ghostscript-7.07/src/idict.c

/* Copyright (C) 1989, 1996, 1997, 1998, 1999, 2000 artofcode LLC.  All rights reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation, Inc.,
  59 Temple Place, Suite 330, Boston, MA, 02111-1307.

*/

/*$Id: idict.c,v 1.4.4.1.2.1 2003/01/17 00:49:04 giles Exp $ */
/* Dictionary implementation */
#include "math_.h"		/* for frexp */
#include "string_.h"		/* for strlen */
#include "ghost.h"
#include "gxalloc.h"		/* for accessing masks */
#include "errors.h"
#include "imemory.h"
#include "idebug.h"		/* for debug_print_name */
#include "inamedef.h"
#include "iname.h"
#include "ipacked.h"
#include "isave.h"		/* for value cache in names */
#include "store.h"
#include "idict.h"		/* interface definition */
#include "idictdef.h"
#include "iutil.h"
#include "ivmspace.h"		/* for store check */

/*
 * Dictionaries per se aren't supposed to know anything about the
 * dictionary stack, let alone the interpreter's dictionary stack.
 * Unfortunately, there is are two design couplings between them:
 * dictionary stacks cache some of the elements of their top dictionary
 * (requiring updating when that dictionary grows or is unpacked),
 * and names may cache a pointer to their definition (requiring a
 * check whether a dictionary appears on the dictionary stack).
 * Therefore, we need iddstack.h here.
 * We'd really like to fix this, but we don't see how.
 */
#include "iddstack.h"

/*
 * Define the size of the largest valid dictionary.
 * This is limited by the size field of the keys and values refs,
 * and by the enumeration interface, which requires the size to
 * fit in an int.  As it happens, max_array_size will always be
 * smaller than max_int.
 */
const uint dict_max_size = max_array_size - 1;

/* Define whether dictionaries expand automatically when full. */
bool dict_auto_expand = false;

/* Define whether dictionaries are packed by default. */
bool dict_default_pack = true;

/*
 * Define the check for whether we can set the 1-element cache.
 * We only set the cache if we aren't inside a save.
 * This way, we never have to undo setting the cache.
 */
#define CAN_SET_PVALUE_CACHE(pds, pdref, mem)\
  (pds && dstack_dict_is_permanent(pds, pdref) && !ref_saving_in(mem))

/* Forward references */
private int dict_create_contents(P3(uint size, const ref * pdref, bool pack));

/* Debugging statistics */
#ifdef DEBUG
struct stats_dict_s {
    long lookups;		/* total lookups */
    long probe1;		/* successful lookups on only 1 probe */
    long probe2;		/* successful lookups on 2 probes */
} stats_dict;

/* Wrapper for dict_find */
int real_dict_find(P3(const ref * pdref, const ref * key, ref ** ppvalue));
int
dict_find(const ref * pdref, const ref * pkey, ref ** ppvalue)
{
    dict *pdict = pdref->value.pdict;
    int code = real_dict_find(pdref, pkey, ppvalue);

    stats_dict.lookups++;
    if (r_has_type(pkey, t_name) && dict_is_packed(pdict)) {
	uint nidx = name_index(pkey);
	uint hash =
	dict_hash_mod(dict_name_index_hash(nidx), npairs(pdict)) + 1;

	if (pdict->keys.value.packed[hash] ==
	    pt_tag(pt_literal_name) + nidx
	    )
	    stats_dict.probe1++;
	else if (pdict->keys.value.packed[hash - 1] ==
		 pt_tag(pt_literal_name) + nidx
	    )
	    stats_dict.probe2++;
    }
    /* Do the cheap flag test before the expensive remainder test. */
    if (gs_debug_c('d') && !(stats_dict.lookups % 1000))
	dlprintf3("[d]lookups=%ld probe1=%ld probe2=%ld\n",
		  stats_dict.lookups, stats_dict.probe1, stats_dict.probe2);
    return code;
}
#define dict_find real_dict_find
#endif

