cpython/Objects/mappingobject.c

/***********************************************************
Copyright 1991, 1992, 1993 by Stichting Mathematisch Centrum,
Amsterdam, The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior permission.

STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* Mapping object implementation; using a hash table */

#include "allobjects.h"
#include "mappingobject.h"
#include "modsupport.h"


/*
Table of primes suitable as keys, in ascending order.
The first line are the largest primes less than some powers of two,
the second line is the largest prime less than 6000,
and the third line is a selection from Knuth, Vol. 3, Sec. 6.1, Table 1.
The final value is a sentinel and should cause the memory allocation
of that many entries to fail (if none of the earlier values cause such
failure already).
*/
static unsigned int primes[] = {
	3, 7, 13, 31, 61, 127, 251, 509, 1021, 2017, 4093,
	5987,
	9551, 15683, 19609, 31397,
	0xffffffff /* All bits set -- truncation OK */
};

/* Object used as dummy key to fill deleted entries */
static object *dummy; /* Initialized by first call to newmappingobject() */

/*
Invariant for entries: when in use, de_value is not NULL and de_key is
not NULL and not dummy; when not in use, de_value is NULL and de_key
is either NULL or dummy.  A dummy key value cannot be replaced by
NULL, since otherwise other keys may be lost.
*/
typedef struct {
	long me_hash;
	object *me_key;
	object *me_value;
} mappingentry;

/*
To ensure the lookup algorithm terminates, the table size must be a
prime number and there must be at least one NULL key in the table.
The value ma_fill is the number of non-NULL keys; ma_used is the number
of non-NULL, non-dummy keys.
To avoid slowing down lookups on a near-full table, we resize the table
when it is more than half filled.
*/
typedef struct {
	OB_HEAD
	int ma_fill;
	int ma_used;
	int ma_size;
	mappingentry *ma_table;
} mappingobject;

object *
newmappingobject()
{
	register mappingobject *mp;
	if (dummy == NULL) { /* Auto-initialize dummy */
		dummy = newstringobject("<dummy key>");
		if (dummy == NULL)
			return NULL;
	}
	mp = NEWOBJ(mappingobject, &Mappingtype);
	if (mp == NULL)
		return NULL;
	mp->ma_size = primes[0];
	mp->ma_table = (mappingentry *) calloc(sizeof(mappingentry), mp->ma_size);
	if (mp->ma_table == NULL) {
		DEL(mp);
		return err_nomem();
	}
	mp->ma_fill = 0;
	mp->ma_used = 0;
	return (object *)mp;
}

/*
The basic lookup function used by all operations.
This is essentially Algorithm D from Knuth Vol. 3, Sec. 6.4.
Open addressing is preferred over chaining since the link overhead for
chaining would be substantial (100% with typical malloc overhead).

First a 32-bit hash value, 'sum', is computed from the key string.
The first character is added an extra time shifted by 8 to avoid hashing
single-character keys (often heavily used variables) too close together.
All arithmetic on sum should ignore overflow.

The initial probe index is then computed as sum mod the table size.
Subsequent probe indices are incr apart (mod table size), where incr
is also derived from sum, with the additional requirement that it is
relative prime to the table size (i.e., 1 <= incr < size, since the size
is a prime number).  My choice for incr is somewhat arbitrary.
*/
static mappingentry *lookmapping PROTO((mappingobject *, object *, long));
static mappingentry *
lookmapping(mp, key, hash)
	register mappingobject *mp;
	object *key;
	long hash;
{
	register int i, incr;
	register unsigned long sum = (unsigned long) hash;
	register mappingentry *freeslot = NULL;
	/* We must come up with (i, incr) such that 0 <= i < ma_size
	   and 0 < incr < ma_size and both are a function of hash */
	i = sum % mp->ma_size;
	do {
		sum = sum + sum + sum + 1;
		incr = sum % mp->ma_size;
	} while (incr == 0);
	for (;;) {
		register mappingentry *ep = &mp->ma_table[i];
		if (ep->me_key == NULL) {
			if (freeslot != NULL)
				return freeslot;
			else
				return ep;
		}
		if (ep->me_key == dummy) {
			if (freeslot != NULL)
				freeslot = ep;
		}
		else if (ep->me_hash == hash &&
			 cmpobject(ep->me_key, key) == 0) {
			return ep;
		}
		i = (i + incr) % mp->ma_size;
	}
}

