firebird-mirror/src/jrd/sym.cpp

/*
 *	PROGRAM:	JRD access method
 *	MODULE:		hsh.cpp
 *	DESCRIPTION:	Hash table and symbol manager
 *
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 */

#include "firebird.h"
#include <string.h>
#include "../jrd/common.h"
#include "../jrd/jrd.h"
#include "../jrd/val.h"
#include "../jrd/err_proto.h"
#include "../jrd/sym.h"
#include "../jrd/thd_proto.h"


using namespace Jrd;

namespace {
	SSHORT hash_func(const Firebird::string&);
}

void Symbol::insert()
{
/**************************************
 *
 *	S Y M _ i n s e r t
 *
 **************************************
 *
 * Functional description
 *	Insert a symbol into the hash table.
 *
 **************************************/
	Database* dbb = GET_DBB;

	const int h = hash_func(sym_string);

	for (Symbol* old = dbb->dbb_hash_table[h]; old; old = old->sym_collision)
	{
		if (sym_string == old->sym_string)
		{
			sym_homonym = old->sym_homonym;
			old->sym_homonym = this;
			return;
		}
	}

	sym_collision = dbb->dbb_hash_table[h];
	dbb->dbb_hash_table[h] = this;
}


Symbol* Symbol::lookup(const Firebird::string& string)
{
/**************************************
 *
 *	S Y M _ l o o k u p
 *
 **************************************
 *
 * Functional description
 *	Perform a string lookup against hash table.
 *
 **************************************/
	Database* dbb = GET_DBB;

	for (Symbol* symbol = dbb->dbb_hash_table[hash_func(string)]; symbol;
		 symbol = symbol->sym_collision)
	{
		if (string == symbol->sym_string) 
			return symbol;
	}

	return NULL;
}


void Symbol::remove()
{
/**************************************
 *
 *	S Y M _ r e m o v e 
 *
 **************************************
 *
 * Functional description
 *	Remove a symbol from the hash table.
 *
 **************************************/
	Database* dbb = GET_DBB;

	const int h = hash_func(sym_string);

	for (Symbol** next = &dbb->dbb_hash_table[h]; *next;
		 next = &(*next)->sym_collision)
	{
		if (this == *next) {
			Symbol* homonym = sym_homonym;
			if (homonym) {
				homonym->sym_collision = sym_collision;
				*next = homonym;
				return;
			}
			else {
				*next = sym_collision;
				return;
			}
		}
		else {
			for (Symbol** ptr = &(*next)->sym_homonym; *ptr;
				 ptr = &(*ptr)->sym_homonym)
			{
				if (this == *ptr) {
					*ptr = sym_homonym;
					return;
				}
			}
		}
	}

	BUGCHECK(164);				/* msg 164 failed to remove symbol from hash table */
}

namespace {

SSHORT hash_func(const Firebird::string& str)
{
/**************************************
 *
 *	h a s h
 *
 **************************************
 *
 * Functional description
 *	Returns the hash function of a string.
 *
 **************************************/

/* It is OK to not Internationalize this function as it is for
   internal optimization of symbol lookup */

	int value = 0;

	for (const char *s = str.c_str(); *s; s++)
	{
		value = (value << 1) + UPPER7(*s);
	}

	return ((value >= 0) ? value : -value) % HASH_SIZE;
}

} //noname namespace