user: Please show me the C implementation that matches the assembly code listed below:

```asm
<strtoul>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x50,%rsp
  mov    %rdi,-0x38(%rbp)
  mov    %rsi,-0x40(%rbp)
  mov    %edx,-0x44(%rbp)
  mov    -0x38(%rbp),%rax
  mov    %rax,-0x18(%rbp)
L303:
  mov    -0x18(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  movzbl (%rax),%eax
  mov    %al,-0x25(%rbp)
  movzbl -0x25(%rbp),%eax
  movzbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L303
  cmpb   $0x2d,-0x25(%rbp)
  jne    L33
  movl   $0x1,-0x24(%rbp)
  mov    -0x18(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  movzbl (%rax),%eax
  mov    %al,-0x25(%rbp)
  jmp    L411
L33:
  movl   $0x0,-0x24(%rbp)
  cmpb   $0x2b,-0x25(%rbp)
  jne    L411
  mov    -0x18(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  movzbl (%rax),%eax
  mov    %al,-0x25(%rbp)
L411:
  cmpl   $0x0,-0x44(%rbp)
  je     L306
  cmpl   $0x10,-0x44(%rbp)
  jne    L318
L306:
  cmpb   $0x30,-0x25(%rbp)
  jne    L318
  mov    -0x18(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x78,%al
  je     L410
  mov    -0x18(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x58,%al
  jne    L318
L410:
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x2f,%al
  jle    L232
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x39,%al
  jle    L427
L232:
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x40,%al
  jle    L167
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x46,%al
  jle    L427
L167:
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x60,%al
  jle    L318
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x66,%al
  jg     L318
L427:
  mov    -0x18(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  mov    %al,-0x25(%rbp)
  addq   $0x2,-0x18(%rbp)
  movl   $0x10,-0x44(%rbp)
L318:
  cmpl   $0x0,-0x44(%rbp)
  jne    L105
  cmpb   $0x30,-0x25(%rbp)
  jne    L2
  mov    $0x8,%eax
  jmp    L38
L2:
  mov    $0xa,%eax
L38:
  mov    %eax,-0x44(%rbp)
L105:
  movl   $0x0,-0x20(%rbp)
  movq   $0x0,-0x10(%rbp)
  cmpl   $0x1,-0x44(%rbp)
  jle    L360
  cmpl   $0x24,-0x44(%rbp)
  jg     L360
  mov    D0(%rip),%rax
  mov    (%rax),%eax
  cltd
  idivl  -0x44(%rbp)
  cltq
  mov    %rax,-0x8(%rbp)
  mov    D0(%rip),%rax
  mov    (%rax),%eax
  cltd
  idivl  -0x44(%rbp)
  mov    %edx,-0x1c(%rbp)
L233:
  cmpb   $0x2f,-0x25(%rbp)
  jle    L415
  cmpb   $0x39,-0x25(%rbp)
  jg     L415
  movzbl -0x25(%rbp),%eax
  sub    $0x30,%eax
  mov    %al,-0x25(%rbp)
  jmp    L434
L415:
  cmpb   $0x40,-0x25(%rbp)
  jle    L304
  cmpb   $0x5a,-0x25(%rbp)
  jg     L304
  movzbl -0x25(%rbp),%eax
  sub    $0x37,%eax
  mov    %al,-0x25(%rbp)
  jmp    L434
L304:
  cmpb   $0x60,-0x25(%rbp)
  jle    L58
  cmpb   $0x7a,-0x25(%rbp)
  jg     L58
  movzbl -0x25(%rbp),%eax
  sub    $0x57,%eax
  mov    %al,-0x25(%rbp)
L434:
  movsbl -0x25(%rbp),%eax
  cmp    %eax,-0x44(%rbp)
  jle    L220
  cmpl   $0x0,-0x20(%rbp)
  js     L151
  mov    -0x10(%rbp),%rax
  cmp    -0x8(%rbp),%rax
  ja     L151
  mov    -0x10(%rbp),%rax
  cmp    -0x8(%rbp),%rax
  jne    L102
  movsbl -0x25(%rbp),%eax
  cmp    %eax,-0x1c(%rbp)
  jge    L102
L151:
  movl   $0xffffffff,-0x20(%rbp)
  jmp    L364
L102:
  movl   $0x1,-0x20(%rbp)
  mov    -0x44(%rbp),%eax
  cltq
  mov    -0x10(%rbp),%rdx
  imul   %rdx,%rax
  mov    %rax,-0x10(%rbp)
  movsbq -0x25(%rbp),%rax
  add    %rax,-0x10(%rbp)
L364:
  mov    -0x18(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  movzbl (%rax),%eax
  mov    %al,-0x25(%rbp)
  jmp    L233
L220:
  nop
L58:
  cmpl   $0x0,-0x20(%rbp)
  jns    L49
  mov    D0(%rip),%rax
  mov    (%rax),%eax
  cltq
  mov    %rax,-0x10(%rbp)
  jmp    L193
L49:
  cmpl   $0x0,-0x20(%rbp)
  je     L193
  cmpl   $0x0,-0x24(%rbp)
  je     L205
  negq   -0x10(%rbp)
  jmp    L193
L360:
  nop
  jmp    L193
L205:
  nop
L193:
  cmpq   $0x0,-0x40(%rbp)
  je     L100
  cmpl   $0x0,-0x20(%rbp)
  je     L435
  mov    -0x18(%rbp),%rax
  sub    $0x1,%rax
  jmp    L52
L435:
  mov    -0x38(%rbp),%rax
L52:
  mov    -0x40(%rbp),%rdx
  mov    %rax,(%rdx)
L100:
  mov    -0x10(%rbp),%rax
  leave
  ret
```

assistant: ```c
unsigned long strtoul(const char *__restrict nptr, char **__restrict endptr, int base) {
  const char *s;
  unsigned long acc;
  char c;
  unsigned long cutoff;
  int neg, any, cutlim;
  s = nptr;
  do {
    c = *s++;
  } while (isspace((unsigned char)c));
  if (c == '-') {
    neg = 1;
    c = *s++;
  } else {
    neg = 0;
    if (c == '+') {
      c = *s++;
    }
  }
  if ((base == 0 || base == 16) && c == '0' && (*s == 'x' || *s == 'X') && ((s[1] >= '0' && s[1] <= '9') || (s[1] >= 'A' && s[1] <= 'F') || (s[1] >= 'a' && s[1] <= 'f'))) {
    c = s[1];
    s += 2;
    base = 16;
  }
  if (base == 0) {
    base = c == '0' ? 8 : 10;
  }
  acc = any = 0;
  if (base < 2 || base > 36) {
    goto noconv;
  }
  cutoff = ULONG_MAX / base;
  cutlim = ULONG_MAX % base;
  for (;; c = *s++) {
    if (c >= '0' && c <= '9') {
      c -= '0';
    } else if (c >= 'A' && c <= 'Z') {
      c -= 'A' - 10;
    } else if (c >= 'a' && c <= 'z') {
      c -= 'a' - 10;
    } else {
      break;
    }
    if (c >= base) {
      break;
    }
    if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim)) {
      any = -1;
    } else {
      any = 1;
      acc *= base;
      acc += c;
    }
  }
  if (any < 0) {
    acc = ULONG_MAX;
  } else if (!any) {
  } else if (neg) {
    acc = -acc;
  }
noconv:
  if (endptr != NULL) {
    *endptr = (char *)(any ? s - 1 : nptr);
  }
  return (acc);
}
```