/* Round up the size of a dictionary.  Return 0 if too large. */
uint
dict_round_size_small(uint rsize)
{
    return (rsize > dict_max_size ? 0 : rsize);
}
uint
dict_round_size_large(uint rsize)
{				/* Round up to a power of 2 if not huge. */
    /* If the addition overflows, the new rsize will be zero, */
    /* which will (correctly) be interpreted as a limitcheck. */
    if (rsize > dict_max_non_huge)
	return (rsize > dict_max_size ? 0 : rsize);
    while (rsize & (rsize - 1))
	rsize = (rsize | (rsize - 1)) + 1;
    return (rsize <= dict_max_size ? rsize : dict_max_non_huge);
}

/* Create a dictionary using the given allocator. */
int
dict_alloc(gs_ref_memory_t * mem, uint size, ref * pdref)
{
    ref arr;
    int code =
	gs_alloc_ref_array(mem, &arr, a_all, sizeof(dict) / sizeof(ref),
			   "dict_alloc");
    dict *pdict;
    ref dref;

    if (code < 0)
	return code;
    pdict = (dict *) arr.value.refs;
    make_tav(&dref, t_dictionary,
	     r_space(&arr) | imemory_new_mask(mem) | a_all,
	     pdict, pdict);
    make_struct(&pdict->memory, avm_foreign, mem);
    code = dict_create_contents(size, &dref, dict_default_pack);
    if (code < 0) {
	gs_free_ref_array(mem, &arr, "dict_alloc");
	return code;
    }
    *pdref = dref;
    return 0;
}
/* Create unpacked keys for a dictionary. */
/* The keys are allocated using the same allocator as the dictionary. */
private int
dict_create_unpacked_keys(uint asize, const ref * pdref)
{
    dict *pdict = pdref->value.pdict;
    gs_ref_memory_t *mem = dict_memory(pdict);
    int code;

    code = gs_alloc_ref_array(mem, &pdict->keys, a_all, asize,
			      "dict_create_unpacked_keys");
    if (code >= 0) {
	uint new_mask = imemory_new_mask(mem);
	ref *kp = pdict->keys.value.refs;

	r_set_attrs(&pdict->keys, new_mask);
	refset_null_new(kp, asize, new_mask);
	r_set_attrs(kp, a_executable);	/* wraparound entry */
    }
    return code;
}
/* Create the contents (keys and values) of a newly allocated dictionary. */
/* Allocate in the current VM space, which is assumed to be the same as */
/* the VM space where the dictionary is allocated. */
private int
dict_create_contents(uint size, const ref * pdref, bool pack)
{
    dict *pdict = pdref->value.pdict;
    gs_ref_memory_t *mem = dict_memory(pdict);
    uint new_mask = imemory_new_mask(mem);
    uint asize = dict_round_size((size == 0 ? 1 : size));
    int code;
    register uint i;

    if (asize == 0 || asize > max_array_size - 1)	/* too large */
	return_error(e_limitcheck);
    asize++;			/* allow room for wraparound entry */
    code = gs_alloc_ref_array(mem, &pdict->values, a_all, asize,
			      "dict_create_contents(values)");
    if (code < 0)
	return code;
    r_set_attrs(&pdict->values, new_mask);
    refset_null_new(pdict->values.value.refs, asize, new_mask);
    if (pack) {
	uint ksize = (asize + packed_per_ref - 1) / packed_per_ref;
	ref arr;
	ref_packed *pkp;
	ref_packed *pzp;

	code = gs_alloc_ref_array(mem, &arr, a_all, ksize,
				  "dict_create_contents(packed keys)");
	if (code < 0)
	    return code;
	pkp = (ref_packed *) arr.value.refs;
	make_tasv(&pdict->keys, t_shortarray,
		  r_space(&arr) | a_all | new_mask,
		  asize, packed, pkp);
	for (pzp = pkp, i = 0; i < asize || i % packed_per_ref; pzp++, i++)
	    *pzp = packed_key_empty;
	*pkp = packed_key_deleted;	/* wraparound entry */
    } else {			/* not packed */
	int code = dict_create_unpacked_keys(asize, pdref);

	if (code < 0)
	    return code;
    }
    make_tav(&pdict->count, t_integer, new_mask, intval, 0);
    make_tav(&pdict->maxlength, t_integer, new_mask, intval, size);
    return 0;
}

