substream.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * 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, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef COMMON_SUBSTREAM_H
#define COMMON_SUBSTREAM_H

#include "common/mutex.h"
#include "common/ptr.h"
#include "common/stream.h"
#include "common/types.h"

namespace Common {

class SubReadStream : virtual public ReadStream {
protected:
    DisposablePtr<ReadStream> _parentStream;
    uint32 _pos;
    uint32 _end;
    bool _eos;
public:
    SubReadStream(ReadStream *parentStream, uint32 end, DisposeAfterUse::Flag disposeParentStream = DisposeAfterUse::NO)
        : _parentStream(parentStream, disposeParentStream),
          _pos(0),
          _end(end),
          _eos(false) {
        assert(parentStream);
    }

    bool eos() const override { return _eos || _parentStream->eos(); }
    bool err() const override { return _parentStream->err(); }
    void clearErr() override { _eos = false; _parentStream->clearErr(); }
    uint32 read(void *dataPtr, uint32 dataSize) override;
};

/*
 * SeekableSubReadStream provides access to a SeekableReadStream restricted to
 * the range [begin, end).
 * The same caveats apply to SeekableSubReadStream as do to SeekableReadStream.
 *
 * Manipulating the parent stream directly /will/ mess up a substream.
 * @see SubReadStream
 */
class SeekableSubReadStream : public SubReadStream, virtual public SeekableReadStream {
protected:
    SeekableReadStream *_parentStream;
    uint32 _begin;
public:
    SeekableSubReadStream(SeekableReadStream *parentStream, uint32 begin, uint32 end, DisposeAfterUse::Flag disposeParentStream = DisposeAfterUse::NO);

    int64 pos() const override { return _pos - _begin; }
    int64 size() const override { return _end - _begin; }

    bool seek(int64 offset, int whence = SEEK_SET) override;
};

class SafeSeekableSubReadStream : public SeekableSubReadStream {
public:
    SafeSeekableSubReadStream(SeekableReadStream *parentStream, uint32 begin, uint32 end, DisposeAfterUse::Flag disposeParentStream = DisposeAfterUse::NO)
        : SeekableSubReadStream(parentStream, begin, end, disposeParentStream) {
    }

    uint32 read(void *dataPtr, uint32 dataSize) override;
};

class SafeMutexedSeekableSubReadStream : public Common::SafeSeekableSubReadStream {
public:
    SafeMutexedSeekableSubReadStream(SeekableReadStream *parentStream, uint32 begin, uint32 end, DisposeAfterUse::Flag disposeParentStream,
        Common::Mutex &mutex)
        : SafeSeekableSubReadStream(parentStream, begin, end, disposeParentStream), _mutex(mutex) {
    }
    uint32 read(void *dataPtr, uint32 dataSize) override;
protected:
    Common::Mutex &_mutex;
};

} // End of namespace Common

#endif