iotc_bsp_rng.h

/* Copyright 2018-2019 Google LLC
 *
 * This is part of the Google Cloud IoT Device SDK for Embedded C.
 * It is licensed under the BSD 3-Clause license; you may not use this file
 * except in compliance with the License.
 *
 * You may obtain a copy of the License at:
 *  https://opensource.org/licenses/BSD-3-Clause
 *
 * 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 __IOTC_BSP_RNG_H__
#define __IOTC_BSP_RNG_H__

/**
 * @file iotc_bsp_rng.h
 * @brief Implement a random number generator (RNG).
 *
 * Don't hardcode the same seed value for all devices; use an
 * entropy-based handware random number generator. The Device SDK
 * prevents DDoS attacks by randomly distributing fleet-wide reconnection
 * attempts, so predictable numbers may corrupt the BackOff system.
 */

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @function
 * @brief Initialize the platform-specific RNG prerequisites.
 *
 * The Device SDK calls this function before requesting the first random
 * number. Implementations of this function must meet all of the
 * platform-specific RNG prerequisites, such as generating a random
 * number seed.
 */
void iotc_bsp_rng_init();

/**
 * @function
 * @brief Generate a 32-bit random number.
 *
 * @return A random, 32-bit integer.
 */
uint32_t iotc_bsp_rng_get();

/**
 * @function
 * @brief Shut down the platform-specific RNG.
 *
 * Free any resources.  The Device SDK will not invoke iotc_bsp_rng_get
 * again without first calling iotc_bsp_rng_init.
 */
void iotc_bsp_rng_shutdown();

#ifdef __cplusplus
}
#endif

#endif /* __IOTC_BSP_RNG_H__ */