mappedfile.h

/* mappedfile.h -- provides a class for memory mapped files
 *
 * Copyright (C) 2008-2009 Benjamin Kramer
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 *
 */

#ifndef MAPPEDFILE_H
#define MAPPEDFILE_H

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

#include <stddef.h>

/*!
 * Maps the specified file into memory.
 * \param path the path of the file being mapped
 * \param length pointer which the mapped length is written to.
 * \return the pointer to the mapping. On failure NULL is returned.
 */
char *map_file(const char *path, size_t *length);

/*! Releases memory allocated by map_file().
 * \param data the pointer returned by map_file().
 * \param length the length returned by map_file().
 */
void unmap_file(char *data, size_t length);

#ifdef __cplusplus
}

#include <cstddef>
#ifdef __EXCEPTIONS
#include <stdexcept>
#include <sstream>
#else /* __EXCEPTIONS */
#include <cstdlib>
#include <iostream>
#endif /* __EXCEPTIONS */

/*!
 * mapped_file allows you to create a simple read-only file mapping in an
 * object-oriented cross-platform way.
 */
class mapped_file
{
private:
	std::size_t size_;
	char *data_;
	mapped_file(const mapped_file&) : size_(), data_() {}
	mapped_file& operator=(const mapped_file&) { return *this; }
public:
	/*!
	 * Maps the named file into memory.
	 * The file is mapped into memory. All filehandles are closed afterwards.
	 * \param path path of the file being mapped
	 * \exception IOException the file couldn't be opened
	 */
	mapped_file(const char *path)  : size_(), data_() {
		data_ = map_file(path, &size_);
		if (!data_) {
#ifdef __EXCEPTIONS
			std::ostringstream o;
			o << "Couldn't open File \"" << path << "\"";
			throw io_exception(o.str());
#else /* __EXCEPTIONS */
			std::cerr << "Couldn't open File \"" << path << "\"" << std::endl;
			std::exit(EXIT_FAILURE);
#endif /* __EXCEPTIONS */
		}
	}
	/*!
	 * Unmaps the file and releases all memory.
	 */
	~mapped_file() {
		unmap_file(data_, size_);
	}
	/*!
	 * Get the size of the file in memory.
	 */
	std::size_t length() const { return size_; }
	/*!
	 * Gets the nth byte from the mapped file.
	 */
	char operator[](std::size_t n) const { return data_[n]; }
	/*!
	 * Gets a read-only pointer to the mapped data.
	 */
	const char* operator*() const { return data_; }

#ifdef __EXCEPTIONS
	struct io_exception : public std::runtime_error
	{
		io_exception(const std::string& message)
				   : std::runtime_error(message) { }
	};
#endif /* __EXCEPTIONS */
};
#endif /* __cplusplus */

#endif /* MAPPEDFILE_H */