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

```asm
<strtoumax>:
  endbr64
  push   %r15
  mov    %rdi,%r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  mov    %edx,%ebp
  push   %rbx
  sub    $0x28,%rsp
  mov    %rdi,0x10(%rsp)
  mov    %rsi,0x8(%rsp)
  nopl   0x0(%rax)
L103:
  mov    %r15,%rbx
  movzbl (%r15),%r14d
  add    $0x1,%r15
  mov    %r14d,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L103
  cmp    $0x2d,%r14d
  je     L63
  movb   $0x0,0x1f(%rsp)
  cmp    $0x2b,%r14d
  je     L48
L143:
  test   $0xffffffef,%ebp
  jne    L33
  cmp    $0x30,%r14d
  je     L198
  test   %ebp,%ebp
  jne    L33
  mov    $0xa,%ebp
L33:
  mov    D28(%rip),%rax
  xor    %ebx,%ebx
  xor    %r12d,%r12d
  mov    (%rax),%eax
  cltd
  idiv   %ebp
  mov    %edx,0x18(%rsp)
  mov    %eax,%r13d
  jmp    L16
  xchg   %ax,%ax
L49:
  cmp    %ecx,%ebp
  jle    L236
L190:
  cmp    $0xffffffff,%ebx
  je     L223
  cmp    %r13d,%r12d
  jg     L47
  jne    L110
  cmp    0x18(%rsp),%ecx
  jle    L110
L47:
  mov    D28(%rip),%rax
  mov    $0xffffffff,%ebx
  mov    (%rax),%r12d
  mov    D10(%rip),%rax
  mov    (%rax),%edx
  mov    D18(%rip),%rax
  mov    %edx,(%rax)
L223:
  movzbl (%r15),%r14d
  add    $0x1,%r15
L16:
  mov    %r14d,%edi
  call   <isdigit@plt>
  lea    -0x30(%r14),%ecx
  test   %rax,%rax
  jne    L49
  mov    %r14d,%edi
  call   <isalpha@plt>
  test   %rax,%rax
  je     L236
  mov    %r14d,%edi
  call   <isupper@plt>
  mov    %r14d,%ecx
  cmp    $0x1,%rax
  sbb    %eax,%eax
  and    $0x20,%eax
  add    $0x37,%eax
  sub    %eax,%ecx
  cmp    %ecx,%ebp
  jg     L190
L236:
  test   %ebx,%ebx
  jle    L221
  cmpb   $0x0,0x1f(%rsp)
  je     L221
  neg    %r12d
  cmpq   $0x0,0x8(%rsp)
  je     L78
L206:
  lea    -0x1(%r15),%rax
  mov    %rax,0x10(%rsp)
  mov    0x8(%rsp),%rax
  mov    0x10(%rsp),%rsi
  mov    %rsi,(%rax)
L78:
  add    $0x28,%rsp
  mov    %r12d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L110:
  imul   %ebp,%r12d
  mov    $0x1,%ebx
  add    %ecx,%r12d
  jmp    L223
  nopl   0x0(%rax)
L221:
  cmpq   $0x0,0x8(%rsp)
  je     L78
  test   %ebx,%ebx
  jne    L206
  mov    0x8(%rsp),%rax
  mov    0x10(%rsp),%rsi
  mov    %rsi,(%rax)
  jmp    L78
  nopl   0x0(%rax,%rax,1)
L48:
  movsbl (%r15),%r14d
  lea    0x2(%rbx),%r15
  jmp    L143
  nopl   (%rax)
L63:
  movsbl (%r15),%r14d
  movb   $0x1,0x1f(%rsp)
  lea    0x2(%rbx),%r15
  jmp    L143
  nopw   0x0(%rax,%rax,1)
L198:
  movzbl (%r15),%eax
  and    $0xffffffdf,%eax
  cmp    $0x58,%al
  jne    L100
  movsbl 0x1(%r15),%r14d
  mov    $0x10,%ebp
  add    $0x2,%r15
  jmp    L33
L100:
  test   %ebp,%ebp
  mov    $0x8,%eax
  cmove  %eax,%ebp
  jmp    L33
```

assistant: ```c
uintmax_t strtoumax(const char *nptr, char **endptr, int base) {
  const char *s;
  uintmax_t acc, cutoff;
  int c;
  int neg, any, cutlim;
  s = nptr;
  do {
    c = (unsigned char)*s++;
  } while (isspace(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')) {
    c = s[1];
    s += 2;
    base = 16;
  }
  if (base == 0)
    base = c == '0' ? 8 : 10;
  cutoff = UINTMAX_MAX / (uintmax_t)base;
  cutlim = UINTMAX_MAX % (uintmax_t)base;
  for (acc = 0, any = 0;; c = (unsigned char)*s++) {
    if (isdigit(c))
      c -= '0';
    else if (isalpha(c))
      c -= isupper(c) ? 'A' - 10 : 'a' - 10;
    else
      break;
    if (c >= base)
      break;
    if (any < 0)
      continue;
    if (acc > cutoff || (acc == cutoff && c > cutlim)) {
      any = -1;
      acc = UINTMAX_MAX;
      errno = ERANGE;
    } else {
      any = 1;
      acc *= (uintmax_t)base;
      acc += c;
    }
  }
  if (neg && any > 0)
    acc = -acc;
  if (endptr != 0)
    *endptr = (char *)(any ? s - 1 : nptr);
  return (acc);
}
```