/*
 * Ensure that a dictionary uses the unpacked representation for keys.
 * We can't just use dict_resize, because the values slots mustn't move.
 */
int
dict_unpack(ref * pdref, dict_stack_t *pds)
{
    dict *pdict = pdref->value.pdict;

    if (!dict_is_packed(pdict))
	return 0;		/* nothing to do */
    {
	gs_ref_memory_t *mem = dict_memory(pdict);
	uint count = nslots(pdict);
	const ref_packed *okp = pdict->keys.value.packed;
	ref old_keys;
	int code;
	ref *nkp;

	old_keys = pdict->keys;
	if (ref_must_save_in(mem, &old_keys))
	    ref_do_save_in(mem, pdref, &pdict->keys, "dict_unpack(keys)");
	code = dict_create_unpacked_keys(count, pdref);
	if (code < 0)
	    return code;
	for (nkp = pdict->keys.value.refs; count--; okp++, nkp++)
	    if (r_packed_is_name(okp)) {
		packed_get(okp, nkp);
		ref_mark_new_in(mem, nkp);
	    } else if (*okp == packed_key_deleted)
		r_set_attrs(nkp, a_executable);
	if (!ref_must_save_in(mem, &old_keys))
	    gs_free_ref_array(mem, &old_keys, "dict_unpack(old keys)");
	if (pds)
	    dstack_set_top(pds);	/* just in case */
    }
    return 0;
}

/*
 * Look up a key in a dictionary.  Store a pointer to the value slot
 * where found, or to the (value) slot for inserting.
 * Return 1 if found, 0 if not and there is room for a new entry,
 * or e_dictfull if the dictionary is full and the key is missing.
 * The caller is responsible for ensuring key is not a null.
 */
int
dict_find(const ref * pdref, const ref * pkey,
	  ref ** ppvalue /* result is stored here */ )
{
    dict *pdict = pdref->value.pdict;
    uint size = npairs(pdict);
    register int etype;
    uint nidx;
    ref_packed kpack;
    uint hash;
    int ktype;

    /* Compute hash.  The only types we bother with are strings, */
    /* names, and (unlikely, but worth checking for) integers. */
    switch (r_type(pkey)) {
    case t_name:
	nidx = name_index(pkey);
    nh:
	hash = dict_name_index_hash(nidx);
	kpack = packed_name_key(nidx);
	ktype = t_name;
	break;
    case t_string:		/* convert to a name first */
	{
	    ref nref;
	    int code;

	    if (!r_has_attr(pkey, a_read))
		return_error(e_invalidaccess);
	    code = name_ref(pkey->value.bytes, r_size(pkey), &nref, 1);
	    if (code < 0)
		return code;
	    nidx = name_index(&nref);
	}
	goto nh;
    case t_real:
	/*
	 * Make sure that equal reals and integers hash the same.
	 */
	{
	    int expt;
	    double mant = frexp(pkey->value.realval, &expt);
	    /*
	     * The value is mant * 2^expt, where 0.5 <= mant < 1,
	     * or else expt == mant == 0.
	     */

