/*    hv.h
 *
 *    Copyright (C) 1991, 1992, 1993, 1996, 1997, 1998, 1999,
 *    2000, 2001, 2002, 2003, 2005, 2006, 2007, 2008, by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/* These control hash traversal randomization and the environment variable PERL_PERTURB_KEYS.
 * Currently disabling this functionality will break a few tests, but should otherwise work fine.
 * See perlrun for more details. */

#if defined(PERL_PERTURB_KEYS_DISABLED)
#   define PL_HASH_RAND_BITS_ENABLED        0
#   define PERL_HASH_ITER_BUCKET(iter)      ((iter)->xhv_riter)
#else
#   define PERL_HASH_RANDOMIZE_KEYS         1
#   if defined(PERL_PERTURB_KEYS_RANDOM)
#       define PL_HASH_RAND_BITS_ENABLED    1
#   elif defined(PERL_PERTURB_KEYS_DETERMINISTIC)
#       define PL_HASH_RAND_BITS_ENABLED    2
#   else
#       define USE_PERL_PERTURB_KEYS        1
#       define PL_HASH_RAND_BITS_ENABLED    PL_hash_rand_bits_enabled
#   endif
#   define PERL_HASH_ITER_BUCKET(iter)      (((iter)->xhv_riter) ^ ((iter)->xhv_rand))
#endif

/* entry in hash value chain */
struct he {
    /* Keep hent_next first in this structure, because sv_free_arenas take
       advantage of this to share code between the he arenas and the SV
       body arenas  */
    HE		*hent_next;	/* next entry in chain */
    HEK		*hent_hek;	/* hash key */
    union {
	SV	*hent_val;	/* scalar value that was hashed */
	Size_t	hent_refcount;	/* references for this shared hash key */
    } he_valu;
};

/* hash key -- defined separately for use as shared pointer */
struct hek {
    U32		hek_hash;	/* hash of key */
    I32		hek_len;	/* length of hash key */
    char	hek_key[1];	/* variable-length hash key */
    /* the hash-key is \0-terminated */
    /* after the \0 there is a byte for flags, such as whether the key
       is UTF-8 */
};

struct shared_he {
    struct he shared_he_he;
    struct hek shared_he_hek;
};

/* Subject to change.
   Don't access this directly.
   Use the funcs in mro_core.c
*/