source: trunk/third/perl/hv.c @ 10724

/*    hv.c
 *
 *    Copyright (c) 1991-1997, Larry Wall
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 * "I sit beside the fire and think of all that I have seen."  --Bilbo
 */

#include "EXTERN.h"
#include "perl.h"

static void hsplit _((HV *hv));
static void hfreeentries _((HV *hv));

static HE* more_he();

static HE*
new_he()
{
    HE* he;
    if (he_root) {
        he = he_root;
        he_root = HeNEXT(he);
        return he;
    }
    return more_he();
}

static void
del_he(p)
HE* p;
{
    HeNEXT(p) = (HE*)he_root;
    he_root = p;
}

static HE*
more_he()
{
    register HE* he;
    register HE* heend;
    he_root = (HE*)safemalloc(1008);
    he = he_root;
    heend = &he[1008 / sizeof(HE) - 1];
    while (he < heend) {
        HeNEXT(he) = (HE*)(he + 1);
        he++;
    }
    HeNEXT(he) = 0;
    return new_he();
}

static HEK *
save_hek(str, len, hash)
char *str;
I32 len;
U32 hash;
{
    char *k;
    register HEK *hek;
    
    New(54, k, HEK_BASESIZE + len + 1, char);
    hek = (HEK*)k;
    Copy(str, HEK_KEY(hek), len, char);
    *(HEK_KEY(hek) + len) = '\0';
    HEK_LEN(hek) = len;
    HEK_HASH(hek) = hash;
    return hek;
}

void
unshare_hek(hek)
HEK *hek;
{
    unsharepvn(HEK_KEY(hek),HEK_LEN(hek),HEK_HASH(hek));
}

/* (klen == HEf_SVKEY) is special for MAGICAL hv entries, meaning key slot
 * contains an SV* */

SV**
hv_fetch(hv,key,klen,lval)
HV *hv;
char *key;
U32 klen;
I32 lval;
{
    register XPVHV* xhv;
    register U32 hash;
    register HE *entry;
    SV *sv;

    if (!hv)
        return 0;

    if (SvRMAGICAL(hv)) {
        if (mg_find((SV*)hv,'P')) {
            sv = sv_newmortal();
            mg_copy((SV*)hv, sv, key, klen);
            Sv = sv;
            return &Sv;
        }
    }

    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array) {
        if (lval 
#ifdef DYNAMIC_ENV_FETCH  /* if it's an %ENV lookup, we may get it on the fly */
                 || (HvNAME(hv) && strEQ(HvNAME(hv),ENV_HV_NAME))
#endif
                                                                  )
            Newz(503,xhv->xhv_array, sizeof(HE*) * (xhv->xhv_max + 1), char);
        else
            return 0;
    }

    PERL_HASH(hash, key, klen);

    entry = ((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (; entry; entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        return &HeVAL(entry);
    }
#ifdef DYNAMIC_ENV_FETCH  /* %ENV lookup?  If so, try to fetch the value now */
    if (HvNAME(hv) && strEQ(HvNAME(hv),ENV_HV_NAME)) {
      char *gotenv;

      if ((gotenv = ENV_getenv(key)) != Nullch) {
        sv = newSVpv(gotenv,strlen(gotenv));
        SvTAINTED_on(sv);
        return hv_store(hv,key,klen,sv,hash);
      }
    }
#endif
    if (lval) {         /* gonna assign to this, so it better be there */
        sv = NEWSV(61,0);
        return hv_store(hv,key,klen,sv,hash);
    }
    return 0;
}

