user: 提供的汇编代码用C语言表示会是什么样子：

```asm
<string_to_char>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  mov    %rdi,%rbp
  push   %rbx
  sub    $0x8,%rsp
  mov    (%rdi),%rbx
  movsbl (%rbx),%eax
  cmp    $0x5c,%al
  je     L305
  xor    %r12d,%r12d
  cmp    $0x4d,%al
  je     L0
L287:
  cmp    $0x5e,%al
  je     L99
  or     %eax,%r12d
  add    $0x1,%rbx
  lea    0x100(%r12),%eax
  test   %r12d,%r12d
  mov    %rbx,0x0(%rbp)
  cmovs  %eax,%r12d
L228:
  add    $0x8,%rsp
  mov    %r12d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopw   0x0(%rax,%rax,1)
L99:
  movzbl 0x1(%rbx),%eax
  cmp    $0x5c,%al
  je     L93
L337:
  cmp    $0x3f,%al
  je     L333
  lea    -0x40(%rax),%edx
  cmp    $0x1f,%dl
  ja     L366
  movsbl %dl,%edx
  or     %edx,%r12d
  cs nopw 0x0(%rax,%rax,1)
L350:
  add    $0x2,%rbx
  mov    %rbx,0x0(%rbp)
  jmp    L228
  nopw   0x0(%rax,%rax,1)
L0:
  cmpb   $0x2d,0x1(%rbx)
  je     L323
  add    $0x1,%rbx
  mov    $0x4d,%r12d
  mov    %rbx,(%rdi)
  jmp    L228
  nopl   0x0(%rax)
L305:
  movzbl 0x1(%rbx),%eax
  cmp    $0x78,%al
  jg     L112
  cmp    $0x5b,%al
  jle    L157
  sub    $0x5c,%eax
  cmp    $0x1c,%al
  ja     L112
  lea    D9(%rip),%rdx
  movzbl %al,%eax
  movslq (%rdx,%rax,4),%rax
  add    %rdx,%rax
  notrack jmp *%rax
  nopw   0x0(%rax,%rax,1)
L157:
  mov    $0x20,%r12d
  cmp    $0x20,%al
  je     L350
  sub    $0x30,%eax
  cmp    $0x7,%al
  jbe    L345
L112:
  sub    $0x1,%rbx
  mov    $0x5c,%r12d
  jmp    L350
  nopl   (%rax)
L345:
  movsbl %al,%r12d
  movzbl 0x2(%rbx),%eax
  sub    $0x30,%eax
  cmp    $0x7,%al
  ja     L350
  movsbl %al,%eax
  lea    (%rax,%r12,8),%r12d
  movzbl 0x3(%rbx),%eax
  sub    $0x30,%eax
  cmp    $0x7,%al
  ja     L388
  movsbl %al,%eax
  add    $0x2,%rbx
  lea    (%rax,%r12,8),%r12d
  jmp    L350
  nopl   0x0(%rax)
L93:
  movzbl 0x2(%rbx),%eax
  add    $0x1,%rbx
  jmp    L337
  nopl   (%rax)
L323:
  movsbl 0x2(%rbx),%eax
  mov    $0x8000,%r12d
  add    $0x2,%rbx
  jmp    L287
  nopl   0x0(%rax,%rax,1)
L333:
  add    $0x7f,%r12d
  jmp    L350
  nopl   0x0(%rax)
L366:
  lea    -0x61(%rax),%edx
  cmp    $0x19,%dl
  jbe    L38
  test   %al,%al
  jne    L382
L129:
  add    $0x2,%rbx
  mov    $0x5e,%r12d
  mov    %rbx,0x0(%rbp)
  jmp    L228
  nopl   0x0(%rax,%rax,1)
L38:
  sub    $0x60,%eax
  movsbl %al,%r12d
  jmp    L350
  mov    $0xd,%r12d
  jmp    L350
  mov    $0xa,%r12d
  jmp    L350
  mov    $0xc,%r12d
  jmp    L350
  movsbl 0x2(%rbx),%r15d
  movzbl 0x3(%rbx),%r14d
  mov    $0x78,%r12d
  mov    %r15d,%edi
  mov    %r15d,%r13d
  call   <isxdigit@plt>
  test   %eax,%eax
  je     L350
  mov    %r15d,%edi
  call   <isdigit@plt>
  test   %eax,%eax
  je     L92
  sub    $0x30,%r13d
L208:
  movsbl %r14b,%r15d
  movsbl %r13b,%r12d
  mov    %r15d,%edi
  call   <isxdigit@plt>
  test   %eax,%eax
