simplestringstorage.h

loki库。。。。。 一个很好的设计模式库

////////////////////////////////////////////////////////////////////////////////
// flex_string
// Copyright (c) 2001 by Andrei Alexandrescu
// Permission to use, copy, modify, distribute and sell this software for any
//     purpose is hereby granted without fee, provided that the above copyright
//     notice appear in all copies and that both that copyright notice and this
//     permission notice appear in supporting documentation.
// The author makes no representations about the
//     suitability of this software for any purpose. It is provided "as is"
//     without express or implied warranty.
////////////////////////////////////////////////////////////////////////////////

#ifndef SIMPLE_STRING_STORAGE_INC_
#define SIMPLE_STRING_STORAGE_INC_

// $Id: simplestringstorage.h 754 2006-10-17 19:59:11Z syntheticpp $


/* This is the template for a storage policy
////////////////////////////////////////////////////////////////////////////////
template <typename E, class A = @>
class StoragePolicy
{
    typedef E value_type;
    typedef @ iterator;
    typedef @ const_iterator;
    typedef A allocator_type;
    typedef @ size_type;
    
    StoragePolicy(const StoragePolicy& s);
    StoragePolicy(const A&);
    StoragePolicy(const E* s, size_type len, const A&);
    StoragePolicy(size_type len, E c, const A&);
    ~StoragePolicy();

    iterator begin();
    const_iterator begin() const;
    iterator end();
    const_iterator end() const;
    
    size_type size() const;
    size_type max_size() const;
    size_type capacity() const;

    void reserve(size_type res_arg);

    template <class ForwardIterator>
    void append(ForwardIterator b, ForwardIterator e);

    void resize(size_type newSize, E fill);

    void swap(StoragePolicy& rhs);
    
    const E* c_str() const;
    const E* data() const;
    
    A get_allocator() const;
};
////////////////////////////////////////////////////////////////////////////////
*/

#include <memory>
#include <algorithm>
#include <functional>
#include <cassert>
#include <limits>
#include <stdexcept>


////////////////////////////////////////////////////////////////////////////////
// class template SimpleStringStorage
// Allocates memory with malloc
////////////////////////////////////////////////////////////////////////////////

template <typename E, class A = std::allocator<E> >
class SimpleStringStorage
{
    // The "public" below exists because MSVC can't do template typedefs
public:
    struct Data
    {
        Data() : pEnd_(buffer_), pEndOfMem_(buffer_) { buffer_[0] = E(0); }

        E* pEnd_;
        E* pEndOfMem_;
        E buffer_[1];
    };
    static const Data emptyString_;
    
    typedef typename A::size_type size_type;

private:
    Data* pData_;

    void Init(size_type size, size_type capacity)
    {
        assert(size <= capacity);
        if (capacity == 0) 
        {
            pData_ = const_cast<Data*>(&emptyString_);
        }
        else
        {
            // 11-17-2000: comment added: 
            //     No need to allocate (capacity + 1) to 
            //     accomodate the terminating 0, because Data already
            //     has one one character in there
            pData_ = static_cast<Data*>(
                malloc(sizeof(Data) + capacity * sizeof(E)));
            if (!pData_) throw std::bad_alloc();
            pData_->pEnd_ = pData_->buffer_ + size;
            pData_->pEndOfMem_ = pData_->buffer_ + capacity;
        }
    }
    
private:
    // Warning - this doesn't initialize pData_. Used in reserve()
    SimpleStringStorage()
    { }
    
public:
    typedef E value_type;
    typedef E* iterator;
    typedef const E* const_iterator;
    typedef A allocator_type;
    typedef typename A::reference reference;

    
    SimpleStringStorage(const SimpleStringStorage& rhs) 
    {
        const size_type sz = rhs.size();
        Init(sz, sz);
        if (sz) flex_string_details::pod_copy(rhs.begin(), rhs.end(), begin());
    }
    
