/*

 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#ifndef SIZECALC_H

#define SIZECALC_H

/*

 * A machinery for safe calculation of sizes used when allocating memory.

 *

 * All size checks are performed against the SIZE_MAX (the maximum value for

 * size_t). All numerical arguments as well as the result of calculation must

 * be non-negative integers less than or equal to SIZE_MAX, otherwise the

 * calculated size is considered unsafe.

 *

 * If the SIZECALC_ALLOC_THROWING_BAD_ALLOC macro is defined, then _ALLOC_

 * helper macros throw the std::bad_alloc instead of returning NULL.

 */

#include <stdint.h> /* SIZE_MAX for C99+ */

/* http://stackoverflow.com/questions/3472311/what-is-a-portable-method-to-find-the-maximum-value-of-size-t */

#ifndef SIZE_MAX

#define SIZE_MAX ((size_t)-1)

#endif

#define IS_SAFE_SIZE_T(x) ((x) >= 0 && (unsigned long long)(x) <= SIZE_MAX)

#define IS_SAFE_SIZE_MUL(m, n) \

    (IS_SAFE_SIZE_T(m) && IS_SAFE_SIZE_T(n) && ((m) == 0 || (n) == 0 || (size_t)(n) <= (SIZE_MAX / (size_t)(m))))

#define IS_SAFE_SIZE_ADD(a, b) \

    (IS_SAFE_SIZE_T(a) && IS_SAFE_SIZE_T(b) && (size_t)(b) <= (SIZE_MAX - (size_t)(a)))

/* Helper macros */

#ifdef SIZECALC_ALLOC_THROWING_BAD_ALLOC

#define FAILURE_RESULT throw std::bad_alloc()

#else

#define FAILURE_RESULT NULL

#endif

/*

 * A helper macro to safely allocate an array of size m*n.

 * Example usage:

 *    int* p = (int*)SAFE_SIZE_ARRAY_ALLOC(malloc, sizeof(int), n);

 *    if (!p) throw OutOfMemory;

 *    // Use the allocated array...

 */

#define SAFE_SIZE_ARRAY_ALLOC(func, m, n) \

    (IS_SAFE_SIZE_MUL((m), (n)) ? ((func)((m) * (n))) : FAILURE_RESULT)

#define SAFE_SIZE_ARRAY_REALLOC(func, p, m, n) \

    (IS_SAFE_SIZE_MUL((m), (n)) ? ((func)((p), (m) * (n))) : FAILURE_RESULT)

/*

 * A helper macro to safely allocate an array of type 'type' with 'n' items

 * using the C++ new[] operator.

 * Example usage:

 *    MyClass* p = SAFE_SIZE_NEW_ARRAY(MyClass, n);

 *    // Use the pointer.

 * This macro throws the std::bad_alloc C++ exception to indicate

 * a failure.

 * NOTE: if 'n' is calculated, the calling code is responsible for using the

 * IS_SAFE_... macros to check if the calculations are safe.

 */

#define SAFE_SIZE_NEW_ARRAY(type, n) \

    (IS_SAFE_SIZE_MUL(sizeof(type), (n)) ? (new type[(n)]) : throw std::bad_alloc())

#define SAFE_SIZE_NEW_ARRAY2(type, n, m) \

    (IS_SAFE_SIZE_MUL((m), (n)) && IS_SAFE_SIZE_MUL(sizeof(type), (n) * (m)) ? \

     (new type[(n) * (m)]) : throw std::bad_alloc())

/*

 * Checks if a data structure of size (a + m*n) can be safely allocated

 * w/o producing an integer overflow when calculating its size.

 */

#define IS_SAFE_STRUCT_SIZE(a, m, n) \

    ( \

      IS_SAFE_SIZE_MUL((m), (n)) && IS_SAFE_SIZE_ADD((m) * (n), (a)) \

    )

/*

 * A helper macro for implementing safe memory allocation for a data structure

 * of size (a + m * n).

 * Example usage:

 *    void * p = SAFE_SIZE_ALLOC(malloc, header, num, itemSize);

 *    if (!p) throw OutOfMemory;

 *    // Use the allocated memory...

 */

#define SAFE_SIZE_STRUCT_ALLOC(func, a, m, n) \

    (IS_SAFE_STRUCT_SIZE((a), (m), (n)) ? ((func)((a) + (m) * (n))) : FAILURE_RESULT)

#endif /* SIZECALC_H */