  je     L350
  mov    %r15d,%edi
  call   <isdigit@plt>
  test   %eax,%eax
  je     L292
  lea    -0x30(%r14),%eax
L264:
  shl    $0x4,%r12d
  movsbl %al,%eax
  add    $0x1,%rbx
  add    %eax,%r12d
  jmp    L350
  mov    $0x9,%r12d
  jmp    L350
  mov    $0x8,%r12d
  jmp    L350
  nopl   (%rax)
L382:
  movsbl %al,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L129
  or     $0xffffffff,%r12d
  jmp    L228
  nopw   0x0(%rax,%rax,1)
L388:
  add    $0x1,%rbx
  jmp    L350
L92:
  mov    %r15d,%edi
  sub    $0x61,%r13d
  call   <isupper@plt>
  mov    %eax,%r8d
  lea    -0x41(%r15),%eax
  test   %r8d,%r8d
  cmovne %eax,%r13d
  jmp    L208
L292:
  mov    %r15d,%edi
  call   <isupper@plt>
  mov    %eax,%r8d
  lea    -0x61(%r14),%eax
  test   %r8d,%r8d
  je     L264
  lea    -0x41(%r14),%eax
  jmp    L264
```

assistant: ```c
int string_to_char(char **ptr) {
  char *str;
  int i;
  char c1, c2;
  str = *ptr;
  if (str[0] == '\\') {
    switch (str[1]) {
    case ' ':
      i = ' ';
      break;
    case '\\':
      i = '\\';
      break;
    case 'b':
      i = '\b';
      break;
    case 'f':
      i = '\f';
      break;
    case 'n':
      i = '\n';
      break;
    case 'r':
      i = '\r';
      break;
    case 't':
      i = '\t';
      break;
    case 'x':
      c1 = str[2];
      c2 = str[3];
      if (isxdigit(c1)) {
        if (isdigit(c1))
          c1 -= '0';
        else if (isupper(c1))
          c1 -= 'A';
        else
          c1 -= 'a';
        if (isxdigit(c2)) {
          if (isdigit(c2))
            c2 -= '0';
          else if (isupper(c2))
            c2 -= 'A';
          else
            c2 -= 'a';
          i = c1 * 0x10 + c2;
          str++;
        } else
          i = c1;
      } else
        i = 'x';
      break;
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
      if (str[2] >= '0' && str[2] <= '7') {
        if (str[3] >= '0' && str[3] <= '7') {
          i = (str[1] - '0') * 0100 + (str[2] - '0') * 010 + (str[3] - '0');
          str += 2;
        } else {
          i = (str[1] - '0') * 010 + (str[2] - '0');
          str++;
        }
      } else
        i = str[1] - '0';
      break;
    default:
      i = str[0];
      --str;
      break;
    }
    str += 2;
    *ptr = str;
    return i;
  }
  if (str[0] == 'M' && str[1] == '-') {
    i = 0x8000;
    str += 2;
  } else
    i = 0;
  if (str[0] == '^') {
    if (str[1] == '\\')
      ++str;
    if (str[1] == '?')
      i += 0x7f;
    else if (str[1] >= '@' && str[1] <= '_')
      i |= str[1] - '@';
    else if (str[1] >= 'a' && str[1] <= 'z')
      i = str[1] - 'a' + 1;
    else if (str[1] == '\0' || isspace(str[1]))
      i = '^';
    else
      return -1;
    str += 2;
  } else {
    i |= str[0];
    str++;
  }
  *ptr = str;
  if (i < 0)
    i += 256;
  return i;
}
```