random_access_file.cpp

    random_access_file_type.h

/*

 * This file is part of OpenTTD.

 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.

 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.

 */

 /** @file random_access_file.cpp Actual implementation of the RandomAccessFile class. */

#include "stdafx.h"

#include "random_access_file_type.h"

#include "debug.h"

#include "fileio_func.h"

#include "string_func.h"

#include "safeguards.h"

/**

 * Create the RandomAccesFile.

 * @param filename Name of the file at the disk.

 * @param subdir   The sub directory to search this file in.

 */

RandomAccessFile::RandomAccessFile(const std::string &filename, Subdirectory subdir) : filename(filename)

{

	this->file_handle = FioFOpenFile(filename, "rb", subdir);

	if (this->file_handle == nullptr) usererror("Cannot open file '%s'", filename.c_str());

	/* When files are in a tar-file, the begin of the file might not be at 0. */

	long pos = ftell(this->file_handle);

	if (pos < 0) usererror("Cannot read file '%s'", filename.c_str());

	/* Store the filename without path and extension */

	auto t = filename.rfind(PATHSEPCHAR);

	std::string name_without_path = filename.substr(t != std::string::npos ? t + 1 : 0);

	this->simplified_filename = name_without_path.substr(0, name_without_path.rfind('.'));

	strtolower(this->simplified_filename);

	this->SeekTo((size_t)pos, SEEK_SET);

}

/**

 * Close the file's file handle.

 */

RandomAccessFile::~RandomAccessFile()

{

	fclose(this->file_handle);

}

/**

 * Get the filename of the opened file with the path from the SubDirectory and the extension.

 * @return Name of the file.

 */

const std::string& RandomAccessFile::GetFilename() const

{

	return this->filename;

}

/**

 * Get the simplified filename of the opened file. The simplified filename is the name of the

 * file without the SubDirectory or extension in lower case.

 * @return Name of the file.

 */

const std::string& RandomAccessFile::GetSimplifiedFilename() const

{

	return this->simplified_filename;

}

/**

 * Get position in the file.

 * @return Position in the file.

 */

size_t RandomAccessFile::GetPos() const

{

	return this->pos + (this->buffer - this->buffer_end);

}

/**

 * Seek in the current file.

 * @param pos New position.

 * @param mode Type of seek (\c SEEK_CUR means \a pos is relative to current position, \c SEEK_SET means \a pos is absolute).

 */

void RandomAccessFile::SeekTo(size_t pos, int mode)

{

	if (mode == SEEK_CUR) pos += this->GetPos();

	this->pos = pos;

	if (fseek(this->file_handle, this->pos, SEEK_SET) < 0) {

		DEBUG(misc, 0, "Seeking in %s failed", this->filename.c_str());

	}

	/* Reset the buffer, so the next ReadByte will read bytes from the file. */

	this->buffer = this->buffer_end = this->buffer_start;

}

/**

 * Read a byte from the file.

 * @return Read byte.

 */

byte RandomAccessFile::ReadByte()

{

	if (this->buffer == this->buffer_end) {

		this->buffer = this->buffer_start;

		size_t size = fread(this->buffer, 1, RandomAccessFile::BUFFER_SIZE, this->file_handle);

		this->pos += size;

		this->buffer_end = this->buffer_start + size;

		if (size == 0) return 0;

	}

	return *this->buffer++;

}

/**

 * Read a word (16 bits) from the file (in low endian format).

 * @return Read word.

 */

uint16 RandomAccessFile::ReadWord()

{

	byte b = this->ReadByte();

	return (this->ReadByte() << 8) | b;

}

/**

 * Read a double word (32 bits) from the file (in low endian format).

 * @return Read word.

 */

uint32 RandomAccessFile::ReadDword()

{

	uint b = this->ReadWord();

	return (this->ReadWord() << 16) | b;

}

/**

 * Read a block.

 * @param ptr  Destination buffer.

 * @param size Number of bytes to read.

 */

void RandomAccessFile::ReadBlock(void *ptr, size_t size)

{

	this->SeekTo(this->GetPos(), SEEK_SET);

	this->pos += fread(ptr, 1, size, this->file_handle);

}

/**

 * Skip \a n bytes ahead in the file.

 * @param n Number of bytes to skip reading.

 */

void RandomAccessFile::SkipBytes(int n)

{

	int remaining = this->buffer_end - this->buffer;

	if (n <= remaining) {

		this->buffer += n;

	} else {

		this->SeekTo(n, SEEK_CUR);

	}

}

/*

 * This file is part of OpenTTD.

 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.

 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.

 */

 /** @file random_access_file_type.h Class related to random access to files. */

#ifndef RANDOM_ACCESS_FILE_TYPE_H

#define RANDOM_ACCESS_FILE_TYPE_H

#include "fileio_type.h"

#include <string>

/**

 * A file from which bytes, words and double words are read in (potentially) a random order.

 *

 * This is mostly intended to be used for things that can be read from GRFs when needed, so

 * the graphics but also the sounds. This also ties into the spritecache as it uses these

 * files to load the sprites from when needed.

 */

class RandomAccessFile {

	/** The number of bytes to allocate for the buffer. */

	static constexpr int BUFFER_SIZE = 512;

	std::string filename;            ///< Full name of the file; relative path to subdir plus the extension of the file.

	std::string simplified_filename; ///< Simplified lowecase name of the file; only the name, no path or extension.

	FILE *file_handle;               ///< File handle of the open file.

	size_t pos;                      ///< Position in the file of the end of the read buffer.

	byte *buffer;                    ///< Current position within the local buffer.

	byte *buffer_end;                ///< Last valid byte of buffer.

	byte buffer_start[BUFFER_SIZE];  ///< Local buffer when read from file.

public:

	RandomAccessFile(const std::string &filename, Subdirectory subdir);

	RandomAccessFile(const RandomAccessFile&) = delete;

	void operator=(const RandomAccessFile&) = delete;

	virtual ~RandomAccessFile();

	const std::string &GetFilename() const;

	const std::string &GetSimplifiedFilename() const;

	size_t GetPos() const;

	void SeekTo(size_t pos, int mode);

	byte ReadByte();

	uint16 ReadWord();

	uint32 ReadDword();

	void ReadBlock(void *ptr, size_t size);

	void SkipBytes(int n);

};

#endif /* RANDOM_ACCESS_FILE_TYPE_H */