stream.h

/* smushplay - A simple LucasArts SMUSH video player
 *
 * smushplay is the legal property of its developers, whose names can be
 * found in the AUTHORS file distributed with this source
 * distribution.
 *
 * This program 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; either version 3
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

// Based on ScummVM Stream classes (GPLv2+)

#ifndef STREAM_H
#define STREAM_H

#include "util.h"

/**
 * Virtual base class for both ReadStream and WriteStream.
 */
class Stream {
public:
	virtual ~Stream() {}

	/**
	 * Returns true if an I/O failure occurred.
	 * This flag is never cleared automatically. In order to clear it,
	 * client code has to call clearErr() explicitly.
	 *
	 * @note The semantics of any implementation of this method are
	 * supposed to match those of ISO C ferror().
	 */
	virtual bool err() const { return false; }

	/**
	 * Reset the I/O error status as returned by err().
	 * For a ReadStream, also reset the end-of-stream status returned by eos().
	 *
	 * @note The semantics of any implementation of this method are
	 * supposed to match those of ISO C clearerr().
	 */
	virtual void clearErr() {}
};

/**
 * Generic interface for a readable data stream.
 */
class ReadStream : virtual public Stream {
public:
	/**
	 * Returns true if a read failed because the stream end has been reached.
	 * This flag is cleared by clearErr().
	 * For a SeekableReadStream, it is also cleared by a successful seek.
	 *
	 * @note The semantics of any implementation of this method are
	 * supposed to match those of ISO C feof(). In particular, in a stream
	 * with N bytes, reading exactly N bytes from the start should *not*
	 * set eos; only reading *beyond* the available data should set it.
	 */
	virtual bool eos() const = 0;

	/**
	 * Read data from the stream. Subclasses must implement this
	 * method; all other read methods are implemented using it.
	 *
	 * @note The semantics of any implementation of this method are
	 * supposed to match those of ISO C fread(), in particular where
	 * it concerns setting error and end of file/stream flags.
	 *
	 * @param dataPtr	pointer to a buffer into which the data is read
	 * @param dataSize	number of bytes to be read
	 * @return the number of bytes which were actually read.
	 */
	virtual uint32 read(void *dataPtr, uint32 dataSize) = 0;


	// The remaining methods all have default implementations; subclasses
	// in general should not overload them.

	/**
	 * Read an unsigned byte from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	byte readByte() {
		byte b = 0; // FIXME: remove initialisation
		read(&b, 1);
		return b;
	}

	/**
	 * Read a signed byte from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	inline int8 readSByte() {
		return (int8)readByte();
	}

	/**
	 * Read an unsigned 16-bit word stored in little endian (LSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	uint16 readUint16LE() {
		uint16 val;
		read(&val, 2);
		return FROM_LE_16(val);
	}

	/**
	 * Read an unsigned 32-bit word stored in little endian (LSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	uint32 readUint32LE() {
		uint32 val;
		read(&val, 4);
		return FROM_LE_32(val);
	}

	/**
	 * Read an unsigned 16-bit word stored in big endian (MSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	uint16 readUint16BE() {
		uint16 val;
		read(&val, 2);
		return FROM_BE_16(val);
	}

	/**
	 * Read an unsigned 32-bit word stored in big endian (MSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	uint32 readUint32BE() {
		uint32 val;
		read(&val, 4);
		return FROM_BE_32(val);
	}

	/**
	 * Read a signed 16-bit word stored in little endian (LSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	inline int16 readSint16LE() {
		return (int16)readUint16LE();
	}

	/**
	 * Read a signed 32-bit word stored in little endian (LSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	inline int32 readSint32LE() {
		return (int32)readUint32LE();
	}

	/**
	 * Read a signed 16-bit word stored in big endian (MSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	inline int16 readSint16BE() {
		return (int16)readUint16BE();
	}

	/**
	 * Read a signed 32-bit word stored in big endian (MSB first) order
	 * from the stream and return it.
	 * Performs no error checking. The return value is undefined
	 * if a read error occurred (for which client code can check by
	 * calling err() and eos() ).
	 */
	inline int32 readSint32BE() {
		return (int32)readUint32BE();
	}
};


/**
 * Interface for a seekable & readable data stream.
 *
 * @todo Get rid of SEEK_SET, SEEK_CUR, or SEEK_END, use our own constants
 */
class SeekableReadStream : virtual public ReadStream {
public:
	/**
	 * Obtains the current value of the stream position indicator of the
	 * stream.
	 *
	 * @return the current position indicator, or -1 if an error occurred.
	 */
	virtual int32 pos() const = 0;

	/**
	 * Obtains the total size of the stream, measured in bytes.
	 * If this value is unknown or can not be computed, -1 is returned.
	 *
	 * @return the size of the stream, or -1 if an error occurred
	 */
	virtual int32 size() const = 0;

	/**
	 * Sets the stream position indicator for the stream. The new position,
	 * measured in bytes, is obtained by adding offset bytes to the position
	 * specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or
	 * SEEK_END, the offset is relative to the start of the file, the current
	 * position indicator, or end-of-file, respectively. A successful call
	 * to the seek() method clears the end-of-file indicator for the stream.
	 *
	 * @note The semantics of any implementation of this method are
	 * supposed to match those of ISO C fseek().
	 *
	 * @param offset	the relative offset in bytes
	 * @param whence	the seek reference: SEEK_SET, SEEK_CUR, or SEEK_END
	 * @return true on success, false in case of a failure
	 */
	virtual bool seek(int32 offset, int whence = SEEK_SET) = 0;
};

/**
 * Simple memory based 'stream', which implements the SeekableReadStream interface for
 * a plain memory block.
 */
class MemoryReadStream : public SeekableReadStream {
public:
	/**
	 * This constructor takes a pointer to a memory buffer and a length, and
	 * wraps it. If disposeMemory is true, the MemoryReadStream takes ownership
	 * of the buffer and hence deletes it when destructed.
	 */
	MemoryReadStream(const byte *dataPtr, uint32 dataSize, bool disposeMemory = false) :
		_ptrOrig(dataPtr),
		_ptr(dataPtr),
		_size(dataSize),
		_pos(0),
		_disposeMemory(disposeMemory),
		_eos(false) {}

	~MemoryReadStream() {
		if (_disposeMemory)
			delete[] const_cast<byte *>(_ptrOrig);
	}

	uint32 read(void *dataPtr, uint32 dataSize);

	bool eos() const { return _eos; }
	void clearErr() { _eos = false; }

	int32 pos() const { return _pos; }
	int32 size() const { return _size; }

	bool seek(int32 offs, int whence = SEEK_SET);

private:
	const byte * const _ptrOrig;
	const byte *_ptr;
	const uint32 _size;
	uint32 _pos;
	bool _disposeMemory;
	bool _eos;
};

/** Open a file with a given path. */
SeekableReadStream *createReadStream(const char *pathName);

/**
 * Take an arbitrary SeekableReadStream and wrap it in a custom stream which
 * provides transparent on-the-fly decompression. Assumes the data it
 * retrieves from the wrapped stream to be either uncompressed or in gzip
 * format. In the former case, the original stream is returned unmodified
 * (and in particular, not wrapped).
 *
 * It is safe to call this with a NULL parameter (in this case, NULL is
 * returned).
 *
 * @param toBeWrapped	the stream to be wrapped (if it is in gzip-format)
 */
SeekableReadStream *wrapCompressedReadStream(SeekableReadStream *toBeWrapped);

#endif