library/common.h

/**
 * \file common.h
 *
 * \brief Utility macros for internal use in the library
 */
/*
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#ifndef MBEDTLS_LIBRARY_COMMON_H
#define MBEDTLS_LIBRARY_COMMON_H

#if defined(MBEDTLS_CONFIG_FILE)
#include MBEDTLS_CONFIG_FILE
#else
#include "mbedtls/config.h"
#endif

/** Helper to define a function as static except when building invasive tests.
 *
 * If a function is only used inside its own source file and should be
 * declared `static` to allow the compiler to optimize for code size,
 * but that function has unit tests, define it with
 * ```
 * MBEDTLS_STATIC_TESTABLE int mbedtls_foo(...) { ... }
 * ```
 * and declare it in a header in the `library/` directory with
 * ```
 * #if defined(MBEDTLS_TEST_HOOKS)
 * int mbedtls_foo(...);
 * #endif
 * ```
 */
#if defined(MBEDTLS_TEST_HOOKS)
#define MBEDTLS_STATIC_TESTABLE
#else
#define MBEDTLS_STATIC_TESTABLE static
#endif

/** Allow library to access its structs' private members.
 *
 * Although structs defined in header files are publicly available,
 * their members are private and should not be accessed by the user.
 */
#define MBEDTLS_ALLOW_PRIVATE_ACCESS

/** Byte Reading Macros
 * 
 * To tidy up code and save horizontal and vertical space, use byte 
 * reading macros to cast
 */
#define BYTE_0( x ) ( (uint8_t) ( ( x ) & 0xff ) )
#define BYTE_1( x ) ( (uint8_t) ( ( ( x ) >> 8  ) & 0xff ) )
#define BYTE_2( x ) ( (uint8_t) ( ( ( x ) >> 16 ) & 0xff ) )
#define BYTE_3( x ) ( (uint8_t) ( ( ( x ) >> 24 ) & 0xff ) )

/** 
 * 
 */
#define BYTES_TO_U32_LE( data, offset )                         \
    ( (uint32_t) (data)[offset]                                 \
      | (uint32_t) ( (uint32_t) (data)[( offset ) + 1] << 8 )   \
      | (uint32_t) ( (uint32_t) (data)[( offset ) + 2] << 16 )  \
      | (uint32_t) ( (uint32_t) (data)[( offset ) + 3] << 24 )  \
    )

#endif /* MBEDTLS_LIBRARY_COMMON_H */