user: 这段汇编代码用C语言表示是什么样的:

```asm
<smtp_chunk_split>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x58,%rsp
  mov    %rdi,0x10(%rsp)
  mov    %rdx,0x18(%rsp)
  mov    %fs:0x28,%rax
  mov    %rax,0x48(%rsp)
  xor    %eax,%eax
  test   %rsi,%rsi
  je     L85
  mov    %rsi,%rbp
  mov    0x10(%rsp),%rdi
  call   <strlen@plt>
  mov    %rax,%rbx
  mov    0x18(%rsp),%rdi
  call   <strlen@plt>
  mov    %rax,%r13
  test   %rbx,%rbx
  je     L29
  lea    0x38(%rsp),%rdx
  mov    $0x1,%esi
  mov    %rax,%rdi
  call   <smtp_si_add_size_t@plt>
  movq   $0x0,0x8(%rsp)
  test   %rax,%rax
  jne    L99
  lea    0x30(%rsp),%rdx
  mov    $0x1,%esi
  mov    %rbx,%rdi
  call   <smtp_si_add_size_t@plt>
  movq   $0x0,0x8(%rsp)
  test   %rax,%rax
  jne    L99
  mov    %rbx,%rax
  mov    $0x0,%edx
  div    %rbp
  mov    %rax,0x28(%rsp)
  lea    0x40(%rsp),%rdx
  lea    0x1(%rax),%rsi
  mov    0x38(%rsp),%rdi
  call   <smtp_si_mul_size_t@plt>
  movq   $0x0,0x8(%rsp)
  test   %rax,%rax
  jne    L99
  lea    0x40(%rsp),%rdx
  mov    0x30(%rsp),%rsi
  mov    0x40(%rsp),%rdi
  call   <smtp_si_add_size_t@plt>
  movq   $0x0,0x8(%rsp)
  test   %rax,%rax
  jne    L99
  mov    0x40(%rsp),%rsi
  mov    $0x1,%edi
  call   <calloc@plt>
  mov    %rax,0x8(%rsp)
  test   %rax,%rax
  je     L99
  movq   $0x0,0x20(%rsp)
  mov    $0x0,%r12d
  mov    $0x0,%r15d
  jmp    L30
L85:
  mov    D5(%rip),%rax
  mov    (%rax),%edx
  mov    D9(%rip),%rax
  mov    %edx,(%rax)
  movq   $0x0,0x8(%rsp)
  jmp    L99
L29:
  mov    0x18(%rsp),%rdi
  call   <smtp_strdup@plt>
  mov    %rax,0x8(%rsp)
L99:
  mov    0x48(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L70
  mov    0x8(%rsp),%rax
  add    $0x58,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L121:
  mov    0x8(%rsp),%rdi
  call   <free@plt>
  movq   $0x0,0x8(%rsp)
  jmp    L99
L48:
  add    %r13,%r12
  lea    0x1(%r15),%rax
  cmp    %r15,0x28(%rsp)
  je     L99
  mov    %rax,%r15
L30:
  mov    0x10(%rsp),%r14
  add    0x20(%rsp),%r14
  mov    %rbp,%rsi
  mov    %r14,%rdi
  call   <smtp_strnlen_utf8@plt>
  mov    %rax,%rbx
  cmp    $0xffffffffffffffff,%rax
  je     L121
  mov    0x8(%rsp),%rax
  lea    (%rax,%r12,1),%rdi
  mov    %rbx,%rdx
  mov    %r14,%rsi
  call   <memcpy@plt>
  cmpb   $0x1,(%r14)
  adc    %rbx,%r12
  add    %rbx,0x20(%rsp)
  test   %r13,%r13
  je     L48
  mov    0x8(%rsp),%rax
  lea    (%rax,%r12,1),%rdi
  mov    %r13,%rdx
  mov    0x18(%rsp),%rsi
  call   <memcpy@plt>
  jmp    L48
L70:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
char *smtp_chunk_split(const char *const s, size_t chunklen, const char *const end) {
  char *snew;
  size_t bodylen;
  size_t bodylen_inc;
  size_t endlen;
  size_t endlen_inc;
  size_t snewlen;
  size_t chunk_i;
  size_t snew_i;
  size_t body_i;
  size_t body_copy_len;
  if (chunklen < 1) {
    errno = EINVAL;
    return NULL;
  }
  bodylen = strlen(s);
  endlen = strlen(end);
  if (bodylen < 1) {
    return smtp_strdup(end);
  }
  if (smtp_si_add_size_t(endlen, 1, &endlen_inc) || smtp_si_add_size_t(bodylen, 1, &bodylen_inc) || smtp_si_mul_size_t(endlen_inc, bodylen / chunklen + 1, &snewlen) || smtp_si_add_size_t(snewlen, bodylen_inc, &snewlen) || (snew = calloc(1, snewlen)) == NULL) {
    return NULL;
  }
  body_i = 0;
  snew_i = 0;
  for (chunk_i = 0; chunk_i < bodylen / chunklen + 1; chunk_i++) {
    body_copy_len = smtp_strnlen_utf8(&s[body_i], chunklen);
    if (body_copy_len == ((size_t)(-1))) {
      free(snew);
      return NULL;
    }
    memcpy(&snew[snew_i], &s[body_i], body_copy_len);
    snew_i += body_copy_len;
    if (s[body_i] == '\0') {
      snew_i += 1;
    }
    body_i += body_copy_len;
    if (endlen > 0) {
      memcpy(&snew[snew_i], end, endlen);
    }
    snew_i += endlen;
  }
  return snew;
}
```