source: src/GenPoly/ErasableScopedMap.h @ 7a15b7e

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// ScopedMap.h --
//
// Author           : Aaron B. Moss
// Created On       : Wed Dec 2 11:37:00 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Sat Jul 22 09:23:24 2017
// Update Count     : 2
//

#pragma once

#include <cassert>
#include <iterator>
#include <map>
#include <utility>
#include <vector>

namespace GenPoly {
        /// A map where the items are placed into nested scopes;
        /// inserted items are placed into the innermost scope, lookup looks from the innermost scope outward;
        /// erasing a key means that find() will no longer report any instance of the key in a scope further
        /// out, but the erasure itself is scoped. Key erasure works by inserting a sentinal value into the
        /// value field, and thus only works for Value types where a meaningful sentinal can be chosen.
        template<typename Key, typename Value>
        class ErasableScopedMap {
                typedef std::map< Key, Value > Scope;
                typedef std::vector< Scope > ScopeList;

                ScopeList scopes; ///< scoped list of maps
                Value erased;     ///< sentinal value for erased keys
        public:
                typedef typename Scope::key_type key_type;
                typedef typename Scope::mapped_type mapped_type;
                typedef typename Scope::value_type value_type;
                typedef typename ScopeList::size_type size_type;
                typedef typename ScopeList::difference_type difference_type;
                typedef typename Scope::reference reference;
                typedef typename Scope::const_reference const_reference;
                typedef typename Scope::pointer pointer;
                typedef typename Scope::const_pointer const_pointer;

                class iterator : public std::iterator< std::bidirectional_iterator_tag,
                                                       value_type > {
                friend class ErasableScopedMap;
                friend class const_iterator;
                        typedef typename std::map< Key, Value >::iterator wrapped_iterator;
                        typedef typename std::vector< std::map< Key, Value > > scope_list;
                        typedef typename scope_list::size_type size_type;

                        /// Checks if this iterator points to a valid item
                        bool is_valid() const {
                                return it != map->scopes[i].end() && it->second != map->erased;
                        }

                        /// Increments on invalid
                        iterator& next_valid() {
                                if ( ! is_valid() ) { ++(*this); }
                                return *this;
                        }

                        /// Decrements on invalid
                        iterator& prev_valid() {
                                if ( ! is_valid() ) { --(*this); }
                                return *this;
                        }
                        
                        iterator(ErasableScopedMap< Key, Value > const &_map, const wrapped_iterator &_it, size_type _i)
                                        : map(&_map), it(_it), i(_i) {}
                        
                public:
                        iterator(const iterator &that) : map(that.map), it(that.it), i(that.i) {}
                        iterator& operator= (const iterator &that) {
                                map = that.map; i = that.i; it = that.it;
                                return *this;
                        }

                        reference operator* () { return *it; }
                        pointer operator-> () { return it.operator->(); }

                        iterator& operator++ () {
                                if ( it == map->scopes[i].end() ) {
                                        if ( i == 0 ) return *this;
                                        --i;
                                        it = map->scopes[i].begin();
                                } else {
                                        ++it;
                                }
                                return next_valid();
                        }
                        iterator& operator++ (int) { iterator tmp = *this; ++(*this); return tmp; }

                        iterator& operator-- () {
                                // may fail if this is the begin iterator; allowed by STL spec
                                if ( it == map->scopes[i].begin() ) {
                                        ++i;
                                        it = map->scopes[i].end();
                                }
                                --it;
                                return prev_valid();
                        }
                        iterator& operator-- (int) { iterator tmp = *this; --(*this); return tmp; }

                        bool operator== (const iterator &that) {
                                return map == that.map && i == that.i && it == that.it;
                        }
                        bool operator!= (const iterator &that) { return !( *this == that ); }

                private:
                        ErasableScopedMap< Key, Value > const *map;
                        wrapped_iterator it;
                        size_type i;
                };

                class const_iterator : public std::iterator< std::bidirectional_iterator_tag,
                                                             value_type > {
                friend class ErasableScopedMap;
                        typedef typename std::map< Key, Value >::iterator wrapped_iterator;
                        typedef typename std::map< Key, Value >::const_iterator wrapped_const_iterator;
                        typedef typename std::vector< std::map< Key, Value > > scope_list;
                        typedef typename scope_list::size_type size_type;

                        /// Checks if this iterator points to a valid item
                        bool is_valid() const {
                                return it != map->scopes[i].end() && it->second != map->erased;
                        }

                        /// Increments on invalid
                        const_iterator& next_valid() {
                                if ( ! is_valid() ) { ++(*this); }
                                return *this;
                        }

                        /// Decrements on invalid
                        const_iterator& prev_valid() {
                                if ( ! is_valid() ) { --(*this); }
                                return *this;
                        }
                        
