include/experimental/functional

// -*- C++ -*-
//===-------------------------- functional --------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_EXPERIMENTAL_FUNCTIONAL
#define _LIBCPP_EXPERIMENTAL_FUNCTIONAL

/*
   experimental/functional synopsis

#include <algorithm>

namespace std {
namespace experimental {
inline namespace fundamentals_v1 {

    // See C++14 20.9.9, Function object binders
    template <class T> constexpr bool is_bind_expression_v
      = is_bind_expression<T>::value;
    template <class T> constexpr int is_placeholder_v
      = is_placeholder<T>::value;

    // 4.2, Class template function
    template<class> class function; // undefined
    template<class R, class... ArgTypes> class function<R(ArgTypes...)>;

    template<class R, class... ArgTypes>
    void swap(function<R(ArgTypes...)>&, function<R(ArgTypes...)>&);

    template<class R, class... ArgTypes>
    bool operator==(const function<R(ArgTypes...)>&, nullptr_t) noexcept;
    template<class R, class... ArgTypes>
    bool operator==(nullptr_t, const function<R(ArgTypes...)>&) noexcept;
    template<class R, class... ArgTypes>
    bool operator!=(const function<R(ArgTypes...)>&, nullptr_t) noexcept;
    template<class R, class... ArgTypes>
    bool operator!=(nullptr_t, const function<R(ArgTypes...)>&) noexcept;

    // 4.3, Searchers
    template<class ForwardIterator, class BinaryPredicate = equal_to<>>
      class default_searcher;

    template<class RandomAccessIterator,
             class Hash = hash<typename iterator_traits<RandomAccessIterator>::value_type>,
             class BinaryPredicate = equal_to<>>
      class boyer_moore_searcher;

    template<class RandomAccessIterator,
             class Hash = hash<typename iterator_traits<RandomAccessIterator>::value_type>,
             class BinaryPredicate = equal_to<>>
      class boyer_moore_horspool_searcher;

    template<class ForwardIterator, class BinaryPredicate = equal_to<>>
    default_searcher<ForwardIterator, BinaryPredicate>
    make_default_searcher(ForwardIterator pat_first, ForwardIterator pat_last,
                          BinaryPredicate pred = BinaryPredicate());

    template<class RandomAccessIterator,
             class Hash = hash<typename iterator_traits<RandomAccessIterator>::value_type>,
             class BinaryPredicate = equal_to<>>
    boyer_moore_searcher<RandomAccessIterator, Hash, BinaryPredicate>
    make_boyer_moore_searcher(
        RandomAccessIterator pat_first, RandomAccessIterator pat_last,
        Hash hf = Hash(), BinaryPredicate pred = BinaryPredicate());

    template<class RandomAccessIterator,
             class Hash = hash<typename iterator_traits<RandomAccessIterator>::value_type>,
             class BinaryPredicate = equal_to<>>
    boyer_moore_horspool_searcher<RandomAccessIterator, Hash, BinaryPredicate>
    make_boyer_moore_horspool_searcher(
        RandomAccessIterator pat_first, RandomAccessIterator pat_last,
        Hash hf = Hash(), BinaryPredicate pred = BinaryPredicate());

  } // namespace fundamentals_v1
  } // namespace experimental

  template<class R, class... ArgTypes, class Alloc>
  struct uses_allocator<experimental::function<R(ArgTypes...)>, Alloc>;

} // namespace std

*/

#include <experimental/__config>
#include <functional>
#include <algorithm>
#include <type_traits>
#include <vector>
#include <array>
#include <unordered_map>

#include <__debug>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


_LIBCPP_BEGIN_NAMESPACE_LFTS

#if _LIBCPP_STD_VER > 11
// default searcher
template<class _ForwardIterator, class _BinaryPredicate = equal_to<>>
class _LIBCPP_TYPE_VIS default_searcher {
public:
    _LIBCPP_INLINE_VISIBILITY
    default_searcher(_ForwardIterator __f, _ForwardIterator __l, 
                       _BinaryPredicate __p = _BinaryPredicate())
        : __first_(__f), __last_(__l), __pred_(__p) {}

