user: Demonstrate the C code that generates the assembly output below:

```asm
<copy_callback>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r12
  push   %rbx
  sub    $0x50,%rsp
  mov    %rdi,-0x48(%rbp)
  mov    %rsi,-0x50(%rbp)
  mov    %rdx,-0x58(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x28(%rbp)
  xor    %eax,%eax
  mov    %rsp,%rax
  mov    %rax,%r12
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  cltq
  lea    -0x1(%rax),%rdx
  mov    -0x48(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x2f,%al
  jne    L52
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  cltq
  lea    -0x1(%rax),%rdx
  mov    -0x48(%rbp),%rax
  add    %rdx,%rax
  movb   $0x0,(%rax)
L52:
  mov    -0x58(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  cltq
  lea    -0x1(%rax),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x2f,%al
  jne    L7
  mov    -0x58(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  cltq
  lea    -0x1(%rax),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movb   $0x0,(%rax)
L7:
  mov    -0x48(%rbp),%rdx
  mov    -0x50(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strstr@plt>
  cmp    %rax,-0x50(%rbp)
  je     L10
  mov    $0xffffffff,%eax
  jmp    L8
L10:
  mov    -0x50(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    %eax,%ebx
  mov    -0x58(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  add    %ebx,%eax
  add    $0x1,%eax
  movslq %eax,%rdx
  sub    $0x1,%rdx
  mov    %rdx,-0x38(%rbp)
  movslq %eax,%rdx
  mov    %rdx,-0x70(%rbp)
  movq   $0x0,-0x68(%rbp)
  movslq %eax,%rdx
  mov    %rdx,%r14
  mov    $0x0,%r15d
  cltq
  mov    $0x10,%edx
  sub    $0x1,%rdx
  add    %rdx,%rax
  mov    $0x10,%ebx
  mov    $0x0,%edx
  div    %rbx
  imul   $0x10,%rax,%rax
  mov    %rax,%rcx
  and    $0xfffffffffffff000,%rcx
  mov    %rsp,%rdx
  sub    %rcx,%rdx
L41:
  cmp    %rdx,%rsp
  je     L66
  sub    $0x1000,%rsp
  orq    $0x0,0xff8(%rsp)
  jmp    L41
L66:
  mov    %rax,%rdx
  and    $0xfff,%edx
  sub    %rdx,%rsp
  mov    %rax,%rdx
  and    $0xfff,%edx
  test   %rdx,%rdx
  je     L62
  and    $0xfff,%eax
  sub    $0x8,%rax
  add    %rsp,%rax
  orq    $0x0,(%rax)
L62:
  mov    %rsp,%rax
  add    $0x0,%rax
  mov    %rax,-0x30(%rbp)
  mov    -0x30(%rbp),%rax
  movb   $0x0,(%rax)
  mov    -0x58(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  movslq %eax,%rdx
  mov    -0x50(%rbp),%rax
  add    %rax,%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
  mov    -0x30(%rbp),%rdx
  mov    -0x50(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <copy_file@plt>
L8:
  mov    %r12,%rsp
  mov    -0x28(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L29
  call   <__stack_chk_fail@plt>
L29:
  lea    -0x20(%rbp),%rsp
  pop    %rbx
  pop    %r12
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
int copy_callback(char *source_root, char *source, char *target_root) {
  if (source_root[strlen(source_root) - 1] == '/')
    source_root[strlen(source_root) - 1] = 0;
  if (target_root[strlen(target_root) - 1] == '/')
    target_root[strlen(target_root) - 1] = 0;
  if (strstr(source, source_root) != source)
    return -1;
  char target[strlen(source) + strlen(target_root) + 1];
  target[0] = 0;
  strcat(target, target_root);
  strcat(target, source + strlen(source_root));
  return copy_file(source, target);
}
```