/inc/lexertl/memory_file.hpp

// memory_file.hpp

// Copyright (c) 2012 Ben Hanson (http://www.benhanson.net/)

// Inspired by http://en.wikibooks.org/wiki/Optimizing_C%2B%2B/General_optimization_techniques/Input/Output#Memory-mapped_file

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file licence_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)



#ifndef LEXERTL_MEMORY_FILE_H

#define LEXERTL_MEMORY_FILE_H



#ifdef __unix__

#include <fcntl.h>

#include <unistd.h>

#include <sys/mman.h>

#include <sys/stat.h>

#elif defined _WIN32

#include <windows.h>

#endif



// Only files small enough to fit into memory are supported.

namespace lexertl

{

template<typename CharT>

class basic_memory_file

{

public:

    basic_memory_file (const char *pathname_) :

        _data (0),

        _size (0)

    {

#ifdef __unix__

        _fh = ::open (pathname_, O_RDONLY);



        if (_fh > -1)

        {

            struct stat sbuf_;



            if (::fstat (_fh, &sbuf_) > -1)

            {

                _data = static_cast<const CharT *>

                    (::mmap (0, sbuf_.st_size, PROT_READ, MAP_SHARED, _fh, 0));



                if (_data == MAP_FAILED)

                {

                    _data = 0;

                }

                else

                {

                    _size = sbuf_.st_size;

                }

            }

        }

#elif defined _WIN32

        _fh = ::CreateFileA (pathname_, GENERIC_READ, FILE_SHARE_READ, 0,

            OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

        _fmh = 0;



        if (_fh != INVALID_HANDLE_VALUE)

        {

            _fmh = ::CreateFileMapping (_fh, 0, PAGE_READONLY, 0, 0, 0);



            if (_fmh != 0)

            {

                _data = static_cast<CharT *>(::MapViewOfFile

                    (_fmh, FILE_MAP_READ, 0, 0, 0));



                if (_data) _size = ::GetFileSize(_fh, 0);

            }

        }

#endif

    }



    ~basic_memory_file ()

    {

#if defined(__unix__)

        ::munmap(const_cast<CharT *>(_data), _size);

        ::close(_fh);

#elif defined(_WIN32)

        ::UnmapViewOfFile(_data);

        ::CloseHandle(_fmh);

        ::CloseHandle(_fh);

#endif

    }



    const CharT *data () const

    {

        return _data;

    }



    std::size_t size () const

    {

        return _size;

    }



private:

    const CharT *_data;

    std::size_t _size;

#ifdef __unix__

    int _fh;

#elif defined _WIN32

    HANDLE _fh;

    HANDLE _fmh;

#else

    #error Only Posix or Windows are supported.

#endif

};



typedef basic_memory_file<char> memory_file;

typedef basic_memory_file<wchar_t> wmemory_file;

}



#endif