    template <typename _ForwardIterator2>
    _LIBCPP_INLINE_VISIBILITY
    pair<_ForwardIterator2, _ForwardIterator2>
    operator () (_ForwardIterator2 __f, _ForwardIterator2 __l) const
    {
        return _VSTD::__search(__f, __l, __first_, __last_, __pred_,
            typename _VSTD::iterator_traits<_ForwardIterator>::iterator_category(),
            typename _VSTD::iterator_traits<_ForwardIterator2>::iterator_category());
    }

private:
    _ForwardIterator __first_;
    _ForwardIterator __last_;
    _BinaryPredicate __pred_;
    };

template<class _ForwardIterator, class _BinaryPredicate = equal_to<>>
_LIBCPP_INLINE_VISIBILITY
default_searcher<_ForwardIterator, _BinaryPredicate>
make_default_searcher( _ForwardIterator __f, _ForwardIterator __l, _BinaryPredicate __p = _BinaryPredicate ())
{
    return default_searcher<_ForwardIterator, _BinaryPredicate>(__f, __l, __p);
}

template<class _Key, class _Value, class _Hash, class _BinaryPredicate, bool /*useArray*/> class _BMSkipTable;

//  General case for BM data searching; use a map
template<class _Key, typename _Value, class _Hash, class _BinaryPredicate>
class _BMSkipTable<_Key, _Value, _Hash, _BinaryPredicate, false> {
public: // TODO private:
    typedef _Value value_type;
    typedef _Key   key_type;

    const _Value __default_value_;
    std::unordered_map<_Key, _Value, _Hash, _BinaryPredicate> __table;
    
public:
    _LIBCPP_INLINE_VISIBILITY
    _BMSkipTable(std::size_t __sz, _Value __default, _Hash __hf, _BinaryPredicate __pred)
        : __default_value_(__default), __table(__sz, __hf, __pred) {}
    
    _LIBCPP_INLINE_VISIBILITY
    void insert(const key_type &__key, value_type __val)
    {
        __table [__key] = __val;    // Would skip_.insert (val) be better here?
    }

    _LIBCPP_INLINE_VISIBILITY
    value_type operator [](const key_type & __key) const
    {
        auto __it = __table.find (__key);
        return __it == __table.end() ? __default_value_ : __it->second;
    }
};
    

//  Special case small numeric values; use an array
template<class _Key, typename _Value, class _Hash, class _BinaryPredicate>
class _BMSkipTable<_Key, _Value, _Hash, _BinaryPredicate, true> {
private:
    typedef _Value value_type;
    typedef _Key   key_type;

    typedef typename std::make_unsigned<key_type>::type unsigned_key_type;
    typedef std::array<value_type, _VSTD::numeric_limits<unsigned_key_type>::max()> skip_map;
    skip_map __table;

public:
    _LIBCPP_INLINE_VISIBILITY
    _BMSkipTable(std::size_t /*__sz*/, _Value __default, _Hash /*__hf*/, _BinaryPredicate /*__pred*/)
    {
        std::fill_n(__table.begin(), __table.size(), __default);
    }
    
    _LIBCPP_INLINE_VISIBILITY
    void insert(key_type __key, value_type __val)
    {
        __table[static_cast<unsigned_key_type>(__key)] = __val;
    }

    _LIBCPP_INLINE_VISIBILITY
    value_type operator [](key_type __key) const
    {
        return __table[static_cast<unsigned_key_type>(__key)];
    }
};


template <class _RandomAccessIterator1, 
          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>, 
          class _BinaryPredicate = equal_to<>>
class _LIBCPP_TYPE_VIS boyer_moore_searcher {
private:
    typedef typename std::iterator_traits<_RandomAccessIterator1>::difference_type difference_type;
    typedef typename std::iterator_traits<_RandomAccessIterator1>::value_type      value_type;
    typedef _BMSkipTable<value_type, difference_type, _Hash, _BinaryPredicate,
                    _VSTD::is_integral<value_type>::value && // what about enums?
                    sizeof(value_type) == 1 &&
                    is_same<_Hash, hash<value_type>>::value &&
                    is_same<_BinaryPredicate, equal_to<>>::value
            > skip_table_type;
    
public:
    boyer_moore_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
                _Hash __hf = _Hash(), _BinaryPredicate __pred = _BinaryPredicate())
            : __first_(__f), __last_(__l), __pred_(__pred),
              __pattern_length_(_VSTD::distance(__first_, __last_)),
              __skip_{make_shared<skip_table_type>(__pattern_length_, -1, __hf, __pred_)},
              __suffix_{make_shared<vector<difference_type>>(__pattern_length_ + 1)}
        {
    //  build the skip table
        for ( difference_type __i = 0; __f != __l; ++__f, (void) ++__i )
            __skip_->insert(*__f, __i);