	    if (expt < sizeof(long) * 8 || pkey->value.realval == min_long)
		hash = (uint)(int)pkey->value.realval * 30503;
	    else
		hash = (uint)(int)(mant * min_long) * 30503;
	}
	goto ih;
    case t_integer:
	hash = (uint)pkey->value.intval * 30503;
    ih:
	kpack = packed_key_impossible;
	ktype = -1;
	nidx = 0;		/* only to pacify gcc */
	break;
    case t_null:		/* not allowed as a key */
	return_error(e_typecheck);
    default:
	hash = r_btype(pkey) * 99;	/* yech */
	kpack = packed_key_impossible;
	ktype = -1;
	nidx = 0;		/* only to pacify gcc */
    }
    /* Search the dictionary */
    if (dict_is_packed(pdict)) {
	const ref_packed *pslot = 0;

	packed_search_1(*ppvalue = packed_search_value_pointer,
			return 1,
			if (pslot == 0) pslot = kp, goto miss);
	packed_search_2(*ppvalue = packed_search_value_pointer,
			return 1,
			if (pslot == 0) pslot = kp, goto miss);
	/*
	 * Double wraparound, dict is full.
	 * Note that even if there was an empty slot (pslot != 0),
	 * we must return dictfull if length = maxlength.
	 */
	if (pslot == 0 || d_length(pdict) == d_maxlength(pdict))
	    return_error(e_dictfull);
	*ppvalue = pdict->values.value.refs + (pslot - kbot);
	return 0;
      miss:			/* Key is missing, not double wrap.  See above re dictfull. */
	if (d_length(pdict) == d_maxlength(pdict))
	    return_error(e_dictfull);
	if (pslot == 0)
	    pslot = kp;
	*ppvalue = pdict->values.value.refs + (pslot - kbot);
	return 0;
    } else {
	ref *kbot = pdict->keys.value.refs;
	register ref *kp;
	ref *pslot = 0;
	int wrap = 0;

	for (kp = kbot + dict_hash_mod(hash, size) + 2;;) {
	    --kp;
	    if ((etype = r_type(kp)) == ktype) {	/* Fast comparison if both keys are names */
		if (name_index(kp) == nidx) {
		    *ppvalue = pdict->values.value.refs + (kp - kbot);
		    return 1;
		}
	    } else if (etype == t_null) {	/* Empty, deleted, or wraparound. */
		/* Figure out which. */
		if (kp == kbot) {	/* wrap */
		    if (wrap++) {	/* wrapped twice */
			if (pslot == 0)
			    return_error(e_dictfull);
			break;
		    }
		    kp += size + 1;
		} else if (r_has_attr(kp, a_executable)) {	/* Deleted entry, save the slot. */
		    if (pslot == 0)
			pslot = kp;
		} else		/* key not found */
		    break;
	    } else {
		if (obj_eq(kp, pkey)) {
		    *ppvalue = pdict->values.value.refs + (kp - kbot);
		    return 1;
		}
	    }
	}
	if (d_length(pdict) == d_maxlength(pdict))
	    return_error(e_dictfull);
	*ppvalue = pdict->values.value.refs +
	    ((pslot != 0 ? pslot : kp) - kbot);
	return 0;
    }
}

/*
 * Look up a (constant) C string in a dictionary.
 * Return 1 if found, <= 0 if not.
 */
int
dict_find_string(const ref * pdref, const char *kstr, ref ** ppvalue)
{
    int code;
    ref kname;

    if ((code = name_ref((const byte *)kstr, strlen(kstr), &kname, -1)) < 0)
	return code;
    return dict_find(pdref, &kname, ppvalue);
}

/*
 * Enter a key-value pair in a dictionary.
 * See idict.h for the possible return values.
 */
int
dict_put(ref * pdref /* t_dictionary */ , const ref * pkey, const ref * pvalue,
	 dict_stack_t *pds)
{
    dict *pdict = pdref->value.pdict;
    gs_ref_memory_t *mem = dict_memory(pdict);
    int rcode = 0;
    int code;
    ref *pvslot;

