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engines/ags/shared/util/memory_stream.h

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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/>.
+ *
+ */
+
+ //=============================================================================
+ //
+ // MemoryStream does reading and writing over the buffer of bytes stored in
+ // memory. Currently has rather trivial implementation. Does not own a buffer
+ // itself, but works with the provided C-buffer pointer, which means that the
+ // buffer object *must* persist until stream is closed.
+ //
+ // VectorStream is a specialized implementation that works with std::vector.
+ // Unlike base MemoryStream provides continiously resizing buffer for writing.
+ // TODO: separate StringStream for reading & writing String object?
+ //
+ //=============================================================================
+
+#ifndef AGS_SHARED_UTIL_MEMORY_STREAM_H
+#define AGS_SHARED_UTIL_MEMORY_STREAM_H
+
+#include "common/std/vector.h"
+#include "ags/shared/util/data_stream.h"
+#include "ags/shared/util/string.h"
+
+namespace AGS3 {
+namespace AGS {
+namespace Shared {
+
+class MemoryStream : public DataStream {
+public:
+	// Construct memory stream in the read-only mode over a const C-buffer;
+	// reading will never exceed buf_sz bytes;
+	// buffer must persist in memory until the stream is closed.
+	MemoryStream(const uint8_t *cbuf, size_t buf_sz, DataEndianess stream_endianess = kLittleEndian);
+	// Construct memory stream in the chosen mode over a given C-buffer;
+	// neither reading nor writing will ever exceed buf_sz bytes;
+	// buffer must persist in memory until the stream is closed.
+	MemoryStream(uint8_t *buf, size_t buf_sz, StreamWorkMode mode, DataEndianess stream_endianess = kLittleEndian);
+	~MemoryStream() override {}
+
+	void    Close() override;
+	bool    Flush() override;
+
+	// Is stream valid (underlying data initialized properly)
+	bool    IsValid() const override;
+	// 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;
+	bool    CanRead() const override;
+	bool    CanWrite() const override;
+	bool    CanSeek() const 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:
+	const uint8_t           *_cbuf = nullptr; // readonly buffer ptr
+	size_t                   _buf_sz = 0u; // hard buffer limit
+	size_t                   _len = 0u; // calculated length of stream
+	const StreamWorkMode     _mode;
+	size_t                   _pos = 0u; // current stream pos
+
+private:
+	uint8_t                 *_buf = nullptr; // writeable buffer ptr
+};
+
+
+class VectorStream : public MemoryStream {
+public:
+	// Construct memory stream in the read-only mode over a const std::vector;
+	// vector must persist in memory until the stream is closed.
+	VectorStream(const std::vector<uint8_t> &cbuf, DataEndianess stream_endianess = kLittleEndian);
+	// Construct memory stream in the chosen mode over a given std::vector;
+	// vector must persist in memory until the stream is closed.
+	VectorStream(std::vector<uint8_t> &buf, StreamWorkMode mode, DataEndianess stream_endianess = kLittleEndian);
+	~VectorStream() override {}
+
+	void    Close() override;
+
+	bool    CanRead() const override;
+	bool    CanWrite() const override;
+
+	size_t  Write(const void *buffer, size_t size) override;
+	int32_t WriteByte(uint8_t b) override;
+
+private:
+	std::vector<uint8_t> *_vec = nullptr; // writeable vector (may be null)
+};
+
+} // namespace Shared
+} // namespace AGS
+} // namespace AGS3
+
+#endif