lsup_rdf/include/structures/index.h

/** Limited-scope, fast implementation of a bi-directional hash table.
 *
 * This data structure holds an array of key-value pairs. It is append-only.
 *
 * A key is the result of a hash function applied to the value, and keys are
 * unique within an index. Hence, both keys and values are uniqure and lookups
 * can be done both ways.
 *
 * A value is a pointer to a `LSUP_SerTerm` structure. Comparison for
 * uniqueness is done by comparing the hashes/keys.
 *
 * To find a key by its value, it is sufficient to apply the hash function to
 * the value without having to look up the table.
 */

#include "structures/buffer.h"
#include "model/rdf/term.h"

typedef struct Index LSUP_Index;

LSUP_Index *LSUP_index_new(size_t capacity);

/**
 * Add a key/value pair. The key must be calculated in advance.
 *
 * This function takes ownership of the serialized term.
 */
int LSUP_index_add_pair(LSUP_Index *idx, LSUP_Key key, LSUP_SerTerm *sterm);

/**
 * Add a term and automatically calculate the key.
 *
 * This function takes ownership of the serialized term.
 */
int LSUP_index_add(LSUP_Index *idx, LSUP_SerTerm *sterm);

LSUP_SerTerm *LSUP_index_lookup(LSUP_Index *idx, LSUP_Key key);

void LSUP_index_free(LSUP_Index *idx);