/* returns a HE * structure with the all fields set */
/* note that hent_val will be a mortal sv for MAGICAL hashes */
HE *
hv_fetch_ent(hv,keysv,lval,hash)
HV *hv;
SV *keysv;
I32 lval;
register U32 hash;
{
    register XPVHV* xhv;
    register char *key;
    STRLEN klen;
    register HE *entry;
    SV *sv;

    if (!hv)
        return 0;

    if (SvRMAGICAL(hv) && mg_find((SV*)hv,'P')) {
        static HE mh;

        sv = sv_newmortal();
        keysv = sv_2mortal(newSVsv(keysv));
        mg_copy((SV*)hv, sv, (char*)keysv, HEf_SVKEY);
        if (!HeKEY_hek(&mh)) {
            char *k;
            New(54, k, HEK_BASESIZE + sizeof(SV*), char);
            HeKEY_hek(&mh) = (HEK*)k;
        }
        HeSVKEY_set(&mh, keysv);
        HeVAL(&mh) = sv;
        return &mh;
    }

    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array) {
        if (lval 
#ifdef DYNAMIC_ENV_FETCH  /* if it's an %ENV lookup, we may get it on the fly */
                 || (HvNAME(hv) && strEQ(HvNAME(hv),ENV_HV_NAME))
#endif
                                                                  )
            Newz(503,xhv->xhv_array, sizeof(HE*) * (xhv->xhv_max + 1), char);
        else
            return 0;
    }

    key = SvPV(keysv, klen);
    
    if (!hash)
        PERL_HASH(hash, key, klen);

    entry = ((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (; entry; entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        return entry;
    }
#ifdef DYNAMIC_ENV_FETCH  /* %ENV lookup?  If so, try to fetch the value now */
    if (HvNAME(hv) && strEQ(HvNAME(hv),ENV_HV_NAME)) {
      char *gotenv;

      if ((gotenv = ENV_getenv(key)) != Nullch) {
        sv = newSVpv(gotenv,strlen(gotenv));
        SvTAINTED_on(sv);
        return hv_store_ent(hv,keysv,sv,hash);
      }
    }
#endif
    if (lval) {         /* gonna assign to this, so it better be there */
        sv = NEWSV(61,0);
        return hv_store_ent(hv,keysv,sv,hash);
    }
    return 0;
}

SV**
hv_store(hv,key,klen,val,hash)
HV *hv;
char *key;
U32 klen;
SV *val;
register U32 hash;
{
    register XPVHV* xhv;
    register I32 i;
    register HE *entry;
    register HE **oentry;

    if (!hv)
        return 0;

    xhv = (XPVHV*)SvANY(hv);
    if (SvMAGICAL(hv)) {
        mg_copy((SV*)hv, val, key, klen);
        if (!xhv->xhv_array
            && (SvMAGIC(hv)->mg_moremagic
                || (SvMAGIC(hv)->mg_type != 'E'
#ifdef OVERLOAD
                    && SvMAGIC(hv)->mg_type != 'A'
#endif /* OVERLOAD */
                    )))
            return 0;
    }
    if (!hash)
        PERL_HASH(hash, key, klen);

    if (!xhv->xhv_array)
        Newz(505, xhv->xhv_array, sizeof(HE**) * (xhv->xhv_max + 1), char);

    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    i = 1;

    for (entry = *oentry; entry; i=0, entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        SvREFCNT_dec(HeVAL(entry));
        HeVAL(entry) = val;
        return &HeVAL(entry);
    }

    entry = new_he();
    if (HvSHAREKEYS(hv))
        HeKEY_hek(entry) = share_hek(key, klen, hash);
    else                                       /* gotta do the real thing */
        HeKEY_hek(entry) = save_hek(key, klen, hash);
    HeVAL(entry) = val;
    HeNEXT(entry) = *oentry;
    *oentry = entry;

    xhv->xhv_keys++;
    if (i) {                            /* initial entry? */
        ++xhv->xhv_fill;
        if (xhv->xhv_keys > xhv->xhv_max)
            hsplit(hv);
    }

    return &HeVAL(entry);
}

HE *
hv_store_ent(hv,keysv,val,hash)
HV *hv;
SV *keysv;
SV *val;
register U32 hash;
{
    register XPVHV* xhv;
    register char *key;
    STRLEN klen;
    register I32 i;
    register HE *entry;
    register HE **oentry;

