/*
 *	aegis - project change supervisor
 *	Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Peter Miller;
 *	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, USA.
 *
 * MANIFEST: functions to manipulate symbol tables
 */

#include <error.h>
#include <fstrcmp.h>
#include <mem.h>
#include <symtab.h>


symtab_ty *
symtab_alloc(size)
	int		size;
{
	symtab_ty	*stp;
	str_hash_ty	j;

	stp = mem_alloc(sizeof(symtab_ty));
	stp->chain = 0;
	stp->reap = 0;
	stp->hash_modulus = 1 << 2; /* MUST be a power of 2 */
	while (stp->hash_modulus < size)
		stp->hash_modulus <<= 1;
	stp->hash_cutover = stp->hash_modulus;
	stp->hash_split = stp->hash_modulus - stp->hash_cutover;
	stp->hash_cutover_mask = stp->hash_cutover - 1;
	stp->hash_cutover_split_mask = (stp->hash_cutover * 2) - 1;
	stp->hash_load = 0;
	stp->hash_table =
		mem_alloc(stp->hash_modulus * sizeof(symtab_row_ty *));
	for (j = 0; j < stp->hash_modulus; ++j)
		stp->hash_table[j] = 0;
	return stp;
}


void
symtab_free(stp)
	symtab_ty	*stp;
{
	str_hash_ty	j;

	for (j = 0; j < stp->hash_modulus; ++j)
	{
		symtab_row_ty	**rpp;

		rpp = &stp->hash_table[j];
		while (*rpp)
		{
			symtab_row_ty	*rp;

			rp = *rpp; 
			*rpp = rp->overflow;
			if (stp->reap)
				stp->reap(rp->data);
			str_free(rp->key);
			mem_free(rp);
		}
	}
}


/*
 * NAME
 *	split - reduce symbol table load
 *
 * SYNOPSIS
 *	void split(symtab_ty);
 *
 * DESCRIPTION
 *	The split function is used to split symbols in the bucket indicated by
 *	the split point.  The symbols are split between that bucket and the one
 *	after the current end of the table.
 *
 * CAVEAT
 *	It is only sensable to do this when the symbol table load exceeds some
 *	reasonable threshold.  A threshold of 80% is suggested.
 */

static void split _((symtab_ty *));

static void
split(stp)
	symtab_ty	*stp;
{
	symtab_row_ty	*p;
	symtab_row_ty	**ipp;
	symtab_row_ty	*p2;
	str_hash_ty	index;

	/*
	 * get the list to be split across buckets 
	 */
	p = stp->hash_table[stp->hash_split];
	stp->hash_table[stp->hash_split] = 0;

	/*
	 * increase the modulus by one
	 */
	stp->hash_modulus++;
	stp->hash_table =
		mem_change_size
		(
			stp->hash_table,
			stp->hash_modulus * sizeof(symtab_row_ty *)
		);
	stp->hash_table[stp->hash_modulus - 1] = 0;
	stp->hash_split = stp->hash_modulus - stp->hash_cutover;
	if (stp->hash_split >= stp->hash_cutover)
	{
		stp->hash_cutover = stp->hash_modulus;
		stp->hash_split = 0;
		stp->hash_cutover_mask = stp->hash_cutover - 1;
		stp->hash_cutover_split_mask = (stp->hash_cutover * 2) - 1;
	}

	/*
	 * now redistribute the list elements
	 *
	 * It is important to preserve the order of the links because
	 * they can be push-down stacks, and to simply add them to the
	 * head of the list will reverse the order of the stack!
	 */
	while (p)
	{
		p2 = p;
		p = p2->overflow;
		p2->overflow = 0;

		index = p2->key->str_hash & stp->hash_cutover_mask;
		if (index < stp->hash_split)
		{
			index =
				(
					p2->key->str_hash
				&
					stp->hash_cutover_split_mask
				);
		}
		for
		(
			ipp = &stp->hash_table[index];
			*ipp;
			ipp = &(*ipp)->overflow
		)
			;
		*ipp = p2;
	}
}


/*
 * NAME
 *	symtab_query - search for a variable
 *
 * SYNOPSIS
 *	int symtab_query(symtab_ty *, string_ty *key);
 *
 * DESCRIPTION
 *	The symtab_query function is used to reference a variable.
 *
 * RETURNS
 *	If the variable has been defined, the function returns a non-zero value
 *	and the value is returned through the 'value' pointer.
 *	If the variable has not been defined, it returns zero,
 *	and 'value' is unaltered.
 */

void *
symtab_query(stp, key)
	symtab_ty	*stp;
	string_ty	*key;
{
	str_hash_ty	index;
	symtab_row_ty	*p;

	while (stp)
	{
		index = key->str_hash & stp->hash_cutover_mask;
		if (index < stp->hash_split)
			index = key->str_hash & stp->hash_cutover_split_mask;
		for (p = stp->hash_table[index]; p; p = p->overflow)
		{
			if (str_equal(key, p->key))
				return p->data;
		}
		stp = stp->chain;
	}
	return 0;
}


