Hashes

Hashes — Key:Value hashes or dictionaries.

Synopsis

typedef             librdf_hash;
typedef             librdf_hash_cursor;
librdf_hash *       librdf_new_hash                     (librdf_world *world,
                                                         const char *name);
librdf_hash *       librdf_new_hash_from_string         (librdf_world *world,
                                                         const char *name,
                                                         const char *string);
librdf_hash *       librdf_new_hash_from_array_of_strings
                                                        (librdf_world *world,
                                                         const char *name,
                                                         const char **array);
librdf_hash *       librdf_new_hash_from_hash           (librdf_hash *old_hash);
void                librdf_free_hash                    (librdf_hash *hash);
char *              librdf_hash_get                     (librdf_hash *hash,
                                                         const char *key);
int                 librdf_hash_get_as_boolean          (librdf_hash *hash,
                                                         const char *key);
long                librdf_hash_get_as_long             (librdf_hash *hash,
                                                         const char *key);
char *              librdf_hash_get_del                 (librdf_hash *hash,
                                                         const char *key);
int                 librdf_hash_put_strings             (librdf_hash *hash,
                                                         const char *key,
                                                         const char *value);
void                librdf_hash_print                   (librdf_hash *hash,
                                                         FILE *fh);
void                librdf_hash_print_keys              (librdf_hash *hash,
                                                         FILE *fh);
void                librdf_hash_print_values            (librdf_hash *hash,
                                                         const char *key_string,
                                                         FILE *fh);
unsigned char *     librdf_hash_interpret_template      (const unsigned char *template_string,
                                                         librdf_hash *dictionary,
                                                         const unsigned char *prefix,
                                                         const unsigned char *suffix);
int                 librdf_hash_from_string             (librdf_hash *hash,
                                                         const char *string);
char *              librdf_hash_to_string               (librdf_hash *hash,
                                                         const char *filter[]);

Description

Interface to implementations of key:value hashes either in memory, on disk and with persistence. Keys may have multiple and duplicate values.

Details

librdf_hash

typedef struct librdf_hash_s librdf_hash;

Redland hash class.

librdf_hash_cursor

typedef struct librdf_hash_cursor_s librdf_hash_cursor;

Redland hash cursor class.

librdf_new_hash ()

librdf_hash *       librdf_new_hash                     (librdf_world *world,
                                                         const char *name);

Constructor - create a new librdf_hash object.

world :

 redland world object

name :

 factory name

Returns :

 a new librdf_hash object or NULL on failure

librdf_new_hash_from_string ()

librdf_hash *       librdf_new_hash_from_string         (librdf_world *world,
                                                         const char *name,
                                                         const char *string);

Constructor - create a new librdf_hash object from a string.

See librdf_hash_from_string for the string format.

world :

 redland world object

name :

 hash name

string :

 hash encoded as a string

Returns :

 a new librdf_hash object or NULL on failure

librdf_new_hash_from_array_of_strings ()

librdf_hash *       librdf_new_hash_from_array_of_strings
                                                        (librdf_world *world,
                                                         const char *name,
                                                         const char **array);

Constructor - create a new librdf_hash object from an array of strings.

world :

 redland world object

name :

 hash name

array :

 address of the start of the array of char* pointers

Returns :

 a new librdf_hash object or NULL on failure

librdf_new_hash_from_hash ()

librdf_hash *       librdf_new_hash_from_hash           (librdf_hash *old_hash);

Copy Constructor - create a new librdf_hash object from an existing one.

old_hash :

 the hash to use to construct the hash

Returns :

 a new librdf_hash object or NULL on failure

librdf_free_hash ()

void                librdf_free_hash                    (librdf_hash *hash);

Destructor - destroy a librdf_hash object.

hash :

 hash object

librdf_hash_get ()

char *              librdf_hash_get                     (librdf_hash *hash,
                                                         const char *key);

Retrieve one value from hash for a given key as string.

The value returned is from newly allocated memory which the caller must free.

hash :

 hash object

key :

 pointer to key

Returns :

 the value or NULL on failure

librdf_hash_get_as_boolean ()

int                 librdf_hash_get_as_boolean          (librdf_hash *hash,
                                                         const char *key);

Lookup a hash key and decode value as a boolean.

False values: "no", "false" True values: "yes", "true"

hash :

 librdf_hash object

key :

 key string to look up

Returns :

 >0 (for true), 0 (for false) or <0 (for key not found or not known boolean value)

librdf_hash_get_as_long ()

long                librdf_hash_get_as_long             (librdf_hash *hash,
                                                         const char *key);

Lookup a hash key and decode value as a long.

hash :

 librdf_hash object

key :

 key string to look up

Returns :

 >0 (for success), <0 (for key not found or not known boolean value)

librdf_hash_get_del ()

char *              librdf_hash_get_del                 (librdf_hash *hash,
                                                         const char *key);

Retrieve one value from hash for a given key as string and remove all values with that key.

The value returned is from newly allocated memory which the caller must free.

hash :

 hash object

key :

 pointer to key

Returns :

 the value or NULL on failure

librdf_hash_put_strings ()

int                 librdf_hash_put_strings             (librdf_hash *hash,
                                                         const char *key,
                                                         const char *value);

Insert key/value pairs into the hash as strings.

The key and values are copied into the hash, no sharing i s done.

hash :

 hash object

key :

 key

value :

 value

Returns :

 non 0 on failure

librdf_hash_print ()

void                librdf_hash_print                   (librdf_hash *hash,
                                                         FILE *fh);

Pretty print the hash to a file descriptor.

hash :

 the hash

fh :

 file handle

librdf_hash_print_keys ()

void                librdf_hash_print_keys              (librdf_hash *hash,
                                                         FILE *fh);

Pretty print the keys to a file descriptor.

hash :

 the hash

fh :

 file handle

librdf_hash_print_values ()

void                librdf_hash_print_values            (librdf_hash *hash,
                                                         const char *key_string,
                                                         FILE *fh);

Pretty print the values of one key to a file descriptor.

hash :

 the hash

key_string :

 the key as a string

fh :

 file handle

librdf_hash_interpret_template ()

unsigned char *     librdf_hash_interpret_template      (const unsigned char *template_string,
                                                         librdf_hash *dictionary,
                                                         const unsigned char *prefix,
                                                         const unsigned char *suffix);

Interpret keys in a template string to their value in a dictionary.

Can be used to do variable substitution for a string where the syntax that marks the variable is defined by the prefix and suffix strings, and the variables are stored in the dictionary hash table.

template_string :

 template string to interprate

dictionary :

 dictionary of key/values to substitute

prefix :

 prefix to mark a key in the template

suffix :

 suffix to mark a key in the template

Returns :

 Newly allocated string, or NULL on failure

librdf_hash_from_string ()

int                 librdf_hash_from_string             (librdf_hash *hash,
                                                         const char *string);

Initialise a hash from a string.

The string format is something like: key1='value1',key2='value2', key3='\'quoted value\''

The 's are required and whitespace can appear around the = and ,s

hash :

 hash object

string :

 hash encoded as a string

Returns :

 non 0 on failure

librdf_hash_to_string ()

char *              librdf_hash_to_string               (librdf_hash *hash,
                                                         const char *filter[]);

Format the hash as a string, suitable for parsing by librdf_hash_from_string.

Note: this method allocates a new string since this is a _to_ method and the caller must call librdf_free_memory() to free the resulting memory.

hash :

 librdf_hash object

filter :

 NULL terminated list of keys to ignore

Returns :

 string representation of the hash or NULL on failure
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