COMMON: Add a BitStream class

Based on eos' BitStream

1 files changed, 102 insertions, 0 deletions

diff --git a/common/bitstream.h b/common/bitstream.h
new file mode 100644
index 0000000000..99aec252a3
--- /dev/null
+++ b/common/bitstream.h
@@ -0,0 +1,102 @@
+/* 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 2
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+// Based on eos' BitStream implementation
+
+#ifndef COMMON_BITSTREAM_H
+#define COMMON_BITSTREAM_H
+
+#include "common/scummsys.h"
+
+namespace Common {
+
+class SeekableReadStream;
+
+/** A bit stream. */
+class BitStream {
+public:
+	BitStream();
+	virtual ~BitStream();
+
+	/** Read a bit. */
+	virtual uint32 getBit() = 0;
+
+	/** Read a number of bits. */
+	virtual uint32 getBits(uint32 n) = 0;
+
+	/** Adding another bit. */
+	virtual void addBit(uint32 &x, uint32 n) = 0;
+
+	/** Skip a number of bits. */
+	void skip(uint32 n);
+
+	/** Get the current position. */
+	virtual uint32 pos()  const = 0;
+	/** Return the number of bits in the stream. */
+	virtual uint32 size() const = 0;
+};
+
+/** A big endian bit stream. */
+class BitStreamBE : public BitStream {
+public:
+	BitStreamBE(SeekableReadStream &stream, uint32 bitCount);
+	BitStreamBE(const byte *data, uint32 bitCount);
+	~BitStreamBE();
+
+	uint32 getBit();
+	uint32 getBits(uint32 n);
+	void addBit(uint32 &x, uint32 n);
+
+	uint32 pos()  const;
+	uint32 size() const;
+
+private:
+	SeekableReadStream *_stream;
+
+	byte  _value;   ///< Current byte.
+	uint8 _inValue; ///< Position within the current byte.
+};
+
+/** A 32bit little endian bit stream. */
+class BitStream32LE : public BitStream {
+public:
+	BitStream32LE(SeekableReadStream &stream, uint32 bitCount);
+	BitStream32LE(const byte *data, uint32 bitCount);
+	~BitStream32LE();
+
+	uint32 getBit();
+	uint32 getBits(uint32 n);
+	void addBit(uint32 &x, uint32 n);
+
+	uint32 pos()  const;
+	uint32 size() const;
+
+private:
+	SeekableReadStream *_stream;
+
+	uint32 _value;   ///< Current 32bit value.
+	uint8  _inValue; ///< Position within the current 32bit value.
+};
+
+} // End of namespace Common
+
+#endif // COMMON_BITSTREAM_H