user: 请从给定的汇编指令推导出C源代码:

```asm
<lex>:
  endbr64
  push   %r13
  lea    D9(%rip),%r13
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  push   %rbx
  mov    %rsi,%rbx
  sub    $0x8,%rsp
  movslq (%rsi),%rax
  movzbl (%rdi,%rax,1),%ebp
L163:
  movsbl %bpl,%edi
  call   <isdigit@plt>
  test   %eax,%eax
  jne    L0
  cmp    $0x3e,%bpl
  jg     L203
  cmp    $0x1f,%bpl
  jg     L214
  test   %bpl,%bpl
  jne    L22
  mov    $0x900,%eax
L13:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopl   0x0(%rax,%rax,1)
L0:
  mov    (%rbx),%eax
  add    $0x1,%eax
  mov    %eax,(%rbx)
  cltq
  movzbl (%r12,%rax,1),%ebp
  movsbl %bpl,%edi
  call   <isdigit@plt>
  test   %eax,%eax
  jne    L0
  cmp    $0x2e,%bpl
  jne    L89
  nopl   0x0(%rax)
L17:
  mov    (%rbx),%eax
  add    $0x1,%eax
  mov    %eax,(%rbx)
  cltq
  movsbl (%r12,%rax,1),%edi
  call   <isdigit@plt>
  test   %eax,%eax
  jne    L17
L89:
  mov    $0x800,%eax
  jmp    L13
  cs nopw 0x0(%rax,%rax,1)
L214:
  sub    $0x20,%ebp
  cmp    $0x1e,%bpl
  ja     L22
  movzbl %bpl,%ebp
  movslq 0x0(%r13,%rbp,4),%rdx
  add    %r13,%rdx
  notrack jmp *%rdx
  mov    (%rbx),%eax
  add    $0x1,%eax
  mov    %eax,(%rbx)
  cltq
  movsbl (%r12,%rax,1),%edi
  call   <isdigit@plt>
  test   %eax,%eax
  jne    L17
L22:
  addl   $0x1,(%rbx)
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopl   (%rax)
L203:
  cmp    $0x76,%bpl
  je     L194
  jle    L41
  cmp    $0x7e,%bpl
  jne    L22
  addl   $0x1,(%rbx)
  mov    $0x500,%eax
  jmp    L13
  nopl   0x0(%rax,%rax,1)
L41:
  cmp    $0x5e,%bpl
  je     L69
  cmp    $0x63,%bpl
  jne    L22
  addl   $0x1,(%rbx)
  mov    $0x800,%eax
  jmp    L13
  mov    (%rbx),%eax
  add    $0x1,%eax
  mov    %eax,(%rbx)
  cltq
  movzbl (%r12,%rax,1),%ebp
  jmp    L163
  addl   $0x1,(%rbx)
  mov    $0x600,%eax
  jmp    L13
  addl   $0x1,(%rbx)
  mov    $0x700,%eax
  jmp    L13
  addl   $0x1,(%rbx)
  mov    $0x100,%eax
  jmp    L13
  addl   $0x1,(%rbx)
  mov    $0x200,%eax
  jmp    L13
L194:
  addl   $0x1,(%rbx)
  mov    $0x400,%eax
  jmp    L13
  nopl   (%rax)
L69:
  addl   $0x1,(%rbx)
  mov    $0x300,%eax
  jmp    L13
```

assistant: ```c
int lex(char *str, int *pos) {
  int estado = 0;
  char c;
  while (1) {
    c = str[*pos];
    switch (estado) {
    case 0:
      if (isdigit(c)) {
        (*pos)++;
        estado = 1;
      } else
        switch (c) {
        case ' ':
          (*pos)++;
          break;
        case '.':
          (*pos)++;
          estado = 2;
          break;
        case '<':
          (*pos)++;
          return 0x0100;
        case '>':
          (*pos)++;
          return 0x0200;
        case '^':
          (*pos)++;
          return 0X0300;
        case 'v':
          (*pos)++;
          return 0x0400;
        case '~':
          (*pos)++;
          return 0x0500;
        case '(':
          (*pos)++;
          return 0x0600;
        case ')':
          (*pos)++;
          return 0x0700;
        case 'c':
          (*pos)++;
          return 0x0800;
        case '\0':
          return 0x0900;
        default:
          (*pos)++;
          return 0x0000;
        }
      break;
    case 1:
      if (isdigit(c))
        (*pos)++;
      else if (c == '.') {
        estado = 3;
        (*pos)++;
      } else {
        return 0x0800;
      }
      break;
    case 2:
      if (isdigit(c)) {
        (*pos)++;
        estado = 3;
      } else {
        (*pos)++;
        return 0x0000;
      }
      break;
    case 3:
      if (isdigit(c))
        (*pos)++;
      else {
        return 0x0800;
      }
      break;
    default:
      printf("Lex:Estado indefinido");
      exit(1);
    }
  }
}
```