Public API for libffuzzy. More...

#include <stdbool.h>
#include <stddef.h>

Data Structures
struct	ffuzzy_digest
	The type to store ssdeep digest after parsing. More...

Macros
#define	FFUZZY_SPAMSUM_LENGTH 64
	Maximum length for the digest block.

#define	FFUZZY_MIN_BLOCKSIZE 3
	Minimum block size to start in ssdeep implementation.

#define	FFUZZY_MIN_MATCH 7
	The minimal match (length of common substring) required for (at least) one of the block digests.

Functions
Comparison and Parsing
bool	ffuzzy_read_digest (ffuzzy_digest digest, const char s)
	Read ssdeep digest from the string. More...

int	ffuzzy_compare_digest (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two fuzzy hashes and compute similarity score. More...

int	ffuzzy_compare (const char str1, const char str2)
	Compute similarity score for given ssdeep hash strings. More...

Block Size Utilities
bool	ffuzzy_blocksize_is_valid (unsigned long block_size)
	Determines whether given block size is valid to use in libffuzzy. More...

bool	ffuzzy_blocksize_is_natural (unsigned long block_size)
	Determines whether given block size is "natural". More...

bool	ffuzzy_blocksize_is_near (unsigned long block_size1, unsigned long block_size2)
	Determines whether given block sizes are "near". More...

bool	ffuzzy_blocksize_is_far_le (unsigned long block_size1, unsigned long block_size2)
	Determines whether given ordered block sizes "far" enough. More...

Digest Utilities
bool	ffuzzy_digest_is_valid_lengths (const ffuzzy_digest *digest)
	Determines whether block lengths of given digest are valid. More...

bool	ffuzzy_digest_is_valid_buffer (const ffuzzy_digest *digest)
	Determines whether digest blocks are valid. More...

bool	ffuzzy_digest_is_natural_buffer (const ffuzzy_digest *digest)
	Determines whether digest blocks are valid and "natural". More...

bool	ffuzzy_digest_is_valid (const ffuzzy_digest *digest)
	Determines whether given digest is valid. More...

bool	ffuzzy_digest_is_natural (const ffuzzy_digest *digest)
	Determines whether given digest is valid and "natural". More...

int	ffuzzy_digestcmp (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two ffuzzy_digest values. More...

int	ffuzzy_digestcmp_blocksize (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two ffuzzy_digest values by block sizes. More...

int	ffuzzy_digestcmp_blocksize_n (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two ffuzzy_digest values by whether block sizes are "natural" and block size values. More...

bool	ffuzzy_pretty_digest (char buf, size_t buflen, const ffuzzy_digest digest)
	Convert ffuzzy_digest to the string. More...

Optimized / Specialized Comparison
int	ffuzzy_compare_digest_near (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two fuzzy hashes assuming two block sizes of given hashes are "near". More...

int	ffuzzy_compare_digest_near_eq (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two fuzzy hashes assuming two block sizes are same. More...

int	ffuzzy_compare_digest_near_lt (const ffuzzy_digest d1, const ffuzzy_digest d2)
	Compare two fuzzy hashes assuming second block size is double as first one. More...

Internal Comparison Utilities
int	ffuzzy_score_cap (int s1len, int s2len, unsigned long block_size)
	Retrieve score cap for given block lengths and the block size. More...

int	ffuzzy_score_cap_1 (int minslen, unsigned long block_size)
	Retrieve score cap for given block length and size. More...

int	ffuzzy_score_strings (const char s1, size_t s1len, const char s2, size_t s2len, unsigned long block_size)
	Compute partial similarity score for given two block strings and block size. More...

Detailed Description

Public API for libffuzzy.

Function Documentation

bool ffuzzy_blocksize_is_far_le	(	unsigned long	block_size1,
		unsigned long	block_size2
	)

Determines whether given ordered block sizes "far" enough.

In this context, "far" means the second block size is greater than double of the first block size.

For block size-sorted digests, "far" means there are no subsequent entries which will match.

This function determines whether given block sizes are "far".

You may want to inline or reimplement this because this function is very easy. There's nothing preventing you to do that.

Parameters

block_size1	Valid block size 1
block_size2	Valid block size 2 (must be equal or greater than block_size1)

Returns: true if the given block sizes are "far"; false otherwise.

bool ffuzzy_blocksize_is_natural ( unsigned long block_size )

Determines whether given block size is "natural".

In this context, "natural" means given parameter of fuzzy hash may be generated by ssdeep or its backend, libfuzzy. Depending on the job, handling only "natural" digests may make your program efficient.

