user: What is the c source code of the assembly code below?

```asm
<line_to_key_value>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x30,%rsp
  mov    %rdi,-0x18(%rbp)
  mov    %rsi,-0x20(%rbp)
  mov    %rdx,-0x28(%rbp)
  mov    -0x18(%rbp),%rax
  mov    %rax,-0x8(%rbp)
  jmp    L60
L86:
  addq   $0x1,-0x8(%rbp)
L60:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L83
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L86
L83:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L15
  mov    $0xffffffff,%eax
  jmp    L22
L15:
  mov    -0x20(%rbp),%rax
  mov    -0x8(%rbp),%rdx
  mov    %rdx,(%rax)
  jmp    L211
L95:
  addq   $0x1,-0x8(%rbp)
L211:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L183
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isalnum@plt>
  test   %rax,%rax
  jne    L95
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x5f,%al
  je     L95
L183:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L118
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  cmp    %rax,-0x8(%rbp)
  jne    L68
L118:
  mov    $0xffffffff,%eax
  jmp    L22
L68:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  je     L257
  mov    -0x8(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x8(%rbp)
  movb   $0x0,(%rax)
  jmp    L79
L1:
  addq   $0x1,-0x8(%rbp)
L79:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L257
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L1
L257:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3d,%al
  je     L206
  mov    $0xffffffff,%eax
  jmp    L22
L206:
  mov    -0x8(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x8(%rbp)
  movb   $0x0,(%rax)
  jmp    L158
L50:
  addq   $0x1,-0x8(%rbp)
L158:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L265
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L50
L265:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L178
  mov    $0xffffffff,%eax
  jmp    L22
L178:
  mov    -0x28(%rbp),%rax
  mov    -0x8(%rbp),%rdx
  mov    %rdx,(%rax)
  jmp    L164
L246:
  addq   $0x1,-0x8(%rbp)
L164:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L246
  subq   $0x1,-0x8(%rbp)
  jmp    L195
L44:
  subq   $0x1,-0x8(%rbp)
L195:
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L44
  addq   $0x1,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  movb   $0x0,(%rax)
  mov    $0x0,%eax
L22:
  leave
  ret
```

assistant: ```c
int line_to_key_value(char *line, char **keyp, char **valp) {
  char *p;
  p = line;
  while (*p != '\0' && isspace(*p)) {
    p++;
  }
  if (*p == '\0') {
    return -1;
  }
  *keyp = p;
  while (*p != '\0' && (isalnum(*p) || *p == '_')) {
    p++;
  }
  if (*p == '\0' || p == *keyp) {
    return -1;
  }
  if (isspace(*p)) {
    *p++ = '\0';
    while (*p != '\0' && isspace(*p)) {
      p++;
    }
  }
  if (*p != '=') {
    return -1;
  }
  *p++ = '\0';
  while (*p != '\0' && isspace(*p)) {
    p++;
  }
  if (*p == '\0') {
    return -1;
  }
  *valp = p;
  while (*p != '\0') {
    p++;
  }
  p--;
  while (isspace(*p)) {
    p--;
  }
  p++;
  *p = '\0';
  return 0;
}
```