    /* Check the value. */
    store_check_dest(pdref, pvalue);
  top:if ((code = dict_find(pdref, pkey, &pvslot)) <= 0) {	/* not found *//* Check for overflow */
	ref kname;
	uint index;

	switch (code) {
	    case 0:
		break;
	    case e_dictfull:
		if (!dict_auto_expand)
		    return_error(e_dictfull);
		code = dict_grow(pdref, pds);
		if (code < 0)
		    return code;
		goto top;	/* keep things simple */
	    default:		/* e_typecheck */
		return code;
	}
	index = pvslot - pdict->values.value.refs;
	/* If the key is a string, convert it to a name. */
	if (r_has_type(pkey, t_string)) {
	    int code;

	    if (!r_has_attr(pkey, a_read))
		return_error(e_invalidaccess);
	    code = name_from_string(pkey, &kname);
	    if (code < 0)
		return code;
	    pkey = &kname;
	}
	if (dict_is_packed(pdict)) {
	    ref_packed *kp;

	    if (!r_has_type(pkey, t_name) ||
		name_index(pkey) > packed_name_max_index
		) {		/* Change to unpacked representation. */
		int code = dict_unpack(pdref, pds);

		if (code < 0)
		    return code;
		goto top;
	    }
	    kp = pdict->keys.value.writable_packed + index;
	    if (ref_must_save_in(mem, &pdict->keys)) {	/* See initial comment for why it is safe */
		/* not to save the change if the keys */
		/* array itself is new. */
		ref_do_save_in(mem, &pdict->keys, kp, "dict_put(key)");
	    }
	    *kp = pt_tag(pt_literal_name) + name_index(pkey);
	} else {
	    ref *kp = pdict->keys.value.refs + index;

	    if_debug2('d', "[d]0x%lx: fill key at 0x%lx\n",
		      (ulong) pdict, (ulong) kp);
	    store_check_dest(pdref, pkey);
	    ref_assign_old_in(mem, &pdict->keys, kp, pkey,
			      "dict_put(key)");	/* set key of pair */
	}
	ref_save_in(mem, pdref, &pdict->count, "dict_put(count)");
	pdict->count.value.intval++;
	/* If the key is a name, update its 1-element cache. */
	if (r_has_type(pkey, t_name)) {
	    name *pname = pkey->value.pname;

	    if (pname->pvalue == pv_no_defn &&
		CAN_SET_PVALUE_CACHE(pds, pdref, mem)
		) {		/* Set the cache. */
		if_debug0('d', "[d]set cache\n");
		pname->pvalue = pvslot;
	    } else {		/* The cache can't be used. */
		if_debug0('d', "[d]no cache\n");
		pname->pvalue = pv_other;
	    }
	}
	rcode = 1;
    }
    if_debug8('d', "[d]0x%lx: put key 0x%lx 0x%lx\n  value at 0x%lx: old 0x%lx 0x%lx, new 0x%lx 0x%lx\n",
	      (ulong) pdref->value.pdict,
	      ((const ulong *)pkey)[0], ((const ulong *)pkey)[1],
	      (ulong) pvslot,
	      ((const ulong *)pvslot)[0], ((const ulong *)pvslot)[1],
	      ((const ulong *)pvalue)[0], ((const ulong *)pvalue)[1]);
    ref_assign_old_in(mem, &pdref->value.pdict->values, pvslot, pvalue,
		      "dict_put(value)");
    return rcode;
}

/*
 * Enter a key-value pair where the key is a (constant) C string.
 */
int
dict_put_string(ref * pdref, const char *kstr, const ref * pvalue,
		dict_stack_t *pds)
{
    int code;
    ref kname;

    if ((code = name_ref((const byte *)kstr, strlen(kstr), &kname, 0)) < 0)
	return code;
    return dict_put(pdref, &kname, pvalue, pds);
}

