42 lines
1.1 KiB
C
42 lines
1.1 KiB
C
/* SPDX-FileCopyrightText: 2002-2017 `Jason Evans <jasone@canonware.com>`. All rights reserved.
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* SPDX-FileCopyrightText: 2007-2012 Mozilla Foundation. All rights reserved.
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* SPDX-FileCopyrightText: 2009-2017 Facebook, Inc. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-2-Clause */
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/** \file
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* \ingroup intern_mem
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*/
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#ifndef __MALLOCN_INLINE_H__
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#define __MALLOCN_INLINE_H__
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#ifdef __cplusplus
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extern "C" {
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#endif
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MEM_INLINE bool MEM_size_safe_multiply(size_t a, size_t b, size_t *result)
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{
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/* A size_t with its high-half bits all set to 1. */
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const size_t high_bits = SIZE_MAX << (sizeof(size_t) * 8 / 2);
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*result = a * b;
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if (UNLIKELY(*result == 0)) {
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return (a == 0 || b == 0);
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}
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/*
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* We got a non-zero size, but we don't know if we overflowed to get
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* there. To avoid having to do a divide, we'll be clever and note that
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* if both A and B can be represented in N/2 bits, then their product
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* can be represented in N bits (without the possibility of overflow).
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*/
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return ((high_bits & (a | b)) == 0 || (*result / b == a));
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* __MALLOCN_INLINE_H__ */
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