This function doesn't only check whether the block size is valid, but it checks the given size is a product of FFUZZY_MIN_BLOCKSIZE and a power of two.

Parameters

block_size Block size (which may not be valid or "natural")

Returns: true if the given block size is valid and "natural"; false otherwise.

bool ffuzzy_blocksize_is_near	(	unsigned long	block_size1,
		unsigned long	block_size2
	)

Determines whether given block sizes are "near".

In this context, "near" means two block sizes are equal or one of the block size is twice as other.

This function determines whether given block sizes are "near". If this function returns true, it is safe to use ffuzzy_compare_digest_near function for two digests which have given block sizes.

Parameters

block_size1	Valid block size 1
block_size2	Valid block size 2

Returns: true if the given block sizes are "near"; false otherwise.

bool ffuzzy_blocksize_is_valid ( unsigned long block_size )

Determines whether given block size is valid to use in libffuzzy.

To prevent arithmetic overflow, not all unsigned long values are valid in libffuzzy. This function determines whether the given block size is valid and safe to use in libffuzzy.

You will not need to use this function if you use ffuzzy_read_digest function because it always returns valid digest on success.

Note that this is not the restriction of ssdeep digest, but restriction of the implementation.

Parameters

block_size Block size (which may not be valid)

Returns: true if the given block size is valid; false otherwise.

int ffuzzy_compare	(	const char *	str1,
		const char *	str2
	)

Compute similarity score for given ssdeep hash strings.

Parameters

[in]	str1	ssdeep hash 1
[in]	str2	ssdeep hash 2

Returns: [0,100] values represent similarity score or negative values on failure.

int ffuzzy_compare_digest	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two fuzzy hashes and compute similarity score.

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2

Returns: [0,100] values represent similarity score or negative values on failure.

int ffuzzy_compare_digest_near	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two fuzzy hashes assuming two block sizes of given hashes are "near".

In this context, "near" means two block sizes are equal or one of the block size is twice as other.

This function assumes two block sizes are "near" (ffuzzy_blocksize_is_near on two block sizes returns true) and make the computation slightly faster.

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2

Returns: [0,100] values represent similarity score or negative values on failure.

int ffuzzy_compare_digest_near_eq	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two fuzzy hashes assuming two block sizes are same.

This function assumes two block sizes are same.

Parameters

[in]	d1	Valid digest 1 (with same block size as d2)
[in]	d2	Valid digest 2 (with same block size as d1)

Returns: [0,100] values represent similarity score or negative values on failure.

See also: int ffuzzy_compare_digest_near(const ffuzzy_digest*, const ffuzzy_digest*)

int ffuzzy_compare_digest_near_lt	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two fuzzy hashes assuming second block size is double as first one.

This function assumes second block size is double as first one.

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2 (with double block size as d1)

Returns: [0,100] values represent similarity score or negative values on failure.

See also: int ffuzzy_compare_digest_near(const ffuzzy_digest*, const ffuzzy_digest*)

bool ffuzzy_digest_is_natural ( const ffuzzy_digest * digest )

Determines whether given digest is valid and "natural".

Parameters

[in] digest Digest (which may not be valid or natural)

Returns: true if the digest is valid and natural; false otherwise.

bool ffuzzy_digest_is_natural_buffer ( const ffuzzy_digest * digest )

Determines whether digest blocks are valid and "natural".

This function determines whether valid range of ffuzzy_digest::digest values consist of base64 characters (in other words, "natural").

This function needs valid digest block lengths. If digest block lengths are not guaranteed to be valid, use ffuzzy_digest_is_valid_lengths first.

You may need to use this function even after success call to ffuzzy_read_digest because this function is not guaranteed to set digests with "natural" digest blocks.

However, if you are just comparing, this check is not necessary because fuzzy hash comparison will not decode base64 characters (it just "compares").

You will need this function ONLY if you need to verify whether given digest is truly "natural".

Parameters

[in] digest Digest (which may not be valid or natural but block lengths are valid)

Returns: true if the digest blocks are valid and "natural"; false otherwise.

bool ffuzzy_digest_is_valid ( const ffuzzy_digest * digest )

Determines whether given digest is valid.

Parameters

[in] digest Digest (which may not be valid)

Returns: true if the digest is valid; false otherwise.

bool ffuzzy_digest_is_valid_buffer ( const ffuzzy_digest * digest )

Determines whether digest blocks are valid.

This function determines whether there are no sequences which consist of four or more identical characters.

