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stream.h

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2004-2005 The ScummVM project
 *
 * 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 2
 * 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.
 *
 * $Header: /cvsroot/scummvm/scummvm/common/stream.h,v 1.23.2.1 2005/10/18 02:11:18 sev Exp $
 *
 */

#ifndef COMMON_STREAM_H
#define COMMON_STREAM_H

#include "common/stdafx.h"
#include "common/scummsys.h"

namespace Common {

class String;

/**
 * Virtual base class for both ReadStream and WriteStream.
 */
00035 class Stream {
public:
      virtual ~Stream() {}

      /**
       * Returns true if any I/O failure occured.
       * This flag is never cleared automatically. In order to clear it,
       * client code has to call clearIOFailed() explicitly.
       *
       * @todo Instead of returning a plain bool, maybe we should define
       *       a list of error codes which can be returned here.
       */
00047       virtual bool ioFailed() const { return false; }

      /**
       * Reset the I/O error status.
       */
00052       virtual void clearIOFailed() {}
};

/**
 * Generic interface for a writable data stream.
 */
00058 class WriteStream : virtual public Stream {
public:
      /**
       * Write data into the stream. Subclasses must implement this
       * method; all other write methods are implemented using it.
       *
       * @param dataPtr pointer to the data to be written
       * @param dataSize      number of bytes to be written
       * @return the number of bytes which were actually written.
       */
      virtual uint32 write(const void *dataPtr, uint32 dataSize) = 0;

      /**
       * Commit any buffered data to the underlying channel or
       * storage medium; unbuffered streams can use the default
       * implementation.
       */
00075       virtual void flush() {}

      // The remaining methods all have default implementations; subclasses
      // need not (and should not) overload them.

      void writeByte(byte value) {
            write(&value, 1);
      }

      void writeSByte(int8 value) {
            write(&value, 1);
      }

      void writeUint16LE(uint16 value) {
            writeByte((byte)(value & 0xff));
            writeByte((byte)(value >> 8));
      }

      void writeUint32LE(uint32 value) {
            writeUint16LE((uint16)(value & 0xffff));
            writeUint16LE((uint16)(value >> 16));
      }

      void writeUint16BE(uint16 value) {
            writeByte((byte)(value >> 8));
            writeByte((byte)(value & 0xff));
      }

      void writeUint32BE(uint32 value) {
            writeUint16BE((uint16)(value >> 16));
            writeUint16BE((uint16)(value & 0xffff));
      }

      void writeSint16LE(int16 value) {
            writeUint16LE((uint16)value);
      }

      void writeSint32LE(int32 value) {
            writeUint32LE((uint32)value);
      }

      void writeSint16BE(int16 value) {
            writeUint16BE((uint16)value);
      }

      void writeSint32BE(int32 value) {
            writeUint32BE((uint32)value);
      }

      void writeString(const String &str);
};


/**
 * Generic interface for a readable data stream.
 */
00131 class ReadStream : virtual public Stream {
public:
      /**
       * Returns true if the end of the stream has been reached.
       */
      virtual bool eos() const = 0;

      /**
       * Read data from the stream. Subclasses must implement this
       * method; all other read methods are implemented using it.
       *
       * @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
      // need not (and should not) overload them.

      byte readByte() {
            byte b = 0;
            read(&b, 1);
            return b;
      }

      int8 readSByte() {
            int8 b = 0;
            read(&b, 1);
            return b;
      }

      uint16 readUint16LE() {
            uint16 a = readByte();
            uint16 b = readByte();
            return a | (b << 8);
      }

      uint32 readUint32LE() {
            uint32 a = readUint16LE();
            uint32 b = readUint16LE();
            return (b << 16) | a;
      }

      uint16 readUint16BE() {
            uint16 b = readByte();
            uint16 a = readByte();
            return a | (b << 8);
      }

      uint32 readUint32BE() {
            uint32 b = readUint16BE();
            uint32 a = readUint16BE();
            return (b << 16) | a;
      }

      int16 readSint16LE() {
            return (int16)readUint16LE();
      }

      int32 readSint32LE() {
            return (int32)readUint32LE();
      }

      int16 readSint16BE() {
            return (int16)readUint16BE();
      }

      int32 readSint32BE() {
            return (int32)readUint32BE();
      }
};


