mlib::bitstream Class Reference

Read and write bit fields. More...

#include <bitstream.h>

Public Member Functions
	bitstream (std::iostream &str, unsigned int pack)
bool	read ()
	Read the next bit.
void	write (int val)
	Write a bit to stream.
void	flush ()
	If there are any leftover bits, encode them in one character and write them out to stream.
int	mread (unsigned int sz, bool is_signed=false)
	Read a variable number of bits.
void	mwrite (int val, unsigned int sz)
	Write a variable number of bits.

Protected Member Functions
virtual void	encode (unsigned char bits, char &chr)
	Encode bit field in a byte.
virtual void	decode (unsigned char &bits, char chr)
	Decode bit field from a byte.

Protected Attributes
const unsigned int	packing
std::iostream &	s

Detailed Description

Read and write bit fields.

This class allows reading and writing of bit fields from or to a byte stream.

It allows for different byte encodings using the protected encode/decode functions.

Remarks

Maximum field width is limited to 32 bits.

Constructor & Destructor Documentation

bitstream()

mlib::bitstream::bitstream	(	std::iostream &	str,
		unsigned int	pack
	)

Parameters

str	Underlining iostream
pack	Number of bits per byte

Member Function Documentation

decode()

void mlib::bitstream::decode ( unsigned char &  bits, char  chr  )

inlineprotectedvirtual

Decode bit field from a byte.

The default implementation unpacks the bit field from the LSB of byte.

Parameters

bits	resulting bit field
chr	encoded byte

encode()

void mlib::bitstream::encode ( unsigned char  bits, char &  chr  )

inlineprotectedvirtual

Encode bit field in a byte.

The default implementation packs the bit field in the LSB of byte.

Parameters

bits	bit field to encode
chr	encoded byte

mread()

int mlib::bitstream::mread	(	unsigned int	sz,
		bool	sign = false
	)

Read a variable number of bits.

Invokes read function repeatedly to read all bits.

Parameters

sz	Width of bit field
sign	"true" if bit field should be interpreted as a signed value.

Returns

value (0 to 2^sz-1 or -2^sz-1 to 2^sz-1)

mwrite()

void mlib::bitstream::mwrite	(	int	val,
		unsigned int	sz
	)

Write a variable number of bits.

Invokes write function repeatedly to write each bit.

Parameters

val	Value to write (0 to 2sz-1 )
sz	Width of bit field

read()

bool mlib::bitstream::read

(

)

Read the next bit.

Read a single bit from stream.

If there are no more bits available in current byte tries to get a new byte and decodes it using decode function.

Returns

Bit value

Remarks

All bits read after stream reaches EOF are 0.

write()

void mlib::bitstream::write

(

int

val

)

Write a bit to stream.

If it has accumulated enough bits calls encode function to encode them and writes a new byte to underlining stream.

Parameters

val	Bit value to write

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The documentation for this class was generated from the following files:

• include/mlib/bitstream.h
• src/bitstream.cpp