GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libcrypto/constant_time_locl.h Lines: 6 6 100.0 %
Date: 2017-11-13 Branches: 0 0 0.0 %

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/* crypto/constant_time_locl.h */
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/*-
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 * Utilities for constant-time cryptography.
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 *
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 * Author: Emilia Kasper (emilia@openssl.org)
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 * Based on previous work by Bodo Moeller, Emilia Kasper, Adam Langley
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 * (Google).
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 * ====================================================================
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 * Copyright (c) 2014 The OpenSSL Project.  All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. All advertising materials mentioning features or use of this software
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 *    must display the following acknowledgement:
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 *    "This product includes cryptographic software written by
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 *     Eric Young (eay@cryptsoft.com)"
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 *    The word 'cryptographic' can be left out if the rouines from the library
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 *    being used are not cryptographic related :-).
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 * 4. If you include any Windows specific code (or a derivative thereof) from
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 *    the apps directory (application code) you must include an acknowledgement:
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 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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 *
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 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 *
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 * The licence and distribution terms for any publically available version or
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 * derivative of this code cannot be changed.  i.e. this code cannot simply be
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 * copied and put under another distribution licence
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 * [including the GNU Public Licence.]
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 */
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#ifndef HEADER_CONSTANT_TIME_LOCL_H
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# define HEADER_CONSTANT_TIME_LOCL_H
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__BEGIN_HIDDEN_DECLS
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/*-
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 * The boolean methods return a bitmask of all ones (0xff...f) for true
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 * and 0 for false. This is useful for choosing a value based on the result
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 * of a conditional in constant time. For example,
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 *
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 * if (a < b) {
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 *   c = a;
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 * } else {
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 *   c = b;
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 * }
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 *
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 * can be written as
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 *
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 * unsigned int lt = constant_time_lt(a, b);
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 * c = constant_time_select(lt, a, b);
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 */
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/*
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 * Returns the given value with the MSB copied to all the other
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 * bits. Uses the fact that arithmetic shift shifts-in the sign bit.
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 * However, this is not ensured by the C standard so you may need to
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 * replace this with something else on odd CPUs.
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 */
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static inline unsigned int constant_time_msb(unsigned int a);
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/*
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 * Returns 0xff..f if a < b and 0 otherwise.
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 */
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static inline unsigned int constant_time_lt(unsigned int a, unsigned int b);
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/* Convenience method for getting an 8-bit mask. */
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static inline unsigned char constant_time_lt_8(unsigned int a,
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                                               unsigned int b);
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/*
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 * Returns 0xff..f if a >= b and 0 otherwise.
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 */
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static inline unsigned int constant_time_ge(unsigned int a, unsigned int b);
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/* Convenience method for getting an 8-bit mask. */
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static inline unsigned char constant_time_ge_8(unsigned int a,
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                                               unsigned int b);
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/*
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 * Returns 0xff..f if a == 0 and 0 otherwise.
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 */
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static inline unsigned int constant_time_is_zero(unsigned int a);
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/* Convenience method for getting an 8-bit mask. */
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static inline unsigned char constant_time_is_zero_8(unsigned int a);
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/*
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 * Returns 0xff..f if a == b and 0 otherwise.
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 */
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static inline unsigned int constant_time_eq(unsigned int a, unsigned int b);
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/* Convenience method for getting an 8-bit mask. */
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static inline unsigned char constant_time_eq_8(unsigned int a,
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                                               unsigned int b);
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/* Signed integers. */
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static inline unsigned int constant_time_eq_int(int a, int b);
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/* Convenience method for getting an 8-bit mask. */
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static inline unsigned char constant_time_eq_int_8(int a, int b);
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/*-
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 * Returns (mask & a) | (~mask & b).
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 *
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 * When |mask| is all 1s or all 0s (as returned by the methods above),
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 * the select methods return either |a| (if |mask| is nonzero) or |b|
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 * (if |mask| is zero).
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 */
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static inline unsigned int constant_time_select(unsigned int mask,
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                                                unsigned int a,
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                                                unsigned int b);
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/* Convenience method for unsigned chars. */
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static inline unsigned char constant_time_select_8(unsigned char mask,
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                                                   unsigned char a,
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                                                   unsigned char b);
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/* Convenience method for signed integers. */
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static inline int constant_time_select_int(unsigned int mask, int a, int b);
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static inline unsigned int constant_time_msb(unsigned int a)
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{
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    return 0 - (a >> (sizeof(a) * 8 - 1));
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}
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static inline unsigned int constant_time_lt(unsigned int a, unsigned int b)
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{
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    return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b)));
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}
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static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b)
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{
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    return (unsigned char)(constant_time_lt(a, b));
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}
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static inline unsigned int constant_time_ge(unsigned int a, unsigned int b)
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{
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    return ~constant_time_lt(a, b);
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}
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static inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b)
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{
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    return (unsigned char)(constant_time_ge(a, b));
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}
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static inline unsigned int constant_time_is_zero(unsigned int a)
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{
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    return constant_time_msb(~a & (a - 1));
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}
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static inline unsigned char constant_time_is_zero_8(unsigned int a)
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{
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    return (unsigned char)(constant_time_is_zero(a));
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}
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static inline unsigned int constant_time_eq(unsigned int a, unsigned int b)
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{
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    return constant_time_is_zero(a ^ b);
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}
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static inline unsigned char constant_time_eq_8(unsigned int a, unsigned int b)
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{
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    return (unsigned char)(constant_time_eq(a, b));
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}
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static inline unsigned int constant_time_eq_int(int a, int b)
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{
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    return constant_time_eq((unsigned)(a), (unsigned)(b));
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}
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static inline unsigned char constant_time_eq_int_8(int a, int b)
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{
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    return constant_time_eq_8((unsigned)(a), (unsigned)(b));
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}
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static inline unsigned int constant_time_select(unsigned int mask,
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                                                unsigned int a,
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                                                unsigned int b)
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{
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    return (mask & a) | (~mask & b);
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}
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static inline unsigned char constant_time_select_8(unsigned char mask,
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                                                   unsigned char a,
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                                                   unsigned char b)
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{
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    return (unsigned char)(constant_time_select(mask, a, b));
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}
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static inline int constant_time_select_int(unsigned int mask, int a, int b)
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{
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    return (int)(constant_time_select(mask, (unsigned)(a), (unsigned)(b)));
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}
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__END_HIDDEN_DECLS
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#endif                          /* HEADER_CONSTANT_TIME_LOCL_H */