    if (!hv)
        return 0;

    xhv = (XPVHV*)SvANY(hv);
    if (SvMAGICAL(hv)) {
        bool save_taint = tainted;
        if (tainting)
            tainted = SvTAINTED(keysv);
        keysv = sv_2mortal(newSVsv(keysv));
        mg_copy((SV*)hv, val, (char*)keysv, HEf_SVKEY);
        TAINT_IF(save_taint);
        if (!xhv->xhv_array
            && (SvMAGIC(hv)->mg_moremagic
                || (SvMAGIC(hv)->mg_type != 'E'
#ifdef OVERLOAD
                    && SvMAGIC(hv)->mg_type != 'A'
#endif /* OVERLOAD */
                    )))
          return Nullhe;
    }

    key = SvPV(keysv, klen);
    
    if (!hash)
        PERL_HASH(hash, key, klen);

    if (!xhv->xhv_array)
        Newz(505, xhv->xhv_array, sizeof(HE**) * (xhv->xhv_max + 1), char);

    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    i = 1;

    for (entry = *oentry; entry; i=0, entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        SvREFCNT_dec(HeVAL(entry));
        HeVAL(entry) = val;
        return entry;
    }

    entry = new_he();
    if (HvSHAREKEYS(hv))
        HeKEY_hek(entry) = share_hek(key, klen, hash);
    else                                       /* gotta do the real thing */
        HeKEY_hek(entry) = save_hek(key, klen, hash);
    HeVAL(entry) = val;
    HeNEXT(entry) = *oentry;
    *oentry = entry;

    xhv->xhv_keys++;
    if (i) {                            /* initial entry? */
        ++xhv->xhv_fill;
        if (xhv->xhv_keys > xhv->xhv_max)
            hsplit(hv);
    }

    return entry;
}

SV *
hv_delete(hv,key,klen,flags)
HV *hv;
char *key;
U32 klen;
I32 flags;
{
    register XPVHV* xhv;
    register I32 i;
    register U32 hash;
    register HE *entry;
    register HE **oentry;
    SV *sv;

    if (!hv)
        return Nullsv;
    if (SvRMAGICAL(hv)) {
        sv = *hv_fetch(hv, key, klen, TRUE);
        mg_clear(sv);
        if (mg_find(sv, 's')) {
            return Nullsv;              /* %SIG elements cannot be deleted */
        }
        if (mg_find(sv, 'p')) {
            sv_unmagic(sv, 'p');        /* No longer an element */
            return sv;
        }
    }
    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array)
        return Nullsv;

    PERL_HASH(hash, key, klen);

    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    entry = *oentry;
    i = 1;
    for (; entry; i=0, oentry = &HeNEXT(entry), entry = *oentry) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        *oentry = HeNEXT(entry);
        if (i && !*oentry)
            xhv->xhv_fill--;
        if (flags & G_DISCARD)
            sv = Nullsv;
        else
            sv = sv_mortalcopy(HeVAL(entry));
        if (entry == xhv->xhv_eiter)
            HvLAZYDEL_on(hv);
        else
            hv_free_ent(hv, entry);
        --xhv->xhv_keys;
        return sv;
    }
    return Nullsv;
}

SV *
hv_delete_ent(hv,keysv,flags,hash)
HV *hv;
SV *keysv;
I32 flags;
U32 hash;
{
    register XPVHV* xhv;
    register I32 i;
    register char *key;
    STRLEN klen;
    register HE *entry;
    register HE **oentry;
    SV *sv;
    
    if (!hv)
        return Nullsv;
    if (SvRMAGICAL(hv)) {
        entry = hv_fetch_ent(hv, keysv, TRUE, hash);
        sv = HeVAL(entry);
        mg_clear(sv);
        if (mg_find(sv, 'p')) {
            sv_unmagic(sv, 'p');        /* No longer an element */
            return sv;
        }
    }
    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array)
        return Nullsv;

    key = SvPV(keysv, klen);
    
    if (!hash)
        PERL_HASH(hash, key, klen);