    SimpleStringStorage(const SimpleStringStorage& s, 
        flex_string_details::Shallow) 
        : pData_(s.pData_)
    {
    }
    
    SimpleStringStorage(const A&)
    { pData_ = const_cast<Data*>(&emptyString_); }
    
    SimpleStringStorage(const E* s, size_type len, const A&)
    {
        Init(len, len);
        flex_string_details::pod_copy(s, s + len, begin());
    }

    SimpleStringStorage(size_type len, E c, const A&)
    {
        Init(len, len);
        flex_string_details::pod_fill(begin(), end(), c);
    }
    
    SimpleStringStorage& operator=(const SimpleStringStorage& rhs)
    {
        const size_type sz = rhs.size();
        reserve(sz);
        flex_string_details::pod_copy(&*rhs.begin(), &*rhs.end(), begin());
        pData_->pEnd_ = &*begin() + sz;
        return *this;
    }

    ~SimpleStringStorage()
    {
        assert(begin() <= end());
        if (pData_ != &emptyString_) free(pData_);
    }

    iterator begin()
    { return pData_->buffer_; }
    
    const_iterator begin() const
    { return pData_->buffer_; }
    
    iterator end()
    { return pData_->pEnd_; }
    
    const_iterator end() const
    { return pData_->pEnd_; }
    
    size_type size() const
    { return pData_->pEnd_ - pData_->buffer_; }

    size_type max_size() const
    { return size_t(-1) / sizeof(E) - sizeof(Data) - 1; }

    size_type capacity() const
    { return pData_->pEndOfMem_ - pData_->buffer_; }

    void reserve(size_type res_arg)
    {
        if (res_arg <= capacity())
        {
            // @@@ insert shrinkage here if you wish
            return;
        }

        if (pData_ == &emptyString_) 
        {
            Init(0, res_arg);
        }
        else
        {
            const size_type sz = size();

            void* p = realloc(pData_, 
                sizeof(Data) + res_arg * sizeof(E));
            if (!p) throw std::bad_alloc();
        
            if (p != pData_)
            {
                pData_ = static_cast<Data*>(p);
                pData_->pEnd_ = pData_->buffer_ + sz;
            }
            pData_->pEndOfMem_ = pData_->buffer_ + res_arg;
        }
    }

    template <class InputIterator>
    void append(InputIterator b, InputIterator e)
    {
        const size_type 
            sz = std::distance(b, e),
            neededCapacity = size() + sz;
        if (capacity() < neededCapacity)
        {
            static std::less_equal<const E*> le;
            (void) le;
            assert(!(le(begin(), &*b) && le(&*b, end()))); // no aliasing
            reserve(neededCapacity);
        }
        std::copy(b, e, end());
        pData_->pEnd_ += sz;
    }
    
    void resize(size_type newSize, E fill)
    {
        const int delta = int(newSize - size());
        if (delta == 0) return;

        if (delta > 0)
        {
            if (newSize > capacity()) 
            {
                reserve(newSize);
            }
            E* e = &*end();
            flex_string_details::pod_fill(e, e + delta, fill);
        }
        pData_->pEnd_ = pData_->buffer_ + newSize;
    }

    void swap(SimpleStringStorage& rhs)
    {
        std::swap(pData_, rhs.pData_);
    }
    
    const E* c_str() const
    {
        if (pData_ != &emptyString_) *pData_->pEnd_ = E();
        return pData_->buffer_; 
    }

    const E* data() const
    { return pData_->buffer_; }
    
    A get_allocator() const
    { return A(); }
};

template <typename E, class A>
const typename SimpleStringStorage<E, A>::Data
SimpleStringStorage<E, A>::emptyString_;
//{ 
//    const_cast<E*>(SimpleStringStorage<E, A>::emptyString_.buffer_), 
//    const_cast<E*>(SimpleStringStorage<E, A>::emptyString_.buffer_), 
//    { E() }
//};



#endif // SIMPLE_STRING_STORAGE_INC_