File: idstack.c

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/* Copyright (C) 2001-2006 Artifex Software, Inc.
   All Rights Reserved.
  
   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied, modified
   or distributed except as expressly authorized under the terms of that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/

/* $Id: idstack.c 9043 2008-08-28 22:48:19Z giles $ */
/* Implementation of dictionary stacks */
#include "ghost.h"
#include "idict.h"
#include "idictdef.h"
#include "idstack.h"
#include "inamedef.h"
#include "iname.h"
#include "ipacked.h"
#include "iutil.h"
#include "ivmspace.h"
/*
#include "idicttpl.h" - Do not remove this comment.
                        "idicttpl.h" is included below.
*/

/* Debugging statistics */
#ifdef DEBUG
#include "idebug.h"
#define MAX_STATS_DEPTH 6
struct stats_dstack_s {
    long lookups;		/* total lookups */
    long probes[2];		/* successful lookups on 1 or 2 probes */
    long depth[MAX_STATS_DEPTH + 1]; /* stack depth of lookups requiring search */
} stats_dstack;
# define INCR(v) (++stats_dstack.v)
#else
# define INCR(v) DO_NOTHING
#endif

#ifdef DEBUG
/* Wrapper for dstack_find_name_by_index */
ref *real_dstack_find_name_by_index(dict_stack_t * pds, uint nidx);
ref *
dstack_find_name_by_index(dict_stack_t * pds, uint nidx)
{
    ref *pvalue = real_dstack_find_name_by_index(pds, nidx);
    dict *pdict = pds->stack.p->value.pdict;

    INCR(lookups);
    if (dict_is_packed(pdict)) {
	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
	    )
	    INCR(probes[0]);
	else if (pdict->keys.value.packed[hash - 1] ==
		 pt_tag(pt_literal_name) + nidx
	    )
	    INCR(probes[1]);
    }
    if (gs_debug_c('d') && !(stats_dstack.lookups % 1000))
	dlprintf3("[d]lookups=%ld probe1=%ld probe2=%ld\n",
		  stats_dstack.lookups, stats_dstack.probes[0],
		  stats_dstack.probes[1]);
    return pvalue;
}
#define dstack_find_name_by_index real_dstack_find_name_by_index
#endif

/* Check whether a dictionary is one of the permanent ones on the d-stack. */
bool
dstack_dict_is_permanent(const dict_stack_t * pds, const ref * pdref)
{
    dict *pdict = pdref->value.pdict;
    int i;

    if (pds->stack.extension_size == 0) {	/* Only one block of d-stack. */
	for (i = 0; i < pds->min_size; ++i)
	    if (pds->stack.bot[i].value.pdict == pdict)
		return true;
    } else {			/* More than one block of d-stack. */
	uint count = ref_stack_count(&pds->stack);

	for (i = count - pds->min_size; i < count; ++i)
	    if (ref_stack_index(&pds->stack, i)->value.pdict == pdict)
		return true;
    }
    return false;
}

/*
 * Look up a name on the dictionary stack.
 * Return the pointer to the value if found, 0 if not.
 */
ref *
dstack_find_name_by_index(dict_stack_t * pds, uint nidx)
{
    ds_ptr pdref = pds->stack.p;

/* Since we know the hash function is the identity function, */
/* there's no point in allocating a separate variable for it. */
#define hash dict_name_index_hash(nidx)
    ref_packed kpack = packed_name_key(nidx);

    do {
	dict *pdict = pdref->value.pdict;
	uint size = npairs(pdict);
#ifdef DEBUG
	if (gs_debug_c('D')) {
	    const gs_memory_t *mem = dict_mem(pdict);
	    ref dnref;

	    name_index_ref(mem, nidx, &dnref);
	    dlputs("[D]lookup ");
	    debug_print_name(mem, &dnref);
	    dprintf3(" in 0x%lx(%u/%u)\n",
		     (ulong) pdict, dict_length(pdref),
		     dict_maxlength(pdref));
	}
#endif
#define INCR_DEPTH(pdref)\
  INCR(depth[min(MAX_STATS_DEPTH, pds->stack.p - pdref)])
	if (dict_is_packed(pdict)) {
#	    define found INCR_DEPTH(pdref); return packed_search_value_pointer
#	    define deleted 
#	    define missing break;
#	    include "idicttpl.h"
#	    undef missing
#	    undef deleted
#	    undef found
	} else {
	    /*
	     * The name_index macro takes mem as its first argument, but
	     * does not actually use it.  The following is a little ugly,
	     * but it avoids a compiler warning.
	     */
	    /*const gs_memory_t *_mem_not_used = dict_mem(pdict);*/
	    ref *kbot = pdict->keys.value.refs;
	    register ref *kp;
	    int wrap = 0;

