/**
 * \file psa_crypto_core_common.h
 *
 * \brief Utility macros for internal use in the PSA cryptography core.
 */
/*
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 */

#ifndef PSA_CRYPTO_CORE_COMMON_H
#define PSA_CRYPTO_CORE_COMMON_H

/** Return an offset into a buffer.
 *
 * This is just the addition of an offset to a pointer, except that this
 * function also accepts an offset of 0 into a buffer whose pointer is null.
 * (`p + n` has undefined behavior when `p` is null, even when `n == 0`.
 * A null pointer is a valid buffer pointer when the size is 0, for example
 * as the result of `malloc(0)` on some platforms.)
 *
 * \param p     Pointer to a buffer of at least n bytes.
 *              This may be \p NULL if \p n is zero.
 * \param n     An offset in bytes.
 * \return      Pointer to offset \p n in the buffer \p p.
 *              Note that this is only a valid pointer if the size of the
 *              buffer is at least \p n + 1.
 */
static inline unsigned char *psa_crypto_buffer_offset(
    unsigned char *p, size_t n)
{
    return p == NULL ? NULL : p + n;
}

/** Return an offset into a read-only buffer.
 *
 * Similar to mbedtls_buffer_offset(), but for const pointers.
 *
 * \param p     Pointer to a buffer of at least n bytes.
 *              This may be \p NULL if \p n is zero.
 * \param n     An offset in bytes.
 * \return      Pointer to offset \p n in the buffer \p p.
 *              Note that this is only a valid pointer if the size of the
 *              buffer is at least \p n + 1.
 */
static inline const unsigned char *psa_crypto_buffer_offset_const(
    const unsigned char *p, size_t n)
{
    return p == NULL ? NULL : p + n;
}

#endif /* PSA_CRYPTO_CORE_COMMON_H */