        this->__build_suffix_table ( __first_, __last_, __pred_ );
        }
        
    template <typename _RandomAccessIterator2>
    pair<_RandomAccessIterator2, _RandomAccessIterator2>
    operator ()(_RandomAccessIterator2 __f, _RandomAccessIterator2 __l) const
    {
        static_assert ( std::is_same<
                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type, 
                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator2>::value_type>::type
                    >::value,
                "Corpus and Pattern iterators must point to the same type" );

        if (__f      == __l )    return make_pair(__l, __l); // empty corpus
        if (__first_ == __last_) return make_pair(__f, __f); // empty pattern

    //  If the pattern is larger than the corpus, we can't find it!
        if ( __pattern_length_ > _VSTD::distance (__f, __l)) 
            return make_pair(__l, __l);

    //  Do the search 
        return this->__search(__f, __l);
    }
        
public: // TODO private:
    _RandomAccessIterator1               __first_;
    _RandomAccessIterator1               __last_;
    _BinaryPredicate                     __pred_;
    difference_type                      __pattern_length_;
    shared_ptr<skip_table_type>          __skip_;
    shared_ptr<vector<difference_type>>  __suffix_;

    template <typename _RandomAccessIterator2>
    pair<_RandomAccessIterator2, _RandomAccessIterator2>
    __search(_RandomAccessIterator2 __f, _RandomAccessIterator2 __l) const
    {
        _RandomAccessIterator2 __cur = __f;
        const _RandomAccessIterator2 __last = __l - __pattern_length_;
        const skip_table_type &         __skip   = *__skip_.get();
        const vector<difference_type> & __suffix = *__suffix_.get();
        
        while (__cur <= __last)
        {

        //  Do we match right where we are?
            difference_type __j = __pattern_length_;
            while (__pred_(__first_ [__j-1], __cur [__j-1])) {
                __j--;
            //  We matched - we're done!
                if ( __j == 0 )
                    return make_pair(__cur, __cur + __pattern_length_);
                }
            
        //  Since we didn't match, figure out how far to skip forward
            difference_type __k = __skip[__cur [ __j - 1 ]];
            difference_type __m = __j - __k - 1;
            if (__k < __j && __m > __suffix[ __j ])
                __cur += __m;
            else
                __cur += __suffix[ __j ];
        }
    
        return make_pair(__l, __l);     // We didn't find anything
    }


    template<typename _Iterator, typename _Container>
    void __compute_bm_prefix ( _Iterator __f, _Iterator __l, _BinaryPredicate __pred, _Container &__prefix )
    {
        const std::size_t __count = _VSTD::distance(__f, __l);
                        
        __prefix[0] = 0;
        std::size_t __k = 0;
        for ( std::size_t __i = 1; __i < __count; ++__i )
        {
            while ( __k > 0 && !__pred ( __f[__k], __f[__i] ))
                __k = __prefix [ __k - 1 ];
                
            if ( __pred ( __f[__k], __f[__i] ))
                __k++;
            __prefix [ __i ] = __k;
        }
    }

    void __build_suffix_table(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
                                                    _BinaryPredicate __pred)
    {
        const std::size_t __count = _VSTD::distance(__f, __l);
        vector<difference_type> & __suffix = *__suffix_.get();
        if (__count > 0)
        {
            _VSTD::vector<value_type> __scratch(__count);
            
            __compute_bm_prefix(__f, __l, __pred, __scratch);
            for ( std::size_t __i = 0; __i <= __count; __i++ )
                __suffix[__i] = __count - __scratch[__count-1];
    
            typedef _VSTD::reverse_iterator<_RandomAccessIterator1> _RevIter;
            __compute_bm_prefix(_RevIter(__l), _RevIter(__f), __pred, __scratch);
     
            for ( std::size_t __i = 0; __i < __count; __i++ )
            {
                const std::size_t     __j = __count - __scratch[__i];
                const difference_type __k = __i     - __scratch[__i] + 1;
     
                if (__suffix[__j] > __k)
                    __suffix[__j] = __k;
            }
        }
    }

