Digests 3 REDLAND Library
Digests Content digests.

## Synopsis

    typedef             librdf_digest;
    typedef             librdf_digest_factory;
    librdf_digest*      librdf_new_digest                   (librdf_world *world,
                                                             const char *name);
    void                librdf_free_digest                  (librdf_digest *digest);
    void                librdf_digest_init                  (librdf_digest *digest);
    void                librdf_digest_update                (librdf_digest *digest,
                                                             unsigned char *buf,
                                                             size_t length);
    void                librdf_digest_update_string         (librdf_digest *digest,
                                                             unsigned char *string);
    void                librdf_digest_final                 (librdf_digest *digest);
    void*               librdf_digest_get_digest            (librdf_digest *digest);
    size_t              librdf_digest_get_digest_length     (librdf_digest *digest);
    char*               librdf_digest_to_string             (librdf_digest *digest);
    void                librdf_digest_print                 (librdf_digest *digest,
                                                             FILE *fh);

## Description

Create a message digest over a block of data. Includes implementations of MD5, RMD160 and SHA1.

## Details

### librdf_digest

    typedef struct librdf_digest_s librdf_digest;

Redland content digest class.

librdf_digest

### librdf_digest_factory

    typedef struct librdf_digest_factory_s librdf_digest_factory;

Redland digest factory class.

librdf_digest_factory

### librdf_new_digest ()

    librdf_digest*      librdf_new_digest                   (librdf_world *world,
                                                             const char *name);

Constructor - create a new librdf_digest object.

After construction, data should be added to the digest using librdf_digest_update or librdf_digest_update_string with librdf_digest_final to signify finishing. Then the digest value can be returned directly with librdf_digest_get_digest of librdf_digest_get_digest_length bytes or as a hex encoded string with librdf_digest_to_string. The digest can be re-initialised for new data with librdf_digest_init.

world :

  redland world object

name :

  the digest name to use to create this digest

Returns :

  new librdf_digest object or NULL

librdf_new_digest

### librdf_free_digest ()

    void                librdf_free_digest                  (librdf_digest *digest);

Destructor- destroy a librdf_digest object.

digest :

  the digest

librdf_free_digest

### librdf_digest_init ()

    void                librdf_digest_init                  (librdf_digest *digest);

(Re)initialise the librdf_digest object.

This is automatically called on construction but can be used to re-initialise the digest to the initial state for digesting new data.

digest :

  the digest

librdf_digest_init

### librdf_digest_update ()

    void                librdf_digest_update                (librdf_digest *digest,
                                                             unsigned char *buf,
                                                             size_t length);

Add more data to the librdf_digest object.

digest :

  the digest

buf :

  the data buffer

length :

  the length of the data

librdf_digest_update

### librdf_digest_update_string ()

    void                librdf_digest_update_string         (librdf_digest *digest,
                                                             unsigned char *string);

Add a string to the librdf_digest object.

digest :

  the digest

string :

  string to add

librdf_digest_update_string

### librdf_digest_final ()

    void                librdf_digest_final                 (librdf_digest *digest);

Finish the digesting of data.

The digest can now be returned via `librdf_digest_get_digest()`.

digest :

  the digest

librdf_digest_final

### librdf_digest_get_digest ()

    void*               librdf_digest_get_digest            (librdf_digest *digest);

Get the calculated digested value.

digest :

  the digest

Returns :

  pointer to the memory containing the digest. It will be librdf_digest_get_digest_length bytes in length.

librdf_digest_get_digest

### librdf_digest_get_digest_length ()

    size_t              librdf_digest_get_digest_length     (librdf_digest *digest);

Get length of the calculated digested.

digest :

  the digest

Returns :

  size of the digest in bytes

librdf_digest_get_digest_length

### librdf_digest_to_string ()

    char*               librdf_digest_to_string             (librdf_digest *digest);

Get a string representation of the digest object.

digest :

  the digest

Returns :

  a newly allocated string that represents the digest. This must be released by the caller using `free()`

librdf_digest_to_string

### librdf_digest_print ()

    void                librdf_digest_print                 (librdf_digest *digest,
                                                             FILE *fh);

Print the digest to a FILE handle.

digest :

  the digest

fh :

  file handle

librdf_digest_print