Fuzzy Hashing API

These functions allow a programmer to compute the fuzzy hashes (also called the contexttriggered piecewise hashes) of a buffer of text , the contents of a file on the disk , and the contents of an open file handle . There is also a function to compute the similarity between any two fuzzy signatures . More...
#include <stdint.h>
#include <stdio.h>
Go to the source code of this file.
Macros  
#define  FUZZY_FLAG_ELIMSEQ 0x1u 
fuzzy_digest flag indicating to eliminate sequences of more than three identical characters  
#define  FUZZY_FLAG_NOTRUNC 0x2u 
fuzzy_digest flag indicating not to truncate the second part to SPAMSUM_LENGTH/2 characters.  
#define  SPAMSUM_LENGTH 64 
#define  FUZZY_MAX_RESULT (2 * SPAMSUM_LENGTH + 20) 
Functions  
struct fuzzy_state *  fuzzy_new (void) 
Construct a fuzzy_state object and return it. More...  
struct fuzzy_state *  fuzzy_clone (const struct fuzzy_state *state) 
Create a copy of a fuzzy_state object and return it. More...  
int  fuzzy_set_total_input_length (struct fuzzy_state *state, uint_least64_t total_fixed_length) 
Set fixed length of input. More...  
int  fuzzy_update (struct fuzzy_state *state, const unsigned char *buffer, size_t buffer_size) 
Feed the data contained in the given buffer to the state. More...  
int  fuzzy_digest (const struct fuzzy_state *state, char *result, unsigned int flags) 
Obtain the fuzzy hash from the state. More...  
void  fuzzy_free (struct fuzzy_state *state) 
Dispose a fuzzy state. More...  
int  fuzzy_hash_buf (const unsigned char *buf, uint32_t buf_len, char *result) 
Compute the fuzzy hash of a buffer. More...  
int  fuzzy_hash_file (FILE *handle, char *result) 
Compute the fuzzy hash of a file using an open handle. More...  
int  fuzzy_hash_stream (FILE *handle, char *result) 
Compute the fuzzy hash of a stream using an open handle. More...  
int  fuzzy_hash_filename (const char *filename, char *result) 
Compute the fuzzy hash of a file. More...  
int  fuzzy_compare (const char *sig1, const char *sig2) 
These functions allow a programmer to compute the fuzzy hashes (also called the contexttriggered piecewise hashes) of a buffer of text , the contents of a file on the disk , and the contents of an open file handle . There is also a function to compute the similarity between any two fuzzy signatures .
#define FUZZY_MAX_RESULT (2 * SPAMSUM_LENGTH + 20) 
The longest possible length for a fuzzy hash signature (without the filename)
#define SPAMSUM_LENGTH 64 
Length of an individual fuzzy hash signature component.
struct fuzzy_state* fuzzy_clone  (  const struct fuzzy_state *  state  ) 
Create a copy of a fuzzy_state object and return it.
It can be used with fuzzy_update and fuzzy_digest independently of the original. It must be disposed with fuzzy_free like the original has to be cleared in this way.
state  The fuzzy state 
int fuzzy_compare  (  const char *  sig1, 
const char *  sig2  
) 
Computes the match score between two fuzzy hash signatures.
int fuzzy_digest  (  const struct fuzzy_state *  state, 
char *  result,  
unsigned int  flags  
) 
Obtain the fuzzy hash from the state.
This operation does not change the state at all. It reports the hash for the concatenation of the data previously fed using fuzzy_update.
state  The fuzzy state 
result  Where the fuzzy hash is stored. This variable must be allocated to hold at least FUZZY_MAX_RESULT bytes. 
flags  is a bitwise or of FUZZY_FLAG_* macros. The absence of flags is represented by a zero. 
void fuzzy_free  (  struct fuzzy_state *  state  ) 
Dispose a fuzzy state.
state  The fuzzy state to dispose 
int fuzzy_hash_buf  (  const unsigned char *  buf, 
uint32_t  buf_len,  
char *  result  
) 
Compute the fuzzy hash of a buffer.
The computes the fuzzy hash of the first buf_len bytes of the buffer. It is the caller's responsibility to append the filename, if any, to result after computation.
buf  The data to be fuzzy hashed 
buf_len  The length of the data being hashed 
result  Where the fuzzy hash of buf is stored. This variable must be allocated to hold at least FUZZY_MAX_RESULT bytes. 
int fuzzy_hash_file  (  FILE *  handle, 
char *  result  
) 
Compute the fuzzy hash of a file using an open handle.
Computes the fuzzy hash of the contents of the open file, starting at the beginning of the file. When finished, the file pointer is returned to its original position. If an error occurs, the file pointer's value is undefined. It is the callers's responsibility to append the filename to the result after computation.
handle  Open handle to the file to be hashed 
result  Where the fuzzy hash of the file is stored. This variable must be allocated to hold at least FUZZY_MAX_RESULT bytes. 
int fuzzy_hash_filename  (  const char *  filename, 
char *  result  
) 
Compute the fuzzy hash of a file.
Opens, reads, and hashes the contents of the file 'filename' The result must be allocated to hold FUZZY_MAX_RESULT characters. It is the caller's responsibility to append the filename to the result after computation.
filename  The file to be hashed 
result  Where the fuzzy hash of the file is stored. This variable must be allocated to hold at least FUZZY_MAX_RESULT bytes. 
int fuzzy_hash_stream  (  FILE *  handle, 
char *  result  
) 
Compute the fuzzy hash of a stream using an open handle.
Computes the fuzzy hash of the contents of the open stream, starting at the current file position until reaching EOF. Unlike fuzzy_hash_file the stream is never seeked. If an error occurs, the result as well as the file position are undefined. It is the callers's responsibility to append the filename to the result after computation.
handle  Open handle to the stream to be hashed 
result  Where the fuzzy hash of the file is stored. This variable must be allocated to hold at least FUZZY_MAX_RESULT bytes. 
struct fuzzy_state* fuzzy_new  (  void  ) 
Construct a fuzzy_state object and return it.
To use it call fuzzy_update and fuzzy_digest on it. It must be disposed with fuzzy_free.
int fuzzy_set_total_input_length  (  struct fuzzy_state *  state, 
uint_least64_t  total_fixed_length  
) 
Set fixed length of input.
If we know the file size to compute fuzzy digest, we can boost computation by restricting range of blocksize.
state  The fuzzy state 
total_fixed_length  Total length of the data to generate digest 
int fuzzy_update  (  struct fuzzy_state *  state, 
const unsigned char *  buffer,  
size_t  buffer_size  
) 
Feed the data contained in the given buffer to the state.
When an error occurs, the state is undefined. In that case it must not be passed to any function besides fuzzy_free.
state  The fuzzy state 
buffer  The data to be hashes 
buffer_size  The length of the given buffer 