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

```asm
<htoi>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x18(%rbp)
  movl   $0x0,-0x4(%rbp)
  mov    -0x4(%rbp),%eax
  mov    %eax,-0x8(%rbp)
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L134
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x30,%al
  jne    L134
  mov    -0x8(%rbp),%eax
  add    $0x1,%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x78,%al
  je     L130
  mov    -0x8(%rbp),%eax
  add    $0x1,%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x58,%al
  jne    L134
L130:
  movl   $0x2,-0x8(%rbp)
  jmp    L134
L65:
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x60,%al
  jle    L8
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x66,%al
  jg     L8
  mov    -0x4(%rbp),%eax
  shl    $0x4,%eax
  mov    %eax,%ecx
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  add    %ecx,%eax
  sub    $0x57,%eax
  mov    %eax,-0x4(%rbp)
  jmp    L118
L8:
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x40,%al
  jle    L33
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x46,%al
  jg     L33
  mov    -0x4(%rbp),%eax
  shl    $0x4,%eax
  mov    %eax,%ecx
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  add    %ecx,%eax
  sub    $0x37,%eax
  mov    %eax,-0x4(%rbp)
  jmp    L118
L33:
  mov    -0x4(%rbp),%eax
  shl    $0x4,%eax
  mov    %eax,%ecx
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  add    %ecx,%eax
  sub    $0x30,%eax
  mov    %eax,-0x4(%rbp)
L118:
  addl   $0x1,-0x8(%rbp)
L134:
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x2f,%al
  jle    L73
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x39,%al
  jle    L65
L73:
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x60,%al
  jle    L13
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x66,%al
  jle    L65
L13:
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x40,%al
  jle    L19
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x46,%al
  jle    L65
L19:
  mov    -0x4(%rbp),%eax
  pop    %rbp
  ret
```

assistant: ```c
unsigned int htoi(char s[]) {
  unsigned int i, n;
  i = n = 0;
  if (s[i] != '\0' && s[i] == '0' && (s[i + 1] == 'x' || s[i + 1] == 'X'))
    i = 2;
  while ((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'f') || (s[i] >= 'A' && s[i] <= 'F')) {
    if (s[i] >= 'a' && s[i] <= 'f')
      n = 16 * n + 10 + (s[i] - 'a');
    else if (s[i] >= 'A' && s[i] <= 'F')
      n = 16 * n + 10 + (s[i] - 'A');
    else
      n = 16 * n + (s[i] - '0');
    ++i;
  }
  return n;
}
```