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/* 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/>.
*
*/
// BufferedStream represents a buffered file stream; uses memory buffer
// during read and write operations to limit number reads and writes on disk
// and thus improve i/o performance.
//
// BufferedSectionStream is a subclass stream that limits reading by an
// arbitrary offset range.
#ifndef AGS_SHARED_UTIL_BUFFEREDSTREAM_H
#define AGS_SHARED_UTIL_BUFFEREDSTREAM_H
#include "common/std/vector.h"
#include "ags/shared/util/file_stream.h"
#include "ags/shared/util/file.h" // TODO: extract filestream mode constants
namespace AGS3 {
namespace AGS {
namespace Shared {
class BufferedStream : public FileStream {
public:
// Needs tuning depending on the platform.
static const size_t BufferSize = 1024u * 8;
// The constructor may raise std::runtime_error if
// - there is an issue opening the file (does not exist, locked, permissions, etc)
// - the open mode could not be determined
// - could not determine the length of the stream
// It is recommended to use File::OpenFile to safely construct this object.
BufferedStream(const String &file_name, FileOpenMode open_mode, FileWorkMode work_mode, DataEndianess stream_endianess = kLittleEndian);
~BufferedStream();
// Is end of stream
bool EOS() const override;
// Total length of stream (if known)
soff_t GetLength() const override;
// Current position (if known)
soff_t GetPosition() const override;
void Close() override;
bool Flush() override;
size_t Read(void *buffer, size_t size) override;
int32_t ReadByte() override;
size_t Write(const void *buffer, size_t size) override;
int32_t WriteByte(uint8_t b) override;
soff_t Seek(soff_t offset, StreamSeek origin) override;
protected:
soff_t _start = 0; // valid section starting offset
soff_t _end = -1; // valid section ending offset
private:
// Reads a chunk of file into the buffer, starting from the given offset
void FillBufferFromPosition(soff_t position);
// Writes a buffer into the file, and reposition to the new offset
void FlushBuffer(soff_t position);
soff_t _position = 0; // absolute read/write offset
soff_t _bufferPosition = 0; // buffer's location relative to file
std::vector<uint8_t> _buffer;
};
// Creates a BufferedStream limited by an arbitrary offset range
class BufferedSectionStream : public BufferedStream {
public:
BufferedSectionStream(const String &file_name, soff_t start_pos, soff_t end_pos,
FileOpenMode open_mode, FileWorkMode work_mode, DataEndianess stream_endianess = kLittleEndian);
};
} // namespace Shared
} // namespace AGS
} // namespace AGS3
#endif
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