harvey/sys/src/cmd/gs/src/idstack.c

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*/

/*$Id: idstack.c,v 1.2 2000/09/19 19:00:43 lpd Exp $ */
/* 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"

/* 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(P2(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')) {
	    ref dnref;

	    name_index_ref(nidx, &dnref);
	    dlputs("[D]lookup ");
	    debug_print_name(&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)) {
	    packed_search_1(INCR_DEPTH(pdref),
			    return packed_search_value_pointer,
			    DO_NOTHING, goto miss);
	    packed_search_2(INCR_DEPTH(pdref),
			    return packed_search_value_pointer,
			    DO_NOTHING, break);
	  miss:;
	} else {
	    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(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;

	name_index_ref(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. */
private 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(&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;
	    }
	}
    }
}