user: What would the C source look like for the assembly code provided here:

```asm
<is_valid_email_address>:
  endbr64
  test   %rdi,%rdi
  je     L404
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  mov    %rdi,%rbx
  movzbl (%rdi),%eax
  mov    $0x0,%edx
  test   %al,%al
  je     L345
  mov    %rdi,%rsi
  mov    $0x0,%ebp
  mov    $0x1,%r8d
  movabs $0x400000000000021,%r9
  jmp    L204
L341:
  test   %dl,%dl
  je     L1
  test   %dil,%dil
  jne    L1
  cmp    $0x40,%al
  je     L424
L156:
  add    $0x1,%rsi
  movzbl (%rsi),%eax
  test   %al,%al
  je     L65
L204:
  lea    -0x21(%rax),%edx
  cmp    $0x5d,%dl
  seta   %dil
  lea    -0x22(%rax),%ecx
  mov    %r8d,%edx
  cmp    $0x3a,%cl
  ja     L341
  mov    %r9,%rdx
  shr    %cl,%rdx
  xor    $0x1,%rdx
  and    $0x1,%edx
  jmp    L341
L424:
  test   %rbp,%rbp
  jne    L209
  mov    %rsi,%rbp
  jmp    L156
L65:
  cmp    %rbx,%rbp
  je     L213
  test   %rbp,%rbp
  je     L213
  movzbl 0x1(%rbp),%edi
  mov    $0x0,%edx
  test   %dil,%dil
  je     L345
  lea    0x1(%rbp),%r12
  jmp    L59
L382:
  cmpb   $0x2e,(%r12)
  je     L367
L142:
  add    $0x1,%r12
  movzbl (%r12),%edi
  test   %dil,%dil
  je     L244
L59:
  movzbl %dil,%edi
  call   <isalnum@plt>
  test   %rax,%rax
  jne    L382
  movzbl (%r12),%eax
  lea    -0x2d(%rax),%edx
  cmp    $0x1,%dl
  jbe    L382
  cmp    $0x5f,%al
  je     L382
  mov    $0x0,%edx
  jmp    L345
L367:
  cmpb   $0x40,-0x1(%r12)
  je     L61
  movzbl 0x1(%r12),%eax
  cmp    $0x2e,%al
  je     L92
  test   %al,%al
  jne    L142
L92:
  mov    $0x0,%edx
  jmp    L345
L244:
  cmp    %rbx,%rbp
  jbe    L375
  mov    %rbx,%r12
  movabs $0xa000a80000000000,%r13
  jmp    L215
L286:
  movzbl %dil,%edi
  call   <isalnum@plt>
  test   %rax,%rax
  jne    L403
  movzbl (%r12),%eax
  mov    %eax,%edx
  and    $0xfffffffd,%edx
  cmp    $0x21,%dl
  je     L403
  cmp    $0x3f,%al
  ja     L102
  cmp    $0x2a,%al
  jbe    L448
  bt     %rax,%r13
  jb     L403
  mov    $0x0,%edx
  jmp    L345
L102:
  cmp    $0x5f,%al
  jbe    L159
  cmp    $0x7e,%al
  jne    L346
L403:
  add    $0x1,%r12
  cmp    %r12,%rbp
  je     L309
L215:
  movzbl (%r12),%edi
  cmp    $0x2e,%dil
  jne    L286
  cmp    %r12,%rbx
  je     L158
  movzbl 0x1(%r12),%eax
  cmp    $0x2e,%al
  je     L154
  cmp    $0x40,%al
  jne    L403
L154:
  mov    $0x0,%edx
  jmp    L345
L159:
  cmp    $0x5d,%al
  ja     L403
  mov    $0x0,%edx
  jmp    L345
L309:
  mov    $0x1,%edx
  jmp    L345
L404:
  mov    $0x0,%edx
  mov    %edx,%eax
  ret
L1:
  mov    $0x0,%edx
L345:
  mov    %edx,%eax
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
L209:
  mov    $0x0,%edx
  jmp    L345
L213:
  mov    $0x0,%edx
  jmp    L345
L61:
  mov    $0x0,%edx
  jmp    L345
L375:
  mov    $0x1,%edx
  jmp    L345
L158:
  mov    $0x0,%edx
  jmp    L345
L448:
  mov    $0x0,%edx
  jmp    L345
L346:
  mov    $0x0,%edx
  jmp    L345
```

assistant: ```c
int is_valid_email_address(const unsigned char *email_address) {
  if (!email_address || !*email_address)
    return 0;
  const unsigned char *p;
  const unsigned char *at_ptr = 0;
  for (p = email_address; *p; ++p) {
    if (*p <= ' ' || *p >= 127 || *p == '\\' || *p == '\'' || *p == '\"')
      return 0;
    if (*p == '@') {
      if (at_ptr)
        return 0;
      at_ptr = p;
    }
  }
  if (!at_ptr)
    return 0;
  if (at_ptr == email_address || !at_ptr[1])
    return 0;
  for (p = at_ptr + 1; *p; ++p) {
    if (!isalnum(*p) && *p != '-' && *p != '_' && *p != '.')
      return 0;
    if (*p == '.' && (p[-1] == '@' || !p[1] || p[1] == '.'))
      return 0;
  }
  for (p = email_address; p < at_ptr; ++p) {
    if (*p == '.') {
      if (p == email_address || p[1] == '@' || p[1] == '.')
        return 0;
    } else if (isalnum(*p)) {
    } else if (*p == '!' || *p == '#' || *p == '+' || *p == '-' || *p == '/' || *p == '=' || *p == '?' || *p == '^' || *p == '_' || *p == '~') {
    } else {
      return 0;
    }
  }
  return 1;
}
```