    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    entry = *oentry;
    i = 1;
    for (; entry; i=0, oentry = &HeNEXT(entry), entry = *oentry) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        *oentry = HeNEXT(entry);
        if (i && !*oentry)
            xhv->xhv_fill--;
        if (flags & G_DISCARD)
            sv = Nullsv;
        else
            sv = sv_mortalcopy(HeVAL(entry));
        if (entry == xhv->xhv_eiter)
            HvLAZYDEL_on(hv);
        else
            hv_free_ent(hv, entry);
        --xhv->xhv_keys;
        return sv;
    }
    return Nullsv;
}

bool
hv_exists(hv,key,klen)
HV *hv;
char *key;
U32 klen;
{
    register XPVHV* xhv;
    register U32 hash;
    register HE *entry;
    SV *sv;

    if (!hv)
        return 0;

    if (SvRMAGICAL(hv)) {
        if (mg_find((SV*)hv,'P')) {
            sv = sv_newmortal();
            mg_copy((SV*)hv, sv, key, klen); 
            magic_existspack(sv, mg_find(sv, 'p'));
            return SvTRUE(sv);
        }
    }

    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array)
        return 0; 

    PERL_HASH(hash, key, klen);

    entry = ((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (; entry; entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        return TRUE;
    }
    return FALSE;
}


bool
hv_exists_ent(hv,keysv,hash)
HV *hv;
SV *keysv;
U32 hash;
{
    register XPVHV* xhv;
    register char *key;
    STRLEN klen;
    register HE *entry;
    SV *sv;

    if (!hv)
        return 0;

    if (SvRMAGICAL(hv)) {
        if (mg_find((SV*)hv,'P')) {
            sv = sv_newmortal();
            keysv = sv_2mortal(newSVsv(keysv));
            mg_copy((SV*)hv, sv, (char*)keysv, HEf_SVKEY); 
            magic_existspack(sv, mg_find(sv, 'p'));
            return SvTRUE(sv);
        }
    }

    xhv = (XPVHV*)SvANY(hv);
    if (!xhv->xhv_array)
        return 0; 

    key = SvPV(keysv, klen);
    if (!hash)
        PERL_HASH(hash, key, klen);

    entry = ((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (; entry; entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != klen)
            continue;
        if (memNE(HeKEY(entry),key,klen))       /* is this it? */
            continue;
        return TRUE;
    }
    return FALSE;
}

static void
hsplit(hv)
HV *hv;
{
    register XPVHV* xhv = (XPVHV*)SvANY(hv);
    I32 oldsize = (I32) xhv->xhv_max + 1; /* sic(k) */
    register I32 newsize = oldsize * 2;
    register I32 i;
    register HE **a;
    register HE **b;
    register HE *entry;
    register HE **oentry;
#ifndef STRANGE_MALLOC
    I32 tmp;
#endif

    a = (HE**)xhv->xhv_array;
    nomemok = TRUE;
#ifdef STRANGE_MALLOC
    Renew(a, newsize, HE*);
#else
    i = newsize * sizeof(HE*);
#define MALLOC_OVERHEAD 16
    tmp = MALLOC_OVERHEAD;
    while (tmp - MALLOC_OVERHEAD < i)
        tmp += tmp;
    tmp -= MALLOC_OVERHEAD;
    tmp /= sizeof(HE*);
    assert(tmp >= newsize);
    New(2,a, tmp, HE*);
    Copy(xhv->xhv_array, a, oldsize, HE*);
    if (oldsize >= 64 && !nice_chunk) {
        nice_chunk = (char*)xhv->xhv_array;
        nice_chunk_size = oldsize * sizeof(HE*) * 2 - MALLOC_OVERHEAD;
    }
    else
        Safefree(xhv->xhv_array);
#endif

