COMMON: Document the BitStream a bit more

1 files changed, 73 insertions, 7 deletions

diff --git a/common/bitstream.h b/common/bitstream.h
index d9610b269a..7be0dccf45 100644
--- a/common/bitstream.h
+++ b/common/bitstream.h
@@ -32,7 +32,7 @@ namespace Common {
 class SeekableReadStream;
 
 /**
- * A bit stream.
+ * A bit stream, giving access to data one bit at a time.
  *
  * Used in engines:
  *  - scumm
@@ -42,33 +42,66 @@ public:
 	BitStream();
 	virtual ~BitStream();
 
-	/** Read a bit. */
+	/** Read a bit from the bitstream. */
 	virtual uint32 getBit() = 0;
 
-	/** Read a number of bits. */
+	/** Read a number of bits, creating a multi-bit value. */
 	virtual uint32 getBits(uint32 n) = 0;
 
-	/** Adding another bit. */
+	/** Add more bits, creating a multi-bit value in stages. */
 	virtual void addBit(uint32 &x, uint32 n) = 0;
 
 	/** Skip a number of bits. */
 	void skip(uint32 n);
 
-	/** Get the current position. */
+	/** Get the current position, in bits. */
 	virtual uint32 pos()  const = 0;
 	/** Return the number of bits in the stream. */
 	virtual uint32 size() const = 0;
 };
 
-/** A big endian bit stream. */
+/**
+ * A big-endian bit stream.
+ *
+ * The input data is read one byte at a time. Their bits are handed out
+ * in the order of MSB to LSB. When all 8 bits of a byte have been consumed,
+ * another input data byte is read.
+ */
 class BitStreamBE : public BitStream {
 public:
+	/**
+	 * Create a big endian bit stream.
+	 *
+	 * Reads and copies bitCount bits from the provided stream.
+	 * Ownership of the stream is not transferred.
+	 */
 	BitStreamBE(SeekableReadStream &stream, uint32 bitCount);
+
+	/**
+	 * Create a big endian bit stream.
+	 *
+	 * Reads and copies bitCount bits from the provided data.
+	 * Ownership of the data is not transferred.
+	 */
 	BitStreamBE(const byte *data, uint32 bitCount);
+
 	~BitStreamBE();
 
 	uint32 getBit();
+
+	/**
+	 * Read a number of bits, creating a multi-bit value.
+	 *
+	 * The bits are read one at a time, in the order MSB to LSB and
+	 * or'd together to create a multi-bit value.
+	 */
 	uint32 getBits(uint32 n);
+
+	/**
+	 * Add more bits, creating a multi-bit value in stages.
+	 *
+	 * Shifts in n new bits into the value x, in the order of MSB to LSB.
+	 */
 	void addBit(uint32 &x, uint32 n);
 
 	uint32 pos()  const;
@@ -81,15 +114,48 @@ private:
 	uint8 _inValue; ///< Position within the current byte.
 };
 
-/** A 32bit little endian bit stream. */
+/**
+ * A little-endian bit stream, reading 32bit values at a time.
+ *
+ * The input data is read one little-endian uint32 at a time. Their bits are
+ * handed out in the order of LSB to MSB. When all 8 bits of a byte have been
+ * consumed, another little-endian input data uint32 is read.
+ */
 class BitStream32LE : public BitStream {
 public:
+	/**
+	 * Create a little-endian bit stream.
+	 *
+	 * Reads and copies bitCount bits from the provided stream.
+	 * Ownership of the stream is not transferred.
+	 */
 	BitStream32LE(SeekableReadStream &stream, uint32 bitCount);
+
+	/**
+	 * Create a little-endian bit stream.
+	 *
+	 * Reads and copies bitCount bits from the provided data.
+	 * Ownership of the data is not transferred.
+	 */
 	BitStream32LE(const byte *data, uint32 bitCount);
+
 	~BitStream32LE();
 
 	uint32 getBit();
+
+	/**
+	 * Read a number of bits, creating a multi-bit value.
+	 *
+	 * The bits are read one at a time, in the order LSB to MSB and
+	 * or'd together to create a multi-bit value.
+	 */
 	uint32 getBits(uint32 n);
+
+	/**
+	 * Add more bits, creating a multi-bit value in stages.
+	 *
+	 * Shifts in n new bits into the value x, in the order of LSB to MSB.
+	 */
 	void addBit(uint32 &x, uint32 n);
 
 	uint32 pos()  const;