/* Remove an element from a dictionary. */
int
dict_undef(ref * pdref, const ref * pkey, dict_stack_t *pds)
{
    gs_ref_memory_t *mem;
    ref *pvslot;
    dict *pdict;
    uint index;

    if (dict_find(pdref, pkey, &pvslot) <= 0)
	return (e_undefined);
    /* Remove the entry from the dictionary. */
    pdict = pdref->value.pdict;
    index = pvslot - pdict->values.value.refs;
    mem = dict_memory(pdict);
    if (dict_is_packed(pdict)) {
	ref_packed *pkp = pdict->keys.value.writable_packed + index;

	if_debug3('d', "[d]0x%lx: removing key at 0%lx: 0x%x\n",
		  (ulong)pdict, (ulong)pkp, (uint)*pkp);
	/* See the initial comment for why it is safe not to save */
	/* the change if the keys array itself is new. */
	if (ref_must_save_in(mem, &pdict->keys))
	    ref_do_save_in(mem, &pdict->keys, pkp, "dict_undef(key)");
	/*
	 * Accumulating deleted entries slows down lookup.
	 * Detect the easy case where we can use an empty entry
	 * rather than a deleted one, namely, when the next entry
	 * in the probe order is empty.
	 */
	if (pkp[-1] == packed_key_empty) {
	    /*
	     * In this case we can replace any preceding deleted keys with
	     * empty ones as well.
	     */
	    uint end = nslots(pdict);

	    *pkp = packed_key_empty;
	    while (++index < end && *++pkp == packed_key_deleted)
		*pkp = packed_key_empty;
	} else
	    *pkp = packed_key_deleted;
    } else {			/* not packed */
	ref *kp = pdict->keys.value.refs + index;

	if_debug4('d', "[d]0x%lx: removing key at 0%lx: 0x%lx 0x%lx\n",
		  (ulong)pdict, (ulong)kp, ((ulong *)kp)[0], ((ulong *)kp)[1]);
	make_null_old_in(mem, &pdict->keys, kp, "dict_undef(key)");
	/*
	 * Accumulating deleted entries slows down lookup.
	 * Detect the easy case where we can use an empty entry
	 * rather than a deleted one, namely, when the next entry
	 * in the probe order is empty.
	 */
	if (!r_has_type(kp - 1, t_null) ||	/* full entry */
	    r_has_attr(kp - 1, a_executable)	/* deleted or wraparound */
	    )
	    r_set_attrs(kp, a_executable);	/* mark as deleted */
    }
    ref_save_in(mem, pdref, &pdict->count, "dict_undef(count)");
    pdict->count.value.intval--;
    /* If the key is a name, update its 1-element cache. */
    if (r_has_type(pkey, t_name)) {
	name *pname = pkey->value.pname;

	if (pv_valid(pname->pvalue)) {
#ifdef DEBUG
	    /* Check the the cache is correct. */
	    if (!(pds && dstack_dict_is_permanent(pds, pdref)))
		lprintf1("dict_undef: cached name value pointer 0x%lx is incorrect!\n",
			 (ulong) pname->pvalue);
#endif
	    /* Clear the cache */
	    pname->pvalue = pv_no_defn;
	}
    }
    make_null_old_in(mem, &pdict->values, pvslot, "dict_undef(value)");
    return 0;
}

/* Return the number of elements in a dictionary. */
uint
dict_length(const ref * pdref /* t_dictionary */ )
{
    return d_length(pdref->value.pdict);
}

/* Return the capacity of a dictionary. */
uint
dict_maxlength(const ref * pdref /* t_dictionary */ )
{
    return d_maxlength(pdref->value.pdict);
}

/* Return the maximum index of a slot within a dictionary. */
uint
dict_max_index(const ref * pdref /* t_dictionary */ )
{
    return npairs(pdref->value.pdict) - 1;
}

