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engines/ags/shared/util/data_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/>.
+ *
+ */
+
+//=============================================================================
+//
+// Standard AGS stream implementation for reading raw data with support for
+// converting to opposite endianess. Most I/O devices should inherit this
+// class and provide implementation for basic reading and writing only.
+//
+//=============================================================================
+
+#ifndef AGS_SHARED_UTIL_DATASTREAM_H
+#define AGS_SHARED_UTIL_DATASTREAM_H
+
+#include "ags/shared/util/bbop.h"
+#include "ags/shared/util/stream.h"
+
+namespace AGS3 {
+namespace AGS {
+namespace Shared {
+
+class DataStream : public Stream {
+public:
+	DataStream(DataEndianess stream_endianess = kLittleEndian);
+	~DataStream() override;
+
+	int16_t ReadInt16() override;
+	int32_t ReadInt32() override;
+	int64_t ReadInt64() override;
+
+	//
+	// Read- and WriteArray methods return number of full elements (NOT bytes)
+	// read or written, or -1 if end of stream is reached
+	//
+	// Note that ReadArray and WriteArray do NOT convert byte order even when
+	// work with data of different endianess; they are meant for optimal
+	// reading and writing blocks of raw bytes
+	inline size_t ReadArray(void *buffer, size_t elem_size, size_t count) override {
+		return Read(buffer, elem_size * count) / elem_size;
+	}
+
+	inline size_t ReadArrayOfInt16(int16_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   ReadAndConvertArrayOfInt16(buffer, count) : ReadArray(buffer, sizeof(int16_t), count);
+	}
+
+	inline size_t ReadArrayOfInt32(int32_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   ReadAndConvertArrayOfInt32(buffer, count) : ReadArray(buffer, sizeof(int32_t), count);
+	}
+
+	inline size_t ReadArrayOfInt64(int64_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   ReadAndConvertArrayOfInt64(buffer, count) : ReadArray(buffer, sizeof(int64_t), count);
+	}
+
+	size_t  WriteInt16(int16_t val) override;
+	size_t  WriteInt32(int32_t val) override;
+	size_t  WriteInt64(int64_t val) override;
+
+	inline size_t WriteArray(const void *buffer, size_t elem_size, size_t count) override {
+		return Write(buffer, elem_size * count) / elem_size;
+	}
+
+	inline size_t WriteArrayOfInt16(const int16_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   WriteAndConvertArrayOfInt16(buffer, count) : WriteArray(buffer, sizeof(int16_t), count);
+	}
+
+	inline size_t WriteArrayOfInt32(const int32_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   WriteAndConvertArrayOfInt32(buffer, count) : WriteArray(buffer, sizeof(int32_t), count);
+	}
+
+	inline size_t WriteArrayOfInt64(const int64_t *buffer, size_t count) override {
+		return MustSwapBytes() ?
+			   WriteAndConvertArrayOfInt64(buffer, count) : WriteArray(buffer, sizeof(int64_t), count);
+	}
+
+	protected:
+	DataEndianess _streamEndianess;
+
+	// Helper methods for reading/writing arrays of basic types and
+	// converting their elements to opposite endianess (swapping bytes).
+	size_t  ReadAndConvertArrayOfInt16(int16_t *buffer, size_t count);
+	size_t  ReadAndConvertArrayOfInt32(int32_t *buffer, size_t count);
+	size_t  ReadAndConvertArrayOfInt64(int64_t *buffer, size_t count);
+	size_t  WriteAndConvertArrayOfInt16(const int16_t *buffer, size_t count);
+	size_t  WriteAndConvertArrayOfInt32(const int32_t *buffer, size_t count);
+	size_t  WriteAndConvertArrayOfInt64(const int64_t *buffer, size_t count);
+
+	inline bool MustSwapBytes() {
+		return kDefaultSystemEndianess != _streamEndianess;
+	}
+
+	inline void ConvertInt16(int16_t &val) {
+		if (MustSwapBytes()) val = BBOp::SwapBytesInt16(val);
+	}
+	inline void ConvertInt32(int32_t &val) {
+		if (MustSwapBytes()) val = BBOp::SwapBytesInt32(val);
+	}
+	inline void ConvertInt64(int64_t &val) {
+		if (MustSwapBytes()) val = BBOp::SwapBytesInt64(val);
+	}
+};
+
+//
+// DataStreamSection wraps another stream and restricts its access
+// to a particular range of offsets of the base stream.
+// StreamSection does NOT own the base stream, and closing
+// a "stream section" does NOT close the base stream.
+// Base stream must stay in memory for as long as there are
+// "stream sections" referring it.
+class DataStreamSection : public DataStream {
+public:
+	// Constructs a StreamSection over a base stream,
+	// restricting working range to [start, end), i.e. end offset is
+	// +1 past allowed position.
+	DataStreamSection(Stream *base, soff_t start, soff_t end);
+	const char *GetPath() const { return _base->GetPath().GetCStr(); }
+	bool EOS() const override { return _position >= _end; }
+	bool GetError() const override { return _base->GetError(); }
+	soff_t GetLength() const override { return _end - _start; }
+	soff_t GetPosition() const override { return _position - _start; }
+	size_t Read(void *buffer, size_t len) override;
+	int32_t ReadByte() override;
+	size_t Write(const void *buffer, size_t len) override;
+	int32_t WriteByte(uint8_t b) override;
+	soff_t Seek(soff_t offset, StreamSeek origin = kSeekCurrent) override;
+	bool Flush() override { return _base->Flush(); }
+	void Close() override;
+
+private:
+	Stream *_base = nullptr;
+	soff_t _start = 0;
+	soff_t _end = 0;
+	soff_t _position = 0;
+};
+
+} // namespace Shared
+} // namespace AGS
+} // namespace AGS3
+
+#endif