src/backend/utils/misc/size.c

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*
 * size.c
 *    routines for manipulating Size data type.
 *
 */

#include "postgres.h"
#include "utils/size.h"

/*
 * Add two Size values, checking for overflow
 */
Size
add_size(Size s1, Size s2)
{
	Size		result;

	result = s1 + s2;
	/* We are assuming Size is an unsigned type here... */
	if (result < s1 || result < s2)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("requested shared memory size overflows size_t")));
	return result;
}

/*
 * Multiply two Size values, checking for overflow
 */
Size
mul_size(Size s1, Size s2)
{
	Size		result;

	if (s1 == 0 || s2 == 0)
		return 0;
	result = s1 * s2;
	/* We are assuming Size is an unsigned type here... */
	if (result / s2 != s1)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("requested shared memory size overflows size_t")));
	return result;
}