/*
 * Copy one dictionary into another.
 * If COPY_NEW_ONLY is set, only copy entries whose keys
 * aren't already present in the destination.
 * If COPY_FOR_RESIZE is set, reset any valid name cache entries to
 * pv_no_defn before doing the dict_put.
 */
#define COPY_NEW_ONLY 1
#define COPY_FOR_RESIZE 2
private int
dict_copy_elements(const ref * pdrfrom /* t_dictionary */ ,
		  ref * pdrto /* t_dictionary */ , int options,
		  dict_stack_t *pds)
{
    int space = r_space(pdrto);
    int index;
    ref elt[2];
    ref *pvslot;
    int code;

    if (space != avm_max) {
	/* Do the store check before starting the copy. */
	index = dict_first(pdrfrom);
	while ((index = dict_next(pdrfrom, index, elt)) >= 0)
	    if (!(options & COPY_NEW_ONLY) ||
		dict_find(pdrto, &elt[0], &pvslot) <= 0
		) {
		store_check_space(space, &elt[0]);
		store_check_space(space, &elt[1]);
	    }
    }
    /* Now copy the contents. */
    index = dict_first(pdrfrom);
    while ((index = dict_next(pdrfrom, index, elt)) >= 0) {
	ref *pvalue = pv_no_defn;

	if ((options & COPY_NEW_ONLY) &&
	    dict_find(pdrto, &elt[0], &pvslot) > 0
	    )
	    continue;
	if ((options & COPY_FOR_RESIZE) &&
	    r_has_type(&elt[0], t_name) &&
	    (pvalue = elt[0].value.pname->pvalue, pv_valid(pvalue))
	    )
	    elt[0].value.pname->pvalue = pv_no_defn;
	if ((code = dict_put(pdrto, &elt[0], &elt[1], pds)) < 0) {
	    /*
	     * If COPY_FOR_RESIZE is set, the dict_put isn't supposed to
	     * be able to fail, but we don't want to depend on this.
	     */
	    if (pvalue != pv_no_defn)
		elt[0].value.pname->pvalue = pvalue;
	    return code;
	}
    }
    return 0;
}
int
dict_copy_entries(const ref *pdrfrom, ref *pdrto, bool new_only,
		  dict_stack_t *pds)
{
    return dict_copy_elements(pdrfrom, pdrto, (new_only ? COPY_NEW_ONLY : 0),
			      pds);
}

/* Resize a dictionary. */
int
dict_resize(ref * pdref, uint new_size, dict_stack_t *pds)
{
    dict *pdict = pdref->value.pdict;
    gs_ref_memory_t *mem = dict_memory(pdict);
    uint new_mask = imemory_new_mask(mem);
    dict dnew;
    ref drto;
    int code;

    if (new_size < d_length(pdict)) {
	if (!dict_auto_expand)
	    return_error(e_dictfull);
	new_size = d_length(pdict);
    }
    make_tav(&drto, t_dictionary, r_space(pdref) | a_all | new_mask,
	     pdict, &dnew);
    dnew.memory = pdict->memory;
    if ((code = dict_create_contents(new_size, &drto, dict_is_packed(pdict))) < 0)
	return code;
    /*
     * We must suppress the store check, in case we are expanding
     * systemdict or another global dictionary that is allowed
     * to reference local objects.
     */
    r_set_space(&drto, avm_local);
    /*
     * If we are expanding a permanent dictionary, we must make sure that
     * dict_put doesn't think this is a second definition for any
     * single-definition names.  This in turn requires that
     * dstack_dict_is_permanent must be true for the second ("to")
     * argument of dict_copy_elements, which requires temporarily
     * setting *pdref = drto.
     */
    if (CAN_SET_PVALUE_CACHE(pds, pdref, mem)) {
	ref drfrom;