    nomemok = FALSE;
    Zero(&a[oldsize], oldsize, HE*);            /* zero 2nd half*/
    xhv->xhv_max = --newsize;
    xhv->xhv_array = (char*)a;

    for (i=0; i<oldsize; i++,a++) {
        if (!*a)                                /* non-existent */
            continue;
        b = a+oldsize;
        for (oentry = a, entry = *a; entry; entry = *oentry) {
            if ((HeHASH(entry) & newsize) != i) {
                *oentry = HeNEXT(entry);
                HeNEXT(entry) = *b;
                if (!*b)
                    xhv->xhv_fill++;
                *b = entry;
                continue;
            }
            else
                oentry = &HeNEXT(entry);
        }
        if (!*a)                                /* everything moved */
            xhv->xhv_fill--;
    }
}

void
hv_ksplit(hv, newmax)
HV *hv;
IV newmax;
{
    register XPVHV* xhv = (XPVHV*)SvANY(hv);
    I32 oldsize = (I32) xhv->xhv_max + 1; /* sic(k) */
    register I32 newsize;
    register I32 i;
    register I32 j;
    register HE **a;
    register HE *entry;
    register HE **oentry;

    newsize = (I32) newmax;                     /* possible truncation here */
    if (newsize != newmax || newmax <= oldsize)
        return;
    while ((newsize & (1 + ~newsize)) != newsize) {
        newsize &= ~(newsize & (1 + ~newsize)); /* get proper power of 2 */
    }
    if (newsize < newmax)
        newsize *= 2;
    if (newsize < newmax)
        return;                                 /* overflow detection */

    a = (HE**)xhv->xhv_array;
    if (a) {
        nomemok = TRUE;
#ifdef STRANGE_MALLOC
        Renew(a, newsize, HE*);
#else
        i = newsize * sizeof(HE*);
        j = MALLOC_OVERHEAD;
        while (j - MALLOC_OVERHEAD < i)
            j += j;
        j -= MALLOC_OVERHEAD;
        j /= sizeof(HE*);
        assert(j >= newsize);
        New(2, a, j, HE*);
        Copy(xhv->xhv_array, a, oldsize, HE*);
        if (oldsize >= 64 && !nice_chunk) {
            nice_chunk = (char*)xhv->xhv_array;
            nice_chunk_size = oldsize * sizeof(HE*) * 2 - MALLOC_OVERHEAD;
        }
        else
            Safefree(xhv->xhv_array);
#endif
        nomemok = FALSE;
        Zero(&a[oldsize], newsize-oldsize, HE*); /* zero 2nd half*/
    }
    else {
        Newz(0, a, newsize, HE*);
    }
    xhv->xhv_max = --newsize;
    xhv->xhv_array = (char*)a;
    if (!xhv->xhv_fill)                         /* skip rest if no entries */
        return;

    for (i=0; i<oldsize; i++,a++) {
        if (!*a)                                /* non-existent */
            continue;
        for (oentry = a, entry = *a; entry; entry = *oentry) {
            if ((j = (HeHASH(entry) & newsize)) != i) {
                j -= i;
                *oentry = HeNEXT(entry);
                if (!(HeNEXT(entry) = a[j]))
                    xhv->xhv_fill++;
                a[j] = entry;
                continue;
            }
            else
                oentry = &HeNEXT(entry);
        }
        if (!*a)                                /* everything moved */
            xhv->xhv_fill--;
    }
}