};

template<class _RandomAccessIterator, 
         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>, 
         class _BinaryPredicate = equal_to<>>
_LIBCPP_INLINE_VISIBILITY
boyer_moore_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>
make_boyer_moore_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l, 
                    _Hash __hf = _Hash(), _BinaryPredicate __p = _BinaryPredicate ())
{
    return boyer_moore_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>(__f, __l, __hf, __p);
}

// boyer-moore-horspool
template <class _RandomAccessIterator1, 
          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>, 
          class _BinaryPredicate = equal_to<>>
class _LIBCPP_TYPE_VIS boyer_moore_horspool_searcher {
private:
    typedef typename std::iterator_traits<_RandomAccessIterator1>::difference_type difference_type;
    typedef typename std::iterator_traits<_RandomAccessIterator1>::value_type      value_type;
    typedef _BMSkipTable<value_type, difference_type, _Hash, _BinaryPredicate,
                    _VSTD::is_integral<value_type>::value && // what about enums?
                    sizeof(value_type) == 1 &&
                    is_same<_Hash, hash<value_type>>::value &&
                    is_same<_BinaryPredicate, equal_to<>>::value
            > skip_table_type;

public:
    boyer_moore_horspool_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
                _Hash __hf = _Hash(), _BinaryPredicate __pred = _BinaryPredicate())
            : __first_(__f), __last_(__l), __pred_(__pred),
              __pattern_length_(_VSTD::distance(__first_, __last_)),
              __skip_{_VSTD::make_shared<skip_table_type>(__pattern_length_, __pattern_length_, __hf, __pred_)}
        {
    //  build the skip table
            if ( __f != __l )
            {
                __l = __l - 1;
                for ( difference_type __i = 0; __f != __l; ++__f, (void) ++__i )
                    __skip_->insert(*__f, __pattern_length_ - 1 - __i);
            }
        }
            
    template <typename _RandomAccessIterator2>
    pair<_RandomAccessIterator2, _RandomAccessIterator2>
    operator ()(_RandomAccessIterator2 __f, _RandomAccessIterator2 __l) const
    {
        static_assert ( std::is_same<
                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type, 
                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator2>::value_type>::type
                    >::value,
                "Corpus and Pattern iterators must point to the same type" );

        if (__f      == __l )    return make_pair(__l, __l); // empty corpus
        if (__first_ == __last_) return make_pair(__f, __f); // empty pattern

    //  If the pattern is larger than the corpus, we can't find it!
        if ( __pattern_length_ > _VSTD::distance (__f, __l)) 
            return make_pair(__l, __l);

    //  Do the search 
        return this->__search(__f, __l);
    }
        
private:
    _RandomAccessIterator1      __first_;
    _RandomAccessIterator1      __last_;
    _BinaryPredicate            __pred_;
    difference_type             __pattern_length_;
    shared_ptr<skip_table_type> __skip_;

    template <typename _RandomAccessIterator2>
    pair<_RandomAccessIterator2, _RandomAccessIterator2>
    __search ( _RandomAccessIterator2 __f, _RandomAccessIterator2 __l ) const {
        _RandomAccessIterator2 __cur = __f;
        const _RandomAccessIterator2 __last = __l - __pattern_length_;
        const skip_table_type & __skip = *__skip_.get();

        while (__cur <= __last)
        {
        //  Do we match right where we are?
            difference_type __j = __pattern_length_;
            while (__pred_(__first_[__j-1], __cur[__j-1]))
            {
                __j--;
            //  We matched - we're done!
                if ( __j == 0 )
                    return make_pair(__cur, __cur + __pattern_length_);
            }
            __cur += __skip[__cur[__pattern_length_-1]];
        }
        
        return make_pair(__l, __l);
    }
};

template<class _RandomAccessIterator, 
         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>, 
         class _BinaryPredicate = equal_to<>>
_LIBCPP_INLINE_VISIBILITY
boyer_moore_horspool_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>
make_boyer_moore_horspool_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l, 
                    _Hash __hf = _Hash(), _BinaryPredicate __p = _BinaryPredicate ())
{
    return boyer_moore_horspool_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>(__f, __l, __hf, __p);
}

#endif // _LIBCPP_STD_VER > 11

_LIBCPP_END_NAMESPACE_LFTS

_LIBCPP_POP_MACROS

#endif /* _LIBCPP_EXPERIMENTAL_FUNCTIONAL */