lsup_rdf/include/term.h

#ifndef _LSUP_TERM_H
#define _LSUP_TERM_H

#include <assert.h>
#include <regex.h>

#include "uthash.h"

#include "buffer.h"
#include "namespace.h"

#define UUID4_URN_SIZE UUIDSTR_SIZE + 10

/*
 * Term types.
 */
/* Undefined placeholder or result of an error. Invalid for most operations. */
#define LSUP_TERM_UNDEFINED     0
/* IRI reference. */
#define LSUP_TERM_IRIREF        1
/* Namespace-prefixed IRI reference. */
#define LSUP_TERM_NS_IRIREF     2
/* Literal without language tag. */
#define LSUP_TERM_LITERAL       3
/* Language-tagged string literal. */
#define LSUP_TERM_LT_LITERAL    4
/* Blank node. */
#define LSUP_TERM_BNODE         5

/** @brief Default data type for untyped literals (prefixed IRI).
 */
#define DEFAULT_DTYPE           "http://www.w3.org/2001/XMLSchema#string"

/** @brief URI parsing regular expression. Conforms to RFC3986.
 */
#define LSUP_URI_REGEX_STR \
    "^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?"


/*
 * Data types.
 */

typedef XXH64_hash_t LSUP_Hash64;
typedef char LSUP_TermType;
typedef char LSUP_LangTag[8];


typedef struct term_t {
    char *              data;       // URI, literal value, or BNode label.
    union {
        LSUP_Key        datatype;   // Data type key for LSUP_TERM_LITERAL.
        LSUP_LangTag    lang;       // Lang tag for LSUP_TERM_LT_LITERAL.
        LSUP_Key        bnode_id;   // BNode ID for comparison & skolemization.
        LSUP_NSMap *    nsm;        // NSM handle for prefixed IRI.
    };
    LSUP_TermType      type;       // Term type.
} LSUP_Term;


/** @brief Hash cache for data types.
 */
struct term_cache_t {
    LSUP_Key            key;
    LSUP_Term *         term;
    UT_hash_handle      hh;
};


typedef struct triple_t {
    LSUP_Term *s;
    LSUP_Term *p;
    LSUP_Term *o;
} LSUP_Triple;


/*
 * Extern variables.
 */

/** @brief Global term cache.
 *
 * Stores frequently used terms, e.g. data type URIs.
 */
extern struct term_cache_t *LSUP_term_cache;

/** @brief Compiled hash of default literal data type.
 */
extern uint32_t LSUP_default_dtype_key;

/** @brief URI validation pattern, compiled in #LSUP_init().
 */
extern regex_t *LSUP_uri_ptn;

/** @brief Default literal data type URI.
 *
 * Literal terms created with undefined data type will have it set to this
 * URI implicitly.
 */
extern LSUP_Term *LSUP_default_datatype;


/*
 * Function prototypes.
 */

/** @brief Create a new term.
 *
 * @param type[in] Term type. One of #LSUP_TermType.
 *
 * @param data[in] Term data: textual URI, literal value without data type
 *  or langtag, etc.
 *
 * @param metadata[in]: language tag (LSUP_LangTag) for language-tagged
 * literals; or data type (LSUP_Term *) for other literals. It may be NULL.
 *
 * @return New term, which must be freed with #LSUP_term_free after use; or
 *  NULL on error.
 */
LSUP_Term *
LSUP_term_new (LSUP_TermType type, const char *data, void *metadata);


/** @brief Placeholder term to use with LSUP_term_reset.
 */
#define TERM_DUMMY LSUP_term_new (LSUP_TERM_UNDEFINED, NULL, NULL)


/** @brief Shortcut to create a URI.
 *
 * Must be freed with #LSUP_term_free.
 *
 * @param data[in] The URI string. If NULL, a UUID4-based URN is generated.
 *
 * @param uri[out] The URI to be created.
 *
 * @return LSUP_OK if successful, LSUP_VALUE_ERR if validation fails.
 */
inline LSUP_Term *
LSUP_uri_new (const char *data)
{
    if (!data) {
        uuid_t uuid;
        uuid_generate_random (uuid);

        uuid_str_t uuid_str;
        uuid_unparse_lower (uuid, uuid_str);

        char uri[UUID4_URN_SIZE];
        snprintf (uri, UUID4_URN_SIZE, "urn:uuid4:%s", uuid_str);

        data = uri;
    }

    return LSUP_term_new (LSUP_TERM_IRIREF, data, NULL);
}


/* @brief Initialize or reuse a pre-allocated term structure.
 *
 * The structure must have been previously created with #LSUP_term_new. It can
 * be reinitialized multiple times without freeing it. It must be eventually
 * freed with #LSUP_term_free.
 */
LSUP_rc
LSUP_term_init(
        LSUP_Term *term, LSUP_TermType type,
        const char *data, void *metadata);


