return v[from].clearBit(to);
}
// Returns true if at least one edge *=>to was removed.
bool removeEdgesTo(const BV &to) {
bool res = 0;
for (uptr from = 0; from < size(); from++) {
if (v[from].setDifference(to))
res = true;
}
return res;
}
// Returns true if at least one edge from=>* was removed.
bool removeEdgesFrom(const BV &from) {
bool res = false;
t1.copyFrom(from);
while (!t1.empty()) {
uptr idx = t1.getAndClearFirstOne();
if (!v[idx].empty()) {
v[idx].clear();
res = true;
}
}
return res;
}
void removeEdgesFrom(uptr from) {
return v[from].clear();
}
bool hasEdge(uptr from, uptr to) const {
check(from, to);
return v[from].getBit(to);
}
// Returns true if there is a path from the node 'from'
// to any of the nodes in 'targets'.
bool isReachable(uptr from, const BV &targets) {
BV &to_visit = t1,
&visited = t2;
to_visit.copyFrom(v[from]);
visited.clear();
visited.setBit(from);
while (!to_visit.empty()) {
uptr idx = to_visit.getAndClearFirstOne();
if (visited.setBit(idx))
to_visit.setUnion(v[idx]);
}
return targets.intersectsWith(visited);
}
// Finds a path from 'from' to one of the nodes in 'target',
// stores up to 'path_size' items of the path into 'path',
// returns the path length, or 0 if there is no path of size 'path_size'.
uptr findPath(uptr from, const BV &targets, uptr *path, uptr path_size) {
if (path_size == 0)
return 0;
path[0] = from;
if (targets.getBit(from))
return 1;
// The function is recursive, so we don't want to create BV on stack.
// Instead of a getAndClearFirstOne loop we use the slower iterator.
for (typename BV::Iterator it(v[from]); it.hasNext(); ) {
uptr idx = it.next();
if (uptr res = findPath(idx, targets, path + 1, path_size - 1))
return res + 1;
}
return 0;
}
// Same as findPath, but finds a shortest path.
uptr findShortestPath(uptr from, const BV &targets, uptr *path,
uptr path_size) {
for (uptr p = 1; p <= path_size; p++)
if (findPath(from, targets, path, p) == p)
return p;
return 0;
}
private:
void check(uptr idx1, uptr idx2) const {
CHECK_LT(idx1, size());
CHECK_LT(idx2, size());
}
BV v[kSize];
// Keep temporary vectors here since we can not create large objects on stack.
BV t1, t2;
};
} // namespace __sanitizer
#endif // SANITIZER_BVGRAPH_H
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