/* utils.h - TinyCrypt interface to platform-dependent run-time operations */

/*
 *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *    - Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *
 *    - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *    - Neither the name of Intel Corporation nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 * @brief Interface to platform-dependent run-time operations.
 *
 */

#ifndef __TC_UTILS_H__
#define __TC_UTILS_H__

#include <stdint.h>
#include <stddef.h>
#include <string.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Copy the the buffer 'from' to the buffer 'to'.
 * @return returns TC_CRYPTO_SUCCESS (1)
 *         returns TC_CRYPTO_FAIL (0) if:
 *                from_len > to_len.
 *
 * @param to OUT -- destination buffer
 * @param to_len IN -- length of destination buffer
 * @param from IN -- origin buffer
 * @param from_len IN -- length of origin buffer
 */
unsigned int _copy(uint8_t *to, unsigned int to_len,
	           const uint8_t *from, unsigned int from_len);

/**
 * @brief Set the value 'val' into the buffer 'to', 'len' times.
 *
 * @param to OUT -- destination buffer
 * @param val IN -- value to be set in 'to'
 * @param len IN -- number of times the value will be copied
 */
void _set(void *to, uint8_t val, unsigned int len);

/**
 * @brief Set the value 'val' into the buffer 'to', 'len' times, in a way
 *         which does not risk getting optimized out by the compiler
 *        In cases where the compiler does not set __GNUC__ and where the
 *         optimization level removes the memset, it may be necessary to
 *         implement a _set_secure function and define the
 *         TINYCRYPT_ARCH_HAS_SET_SECURE, which then can ensure that the
 *         memset does not get optimized out.
 *
 * @param to OUT -- destination buffer
 * @param val IN -- value to be set in 'to'
 * @param len IN -- number of times the value will be copied
 */
#ifdef TINYCRYPT_ARCH_HAS_SET_SECURE
extern void _set_secure(void *to, uint8_t val, unsigned int len);
#else /* ! TINYCRYPT_ARCH_HAS_SET_SECURE */
static inline void _set_secure(void *to, uint8_t val, unsigned int len)
{
  (void) memset(to, val, len);
#ifdef __GNUC__
  __asm__ __volatile__("" :: "g"(to) : "memory");
#endif /* __GNUC__ */
}
#endif /* TINYCRYPT_ARCH_HAS_SET_SECURE */

/*
 * @brief AES specific doubling function, which utilizes
 * the finite field used by AES.
 * @return Returns a^2
 *
 * @param a IN/OUT -- value to be doubled
 */
uint8_t _double_byte(uint8_t a);

/*
 * @brief Constant-time algorithm to compare if two sequences of bytes are equal
 * @return Returns 0 if equal, and non-zero otherwise
 *
 * @param a IN -- sequence of bytes a
 * @param b IN -- sequence of bytes b
 * @param size IN -- size of sequences a and b
 */
int _compare(const uint8_t *a, const uint8_t *b, size_t size);

#ifdef __cplusplus
}
#endif

#endif /* __TC_UTILS_H__ */