HV *
newHV()
{
    register HV *hv;
    register XPVHV* xhv;

    hv = (HV*)NEWSV(502,0);
    sv_upgrade((SV *)hv, SVt_PVHV);
    xhv = (XPVHV*)SvANY(hv);
    SvPOK_off(hv);
    SvNOK_off(hv);
#ifndef NODEFAULT_SHAREKEYS    
    HvSHAREKEYS_on(hv);         /* key-sharing on by default */
#endif    
    xhv->xhv_max = 7;           /* start with 8 buckets */
    xhv->xhv_fill = 0;
    xhv->xhv_pmroot = 0;
    (void)hv_iterinit(hv);      /* so each() will start off right */
    return hv;
}

void
hv_free_ent(hv, entry)
HV *hv;
register HE *entry;
{
    if (!entry)
        return;
    if (isGV(HeVAL(entry)) && GvCVu(HeVAL(entry)) && HvNAME(hv))
        sub_generation++;       /* may be deletion of method from stash */
    SvREFCNT_dec(HeVAL(entry));
    if (HeKLEN(entry) == HEf_SVKEY) {
        SvREFCNT_dec(HeKEY_sv(entry));
        Safefree(HeKEY_hek(entry));
    }
    else if (HvSHAREKEYS(hv))
        unshare_hek(HeKEY_hek(entry));
    else
        Safefree(HeKEY_hek(entry));
    del_he(entry);
}

void
hv_delayfree_ent(hv, entry)
HV *hv;
register HE *entry;
{
    if (!entry)
        return;
    if (isGV(HeVAL(entry)) && GvCVu(HeVAL(entry)) && HvNAME(hv))
        sub_generation++;       /* may be deletion of method from stash */
    sv_2mortal(HeVAL(entry));   /* free between statements */
    if (HeKLEN(entry) == HEf_SVKEY) {
        sv_2mortal(HeKEY_sv(entry));
        Safefree(HeKEY_hek(entry));
    }
    else if (HvSHAREKEYS(hv))
        unshare_hek(HeKEY_hek(entry));
    else
        Safefree(HeKEY_hek(entry));
    del_he(entry);
}

void
hv_clear(hv)
HV *hv;
{
    register XPVHV* xhv;
    if (!hv)
        return;
    xhv = (XPVHV*)SvANY(hv);
    hfreeentries(hv);
    xhv->xhv_fill = 0;
    xhv->xhv_keys = 0;
    if (xhv->xhv_array)
        (void)memzero(xhv->xhv_array, (xhv->xhv_max + 1) * sizeof(HE*));

    if (SvRMAGICAL(hv))
        mg_clear((SV*)hv); 
}

static void
hfreeentries(hv)
HV *hv;
{
    register HE **array;
    register HE *entry;
    register HE *oentry = Null(HE*);
    I32 riter;
    I32 max;

    if (!hv)
        return;
    if (!HvARRAY(hv))
        return;

    riter = 0;
    max = HvMAX(hv);
    array = HvARRAY(hv);
    entry = array[0];
    for (;;) {
        if (entry) {
            oentry = entry;
            entry = HeNEXT(entry);
            hv_free_ent(hv, oentry);
        }
        if (!entry) {
            if (++riter > max)
                break;
            entry = array[riter];
        } 
    }
    (void)hv_iterinit(hv);
}

void
hv_undef(hv)
HV *hv;
{
    register XPVHV* xhv;
    if (!hv)
        return;
    xhv = (XPVHV*)SvANY(hv);
    hfreeentries(hv);
    Safefree(xhv->xhv_array);
    if (HvNAME(hv)) {
        Safefree(HvNAME(hv));
        HvNAME(hv) = 0;
    }
    xhv->xhv_array = 0;
    xhv->xhv_max = 7;           /* it's a normal hash */
    xhv->xhv_fill = 0;
    xhv->xhv_keys = 0;

    if (SvRMAGICAL(hv))
        mg_clear((SV*)hv); 
}

I32
hv_iterinit(hv)
HV *hv;
{
    register XPVHV* xhv;
    HE *entry;

    if (!hv)
        croak("Bad hash");
    xhv = (XPVHV*)SvANY(hv);
    entry = xhv->xhv_eiter;
#ifdef DYNAMIC_ENV_FETCH  /* set up %ENV for iteration */
    if (HvNAME(hv) && strEQ(HvNAME(hv), ENV_HV_NAME))
        prime_env_iter();
#endif
    if (entry && HvLAZYDEL(hv)) {       /* was deleted earlier? */
        HvLAZYDEL_off(hv);
        hv_free_ent(hv, entry);
    }
    xhv->xhv_riter = -1;
    xhv->xhv_eiter = Null(HE*);
    return xhv->xhv_fill;       /* should be xhv->xhv_keys? May change later */
}