/**
 * Interface for a seekable & readable data stream.
 *
 * @todo We really need better error handling here!
 *       Like seek should somehow indicate whether it failed.
 */
00212 class SeekableReadStream : public ReadStream {
public:

      virtual uint32 pos() const = 0;
      virtual uint32 size() const = 0;

      virtual void seek(int32 offs, int whence = SEEK_SET) = 0;

      /**
       * Read one line of text from a CR or CR/LF terminated plain text file.
       * This method is a rough analog of the (f)gets function.
       *
       * @param buf     the buffer to store into
       * @param bufSize the size of the buffer
       * @return a pointer to the read string, or NULL if an error occured
       * @note The line terminator (CR or CR/LF) is stripped and not inserted
       *       into the buffer.
       */
      virtual char *readLine(char *buf, size_t bufSize);
};


/**
 * XORReadStream is a wrapper around an arbitrary other ReadStream,
 * which 'decrypts' the data being read by XORing all data bytes with the given
 * encryption 'key'.
 *
 * Currently, this is not used anywhere, it's just a demo of how one can chain
 * streams if necessary.
 */
00242 class XORReadStream : public ReadStream {
private:
      byte _encbyte;
      ReadStream *_realStream;
public:
      XORReadStream(ReadStream *in = 0, byte enc = 0) :  _encbyte(enc), _realStream(in) {}
      void setStream(ReadStream *in) { _realStream = in; }
      void setEnc(byte value) { _encbyte = value; }

00251       virtual bool eos() const { return _realStream->eos(); }
00252       virtual bool ioFailed() const { return _realStream->ioFailed(); }
00253       virtual void clearIOFailed() { _realStream->clearIOFailed(); }

00255       uint32 read(void *dataPtr, uint32 dataSize) {
            assert(_realStream);
            uint32 len = _realStream->read(dataPtr, dataSize);
            if (_encbyte) {
                  byte *p = (byte *)dataPtr;
                  byte *end = p + len;
                  while (p < end)
                        *p++ ^= _encbyte;
            }
            return len;
      }
};

/**
 * Simple memory based 'stream', which implements the ReadStream interface for
 * a plain memory block.
 */
00272 class MemoryReadStream : public SeekableReadStream {
private:
      const byte *_ptr;
      const byte * const _ptrOrig;
      const uint32 _bufSize;
      uint32 _pos;
      byte _encbyte;

public:
      MemoryReadStream(const byte *buf, uint32 len) : _ptr(buf), _ptrOrig(buf), _bufSize(len), _pos(0), _encbyte(0) {}

      void setEnc(byte value) { _encbyte = value; }

00285       uint32 read(void *dataPtr, uint32 dataSize) {
            // Read at most as many bytes as are still available...
            if (dataSize > _bufSize - _pos)
                  dataSize = _bufSize - _pos;
            memcpy(dataPtr, _ptr, dataSize);

            if (_encbyte) {
                  byte *p = (byte *)dataPtr;
                  byte *end = p + dataSize;
                  while (p < end)
                        *p++ ^= _encbyte;
            }

            _ptr += dataSize;
            _pos += dataSize;

            return dataSize;
      }

00304       bool eos() const { return _pos == _bufSize; }
      uint32 pos() const { return _pos; }
      uint32 size() const { return _bufSize; }

      void seek(int32 offs, int whence = SEEK_SET);
};

/**
 * Simple memory based 'stream', which implements the WriteStream interface for
 * a plain memory block.
 */
00315 class MemoryWriteStream : public WriteStream {
private:
      byte *_ptr;
      const byte * const _ptrOrig;
      const uint32 _bufSize;
      uint32 _pos;
public:
      MemoryWriteStream(byte *buf, uint32 len) : _ptr(buf), _ptrOrig(buf), _bufSize(len), _pos(0) {}

00324       uint32 write(const void *dataPtr, uint32 dataSize) {
            // Write at most as many bytes as are still available...
            if (dataSize > _bufSize - _pos)
                  dataSize = _bufSize - _pos;
            memcpy(_ptr, dataPtr, dataSize);
            _ptr += dataSize;
            _pos += dataSize;
            return dataSize;
      }

      bool eos() const { return _pos == _bufSize; }
      uint32 pos() const { return _pos; }
      uint32 size() const { return _bufSize; }
};

}     // End of namespace Common

#endif

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