/*
Internal routine to insert a new item into the table.
Used both by the internal resize routine and by the public insert routine.
Eats a reference to key and one to value.
*/
static void insertmapping PROTO((mappingobject *, object *, long, object *));
static void
insertmapping(mp, key, hash, value)
	register mappingobject *mp;
	object *key;
	long hash;
	object *value;
{
	register mappingentry *ep;
	ep = lookmapping(mp, key, hash);
	if (ep->me_value != NULL) {
		DECREF(ep->me_value);
		DECREF(key);
	}
	else {
		if (ep->me_key == NULL)
			mp->ma_fill++;
		else
			DECREF(ep->me_key);
		ep->me_key = key;
		ep->me_hash = hash;
		mp->ma_used++;
	}
	ep->me_value = value;
}

/*
Restructure the table by allocating a new table and reinserting all
items again.  When entries have been deleted, the new table may
actually be smaller than the old one.
*/
static int mappingresize PROTO((mappingobject *));
static int
mappingresize(mp)
	mappingobject *mp;
{
	register int oldsize = mp->ma_size;
	register int newsize;
	register mappingentry *oldtable = mp->ma_table;
	register mappingentry *newtable;
	register mappingentry *ep;
	register int i;
	newsize = mp->ma_size;
	for (i = 0; ; i++) {
		if (primes[i] > mp->ma_used*2) {
			newsize = primes[i];
			break;
		}
	}
	newtable = (mappingentry *) calloc(sizeof(mappingentry), newsize);
	if (newtable == NULL) {
		err_nomem();
		return -1;
	}
	mp->ma_size = newsize;
	mp->ma_table = newtable;
	mp->ma_fill = 0;
	mp->ma_used = 0;
	for (i = 0, ep = oldtable; i < oldsize; i++, ep++) {
		if (ep->me_value != NULL)
			insertmapping(mp,ep->me_key,ep->me_hash,ep->me_value);
		else {
			XDECREF(ep->me_key);
		}
	}
	DEL(oldtable);
	return 0;
}

object *
mappinglookup(op, key)
	object *op;
	object *key;
{
	long hash;
	if (!is_mappingobject(op)) {
		err_badcall();
		return NULL;
	}
	hash = hashobject(key);
	if (hash == -1)
		return NULL;
	return lookmapping((mappingobject *)op, key, hash) -> me_value;
}

int
mappinginsert(op, key, value)
	register object *op;
	object *key;
	object *value;
{
	register mappingobject *mp;
	register long hash;
	if (!is_mappingobject(op)) {
		err_badcall();
		return -1;
	}
	hash = hashobject(key);
	if (hash == -1)
		return -1;
	mp = (mappingobject *)op;
	/* if fill >= 2/3 size, resize */
	if (mp->ma_fill*3 >= mp->ma_size*2) {
		if (mappingresize(mp) != 0) {
			if (mp->ma_fill+1 > mp->ma_size)
				return -1;
		}
	}
	INCREF(value);
	INCREF(key);
	insertmapping(mp, key, hash, value);
	return 0;
}

int
mappingremove(op, key)
	object *op;
	object *key;
{
	register mappingobject *mp;
	register long hash;
	register mappingentry *ep;
	if (!is_mappingobject(op)) {
		err_badcall();
		return -1;
	}
	hash = hashobject(key);
	if (hash == -1)
		return -1;
	mp = (mappingobject *)op;
	ep = lookmapping(mp, key, hash);
	if (ep->me_value == NULL) {
		err_setval(KeyError, key);
		return -1;
	}
	DECREF(ep->me_key);
	INCREF(dummy);
	ep->me_key = dummy;
	DECREF(ep->me_value);
	ep->me_value = NULL;
	mp->ma_used--;
	return 0;
}

int
getmappingsize(op)
	register object *op;
{
	if (!is_mappingobject(op)) {
		err_badcall();
		return -1;
	}
	return ((mappingobject *)op) -> ma_size;
}

object *
getmappingkey(op, i)
	object *op;
	register int i;
{
	/* XXX This can't return errors since its callers assume
	   that NULL means there was no key at that point */
	register mappingobject *mp;
	if (!is_mappingobject(op)) {
		/* err_badcall(); */
		return NULL;
	}
	mp = (mappingobject *)op;
	if (i < 0 || i >= mp->ma_size) {
		/* err_badarg(); */
		return NULL;
	}
	if (mp->ma_table[i].me_value == NULL) {
		/* Not an error! */
		return NULL;
	}
	return (object *) mp->ma_table[i].me_key;
}