HE *
hv_iternext(hv)
HV *hv;
{
    register XPVHV* xhv;
    register HE *entry;
    HE *oldentry;
    MAGIC* mg;

    if (!hv)
        croak("Bad hash");
    xhv = (XPVHV*)SvANY(hv);
    oldentry = entry = xhv->xhv_eiter;

    if (SvRMAGICAL(hv) && (mg = mg_find((SV*)hv,'P'))) {
        SV *key = sv_newmortal();
        if (entry) {
            sv_setsv(key, HeSVKEY_force(entry));
            SvREFCNT_dec(HeSVKEY(entry));       /* get rid of previous key */
        }
        else {
            char *k;
            HEK *hek;

            xhv->xhv_eiter = entry = new_he();  /* one HE per MAGICAL hash */
            Zero(entry, 1, HE);
            Newz(54, k, HEK_BASESIZE + sizeof(SV*), char);
            hek = (HEK*)k;
            HeKEY_hek(entry) = hek;
            HeKLEN(entry) = HEf_SVKEY;
        }
        magic_nextpack((SV*) hv,mg,key);
        if (SvOK(key)) {
            /* force key to stay around until next time */
            HeSVKEY_set(entry, SvREFCNT_inc(key));
            return entry;               /* beware, hent_val is not set */
        }
        if (HeVAL(entry))
            SvREFCNT_dec(HeVAL(entry));
        Safefree(HeKEY_hek(entry));
        del_he(entry);
        xhv->xhv_eiter = Null(HE*);
        return Null(HE*);
    }

    if (!xhv->xhv_array)
        Newz(506,xhv->xhv_array, sizeof(HE*) * (xhv->xhv_max + 1), char);
    if (entry)
        entry = HeNEXT(entry);
    while (!entry) {
        ++xhv->xhv_riter;
        if (xhv->xhv_riter > xhv->xhv_max) {
            xhv->xhv_riter = -1;
            break;
        }
        entry = ((HE**)xhv->xhv_array)[xhv->xhv_riter];
    }

    if (oldentry && HvLAZYDEL(hv)) {            /* was deleted earlier? */
        HvLAZYDEL_off(hv);
        hv_free_ent(hv, oldentry);
    }

    xhv->xhv_eiter = entry;
    return entry;
}

char *
hv_iterkey(entry,retlen)
register HE *entry;
I32 *retlen;
{
    if (HeKLEN(entry) == HEf_SVKEY) {
        STRLEN len;
        char *p = SvPV(HeKEY_sv(entry), len);
        *retlen = len;
        return p;
    }
    else {
        *retlen = HeKLEN(entry);
        return HeKEY(entry);
    }
}

/* unlike hv_iterval(), this always returns a mortal copy of the key */
SV *
hv_iterkeysv(entry)
register HE *entry;
{
    if (HeKLEN(entry) == HEf_SVKEY)
        return sv_mortalcopy(HeKEY_sv(entry));
    else
        return sv_2mortal(newSVpv((HeKLEN(entry) ? HeKEY(entry) : ""),
                                  HeKLEN(entry)));
}

