diff options
Diffstat (limited to 'common')
| -rw-r--r-- | common/bitstream.h | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/common/bitstream.h b/common/bitstream.h index 61ec4abc76..c8c8c11fca 100644 --- a/common/bitstream.h +++ b/common/bitstream.h @@ -64,7 +64,7 @@ public: /** Read a multi-bit value from the bit stream, without changing the stream's position. */ virtual uint32 peekBits(uint8 n) = 0; - /** Add a bit to the value x, making it an n-bit value. */ + /** Add a bit to the value x, making it an n+1-bit value. */ virtual void addBit(uint32 &x, uint32 n) = 0; protected: @@ -76,7 +76,7 @@ protected: * A template implementing a bit stream for different data memory layouts. * * Such a bit stream reads valueBits-wide values from the data stream and - * gives * access to their bits, one at a time. + * gives access to their bits, one at a time. * * For example, a bit stream with the layout parameters 32, true, false * for valueBits, isLE and isMSB2LSB, reads 32bit little-endian values @@ -174,7 +174,16 @@ public: return b; } - /** Read a multi-bit value from the bit stream. */ + /** + * Read a multi-bit value from the bit stream. + * + * The value is read as if just taken as a whole from the bitstream. + * + * For example: + * Reading a 4-bit value from an 8-bit bitstream with the contents 01010011: + * If the bitstream is MSB2LSB, the 4-bit value would be 0101. + * If the bitstream is LSB2MSB, the 4-bit value would be 0011. + */ uint32 getBits(uint8 n) { if (n == 0) return 0; @@ -198,6 +207,7 @@ public: return v; } + /** Read a bit from the bit stream, without changing the stream's position. */ uint32 peekBit() { uint32 value = _value; uint8 inValue = _inValue; @@ -212,6 +222,11 @@ public: return v; } + /** + * Read a multi-bit value from the bit stream, without changing the stream's position. + * + * The bit order is the same as in getBits(). + */ uint32 peekBits(uint8 n) { uint32 value = _value; uint8 inValue = _inValue; @@ -226,7 +241,17 @@ public: return v; } - /** Add a bit to the value x, making it an n-bit value. */ + /** + * Add a bit to the value x, making it an n+1-bit value. + * + * The current value is shifted and the bit is added to the + * appropriate place, dependant on the stream's bitorder. + * + * For example: + * A bit y is added to the value 00001100 with size 4. + * If the stream's bitorder is MSB2LSB, the resulting value is 0001100y. + * If the stream's bitorder is LSB2MSB, the resulting value is 000y1100. + */ void addBit(uint32 &x, uint32 n) { if (n >= 32) error("BitStreamImpl::addBit(): Too many bits requested to be read"); |