	    /* Search the dictionary */
	    for (kp = kbot + dict_hash_mod(hash, size) + 2;;) {
		--kp;
		if (r_has_type(kp, t_name)) {
		    if (name_index(_mem_not_used, kp) == nidx) {
			INCR_DEPTH(pdref);
			return pdict->values.value.refs + (kp - kbot);
		    }
		} else if (r_has_type(kp, t_null)) {	/* Empty, deleted, or wraparound. */
		    /* Figure out which. */
		    if (!r_has_attr(kp, a_executable))
			break;
		    if (kp == kbot) {	/* wrap */
			if (wrap++)
			    break;	/* 2 wraps */
			kp += size + 1;
		    }
		}
	    }
	}
#undef INCR_DEPTH
    }
    while (pdref-- > pds->stack.bot);
    /* The name isn't in the top dictionary block. */
    /* If there are other blocks, search them now (more slowly). */
    if (!pds->stack.extension_size)	/* no more blocks */
	return (ref *) 0;
    {				/* We could use the STACK_LOOP macros, but for now, */
	/* we'll do things the simplest way. */
	ref key;
	uint i = pds->stack.p + 1 - pds->stack.bot;
	uint size = ref_stack_count(&pds->stack);
	ref *pvalue;	
	
	dict *pdict = pds->stack.p->value.pdict;
	const gs_memory_t *mem = dict_mem(pdict);

	name_index_ref(mem, nidx, &key);
	for (; i < size; i++) {
	    if (dict_find(ref_stack_index(&pds->stack, i),
			  &key, &pvalue) > 0
		) {
		INCR(depth[min(MAX_STATS_DEPTH, i)]);
		return pvalue;
	    }
	}
    }
    return (ref *) 0;
#undef hash
}

/* Set the cached values computed from the top entry on the dstack. */
/* See idstack.h for details. */
static const ref_packed no_packed_keys[2] =
{packed_key_deleted, packed_key_empty};
void
dstack_set_top(dict_stack_t * pds)
{
    ds_ptr dsp = pds->stack.p;
    dict *pdict = dsp->value.pdict;

    if_debug3('d', "[d]dsp = 0x%lx -> 0x%lx, key array type = %d\n",
	      (ulong) dsp, (ulong) pdict, r_type(&pdict->keys));
    if (dict_is_packed(pdict) &&
	r_has_attr(dict_access_ref(dsp), a_read)
	) {
	pds->top_keys = pdict->keys.value.packed;
	pds->top_npairs = npairs(pdict);
	pds->top_values = pdict->values.value.refs;
    } else {
	pds->top_keys = no_packed_keys;
	pds->top_npairs = 1;
    }
    if (!r_has_attr(dict_access_ref(dsp), a_write))
	pds->def_space = -1;
    else
	pds->def_space = r_space(dsp);
}

/* After a garbage collection, scan the permanent dictionaries and */
/* update the cached value pointers in names. */
void
dstack_gc_cleanup(dict_stack_t * pds)
{
    uint count = ref_stack_count(&pds->stack);
    uint dsi;

    for (dsi = pds->min_size; dsi > 0; --dsi) {
	const dict *pdict =
	ref_stack_index(&pds->stack, count - dsi)->value.pdict;
	uint size = nslots(pdict);
	ref *pvalue = pdict->values.value.refs;
	uint i;

	for (i = 0; i < size; ++i, ++pvalue) {
	    ref key;
	    ref *old_pvalue;

	    array_get(dict_mem(pdict), &pdict->keys, (long)i, &key);
	    if (r_has_type(&key, t_name) &&
		pv_valid(old_pvalue = key.value.pname->pvalue)
		) {		/*
				 * The name only has a single definition,
				 * so it must be this one.  Check to see if
				 * no relocation is actually needed; if so,
				 * we can skip the entire dictionary.
				 */
		if (old_pvalue == pvalue) {
		    if_debug1('d', "[d]skipping dstack entry %d\n",
			      dsi - 1);
		    break;
		}
		/* Update the value pointer. */
		key.value.pname->pvalue = pvalue;
	    }
	}
    }
}