SV *
hv_iterval(hv,entry)
HV *hv;
register HE *entry;
{
    if (SvRMAGICAL(hv)) {
        if (mg_find((SV*)hv,'P')) {
            SV* sv = sv_newmortal();
            if (HeKLEN(entry) == HEf_SVKEY)
                mg_copy((SV*)hv, sv, (char*)HeKEY_sv(entry), HEf_SVKEY);
            else mg_copy((SV*)hv, sv, HeKEY(entry), HeKLEN(entry));
            return sv;
        }
    }
    return HeVAL(entry);
}

SV *
hv_iternextsv(hv, key, retlen)
    HV *hv;
    char **key;
    I32 *retlen;
{
    HE *he;
    if ( (he = hv_iternext(hv)) == NULL)
        return NULL;
    *key = hv_iterkey(he, retlen);
    return hv_iterval(hv, he);
}

void
hv_magic(hv, gv, how)
HV* hv;
GV* gv;
int how;
{
    sv_magic((SV*)hv, (SV*)gv, how, Nullch, 0);
}

char*   
sharepvn(sv, len, hash)
char* sv;
I32 len;
U32 hash;
{
    return HEK_KEY(share_hek(sv, len, hash));
}

/* possibly free a shared string if no one has access to it
 * len and hash must both be valid for str.
 */
void
unsharepvn(str, len, hash)
char* str;
I32 len;
U32 hash;
{
    register XPVHV* xhv;
    register HE *entry;
    register HE **oentry;
    register I32 i = 1;
    I32 found = 0;
    
    /* what follows is the moral equivalent of:
    if ((Svp = hv_fetch(strtab, tmpsv, FALSE, hash))) {
        if (--*Svp == Nullsv)
            hv_delete(strtab, str, len, G_DISCARD, hash);
    } */
    xhv = (XPVHV*)SvANY(strtab);
    /* assert(xhv_array != 0) */
    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (entry = *oentry; entry; i=0, oentry = &HeNEXT(entry), entry = *oentry) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != len)
            continue;
        if (memNE(HeKEY(entry),str,len))        /* is this it? */
            continue;
        found = 1;
        if (--HeVAL(entry) == Nullsv) {
            *oentry = HeNEXT(entry);
            if (i && !*oentry)
                xhv->xhv_fill--;
            Safefree(HeKEY_hek(entry));
            del_he(entry);
            --xhv->xhv_keys;
        }
        break;
    }
    
    if (!found)
        warn("Attempt to free non-existent shared string");    
}

/* get a (constant) string ptr from the global string table
 * string will get added if it is not already there.
 * len and hash must both be valid for str.
 */
HEK *
share_hek(str, len, hash)
char *str;
I32 len;
register U32 hash;
{
    register XPVHV* xhv;
    register HE *entry;
    register HE **oentry;
    register I32 i = 1;
    I32 found = 0;

    /* what follows is the moral equivalent of:
       
    if (!(Svp = hv_fetch(strtab, str, len, FALSE)))
        hv_store(strtab, str, len, Nullsv, hash);
    */
    xhv = (XPVHV*)SvANY(strtab);
    /* assert(xhv_array != 0) */
    oentry = &((HE**)xhv->xhv_array)[hash & (I32) xhv->xhv_max];
    for (entry = *oentry; entry; i=0, entry = HeNEXT(entry)) {
        if (HeHASH(entry) != hash)              /* strings can't be equal */
            continue;
        if (HeKLEN(entry) != len)
            continue;
        if (memNE(HeKEY(entry),str,len))        /* is this it? */
            continue;
        found = 1;
        break;
    }
    if (!found) {
        entry = new_he();
        HeKEY_hek(entry) = save_hek(str, len, hash);
        HeVAL(entry) = Nullsv;
        HeNEXT(entry) = *oentry;
        *oentry = entry;
        xhv->xhv_keys++;
        if (i) {                                /* initial entry? */
            ++xhv->xhv_fill;
            if (xhv->xhv_keys > xhv->xhv_max)
                hsplit(strtab);
        }
    }

    ++HeVAL(entry);                             /* use value slot as REFCNT */
    return HeKEY_hek(entry);
}