/* Methods */

static void
mapping_dealloc(mp)
	register mappingobject *mp;
{
	register int i;
	register mappingentry *ep;
	for (i = 0, ep = mp->ma_table; i < mp->ma_size; i++, ep++) {
		if (ep->me_key != NULL)
			DECREF(ep->me_key);
		if (ep->me_value != NULL)
			DECREF(ep->me_value);
	}
	if (mp->ma_table != NULL)
		DEL(mp->ma_table);
	DEL(mp);
}

static int
mapping_print(mp, fp, flags)
	register mappingobject *mp;
	register FILE *fp;
	register int flags;
{
	register int i;
	register int any;
	register mappingentry *ep;
	fprintf(fp, "{");
	any = 0;
	for (i = 0, ep = mp->ma_table; i < mp->ma_size; i++, ep++) {
		if (ep->me_value != NULL) {
			if (any++ > 0)
				fprintf(fp, ", ");
			if (printobject((object *)ep->me_key, fp, flags) != 0)
				return -1;
			fprintf(fp, ": ");
			if (printobject(ep->me_value, fp, flags) != 0)
				return -1;
		}
	}
	fprintf(fp, "}");
	return 0;
}

static void
js(pv, w)
	object **pv;
	object *w;
{
	joinstring(pv, w);
	XDECREF(w);
}

static object *
mapping_repr(mp)
	mappingobject *mp;
{
	auto object *v;
	object *sepa, *colon;
	register int i;
	register int any;
	register mappingentry *ep;
	v = newstringobject("{");
	sepa = newstringobject(", ");
	colon = newstringobject(": ");
	any = 0;
	for (i = 0, ep = mp->ma_table; i < mp->ma_size; i++, ep++) {
		if (ep->me_value != NULL) {
			if (any++)
				joinstring(&v, sepa);
			js(&v, reprobject(ep->me_key));
			joinstring(&v, colon);
			js(&v, reprobject(ep->me_value));
		}
	}
	js(&v, newstringobject("}"));
	XDECREF(sepa);
	XDECREF(colon);
	return v;
}

static int
mapping_length(mp)
	mappingobject *mp;
{
	return mp->ma_used;
}

static object *
mapping_subscript(mp, key)
	mappingobject *mp;
	register object *key;
{
	object *v;
	long hash = hashobject(key);
	if (hash == -1)
		return NULL;
	v = lookmapping(mp, key, hash) -> me_value;
	if (v == NULL)
		err_setval(KeyError, key);
	else
		INCREF(v);
	return v;
}

static int
mapping_ass_sub(mp, v, w)
	mappingobject *mp;
	object *v, *w;
{
	if (w == NULL)
		return mappingremove((object *)mp, v);
	else
		return mappinginsert((object *)mp, v, w);
}

static mapping_methods mapping_as_mapping = {
	mapping_length,	/*mp_length*/
	mapping_subscript,	/*mp_subscript*/
	mapping_ass_sub,	/*mp_ass_subscript*/
};

static object *
mapping_keys(mp, args)
	register mappingobject *mp;
	object *args;
{
	register object *v;
	register int i, j;
	if (!getnoarg(args))
		return NULL;
	v = newlistobject(mp->ma_used);
	if (v == NULL)
		return NULL;
	for (i = 0, j = 0; i < mp->ma_size; i++) {
		if (mp->ma_table[i].me_value != NULL) {
			object *key = mp->ma_table[i].me_key;
			INCREF(key);
			setlistitem(v, j, key);
			j++;
		}
	}
	return v;
}

object *
getmappingkeys(mp)
	object *mp;
{
	if (mp == NULL || !is_mappingobject(mp)) {
		err_badcall();
		return NULL;
	}
	return mapping_keys((mappingobject *)mp, (object *)NULL);
}

