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"

// "NULL" triple, a value that is never user-provided. Used to fill deleted
// triples in a keyset.
#define NULL_TRP {NULL_KEY, NULL_KEY, NULL_KEY}

#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
/* Blank node. */
#define LSUP_TERM_BNODE          2
/* Literal without language tag. */
#define LSUP_TERM_LITERAL        3
/* Language-tagged string literal. */
#define LSUP_TERM_LT_LITERAL     4

/*
 * In-term identifier types.
 */
/* Data type IRI. */
#define LSUP_ID_DATATYPE        10
/* Language tag string. */
#define LSUP_ID_LANG            11
/* Temporary blank node ID. TODO implement. */
#define LSUP_ID_BNODE           12

/** @brief Default data type for untyped literals.
 */
#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 struct term_t {
    char *              data;       // URI, literal value, or BNode label.
    union {
        uint32_t        datatype;   // Data type hash for LSUP_TERM_LITERAL.
        uint32_t        lang;       // Lang tag hash for LSUP_TERM_LT_LITERAL.
        uint32_t        bnode_id;   // Blank node ID. TODO implement.
    };
    LSUP_TermType      type;       // Term type.
} LSUP_Term;


/** @brief Hash cache for lang tags and data types.
 */
typedef struct id_cache_t {
    uint32_t            key;
    char *              data;
    UT_hash_handle      hh;
} IDCache;


/*
 * Extern variables.
 */

/** @brief Global ID cache.
 *
 * Map of internal term identifiers, such as literal data types, language tags
 * and BNode identifiers.
 */
extern IDCache *LSUP_id_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;



/*
 * 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 for language-tagged literals or data type
 *  for other literals.
 *
 * @param term[out] Pointer to a new term, which must be freed with
 *  #LSUP_term_free after use.
 *
 * @return LSUP_OK if successful, LSUP_VALUE_ERR if validation fails.
 */
LSUP_Term *
LSUP_term_new (LSUP_TermType type, const char *data, const char *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, const char *metadata);


LSUP_Term *
LSUP_term_new_from_buffer (const LSUP_Buffer *sterm);


LSUP_Buffer *
LSUP_buffer_new_from_term (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.
 */
inline LSUP_Key
LSUP_term_hash (const LSUP_Term *term)
{
    LSUP_Buffer *buf;

    if (UNLIKELY (!term)) buf = BUF_DUMMY;
    else buf = LSUP_buffer_new_from_term (term);

    LSUP_Key key = LSUP_buffer_hash (buf);

    LSUP_buffer_free (buf);

    return key;
}


/**
 * 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 Add an identifier to the term cache.
 *
 * @param[in] key 32-bit hash of the inserted term.
 *
 * @param[in] data Term to insert.
 */
LSUP_rc
LSUP_tcache_add_id (const uint32_t key, const char *data);


/** @brief Get an identifier from the cache.
 *
 * @param[in] key Key for the queried term.
 *
 * @return The retieved term if found, or NULL. The string must not be modified
 *  or freed.
 */
const char *
LSUP_tcache_get_id (const uint32_t key);

#endif