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Diffstat (limited to 'src/context/backtrackable.h')
-rw-r--r-- | src/context/backtrackable.h | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/src/context/backtrackable.h b/src/context/backtrackable.h new file mode 100644 index 000000000..5492dd8b5 --- /dev/null +++ b/src/context/backtrackable.h @@ -0,0 +1,222 @@ +/********************* */ +/*! \file backtrackable.h + ** \verbatim + ** Original author: Morgan Deters + ** Major contributors: none + ** Minor contributors (to current version): none + ** This file is part of the CVC4 project. + ** Copyright (c) 2009-2014 New York University and The University of Iowa + ** 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 */ |