text: /*
   * Copyright Amazon.com, Inc. or its affiliates. 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.
   * A copy of the License is located at
   *
   *  http://aws.amazon.com/apache2.0
   *
   * or in the "license" file accompanying this file. This file 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.
   */
  
  #pragma once
  
  #include <stdint.h>
  
  #include "crypto/s2n_hash.h"
  
  typedef enum {
      S2N_HMAC_NONE,
      S2N_HMAC_MD5,
      S2N_HMAC_SHA1,
      S2N_HMAC_SHA224,
      S2N_HMAC_SHA256,
      S2N_HMAC_SHA384,
      S2N_HMAC_SHA512,
      S2N_HMAC_SSLv3_MD5,
      S2N_HMAC_SSLv3_SHA1
  } s2n_hmac_algorithm;
  
  struct s2n_hmac_state {
      s2n_hmac_algorithm alg;
  
      uint16_t hash_block_size;
      uint32_t currently_in_hash_block;
      uint16_t xor_pad_size;
      uint8_t digest_size;
  
      struct s2n_hash_state inner;
      struct s2n_hash_state inner_just_key;
      struct s2n_hash_state outer;
      struct s2n_hash_state outer_just_key;
  
  
      /* key needs to be as large as the biggest block size */
      uint8_t xor_pad[128];
  
      /* For storing the inner digest */
      uint8_t digest_pad[SHA512_DIGEST_LENGTH];
  };
  
  struct s2n_hmac_evp_backup {
      struct s2n_hash_evp_digest inner;
      struct s2n_hash_evp_digest inner_just_key;
      struct s2n_hash_evp_digest outer;
      struct s2n_hash_evp_digest outer_just_key;
  };
  
  extern int s2n_hmac_digest_size(s2n_hmac_algorithm alg, uint8_t *out);
  extern bool s2n_hmac_is_available(s2n_hmac_algorithm alg);
  extern int s2n_hmac_hash_alg(s2n_hmac_algorithm hmac_alg, s2n_hash_algorithm *out);
  extern int s2n_hash_hmac_alg(s2n_hash_algorithm hash_alg, s2n_hmac_algorithm *out);
  
  extern int s2n_hmac_new(struct s2n_hmac_state *state);
  extern int s2n_hmac_init(struct s2n_hmac_state *state, s2n_hmac_algorithm alg, const void *key, uint32_t klen);
  extern int s2n_hmac_update(struct s2n_hmac_state *state, const void *in, uint32_t size);
  extern int s2n_hmac_digest(struct s2n_hmac_state *state, void *out, uint32_t size);
  extern int s2n_hmac_digest_two_compression_rounds(struct s2n_hmac_state *state, void *out, uint32_t size);
  extern int s2n_hmac_digest_verify(const void *a, const void *b, uint32_t len);
  extern int s2n_hmac_free(struct s2n_hmac_state *state);
  extern int s2n_hmac_reset(struct s2n_hmac_state *state);
  extern int s2n_hmac_copy(struct s2n_hmac_state *to, struct s2n_hmac_state *from);
  extern int s2n_hmac_save_evp_hash_state(struct s2n_hmac_evp_backup* backup, struct s2n_hmac_state* hmac);
  extern int s2n_hmac_restore_evp_hash_state(struct s2n_hmac_evp_backup* backup, struct s2n_hmac_state* hmac);
  