RsyncSum Class Reference

A 32 bit checksum with the special property that you do not need to recalculate the checksum when data is added to the front/end of the checksummed area, or removed from it. More...

#include <rsyncsum.hh>

List of all members.

Public Member Functions
	RsyncSum ()
	Initialises the checksum with zero.
	RsyncSum (const byte *mem, size_t len)
	Initialises with the checksum of a memory area.
bool	operator== (const RsyncSum &x) const
	Compare two RsyncSum objects.
bool	operator!= (const RsyncSum &x) const
bool	operator< (const RsyncSum &x) const
bool	operator> (const RsyncSum &x) const
bool	operator<= (const RsyncSum &x) const
bool	operator>= (const RsyncSum &x) const
RsyncSum &	addBack (const byte *mem, size_t len)
	Append memory area to end of area covered by the checksum.
RsyncSum &	addBack (byte x)
	Append one byte at end of area covered by the checksum.
RsyncSum &	addBackNtimes (byte x, size_t n)
	Append the same byte n times at end of area covered by the checksum.
RsyncSum &	removeFront (const byte *mem, size_t len, size_t areaSize)
	Remove memory area from start of area covered by the checksum.
RsyncSum &	removeFront (byte x, size_t areaSize)
	Remove one byte from start of area covered by checksum.
uint32	get () const
	Read stored checksum.
RsyncSum &	reset ()
	Reset to initial state.
bool	empty () const
	Check whether sum is zero.

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Detailed Description

A 32 bit checksum with the special property that you do not need to recalculate the checksum when data is added to the front/end of the checksummed area, or removed from it.

Currently only adding to the end and removing from the front is supported. Adding to the end is very slightly faster.

Many thanks to Andrew Tridgell and Paul Mackerras for the algorithm - NB none of rsync's code is used.

Unless described otherwise, if a method returns an RsyncSum&, then this is a reference to the object itself, to allow chaining of calls, e.g. obj.addBack(x).addBack(y)

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Constructor & Destructor Documentation

RsyncSum::RsyncSum

(

)

[inline]

Initialises the checksum with zero.

RsyncSum::RsyncSum	(	const byte *	mem,
		size_t	len
	)			[inline]

Initialises with the checksum of a memory area.

References addBack().

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Member Function Documentation

bool RsyncSum::operator==

(

const RsyncSum &

x

)

const [inline]

Compare two RsyncSum objects.

References get().

bool RsyncSum::operator!=

(

const RsyncSum &

x

)

const [inline]

References get().

bool RsyncSum::operator<

(

const RsyncSum &

x

)

const [inline]

References get().

bool RsyncSum::operator>

(

const RsyncSum &

x

)

const [inline]

References get().

bool RsyncSum::operator<=

(

const RsyncSum &

x

)

const [inline]

References get().

bool RsyncSum::operator>=

(

const RsyncSum &

x

)

const [inline]

References get().

RsyncSum & RsyncSum::addBack	(	const byte *	mem,
		size_t	len
	)

Append memory area to end of area covered by the checksum.

Referenced by main(), and RsyncSum().

RsyncSum & RsyncSum::addBack

(

byte

x

)

[inline]

Append one byte at end of area covered by the checksum.

RsyncSum & RsyncSum::addBackNtimes	(	byte	x,
		size_t	n
	)			[inline]

Append the same byte n times at end of area covered by the checksum.

(addBack() is not overloaded for this in order to avoid confusion with removeFront(byte, size_t), which has the same signature, but only removes one byte.)

RsyncSum & RsyncSum::removeFront	(	const byte *	mem,
		size_t	len,
		size_t	areaSize
	)

Remove memory area from start of area covered by the checksum.

Parameters:

	mem	Data to remove
	len	Number of bytes to remove from area, so it will cover area-len bytes after call
	areaSize	Size covered by area before call (necessary for calculcations)

References get().

Referenced by main().

RsyncSum & RsyncSum::removeFront	(	byte	x,
		size_t	areaSize
	)			[inline]

Remove one byte from start of area covered by checksum.

uint32 RsyncSum::get

(

)

const [inline]

Read stored checksum.

Referenced by get_checksum1(), main(), operator!=(), operator<(), operator<=(), operator==(), operator>(), operator>=(), and removeFront().

RsyncSum& RsyncSum::reset

(

)

[inline]

Reset to initial state.

Referenced by main().

bool RsyncSum::empty

(

)

const [inline]

Check whether sum is zero.

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

• util/rsyncsum.hh
• util/rsyncsum.cc