static int
mapping_compare(a, b)
	mappingobject *a, *b;
{
	object *akeys, *bkeys;
	int i, n, res;
	if (a == b)
		return 0;
	if (a->ma_used == 0) {
		if (b->ma_used != 0)
			return -1;
		else
			return 0;
	}
	else {
		if (b->ma_used == 0)
			return 1;
	}
	akeys = mapping_keys(a, (object *)NULL);
	bkeys = mapping_keys(b, (object *)NULL);
	if (akeys == NULL || bkeys == NULL) {
		/* Oops, out of memory -- what to do? */
		/* For now, sort on address! */
		XDECREF(akeys);
		XDECREF(bkeys);
		if (a < b)
			return -1;
		else
			return 1;
	}
	sortlist(akeys);
	sortlist(bkeys);
	n = a->ma_used < b->ma_used ? a->ma_used : b->ma_used; /* smallest */
	res = 0;
	for (i = 0; i < n; i++) {
		object *akey, *bkey, *aval, *bval;
		long ahash, bhash;
		akey = getlistitem(akeys, i);
		bkey = getlistitem(bkeys, i);
		res = cmpobject(akey, bkey);
		if (res != 0)
			break;
		ahash = hashobject(akey);
		if (ahash == -1)
			err_clear(); /* Don't want errors here */
		bhash = hashobject(bkey);
		if (bhash == -1)
			err_clear(); /* Don't want errors here */
		aval = lookmapping(a, akey, ahash) -> me_value;
		bval = lookmapping(b, bkey, bhash) -> me_value;
		res = cmpobject(aval, bval);
		if (res != 0)
			break;
	}
	if (res == 0) {
		if (a->ma_used < b->ma_used)
			res = -1;
		else if (a->ma_used > b->ma_used)
			res = 1;
	}
	DECREF(akeys);
	DECREF(bkeys);
	return res;
}

static object *
mapping_has_key(mp, args)
	register mappingobject *mp;
	object *args;
{
	object *key;
	long hash;
	register long ok;
	if (!getargs(args, "O", &key))
		return NULL;
	hash = hashobject(key);
	if (hash == -1)
		return NULL;
	ok = lookmapping(mp, key, hash)->me_value != NULL;
	return newintobject(ok);
}

static struct methodlist mapp_methods[] = {
	{"keys",	mapping_keys},
	{"has_key",	mapping_has_key},
	{NULL,		NULL}		/* sentinel */
};

static object *
mapping_getattr(mp, name)
	mappingobject *mp;
	char *name;
{
	return findmethod(mapp_methods, (object *)mp, name);
}

typeobject Mappingtype = {
	OB_HEAD_INIT(&Typetype)
	0,
	"mapping",
	sizeof(mappingobject),
	0,
	mapping_dealloc,	/*tp_dealloc*/
	mapping_print,		/*tp_print*/
	mapping_getattr,	/*tp_getattr*/
	0,			/*tp_setattr*/
	mapping_compare,	/*tp_compare*/
	mapping_repr,		/*tp_repr*/
	0,			/*tp_as_number*/
	0,			/*tp_as_sequence*/
	&mapping_as_mapping,	/*tp_as_mapping*/
};

/* For backward compatibility with old dictionary interface */

static object *last_name_object;
static char *last_name_char;

object *
getattro(v, name)
	object *v;
	object *name;
{
	if (name != last_name_object) {
		XDECREF(last_name_object);
		INCREF(name);
		last_name_object = name;
		last_name_char = getstringvalue(name);
	}
	return getattr(v, last_name_char);
}

int
setattro(v, name, value)
	object *v;
	object *name;
	object *value;
{
	if (name != last_name_object) {
		XDECREF(last_name_object);
		INCREF(name);
		last_name_object = name;
		last_name_char = getstringvalue(name);
	}
	return setattr(v, last_name_char, value);
}

object *
dictlookup(v, key)
	object *v;
	char *key;
{
	if (key != last_name_char) {
		XDECREF(last_name_object);
		last_name_object = newstringobject(key);
		if (last_name_object == NULL) {
			last_name_char = NULL;
			return NULL;
		}
		last_name_char = key;
	}
	return mappinglookup(v, last_name_object);
}

int
dictinsert(v, key, item)
	object *v;
	char *key;
	object *item;
{
	if (key != last_name_char) {
		XDECREF(last_name_object);
		last_name_object = newstringobject(key);
		if (last_name_object == NULL) {
			last_name_char = NULL;
			return NULL;
		}
		last_name_char = key;
	}
	return mappinginsert(v, last_name_object, item);
}

int
dictremove(v, key)
	object *v;
	char *key;
{
	if (key != last_name_char) {
		XDECREF(last_name_object);
		last_name_object = newstringobject(key);
		if (last_name_object == NULL) {
			last_name_char = NULL;
			return NULL;
		}
		last_name_char = key;
	}
	return mappingremove(v, last_name_object);
}

char *
getdictkey(v, i)
	object *v;
	int i;
{
	object *key = getmappingkey(v, i);
	if (key == NULL)
		return NULL;
	return getstringvalue(key);
}