This function needs valid digest block lengths. If digest block lengths are not guaranteed to be valid, use ffuzzy_digest_is_valid_lengths first.

You will not need to use this function if you use ffuzzy_read_digest function because it always returns valid digests on success.

Parameters

[in] digest Digest (which may not be valid but block lengths are valid)

Returns: true if the digest blocks are valid; false otherwise.

bool ffuzzy_digest_is_valid_lengths ( const ffuzzy_digest * digest )

Determines whether block lengths of given digest are valid.

Parameters

[in] digest Digest (which may not be valid)

Returns: true if values of ffuzzy_digest::len1 and ffuzzy_digest::len2 are valid.

int ffuzzy_digestcmp	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two ffuzzy_digest values.

This comparison has priorities.

Compare block sizes.
Compare block lengths of the first block.
Compare block lengths of the second block.
Compare block buffer contents (first and second).

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2

Returns: Positive value if d1 < d2, negativa value if d2 > d1 and 0 if d1 is equal to d2.

int ffuzzy_digestcmp_blocksize	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two ffuzzy_digest values by block sizes.

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2

Returns: Positive value if d1 < d2, negativa value if d2 > d1 and 0 if block size of d1 is equal to d2.

See also: int ffuzzy_digestcmp(const ffuzzy_digest*, const ffuzzy_digest*)

int ffuzzy_digestcmp_blocksize_n	(	const ffuzzy_digest *	d1,
		const ffuzzy_digest *	d2
	)

Compare two ffuzzy_digest values by whether block sizes are "natural" and block size values.

This comparison has priorities.

Compare whether block sizes are "natural" (for ffuzzy_blocksize_is_natural return value, true comes first)
Compare block sizes.

Parameters

[in]	d1	Valid digest 1
[in]	d2	Valid digest 2

Returns: Positive value if d1 < d2, negativa value if d2 > d1 and 0 if block size of d1 is equal to d2.

See also: bool ffuzzy_blocksize_is_natural(unsigned long); int ffuzzy_digestcmp(const ffuzzy_digest*, const ffuzzy_digest*)

bool ffuzzy_pretty_digest	(	char *	buf,
		size_t	buflen,
		const ffuzzy_digest *	digest
	)

Convert ffuzzy_digest to the string.

Parameters

[out]	buf	Buffer to store string
	buflen	Size of buf
[in]	digest	A valid digest to convert

Returns: true if succeeds; false otherwise.

bool ffuzzy_read_digest	(	ffuzzy_digest *	digest,
		const char *	s
	)

Read ssdeep digest from the string.

This function always sets valid digest if succeeds.

Parameters

[out]	digest	The pointer to the buffer to store valid digest after parsing.
[in]	s	The string which contains a ssdeep digest.

Returns: true if succeeds; false otherwise.

int ffuzzy_score_cap	(	int	s1len,
		int	s2len,
		unsigned long	block_size
	)

Retrieve score cap for given block lengths and the block size.

The (partial) similarity score is capped when the block is short and the block size is small to prevent exaggerate match. This function returns this score cap for given block lengths and the block size.

Parameters

s1len	Length of block 1
s2len	Length of block 2
block_size	Block size

Returns: Maximum (partial) similarity score value. If the return value is greater than 100, the score cap is 100.

If s1len or s2len is out of range [0,FFUZZY_SPAMSUM_LENGTH], the value is undefined.

int ffuzzy_score_cap_1	(	int	minslen,
		unsigned long	block_size
	)

Retrieve score cap for given block length and size.

ffuzzy_score_cap function computes the score cap by the block size and "minimum" length of the given blocks. This function exposes internal interface of ffuzzy_score_cap.

Parameters

minslen	Minimum length of the blocks
block_size	Block size

Returns: Maximum (partial) similarity score value. If the return value is greater than 100, the score cap is 100.

If minslen is out of range [0,FFUZZY_SPAMSUM_LENGTH], the value is undefined.

int ffuzzy_score_strings	(	const char *	s1,
		size_t	s1len,
		const char *	s2,
		size_t	s2len,
		unsigned long	block_size
	)

Compute partial similarity score for given two block strings and block size.

In the fuzzy computation, the digest block of the same block sizes are selected to compare. This is the internal interface for ffuzzy_compare and ffuzzy_compare_digest.

Parameters

[in]	s1	Digest block 1
	s1len	Length of s1
[in]	s2	Digest block 2
	s2len	Length of s2
	block_size	Block size for two digest blocks

Returns: [0,100] values represent partial similarity score or negative values on failure.

Data Structures

Macros

Functions

Detailed Description

Function Documentation