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/********************* */
/*! \file backtrackable.h
** \verbatim
** Top contributors (to current version):
** Morgan Deters
** This file is part of the CVC4 project.
** Copyright (c) 2009-2019 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief Contains a backtrackable list
**
** Contains a backtrackable list.
**/
#include "cvc4_private.h"
#ifndef CVC4__UTIL__BACKTRACKABLE_H
#define CVC4__UTIL__BACKTRACKABLE_H
#include <cstdlib>
#include <vector>
#include "context/cdo.h"
namespace CVC4 {
template <class T> class List;
template <class T> class List_iterator;
template <class T> class Backtracker;
template <class T>
class ListNode {
private:
T data;
ListNode<T>* next;
bool empty;
ListNode(const T& t, ListNode<T>* n, bool e = false) : data(t), next(n), empty(e) {}
~ListNode() {
// maybe set to NULL
delete next;
}
friend class List<T>;
friend class List_iterator<T>;
};/* class ListNode<T> */
template <class T>
class List_iterator : public std::iterator <std::forward_iterator_tag, T> {
friend class List<T>;
public:
const T& operator*();
List_iterator<T>& operator++();
List_iterator<T> operator++(int);
bool operator!=(const List_iterator<T> & other) const;
private:
const ListNode<T>* pointee;
List_iterator(const ListNode<T>* p) : pointee(p) {}
};/* class List_iterator<T> */
template <class T>
const T& List_iterator<T>::operator*() {
return pointee->data;
}
template <class T>
List_iterator<T>& List_iterator<T>::operator++() {
Assert(pointee != NULL);
pointee = pointee->next;
while(pointee != NULL && pointee->empty ) {
pointee = pointee->next;
}
return *this;
}
template <class T>
List_iterator<T> List_iterator<T>::operator++(int) {
List_iterator<T> it = *this;
++*this;
return it;
}
template <class T>
bool List_iterator<T>::operator!=(const List_iterator<T>& other) const {
return (this->pointee != other.pointee);
}
// !! for the backtracking to work the lists must be allocated on the heap
// therefore the hashmap from TNode to List<TNode> should store pointers!
template <class T>
class List {
ListNode<T>* head;
ListNode<T>* tail;
ListNode<T>* ptr_to_head;
bool uninitialized;
Backtracker<T>* bck;
List (const List&) {}
public:
List(Backtracker<T>* b) : ptr_to_head(NULL), uninitialized(true), bck(b) {
head = tail = (ListNode<T>*)calloc(1,sizeof(ListNode<T>));
head->next = NULL;
head->empty = true;
}
~List() {delete head;}
bool empty() {
bck->checkConsistency();
return head == NULL;
}
void append(const T& d);
//typedef List_iterator<T> iterator;
typedef List_iterator<T> const_iterator;
const_iterator begin() {
bck->checkConsistency();
if(head->empty) {
ListNode<T>* temp = head;
// if the head is empty return the first non-empty element or NULL
while(temp != NULL && temp->empty ) {
temp = temp->next;
}
return List_iterator<T>(temp);
}
return List_iterator<T>(head);
}
const_iterator end() {
bck->checkConsistency();
return List_iterator<T>(NULL);
}
void concat(List<T>* other);
void unconcat(List<T>* other);
};/* class List */
template <class T>
void List<T>::append (const T& d) {
bck->checkConsistency();
if(uninitialized) {
new(head)ListNode<T> (d, head->next);
//head->data = d;
head->empty = false;
//Assert(tail == head); FIXME: do I need this because this list might be empty but append to another one
uninitialized = false;
} else {
ListNode<T>* new_node = new ListNode<T>(d, head);
head = new_node;
}
if(ptr_to_head != NULL) {
ptr_to_head->next = head;
}
}
template <class T>
void List<T>::concat (List<T>* other) {
bck->checkConsistency();
bck->notifyConcat(this, other);
Assert(tail->next==NULL);
tail->next = other->head;
Assert(other->ptr_to_head == NULL);
other->ptr_to_head = tail;
tail = other->tail;
}
template <class T>
void List<T>::unconcat(List<T>* other) {
// we do not need to check consistency since this is only called by the
// Backtracker when we are inconsistent
Assert(other->ptr_to_head != NULL);
other->ptr_to_head->next = NULL;
tail = other->ptr_to_head;
other->ptr_to_head = NULL;
}
/* Backtrackable Table */
template <class T>
class Backtracker {
friend class List<T>;
std::vector<std::pair<List<T>*,List<T>*> > undo_stack;
int curr_level;
context::CDO<int> pop_level;
void checkConsistency();
void notifyConcat(List<T>* a, List<T>* b);
public:
Backtracker(context::Context* c) : undo_stack(), curr_level(0), pop_level(c, 0) {}
~Backtracker() {}
};/* class Backtrackable */
template <class T> void Backtracker<T>::notifyConcat(List<T>* a, List<T>* b) {
curr_level++;
pop_level.set(pop_level.get()+1);
undo_stack.push_back( std::make_pair(a, b));
}
template <class T> void Backtracker<T>::checkConsistency() {
if( curr_level == pop_level || pop_level == -1) {
return;
}
Assert(curr_level > pop_level);
while (curr_level > pop_level) {
curr_level--;
List<T>* l1 = undo_stack[curr_level].first;
List<T>* l2 = undo_stack[curr_level].second;
l1->unconcat(l2);
undo_stack.pop_back();
}
Assert(curr_level == pop_level);
}
}/* CVC4 namespace */
#endif /* CVC4__UTIL__BACKTRACKABLE_H */
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