// 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