127 lines
4.3 KiB
C
127 lines
4.3 KiB
C
/*
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* Copyright (c) 2015-2018 Apple Inc. All rights reserved.
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*
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* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
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*
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* This file contains Original Code and/or Modifications of Original Code
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* as defined in and that are subject to the Apple Public Source License
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* Version 2.0 (the 'License'). You may not use this file except in
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* compliance with the License. The rights granted to you under the License
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* may not be used to create, or enable the creation or redistribution of,
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* unlawful or unlicensed copies of an Apple operating system, or to
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* circumvent, violate, or enable the circumvention or violation of, any
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* terms of an Apple operating system software license agreement.
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*
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* Please obtain a copy of the License at
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* http://www.opensource.apple.com/apsl/ and read it before using this file.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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* Please see the License for the specific language governing rights and
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* limitations under the License.
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*
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* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
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*/
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/*
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* Facilities for performing type- and overflow-checked arithmetic. These
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* functions return non-zero if overflow occured, zero otherwise. In either case,
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* the potentially overflowing operation is fully performed, mod the size of the
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* output type. See:
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* http://clang.llvm.org/docs/LanguageExtensions.html#checked-arithmetic-builtins
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* for full details.
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*
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* The compiler enforces that users of os_*_overflow() check the return value to
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* determine whether overflow occured.
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*/
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#ifndef _OS_OVERFLOW_H
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#define _OS_OVERFLOW_H
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#include <sys/cdefs.h>
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#include <stdbool.h>
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#include <os/base.h>
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bool __header_always_inline OS_WARN_RESULT
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__os_warn_unused(__const bool x)
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{
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return x;
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}
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#if __has_builtin(__builtin_add_overflow) && \
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__has_builtin(__builtin_sub_overflow) && \
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__has_builtin(__builtin_mul_overflow)
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#define os_add_overflow(a, b, res) __os_warn_unused(__builtin_add_overflow((a), (b), (res)))
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#define os_sub_overflow(a, b, res) __os_warn_unused(__builtin_sub_overflow((a), (b), (res)))
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#define os_mul_overflow(a, b, res) __os_warn_unused(__builtin_mul_overflow((a), (b), (res)))
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#else
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# error os_overflow expects type-generic builtins
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#endif /* __has_builtin(...) */
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/* os_add3_overflow(a, b, c) -> (a + b + c) */
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#define os_add3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \
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__typeof(*(res)) _tmp; \
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bool _s, _t; \
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_s = os_add_overflow((a), (b), &_tmp); \
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_t = os_add_overflow((c), _tmp, (res)); \
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_s | _t; \
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}))
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/* os_sub3_overflow(a, b, c) -> ((a - b) - c) */
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#define os_sub3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \
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__typeof(*(res)) _tmp; \
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bool _s, _t; \
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_s = os_sub_overflow((a), (b), &_tmp); \
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_t = os_sub_overflow(_tmp, (c), (res)); \
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_s | _t; \
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}))
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/* os_mul3_overflow(a, b, c) -> (a * b * c) */
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#define os_mul3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \
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__typeof(*(res)) _tmp; \
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bool _s, _t; \
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_s = os_mul_overflow((a), (b), &_tmp); \
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_t = os_mul_overflow((c), _tmp, (res)); \
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_s | _t; \
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}))
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/* os_add_and_mul_overflow(a, b, x) -> (a + b)*x */
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#define os_add_and_mul_overflow(a, b, x, res) __os_warn_unused(__extension__({ \
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__typeof(*(res)) _tmp; \
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bool _s, _t; \
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_s = os_add_overflow((a), (b), &_tmp); \
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_t = os_mul_overflow((x), _tmp, (res)); \
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_s | _t; \
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}))
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/* os_mul_and_add_overflow(a, x, b) -> a*x + b */
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#define os_mul_and_add_overflow(a, x, b, res) __os_warn_unused(__extension__({ \
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__typeof(*(res)) _tmp; \
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bool _s, _t; \
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_s = os_mul_overflow((a), (x), &_tmp); \
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_t = os_add_overflow((b), _tmp, (res)); \
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_s | _t; \
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}))
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/* os_convert_overflow(a) -> a [converted to the result type] */
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#define os_convert_overflow(a, res) os_add_overflow((a), 0, (res))
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/* os_inc_overflow(res) -> *res += 1 */
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#define os_inc_overflow(res) __os_warn_unused(__extension__({ \
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__typeof((res)) _tmp = (res); \
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os_add_overflow(*_tmp, 1, _tmp); \
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}))
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/* os_dec_overflow(res) -> *res -= 1 */
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#define os_dec_overflow(res) __os_warn_unused(__extension__({ \
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__typeof((res)) _tmp = (res); \
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os_sub_overflow(*_tmp, 1, _tmp); \
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}))
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#endif /* _OS_OVERFLOW_H */
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