checksum.h File Reference

Abstract wrappers around different weaksum and strongsum implementations. More...

Include dependency graph for checksum.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Data Structures
struct	weaksum
	Abstract wrapper around weaksum implementations. More...

Typedefs
typedef struct weaksum	weaksum_t
	Abstract wrapper around weaksum implementations. More...

Enumerations
enum	weaksum_kind_t { RS_ROLLSUM , RS_RABINKARP }
	Weaksum implementations. More...
enum	strongsum_kind_t { RS_MD4 , RS_BLAKE2 }
	Strongsum implementations. More...

Functions
static void	weaksum_reset (weaksum_t *sum)
static void	weaksum_init (weaksum_t *sum, weaksum_kind_t kind)
static size_t	weaksum_count (weaksum_t *sum)
static void	weaksum_update (weaksum_t *sum, const unsigned char *buf, size_t len)
static void	weaksum_rotate (weaksum_t *sum, unsigned char out, unsigned char in)
static void	weaksum_rollin (weaksum_t *sum, unsigned char in)
static void	weaksum_rollout (weaksum_t *sum, unsigned char out)
static rs_weak_sum_t	weaksum_digest (weaksum_t *sum)
rs_weak_sum_t	rs_calc_weak_sum (weaksum_kind_t kind, void const *buf, size_t len)
	Calculate a weaksum. More...
void	rs_calc_strong_sum (strongsum_kind_t kind, void const *buf, size_t len, rs_strong_sum_t *sum)
	Calculate a strongsum. More...

Detailed Description

Abstract wrappers around different weaksum and strongsum implementations.

Definition in file checksum.h.

Typedef Documentation

weaksum_t

typedef struct weaksum weaksum_t

Abstract wrapper around weaksum implementations.

This is a polymorphic interface to the different rollsum implementations.

Historically rollsum methods were implemented as static inline functions because they were small and needed to be fast. Now that we need to call different methods for different rollsum implementations, they are getting more complicated. Is it better to delegate calls to the right implementation using static inline switch statements, or stop inlining them and use virtual method pointers? Tests suggest inlined switch statements is faster.

Enumeration Type Documentation

weaksum_kind_t

enum weaksum_kind_t

Weaksum implementations.

Definition at line 35 of file checksum.h.

strongsum_kind_t

enum strongsum_kind_t

Strongsum implementations.

Definition at line 41 of file checksum.h.

Function Documentation

weaksum_reset()

static void weaksum_reset ( weaksum_t *  sum )

inlinestatic

Definition at line 64 of file checksum.h.

weaksum_init()

static void weaksum_init ( weaksum_t *  sum, weaksum_kind_t  kind  )

inlinestatic

Definition at line 72 of file checksum.h.

weaksum_count()

static size_t weaksum_count ( weaksum_t *  sum )

inlinestatic

Definition at line 79 of file checksum.h.

weaksum_update()

static void weaksum_update ( weaksum_t *  sum, const unsigned char *  buf, size_t  len  )

inlinestatic

Definition at line 85 of file checksum.h.

weaksum_rotate()

static void weaksum_rotate ( weaksum_t *  sum, unsigned char  out, unsigned char  in  )

inlinestatic

Definition at line 94 of file checksum.h.

weaksum_rollin()

static void weaksum_rollin ( weaksum_t *  sum, unsigned char  in  )

inlinestatic

Definition at line 103 of file checksum.h.

weaksum_rollout()

static void weaksum_rollout ( weaksum_t *  sum, unsigned char  out  )

inlinestatic

Definition at line 111 of file checksum.h.

weaksum_digest()

static rs_weak_sum_t weaksum_digest ( weaksum_t *  sum )

inlinestatic

Definition at line 119 of file checksum.h.

rs_calc_weak_sum()

rs_weak_sum_t rs_calc_weak_sum	(	weaksum_kind_t	kind,
		void const *	buf,
		size_t	len
	)

Calculate a weaksum.

Note this does not apply mix32() to rollsum digests, unlike weaksum_digest(). This is because rollsums are stored raw without mix32() applied for backwards-compatibility, but we apply mix32() when adding them into a signature and when getting the digest for calculating deltas.

Calculate a weaksum.

Definition at line 34 of file checksum.c.

rs_calc_strong_sum()

void rs_calc_strong_sum	(	strongsum_kind_t	kind,
		void const *	buf,
		size_t	len,
		rs_strong_sum_t *	sum
	)

Calculate a strongsum.

Calculate a strongsum.

In plain rsync, the checksum is perturbed by a seed value. This is used when retrying a failed transmission: we've discovered that the hashes collided at some point, so we're going to try again with different hashes to see if we can get it right. (Check tridge's thesis for details and to see if that's correct.)

Since we can't retry I'm not sure if it's very useful for librsync, except perhaps as protection against hash collision attacks.

Definition at line 59 of file checksum.c.