user: 请从给定的汇编指令推导出C源代码：

```asm
<substring>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  test   %rdi,%rdi
  je     L87
  mov    %esi,%r12d
  test   %esi,%esi
  js     L87
  mov    %edx,%ebx
  mov    %rdi,%rbp
  call   <strlen@plt>
  cmp    %ebx,%eax
  jle    L87
  sub    %r12d,%ebx
  lea    0x2(%rbx),%edi
  lea    0x1(%rbx),%r13d
  call   <malloc@plt>
  mov    %rax,%r8
  test   %r13d,%r13d
  jle    L173
  movslq %r12d,%rdx
  lea    0x1(%rbp,%rdx,1),%rcx
  sub    %rcx,%rax
  cmp    $0xe,%rax
  jbe    L188
  cmp    $0x6,%ebx
  jbe    L188
  cmp    $0xe,%ebx
  jbe    L60
  mov    %r13d,%ecx
  add    %rbp,%rdx
  xor    %eax,%eax
  shr    $0x4,%ecx
  shl    $0x4,%rcx
  nopl   (%rax)
L181:
  movdqu (%rdx,%rax,1),%xmm0
  movups %xmm0,(%r8,%rax,1)
  add    $0x10,%rax
  cmp    %rcx,%rax
  jne    L181
  mov    %r13d,%ecx
  and    $0xfffffff0,%ecx
  mov    %ecx,%eax
  cmp    %ecx,%r13d
  je     L173
  mov    %ebx,%edi
  sub    %ecx,%edi
  lea    0x1(%rdi),%esi
  cmp    $0x6,%edi
  jbe    L130
L88:
  mov    (%rdx,%rcx,1),%rdx
  mov    %rdx,(%r8,%rcx,1)
  mov    %esi,%edx
  and    $0xfffffff8,%edx
  add    %edx,%eax
  cmp    %edx,%esi
  je     L173
L130:
  lea    (%r12,%rax,1),%edx
  movslq %edx,%rdx
  movzbl 0x0(%rbp,%rdx,1),%ecx
  movslq %eax,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x1(%rax),%edx
  cmp    %eax,%ebx
  jle    L173
  lea    (%r12,%rdx,1),%ecx
  movslq %ecx,%rcx
  movzbl 0x0(%rbp,%rcx,1),%esi
  movslq %edx,%rcx
  mov    %sil,(%r8,%rcx,1)
  lea    0x2(%rax),%ecx
  cmp    %edx,%ebx
  jle    L173
  lea    (%r12,%rcx,1),%edx
  movslq %edx,%rdx
  movzbl 0x0(%rbp,%rdx,1),%esi
  movslq %ecx,%rdx
  mov    %sil,(%r8,%rdx,1)
  lea    0x3(%rax),%edx
  cmp    %ecx,%ebx
  jle    L173
  lea    (%r12,%rdx,1),%ecx
  movslq %ecx,%rcx
  movzbl 0x0(%rbp,%rcx,1),%esi
  movslq %edx,%rcx
  mov    %sil,(%r8,%rcx,1)
  lea    0x4(%rax),%ecx
  cmp    %edx,%ebx
  jle    L173
  lea    (%r12,%rcx,1),%edx
  movslq %edx,%rdx
  movzbl 0x0(%rbp,%rdx,1),%esi
  movslq %ecx,%rdx
  mov    %sil,(%r8,%rdx,1)
  lea    0x5(%rax),%edx
  cmp    %ecx,%ebx
  jle    L173
  lea    (%r12,%rdx,1),%ecx
  add    $0x6,%eax
  movslq %ecx,%rcx
  movzbl 0x0(%rbp,%rcx,1),%esi
  movslq %edx,%rcx
  mov    %sil,(%r8,%rcx,1)
  cmp    %edx,%ebx
  jle    L173
  add    %eax,%r12d
  cltq
  movslq %r12d,%r12
  movzbl 0x0(%rbp,%r12,1),%edx
  mov    %dl,(%r8,%rax,1)
L173:
  movslq %r13d,%r13
  mov    %r8,%rax
  movb   $0x0,(%r8,%r13,1)
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopw   0x0(%rax,%rax,1)
L87:
  lea    D4(%rip),%rdi
  call   <printf@plt>
  add    $0x8,%rsp
  xor    %r8d,%r8d
  pop    %rbx
  mov    %r8,%rax
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopl   (%rax)
L188:
  xor    %eax,%eax
  add    %rbp,%rdx
  nopl   (%rax)
L32:
  movzbl (%rdx,%rax,1),%ecx
  mov    %cl,(%r8,%rax,1)
  mov    %rax,%rcx
  add    $0x1,%rax
  cmp    %rbx,%rcx
  jne    L32
  jmp    L173
L60:
  mov    %r13d,%esi
  xor    %ecx,%ecx
  xor    %eax,%eax
  add    %rbp,%rdx
  jmp    L88
```

tool_calls: name: extract_symbolic_data
arguments: data_label: D4
data_type: string

tool: D4: Error substring. Indice fuera de memoria.


assistant: ```c
char *substring(char *input, int start, int end) {
  char *substring = NULL;
  if (input == NULL || start < 0 || end >= strlen(input)) {
    printf("Error substring. Indice fuera de memoria.\n");
    return NULL;
  }
  int n = end - start + 1;
  substring = malloc((n + 1) * sizeof(char));
  for (int i = 0; i < n; i++) {
    substring[i] = input[i + start];
  }
  substring[n] = '\0';
  return substring;
}
```