	drfrom = *pdref;
	*pdref = drto;
	dict_copy_elements(&drfrom, pdref, COPY_FOR_RESIZE, pds);
	*pdref = drfrom;
    } else {
	dict_copy_elements(pdref, &drto, 0, pds);
    }
    /* Save or free the old dictionary. */
    if (ref_must_save_in(mem, &pdict->values))
	ref_do_save_in(mem, pdref, &pdict->values, "dict_resize(values)");
    else
	gs_free_ref_array(mem, &pdict->values, "dict_resize(old values)");
    if (ref_must_save_in(mem, &pdict->keys))
	ref_do_save_in(mem, pdref, &pdict->keys, "dict_resize(keys)");
    else
	gs_free_ref_array(mem, &pdict->keys, "dict_resize(old keys)");
    ref_assign(&pdict->keys, &dnew.keys);
    ref_assign(&pdict->values, &dnew.values);
    ref_save_in(dict_memory(pdict), pdref, &pdict->maxlength,
		"dict_resize(maxlength)");
    d_set_maxlength(pdict, new_size);
    if (pds)
	dstack_set_top(pds);	/* just in case this is the top dict */
    return 0;
}

/* Grow a dictionary for dict_put. */
int
dict_grow(ref * pdref, dict_stack_t *pds)
{
    dict *pdict = pdref->value.pdict;
    /* We might have maxlength < npairs, if */
    /* dict_round_size increased the size. */
    ulong new_size = (ulong) d_maxlength(pdict) * 3 / 2 + 2;

#if arch_sizeof_int < arch_sizeof_long
    if (new_size > max_uint)
	new_size = max_uint;
#endif
    if (new_size > npairs(pdict)) {
	int code = dict_resize(pdref, (uint) new_size, pds);

	if (code >= 0)
	    return code;
	/* new_size was too big. */
	if (npairs(pdict) < dict_max_size) {
	    code = dict_resize(pdref, dict_max_size, pds);
	    if (code >= 0)
		return code;
	}
	if (npairs(pdict) == d_maxlength(pdict)) {	/* Can't do it. */
	    return code;
	}
	/* We can't grow to new_size, but we can grow to npairs. */
	new_size = npairs(pdict);
    }
    /* maxlength < npairs, we can grow in place */
    ref_save_in(dict_memory(pdict), pdref, &pdict->maxlength,
		"dict_put(maxlength)");
    d_set_maxlength(pdict, new_size);
    return 0;
}

/* Prepare to enumerate a dictionary. */
int
dict_first(const ref * pdref)
{
    return (int)nslots(pdref->value.pdict);
}

/* Enumerate the next element of a dictionary. */
int
dict_next(const ref * pdref, int index, ref * eltp /* ref eltp[2] */ )
{
    dict *pdict = pdref->value.pdict;
    ref *vp = pdict->values.value.refs + index;

    while (vp--, --index >= 0) {
	array_get(&pdict->keys, (long)index, eltp);
	/* Make sure this is a valid entry. */
	if (r_has_type(eltp, t_name) ||
	    (!dict_is_packed(pdict) && !r_has_type(eltp, t_null))
	    ) {
	    eltp[1] = *vp;
	    if_debug6('d', "[d]0x%lx: index %d: %lx %lx, %lx %lx\n",
		      (ulong) pdict, index,
		      ((ulong *) eltp)[0], ((ulong *) eltp)[1],
		      ((ulong *) vp)[0], ((ulong *) vp)[1]);
	    return index;
	}
    }
    return -1;			/* no more elements */
}

/* Return the index of a value within a dictionary. */
int
dict_value_index(const ref * pdref, const ref * pvalue)
{
    return (int)(pvalue - pdref->value.pdict->values.value.refs - 1);
}

/* Return the entry at a given index within a dictionary. */
/* If the index designates an unoccupied entry, return e_undefined. */
int
dict_index_entry(const ref * pdref, int index, ref * eltp /* ref eltp[2] */ )
{
    const dict *pdict = pdref->value.pdict;

    array_get(&pdict->keys, (long)(index + 1), eltp);
    if (r_has_type(eltp, t_name) ||
	(!dict_is_packed(pdict) && !r_has_type(eltp, t_null))
	) {
	eltp[1] = pdict->values.value.refs[index + 1];
	return 0;
    }
    return e_undefined;
}