user: 提供的汇编代码用C语言表示会是什么样子:

```asm
<strntoumax>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  mov    %rsi,%r13
  push   %r12
  mov    %edx,%r12d
  push   %rbp
  lea    (%rdi,%rcx,1),%rbp
  push   %rbx
  mov    %rdi,%rbx
  sub    $0x8,%rsp
  cmp    %rbp,%rdi
  jb     L242
  jmp    L294
  nopl   0x0(%rax)
L248:
  add    $0x1,%rbx
  cmp    %rbx,%rbp
  je     L294
L242:
  movzbl (%rbx),%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L248
  cmp    %rbx,%rbp
  jbe    L294
  movzbl (%rbx),%eax
  xor    %r14d,%r14d
  lea    -0x2b(%rax),%edx
  and    $0xfd,%edx
  je     L301
L177:
  test   %r12d,%r12d
  jne    L84
L218:
  lea    0x2(%rbx),%rax
  cmp    %rbp,%rax
  jae    L32
  cmpb   $0x30,(%rbx)
  mov    $0xa,%r12d
  je     L115
  nopl   (%rax)
L305:
  cmp    %rbp,%rbx
  jae    L36
L249:
  xor    %r15d,%r15d
  jmp    L26
  xchg   %ax,%ax
L201:
  cmp    %eax,%r12d
  jle    L200
  imul   %r12d,%r15d
  add    $0x1,%rbx
  add    %eax,%r15d
  cmp    %rbx,%rbp
  jbe    L200
L26:
  movzbl (%rbx),%edi
  call   <digitval@plt>
  test   %eax,%eax
  jns    L201
L200:
  test   %r13,%r13
  je     L0
  mov    %rbx,0x0(%r13)
L0:
  mov    %r15d,%eax
  neg    %eax
  test   %r14d,%r14d
  cmovne %eax,%r15d
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  mov    %r15d,%eax
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax,%rax,1)
L294:
  xor    %r14d,%r14d
  test   %r12d,%r12d
  je     L218
L84:
  cmp    $0x10,%r12d
  jne    L305
  lea    0x2(%rbx),%rax
  cmp    %rbp,%rax
  jae    L305
  cmpb   $0x30,(%rbx)
  jne    L305
  movzbl 0x1(%rbx),%edx
  and    $0xffffffdf,%edx
  cmp    $0x58,%dl
  jne    L305
  mov    %rax,%rbx
  jmp    L249
  nopl   0x0(%rax,%rax,1)
L32:
  lea    0x1(%rbx),%rax
  cmp    %rbp,%rax
  jae    L37
  cmpb   $0x30,(%rbx)
  jne    L37
L38:
  mov    %rax,%rbx
  mov    $0x8,%r12d
  jmp    L249
  nopl   0x0(%rax)
L301:
  xor    %r14d,%r14d
  cmp    $0x2d,%al
  sete   %r14b
  add    $0x1,%rbx
  jmp    L177
  nopw   0x0(%rax,%rax,1)
L37:
  mov    $0xa,%r12d
  jmp    L305
L115:
  movzbl 0x1(%rbx),%edx
  and    $0xffffffdf,%edx
  cmp    $0x58,%dl
  jne    L165
  mov    %rax,%rbx
  mov    $0x10,%r12d
  jmp    L249
L165:
  lea    0x1(%rbx),%rax
  cmp    %rax,%rbp
  jbe    L305
  jmp    L38
L36:
  xor    %r15d,%r15d
  jmp    L200
```

assistant: ```c
uintmax_t strntoumax(const char *nptr, char **endptr, int base, size_t n) {
  const unsigned char *p = (const unsigned char *)nptr;
  const unsigned char *end = p + n;
  int minus = 0;
  uintmax_t v = 0;
  int d;
  while (p < end && isspace(*p))
    p++;
  if (p < end) {
    char c = p[0];
    if (c == '-' || c == '+') {
      minus = (c == '-');
      p++;
    }
  }
  if (base == 0) {
    if (p + 2 < end && p[0] == '0' && (p[1] == 'x' || p[1] == 'X')) {
      p += 2;
      base = 16;
    } else if (p + 1 < end && p[0] == '0') {
      p += 1;
      base = 8;
    } else {
      base = 10;
    }
  } else if (base == 16) {
    if (p + 2 < end && p[0] == '0' && (p[1] == 'x' || p[1] == 'X')) {
      p += 2;
    }
  }
  while (p < end && (d = digitval(*p)) >= 0 && d < base) {
    v = v * base + d;
    p += 1;
  }
  if (endptr)
    *endptr = (char *)p;
  return minus ? -v : v;
}
```