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   *
   * Copyright 2019 Samsung Electronics All Rights Reserved.
   *
   * 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
   *
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  // Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
  //
  // 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 _ESP_SHA_H_
  #define _ESP_SHA_H_
  
  #include "rom/sha.h"
  #include "esp_types.h"
  
  /** @brief Low-level support functions for the hardware SHA engine
   *
   * @note If you're looking for a SHA API to use, try mbedtls component
   * mbedtls/shaXX.h. That API supports hardware acceleration.
   *
   * The API in this header provides some building blocks for implementing a
   * full SHA API such as the one in mbedtls, and also a basic SHA function esp_sha().
   *
   * Some technical details about the hardware SHA engine:
   *
   * - SHA accelerator engine calculates one digest at a time, per SHA
   *   algorithm type. It initialises and maintains the digest state
   *   internally. It is possible to read out an in-progress SHA digest
   *   state, but it is not possible to restore a SHA digest state
   *   into the engine.
   *
   * - The memory block SHA_TEXT_BASE is shared between all SHA digest
   *   engines, so all engines must be idle before this memory block is
   *   modified.
   *
   */
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /* Defined in rom/sha.h */
  typedef enum SHA_TYPE esp_sha_type;
  
  /** @brief Calculate SHA1 or SHA2 sum of some data, using hardware SHA engine
   *
   * @note For more versatile SHA calculations, where data doesn't need
   * to be passed all at once, try the mbedTLS mbedtls/shaX.h APIs. The
   * hardware-accelerated mbedTLS implementation is also faster when
   * hashing large amounts of data.
   *
   * @note It is not necessary to lock any SHA hardware before calling
   * this function, thread safety is managed internally.
   *
   * @note If a TLS connection is open then this function may block
   * indefinitely waiting for a SHA engine to become available. Use the
   * mbedTLS SHA API to avoid this problem.
   *
   * @param sha_type SHA algorithm to use.
   *
   * @param input Input data buffer.
   *
   * @param ilen Length of input data in bytes.
   *
   * @param output Buffer for output SHA digest. Output is 20 bytes for
   * sha_type SHA1, 32 bytes for sha_type SHA2_256, 48 bytes for
   * sha_type SHA2_384, 64 bytes for sha_type SHA2_512.
   */
  void esp_sha(esp_sha_type sha_type, const unsigned char *input, size_t ilen, unsigned char *output);
  
  /* @brief Begin to execute a single SHA block operation
   *
   * @note This is a piece of a SHA algorithm, rather than an entire SHA
   * algorithm.
   *
   * @note Call esp_sha_try_lock_engine() before calling this
   * function. Do not call esp_sha_lock_memory_block() beforehand, this
   * is done inside the function.
   *
   * @param sha_type SHA algorithm to use.
   *
   * @param data_block Pointer to block of data. Block size is
   * determined by algorithm (SHA1/SHA2_256 = 64 bytes,
   * SHA2_384/SHA2_512 = 128 bytes)
   *
   * @param is_first_block If this parameter is true, the SHA state will
   * be initialised (with the initial state of the given SHA algorithm)
   * before the block is calculated. If false, the existing state of the
   * SHA engine will be used.
   *
   * @return As a performance optimisation, this function returns before
   * the SHA block operation is complete. Both this function and
   * esp_sha_read_state() will automatically wait for any previous
   * operation to complete before they begin. If using the SHA registers
   * directly in another way, call esp_sha_wait_idle() after calling this
   * function but before accessing the SHA registers.
   */
  void esp_sha_block(esp_sha_type sha_type, const void *data_block, bool is_first_block);
  
  /** @brief Read out the current state of the SHA digest loaded in the engine.
   *
   * @note This is a piece of a SHA algorithm, rather than an entire SHA algorithm.
   *
   * @note Call esp_sha_try_lock_engine() before calling this
   * function. Do not call esp_sha_lock_memory_block() beforehand, this
   * is done inside the function.
   *
   * If the SHA suffix padding block has been executed already, the
   * value that is read is the SHA digest (in big endian
   * format). Otherwise, the value that is read is an interim SHA state.
   *
   * @note If sha_type is SHA2_384, only 48 bytes of state will be read.
   * This is enough for the final SHA2_384 digest, but if you want the
   * interim SHA-384 state (to continue digesting) then pass SHA2_512 instead.
   *
   * @param sha_type SHA algorithm in use.
   *
   * @param state Pointer to a memory buffer to hold the SHA state. Size
   * is 20 bytes (SHA1), 32 bytes (SHA2_256), 48 bytes (SHA2_384) or 64 bytes (SHA2_512).
   *
   */
  void esp_sha_read_digest_state(esp_sha_type sha_type, void *digest_state);
  
  /**
   * @brief Obtain exclusive access to a particular SHA engine
   *
   * @param sha_type Type of SHA engine to use.
   *
   * Blocks until engine is available. Note: Can block indefinitely
   * while a TLS connection is open, suggest using
   * esp_sha_try_lock_engine() and failing over to software SHA.
   */
  void esp_sha_lock_engine(esp_sha_type sha_type);
  
  /**
   * @brief Try and obtain exclusive access to a particular SHA engine
   *
   * @param sha_type Type of SHA engine to use.
   *
   * @return Returns true if the SHA engine is locked for exclusive
   * use. Call esp_sha_unlock_sha_engine() when done.  Returns false if
   * the SHA engine is already in use, caller should use software SHA
   * algorithm for this digest.
   */
  bool esp_sha_try_lock_engine(esp_sha_type sha_type);
  
  /**
   * @brief Unlock an engine previously locked with esp_sha_lock_engine() or esp_sha_try_lock_engine()
   *
   * @param sha_type Type of engine to release.
   */
  void esp_sha_unlock_engine(esp_sha_type sha_type);
  
  /**
   * @brief Acquire exclusive access to the SHA shared memory block at SHA_TEXT_BASE
   *
   * This memory block is shared across all the SHA algorithm types.
   *
   * Caller should have already locked a SHA engine before calling this function.
   *
   * Note that it is possible to obtain exclusive access to the memory block even
   * while it is in use by the SHA engine. Caller should use esp_sha_wait_idle()
   * to ensure the SHA engine is not reading from the memory block in hardware.
   *
   * @note You do not need to lock the memory block before calling esp_sha_block() or esp_sha_read_digest_state(), these functions handle memory block locking internally.
   *
   * Call esp_sha_unlock_memory_block() when done.
   */
  void esp_sha_lock_memory_block(void);
  
  /**
   * @brief Release exclusive access to the SHA register memory block at SHA_TEXT_BASE
   *
   * Caller should have already locked a SHA engine before calling this function.
   *
   * Call following esp_sha_lock_memory_block().
   */
  void esp_sha_unlock_memory_block(void);
  
  /** @brief Wait for the SHA engine to finish any current operation
   *
   * @note This function does not ensure exclusive access to any SHA
   * engine. Caller should use esp_sha_try_lock_engine() and
   * esp_sha_lock_memory_block() as required.
   *
   * @note Functions declared in this header file wait for SHA engine
   * completion automatically, so you don't need to use this API for
   * these. However if accessing SHA registers directly, you will need
   * to call this before accessing SHA registers if using the
   * esp_sha_block() function.
   *
   * @note This function busy-waits, so wastes CPU resources.
   * Best to delay calling until you are about to need it.
   *
   */
  void esp_sha_wait_idle(void);
  
  #ifdef __cplusplus
  }
  #endif
  #endif
  