                        const_iterator(ErasableScopedMap< Key, Value > const &_map, const wrapped_const_iterator &_it, size_type _i)
                                        : map(&_map), it(_it), i(_i) {}
                public:
                        const_iterator(const iterator &that) : map(that.map), it(that.it), i(that.i) {}
                        const_iterator(const const_iterator &that) : map(that.map), it(that.it), i(that.i) {}
                        const_iterator& operator= (const iterator &that) {
                                map = that.map; i = that.i; it = that.it;
                                return *this;
                        }
                        const_iterator& operator= (const const_iterator &that) {
                                map = that.map; i = that.i; it = that.it;
                                return *this;
                        }

                        const_reference operator* () { return *it; }
                        const_pointer operator-> () { return it.operator->(); }

                        const_iterator& operator++ () {
                                if ( it == map->scopes[i].end() ) {
                                        if ( i == 0 ) return *this;
                                        --i;
                                        it = map->scopes[i].begin();
                                } else {
                                        ++it;
                                }
                                return next_valid();
                        }
                        const_iterator& operator++ (int) { const_iterator tmp = *this; ++(*this); return tmp; }

                        const_iterator& operator-- () {
                                // may fail if this is the begin iterator; allowed by STL spec
                                if ( it == map->scopes[i].begin() ) {
                                        ++i;
                                        it = map->scopes[i].end();
                                }
                                --it;
                                return prev_valid();
                        }
                        const_iterator& operator-- (int) { const_iterator tmp = *this; --(*this); return tmp; }

                        bool operator== (const const_iterator &that) {
                                return map == that.map && i == that.i && it == that.it;
                        }
                        bool operator!= (const const_iterator &that) { return !( *this == that ); }

                private:
                        ErasableScopedMap< Key, Value > const *map;
                        wrapped_const_iterator it;
                        size_type i;
                };

                /// Starts a new scope
                void beginScope() {
                        Scope scope;
                        scopes.push_back(scope);
                }

                /// Ends a scope; invalidates any iterators pointing to elements of that scope
                void endScope() {
                        scopes.pop_back();
                        assert( ! scopes.empty() );
                }

                /// Default constructor initializes with one scope
                ErasableScopedMap( const Value &erased_ ) : erased( erased_ ) { beginScope(); }

                iterator begin() { return iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
                const_iterator begin() const { return const_iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
                const_iterator cbegin() const { return const_iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
                iterator end() { return iterator(*this, scopes[0].end(), 0); }
                const_iterator end() const { return const_iterator(*this, scopes[0].end(), 0); }
                const_iterator cend() const { return const_iterator(*this, scopes[0].end(), 0); }

                /// Gets the index of the current scope (counted from 1)
                size_type currentScope() const { return scopes.size(); }

                /// Finds the given key in the outermost scope it occurs; returns end() for none such
                iterator find( const Key &key ) {
                        for ( size_type i = scopes.size() - 1; ; --i ) {
                                typename Scope::iterator val = scopes[i].find( key );
                                if ( val != scopes[i].end() ) {
                                        return val->second == erased ? end() : iterator( *this, val, i );
                                }
                                if ( i == 0 ) break;
                        }
                        return end();
                }
                const_iterator find( const Key &key ) const {
                                return const_iterator( const_cast< ErasableScopedMap< Key, Value >* >(this)->find( key ) );
                }

                /// Finds the given key in the outermost scope inside the given scope where it occurs
                iterator findNext( const_iterator &it, const Key &key ) {
                        if ( it.i == 0 ) return end();
                        for ( size_type i = it.i - 1; ; --i ) {
                                typename Scope::iterator val = scopes[i].find( key );
                                if ( val != scopes[i].end() ) {
                                        return val->second == erased ? end() : iterator( *this, val, i );
                                }
                                if ( i == 0 ) break;
                        }
                        return end();
                }
                const_iterator findNext( const_iterator &it, const Key &key ) const {
                                return const_iterator( const_cast< ErasableScopedMap< Key, Value >* >(this)->findNext( it, key ) );
                }

                /// Inserts the given key-value pair into the outermost scope
                std::pair< iterator, bool > insert( const value_type &value ) {
                        std::pair< typename Scope::iterator, bool > res = scopes.back().insert( value );
                        return std::make_pair( iterator(*this, res.first, scopes.size()-1), res.second );
                }
                std::pair< iterator, bool > insert( const Key &key, const Value &value ) { return insert( std::make_pair( key, value ) ); }

                /// Marks the given element as erased from this scope inward; returns 1 for erased an element, 0 otherwise
                size_type erase( const Key &key ) {
                        typename Scope::iterator val = scopes.back().find( key );
                        if ( val != scopes.back().end() ) {
                                val->second = erased;
                                return 1;
                        } else {
                                scopes.back().insert( val, std::make_pair( key, erased ) );
                                return 0;
                        }
                }

                Value& operator[] ( const Key &key ) {
                        iterator slot = find( key );
                        if ( slot != end() ) return slot->second;
                        return insert( key, Value() ).first->second;
                }
        };
} // namespace GenPoly

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