user: 这段汇编代码用C语言表示是什么样的：

```asm
<abs2rel>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  mov    %rdi,%r12
  mov    %rdx,%rbx
  mov    %rcx,%rbp
  cmpb   $0x2f,(%rdi)
  je     L203
  call   <strlen@plt>
  mov    %eax,%eax
  cmp    %rbp,%rax
  jae    L216
  mov    %r12,%rsi
  mov    %rbx,%rdi
  call   <strcpy@plt>
  mov    %rbx,%rax
  jmp    L295
L203:
  mov    %rsi,%r8
  cmpb   $0x2f,(%rsi)
  jne    L269
  test   %rcx,%rcx
  je     L269
  cmp    $0x1,%rcx
  je     L216
  lea    -0x1(%rdx,%rcx,1),%rbp
  mov    %rsi,%rcx
  mov    %rdi,%rax
L245:
  add    $0x1,%rax
  add    $0x1,%rcx
  movzbl (%rax),%edx
  test   %dl,%dl
  je     L141
  movzbl (%rcx),%esi
  cmp    %sil,%dl
  jne    L6
  test   %sil,%sil
  je     L6
  cmp    $0x2f,%dl
  cmove  %rax,%rdi
  jmp    L245
L269:
  mov    D22(%rip),%rax
  mov    (%rax),%edx
  mov    D14(%rip),%rax
  mov    %edx,(%rax)
  mov    $0x0,%eax
  jmp    L295
L6:
  cmp    $0x2f,%dl
  je     L172
L252:
  mov    %rdi,%rdx
  sub    %r12,%rdx
  add    %r8,%rdx
  movzbl (%rdx),%eax
  test   %al,%al
  je     L167
  mov    %rbx,%r12
  jmp    L268
L172:
  cmpb   $0x0,0x1(%rax)
  jne    L75
L141:
  movzbl (%rcx),%esi
  test   %sil,%sil
  je     L258
  cmp    $0x2f,%sil
  jne    L252
  cmpb   $0x0,0x1(%rcx)
  jne    L278
L258:
  movb   $0x2e,(%rbx)
  cmpb   $0x2f,(%rax)
  je     L215
  cmpb   $0x2f,-0x1(%rax)
  je     L215
  lea    0x1(%rbx),%rax
  jmp    L187
L215:
  lea    0x2(%rbx),%rax
  movb   $0x2f,0x1(%rbx)
L187:
  cmp    %rbp,%rax
  ja     L216
  movb   $0x0,(%rax)
  mov    %rbx,%rax
  jmp    L295
L75:
  cmpb   $0x0,(%rcx)
  cmove  %rax,%rdi
  jmp    L252
L235:
  add    $0x1,%rdx
  movzbl (%rdx),%eax
  test   %al,%al
  je     L74
L268:
  cmp    $0x2f,%al
  jne    L235
  movzbl 0x1(%rdx),%eax
  cmp    $0x2f,%al
  je     L235
  test   %al,%al
  je     L235
  lea    0x3(%r12),%rax
  cmp    %rax,%rbp
  jb     L216
  movb   $0x2e,(%r12)
  movb   $0x2e,0x1(%r12)
  movb   $0x2f,0x2(%r12)
  mov    %rax,%r12
  jmp    L235
L167:
  mov    %rbx,%r12
L74:
  cmp    %r12,%rbp
  jb     L216
  movb   $0x0,(%r12)
  cmpb   $0x0,(%rdi)
  je     L347
  lea    0x1(%rdi),%r13
  mov    %r13,%rdi
  call   <strlen@plt>
  cltq
  add    %r12,%rax
  cmp    %rax,%rbp
  jb     L216
  mov    %r13,%rsi
  mov    %r12,%rdi
  call   <strcpy@plt>
  mov    %rbx,%rax
  jmp    L295
L347:
  movb   $0x0,-0x1(%r12)
  mov    %rbx,%rax
  jmp    L295
L216:
  mov    D27(%rip),%rax
  mov    (%rax),%edx
  mov    D14(%rip),%rax
  mov    %edx,(%rax)
  mov    $0x0,%eax
L295:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
L278:
  test   %dl,%dl
  cmove  %rax,%rdi
  jmp    L252
```

assistant: ```c
char *abs2rel(const char *path, const char *base, char *result, const size_t size) {
  const char *pp, *bp, *branch;
  const char *endp = result + size - 1;
  char *rp;
  if (*path != '/') {
    if ((unsigned int)strlen(path) >= size)
      goto erange;
    strcpy(result, path);
    goto finish;
  } else if (*base != '/' || !size) {
    errno = EINVAL;
    return (NULL);
  } else if (size == 1)
    goto erange;
  branch = path;
  for (pp = path, bp = base; *pp && *bp && *pp == *bp; pp++, bp++)
    if (*pp == '/')
      branch = pp;
  if ((*pp == 0 || (*pp == '/' && *(pp + 1) == 0)) && (*bp == 0 || (*bp == '/' && *(bp + 1) == 0))) {
    rp = result;
    *rp++ = '.';
    if (*pp == '/' || *(pp - 1) == '/')
      *rp++ = '/';
    if (rp > endp)
      goto erange;
    *rp = 0;
    goto finish;
  }
  if ((*pp == 0 && *bp == '/') || (*pp == '/' && *bp == 0))
    branch = pp;
  rp = result;
  for (bp = base + (branch - path); *bp; bp++)
    if (*bp == '/' && *(bp + 1) != 0 && *(bp + 1) != '/') {
      if (rp + 3 > endp)
        goto erange;
      *rp++ = '.';
      *rp++ = '.';
      *rp++ = '/';
    }
  if (rp > endp)
    goto erange;
  *rp = 0;
  if (*branch) {
    if (rp + (int)strlen(branch + 1) > endp)
      goto erange;
    strcpy(rp, branch + 1);
  } else
    *--rp = 0;
finish:
  return result;
erange:
  errno = ERANGE;
  return (NULL);
}
```