98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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// BufferedStream represents a buffered file stream; uses memory buffer
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// during read and write operations to limit number reads and writes on disk
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// and thus improve i/o performance.
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//
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// BufferedSectionStream is a subclass stream that limits reading by an
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// arbitrary offset range.
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#ifndef AGS_SHARED_UTIL_BUFFEREDSTREAM_H
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#define AGS_SHARED_UTIL_BUFFEREDSTREAM_H
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#include "common/std/vector.h"
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#include "ags/shared/util/file_stream.h"
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#include "ags/shared/util/file.h" // TODO: extract filestream mode constants
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namespace AGS3 {
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namespace AGS {
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namespace Shared {
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class BufferedStream : public FileStream {
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public:
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// Needs tuning depending on the platform.
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static const size_t BufferSize = 1024u * 8;
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// The constructor may raise std::runtime_error if
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// - there is an issue opening the file (does not exist, locked, permissions, etc)
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// - the open mode could not be determined
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// - could not determine the length of the stream
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// It is recommended to use File::OpenFile to safely construct this object.
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BufferedStream(const String &file_name, FileOpenMode open_mode, FileWorkMode work_mode, DataEndianess stream_endianess = kLittleEndian);
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~BufferedStream();
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// Is end of stream
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bool EOS() const override;
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// Total length of stream (if known)
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soff_t GetLength() const override;
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// Current position (if known)
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soff_t GetPosition() const override;
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void Close() override;
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bool Flush() override;
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size_t Read(void *buffer, size_t size) override;
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int32_t ReadByte() override;
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size_t Write(const void *buffer, size_t size) override;
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int32_t WriteByte(uint8_t b) override;
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soff_t Seek(soff_t offset, StreamSeek origin) override;
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protected:
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soff_t _start = 0; // valid section starting offset
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soff_t _end = -1; // valid section ending offset
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private:
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// Reads a chunk of file into the buffer, starting from the given offset
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void FillBufferFromPosition(soff_t position);
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// Writes a buffer into the file, and reposition to the new offset
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void FlushBuffer(soff_t position);
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soff_t _position = 0; // absolute read/write offset
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soff_t _bufferPosition = 0; // buffer's location relative to file
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std::vector<uint8_t> _buffer;
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};
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// Creates a BufferedStream limited by an arbitrary offset range
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class BufferedSectionStream : public BufferedStream {
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public:
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BufferedSectionStream(const String &file_name, soff_t start_pos, soff_t end_pos,
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FileOpenMode open_mode, FileWorkMode work_mode, DataEndianess stream_endianess = kLittleEndian);
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};
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} // namespace Shared
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} // namespace AGS
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} // namespace AGS3
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#endif
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