/** @brief Deserialize a buffer into a term.
 *
 * @param[in] sterm Buffer to convert into a term. It must be a valid
 *  serialized term from store or obtained with #LSUP_term_serialize().
 *
 * @return New term handle. It must be freed with #LSUP_term_free().
 */
LSUP_Term *
LSUP_term_new_from_buffer (const LSUP_Buffer *sterm);


/** @brief Serialize a term into a buffer.
 *
 * @param[in] sterm Term to convert into a buffer.
 *
 * @return New buffer handle. It must be freed with #LSUP_buffer_free().
 */
LSUP_Buffer *
LSUP_term_serialize (const LSUP_Term *term);


/**
 * @brief Shortcut to initialize a URI.
 */
LSUP_rc
LSUP_uri_init (LSUP_Term *term, const char *data);


/** @brief Hash a buffer.
 */
LSUP_Key
LSUP_term_hash (const LSUP_Term *term);


/**
 * Compare two terms.
 */
bool LSUP_term_equals (const LSUP_Term *term1, const LSUP_Term *term2);

void
LSUP_term_done (LSUP_Term *term);

void
LSUP_term_free (LSUP_Term *term);


/** @brief Create a new triple from three terms.
 *
 * TODO Term types are not validated at the moment.
 *
 * @param[in] s Triple subject. It must be an IRIRef or BNode.
 *
 * @param[in] p Triple predicate. It must be an IRIRef.
 *
 * @param[in] o Triple object.
 *
 */
LSUP_Triple *
LSUP_triple_new(LSUP_Term *s, LSUP_Term *p, LSUP_Term *o);


/** @brief Dummy triple with NULL slots. It is not a valid triple.
 */
#define TRP_DUMMY LSUP_triple_new (NULL, NULL, NULL)


LSUP_Triple *
LSUP_triple_new_from_btriple (const LSUP_BufferTriple *sspo);


LSUP_BufferTriple *
LSUP_triple_serialize (const LSUP_Triple *spo);


/** @brief Initialize internal term pointers in a heap-allocated triple.
 *
 * NOTE: the term structures are not copied. If the triple is freed with
 * #LSUP_triple_free(), the originally provided terms are freed too.
 *
 * @param spo[in] Triple pointer to initialize.
 */
LSUP_rc
LSUP_triple_init (LSUP_Triple *spo, LSUP_Term *s, LSUP_Term *p, LSUP_Term *o);


/** @brief Free the internal pointers of a triple.
 *
 * @param spo[in] Triple to be freed.
 */
void
LSUP_triple_done (LSUP_Triple *spo);


/** @brief Free a triple and all its internal pointers.
 *
 * NOTE: If the term pointers are not to be freed (e.g. they are owned by a
 * back end), use a simple free(spo) instead of this.
 *
 * @param spo[in] Triple to be freed.
 */
void
LSUP_triple_free (LSUP_Triple *spo);


/** @brief Get triple by term position.
 *
 * Useful for looping over all terms.
 *
 * @param trp[in] Triple pointer.
 *
 * @param n[in] A number between 0÷2.
 *
 * @return Corresponding triple term or NULL if n is out of range.
 */
inline LSUP_Term *
LSUP_triple_pos (const LSUP_Triple *trp, LSUP_TriplePos n)
{
    if (n == TRP_POS_S) return trp->s;
    if (n == TRP_POS_P) return trp->p;
    if (n == TRP_POS_O) return trp->o;
    return NULL;
}


/** @brief Hash a triple.
 *
 * TODO This doesn't handle blank nodes correctly.
 */
inline LSUP_Key
LSUP_triple_hash (const LSUP_Triple *trp)
{
    LSUP_BufferTriple *strp = LSUP_triple_serialize (trp);
    LSUP_Key hash = LSUP_btriple_hash (strp);
    LSUP_btriple_free (strp);

    return hash;
}


/** @brief Add an identifier to the term cache.
 *
 * @param[in] key Hash of the inserted term.
 *
 * @param[in] term Term to insert.
 */
LSUP_rc
LSUP_tcache_add (const LSUP_Key key, LSUP_Term *term);

/** @brief Get an identifier from the cache.
 *
 * @param[in] key Key for the queried term.
 *
 * @return The retrieved term if found, or NULL. The string must not be
 *  modified or freed.
 */
const LSUP_Term *
LSUP_tcache_get (const LSUP_Key key);

#endif