source: src/GenPoly/ErasableScopedMap.h@ a55ebcc

//
// 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.
//
// ErasableScopedMap.h -- A map that supports scoping and erasing elements.
//
// 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;

        /// Scoped list of maps.
        ScopeList scopes;
        /// Sentinal value for erased keys.
        Value erased;
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;

        // Both iterator types are complete bidirectional iterators, see below.
        class iterator;
        class const_iterator;

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

        /// 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 ) ); }

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

        /// 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;
                }
        }

        bool contains( const Key & key ) const {
                return find( key ) != cend();
        }
};

template<typename Key, typename Value>
class ErasableScopedMap<Key, Value>::iterator :
                public std::iterator< std::bidirectional_iterator_tag, value_type > {
        friend class ErasableScopedMap;
        typedef typename Scope::iterator wrapped_iterator;
        typedef typename ScopeList::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;
};

template<typename Key, typename Value>
class ErasableScopedMap<Key, Value>::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;
};

} // namespace GenPoly

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