/*
 * NAME
 *	symtab_query_fuzzy - search for a variable name
 *
 * SYNOPSIS
 *	string_ty *symtab_query_fuzzy(symtab_ty *, string_ty *key);
 *
 * DESCRIPTION
 *	The symtab_query_fuzzy function is used to search for a variable name.
 *
 * RETURNS
 *	The closest match for the variable name given.
 *	If no match is particularly close, it returns 0.
 */

string_ty *
symtab_query_fuzzy(stp, key)
	symtab_ty	*stp;
	string_ty	*key;
{
	str_hash_ty	index;
	symtab_row_ty	*p;
	string_ty	*best_name;
	double		best_weight;
	double		weight;

	best_name = 0;
	best_weight = 0.6;
	while (stp)
	{
		for (index = 0; index < stp->hash_modulus; ++index)
		{
			for (p = stp->hash_table[index]; p; p = p->overflow)
			{
				weight =
					fstrcmp
					(
						key->str_text,
						p->key->str_text
					);
				if (weight > best_weight)
					best_name = p->key;
			}
		}
		stp = stp->chain;
	}
	return best_name;
}


/*
 * NAME
 *	symtab_assign - assign a variable
 *
 * SYNOPSIS
 *	void symtab_assign(symtab_ty *, string_ty *key, void *data);
 *
 * DESCRIPTION
 *	The symtab_assign function is used to assign
 *	a value to a given variable.
 *
 * CAVEAT
 *	The name is copied, the data is not.
 */

void
symtab_assign(stp, key, data)
	symtab_ty	*stp;
	string_ty	*key;
	void		*data;
{
	str_hash_ty	index;
	symtab_row_ty	*p;

	index = key->str_hash & stp->hash_cutover_mask;
	if (index < stp->hash_split)
		index = key->str_hash & stp->hash_cutover_split_mask;

	for (p = stp->hash_table[index]; p; p = p->overflow)
	{
		if (str_equal(key, p->key))
		{
			if (stp->reap)
				stp->reap(p->data);
			p->data = data;
			return;
		}
	}

	p = mem_alloc(sizeof(symtab_row_ty));
	p->key = str_copy(key);
	p->overflow = stp->hash_table[index];
	p->data = data;
	stp->hash_table[index] = p;

	stp->hash_load++;
	while (stp->hash_load * 10 >= stp->hash_modulus * 8)
		split(stp);
}


/*
 * NAME
 *	symtab_assign_push - assign a variable
 *
 * SYNOPSIS
 *	void symtab_assign_push(symtab_ty *, string_ty *key, void *data);
 *
 * DESCRIPTION
 *	The symtab_assign function is used to assign
 *	a value to a given variable.
 *	Any previous value will be obscured until this one
 *	is deleted with symtab_delete.
 *
 * CAVEAT
 *	The name is copied, the data is not.
 */

void
symtab_assign_push(stp, key, data)
	symtab_ty	*stp;
	string_ty	*key;
	void		*data;
{
	str_hash_ty	index;
	symtab_row_ty	*p;

	index = key->str_hash & stp->hash_cutover_mask;
	if (index < stp->hash_split)
		index = key->str_hash & stp->hash_cutover_split_mask;

	p = mem_alloc(sizeof(symtab_row_ty));
	p->key = str_copy(key);
	p->overflow = stp->hash_table[index];
	p->data = data;
	stp->hash_table[index] = p;

	stp->hash_load++;
	while (stp->hash_load * 10 >= stp->hash_modulus * 8)
		split(stp);
}


/*
 * NAME
 *	symtab_delete - delete a variable
 *
 * SYNOPSIS
 *	void symtab_delete(string_ty *name, symtab_class_ty class);
 *
 * DESCRIPTION
 *	The symtab_delete function is used to delete variables.
 *
 * CAVEAT
 *	The name is freed, the data is reaped.
 *	(By default, reap does nothing.)
 */

void
symtab_delete(stp, key)
	symtab_ty	*stp;
	string_ty	*key;
{
	str_hash_ty	index;
	symtab_row_ty	**pp;

	index = key->str_hash & stp->hash_cutover_mask;
	if (index < stp->hash_split)
		index = key->str_hash & stp->hash_cutover_split_mask;

	pp = &stp->hash_table[index];
	for (;;)
	{
		symtab_row_ty	*p;

		p = *pp;
		if (!p)
			break;
		if (str_equal(key, p->key))
		{
			if (stp->reap)
				stp->reap(p->data);
			str_free(p->key);
			*pp = p->overflow;
			mem_free(p);
			stp->hash_load--;
			break;
		}
		pp = &p->overflow;
	}
}


/*
 * NAME
 *	symtab_dump - dump id table
 *
 * SYNOPSIS
 *	void symtab_dump(symtab_ty *stp, char *caption);
 *
 * DESCRIPTION
 *	The symtab_dump function is used to dump the contents of the
 *	symbol table.  The caption will be used to indicate why the
 *	symbol table was dumped.
 *
 * CAVEAT
 *	This function is only available when symbol DEBUG is defined.
 */

#ifdef DEBUG

void
symtab_dump(stp, caption)
	symtab_ty	*stp;
	char		*caption;
{
	int		j;
	symtab_row_ty	*p;

	error_raw("symbol table %s = {", caption);
	for (j = 0; j < stp->hash_modulus; ++j)
	{
		for (p = stp->hash_table[j]; p; p = p->overflow)
		{
			error_raw
			(
				"key = \"%s\", data = %08lX",
				p->key->str_text,
				(long)p->data
			);
		}
	}
	error_raw("}");
}

#endif


void
symtab_walk(stp, func, arg)
	symtab_ty	*stp;
	void		(*func)_((symtab_ty *, string_ty *, void *, void *));
	void		*arg;
{
	long		j;
	symtab_row_ty	*rp;

	for (j = 0; j < stp->hash_modulus; ++j)
		for (rp = stp->hash_table[j]; rp; rp = rp->overflow)
			func(stp, rp->key, rp->data, arg);
}