user: Converte this assembly snippet into its equivalent C code:

```asm
<crypto_aead_decrypt>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0xf8,%rsp
  mov    %rdi,%r14
  mov    %rsi,%rbp
  mov    %rcx,%r13
  mov    %r8,0x20(%rsp)
  mov    %r9,%rbx
  mov    %r9,0x28(%rsp)
  mov    0x130(%rsp),%r12
  mov    %fs:0x28,%rax
  mov    %rax,0xe8(%rsp)
  xor    %eax,%eax
  lea    0x30(%rsp),%rdx
  mov    0x138(%rsp),%rsi
  mov    0x140(%rsp),%rdi
  call   <morus_initialization@plt>
  cmp    $0x1f,%r12
  jbe    L29
  mov    $0x20,%eax
  sub    %ebx,%eax
  mov    %eax,(%rsp)
  lea    0x30(%rsp),%rax
  mov    %rax,0x8(%rsp)
  lea    0x60(%rsp),%rax
  mov    %rax,0x10(%rsp)
  mov    $0x20,%eax
  sub    %rbx,%rax
  mov    %rax,0x18(%rsp)
L100:
  mov    (%rsp),%eax
  lea    (%rax,%rbx,1),%r15d
  mov    0x8(%rsp),%rdx
  mov    0x10(%rsp),%rsi
  mov    %rbx,%rdi
  call   <morus_enc_aut_step@plt>
  add    $0x20,%rbx
  mov    0x18(%rsp),%rax
  add    %rbx,%rax
  cmp    %rax,%r12
  jae    L100
L63:
  mov    %r12,%rdx
  and    $0x1f,%edx
  jne    L97
L72:
  mov    0x20(%rsp),%rdx
  sub    $0x10,%rdx
  mov    %rdx,0x0(%rbp)
  cmp    $0x1f,%rdx
  jbe    L70
  mov    $0x40,%ebx
  lea    0x30(%rsp),%rax
  mov    %rax,(%rsp)
L7:
  lea    -0x20(%rbx),%r15d
  lea    -0x40(%r13,%rbx,1),%rsi
  lea    -0x40(%r14,%rbx,1),%rdi
  mov    (%rsp),%rdx
  call   <morus_dec_aut_step@plt>
  mov    0x0(%rbp),%rdx
  mov    %rbx,%rax
  add    $0x20,%rbx
  cmp    %rax,%rdx
  jae    L7
L13:
  and    $0x1f,%edx
  jne    L82
L73:
  lea    0x30(%rsp),%rcx
  mov    %r13,%rdx
  mov    %r12,%rsi
  mov    0x0(%rbp),%rdi
  call   <morus_tag_verification@plt>
  mov    0xe8(%rsp),%rdx
  sub    %fs:0x28,%rdx
  jne    L11
  add    $0xf8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L29:
  mov    $0x0,%r15d
  jmp    L63
L97:
  lea    0x30(%rsp),%rcx
  lea    0x60(%rsp),%rsi
  movslq %r15d,%r15
  mov    0x28(%rsp),%rdi
  add    %r15,%rdi
  call   <morus_enc_aut_partialblock@plt>
  jmp    L72
L70:
  mov    $0x0,%r15d
  jmp    L13
L82:
  movslq %r15d,%r15
  lea    0x30(%rsp),%rcx
  lea    0x0(%r13,%r15,1),%rsi
  lea    (%r14,%r15,1),%rdi
  call   <morus_dec_aut_partialblock@plt>
  jmp    L73
L11:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int crypto_aead_decrypt(unsigned char *m, unsigned long long *mlen, unsigned char *nsec, const unsigned char *c, unsigned long long clen, const unsigned char *ad, unsigned long long adlen, const unsigned char *npub, const unsigned char *k) {
  uint64_t i;
  uint8_t ciphertextblock[32];
  __m128i morus_state[5][2];
  morus_initialization(k, npub, morus_state);
  for (i = 0; (i + 32) <= adlen; i += 32) {
    morus_enc_aut_step(ad + i, ciphertextblock, morus_state);
  }
  if ((adlen & 0x1f) != 0) {
    morus_enc_aut_partialblock(ad + i, ciphertextblock, adlen & 0x1f, morus_state);
  }
  *mlen = clen - 16;
  for (i = 0; (i + 32) <= *mlen; i += 32) {
    morus_dec_aut_step(m + i, c + i, morus_state);
  }
  if ((*mlen & 0x1f) != 0) {
    morus_dec_aut_partialblock(m + i, c + i, *mlen & 0x1f, morus_state);
  }
  return morus_tag_verification(*mlen, adlen, c, morus_state);
}
```