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

```asm
<Base64Decode>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x78,%rsp
  mov    %rdi,%rbx
  mov    %rsi,(%rsp)
  mov    %edx,0xc(%rsp)
  mov    %ecx,%r15d
  mov    %fs:0x28,%rax
  mov    %rax,0x68(%rsp)
  xor    %eax,%eax
  movl   $0x0,0x1b(%rsp)
  movb   $0x0,0x1f(%rsp)
  movabs $0x4847464544434241,%rax
  movabs $0x504f4e4d4c4b4a49,%rdx
  mov    %rax,0x20(%rsp)
  mov    %rdx,0x28(%rsp)
  movabs $0x5857565554535251,%rax
  movabs $0x6665646362615a59,%rdx
  mov    %rax,0x30(%rsp)
  mov    %rdx,0x38(%rsp)
  movabs $0x6e6d6c6b6a696867,%rax
  movabs $0x767574737271706f,%rdx
  mov    %rax,0x40(%rsp)
  mov    %rdx,0x48(%rsp)
  movabs $0x333231307a797877,%rax
  movabs $0x5f2d393837363534,%rdx
  mov    %rax,0x50(%rsp)
  mov    %rdx,0x58(%rsp)
  call   <strlen@plt>
  test   %eax,%eax
  jle    L86
  mov    %rbx,%rbp
  lea    -0x1(%rax),%eax
  lea    0x1(%rbx,%rax,1),%r13
  mov    $0x3,%r14d
  movl   $0x0,0x8(%rsp)
  mov    $0x0,%ebx
  lea    0x20(%rsp),%r12
  jmp    L79
L21:
  lea    0x1b(%rsp),%rdi
  mov    %r14d,%r8d
  mov    %r15d,%ecx
  mov    0xc(%rsp),%edx
  mov    (%rsp),%rsi
  call   <decodeblock@plt>
  mov    %eax,0x8(%rsp)
L13:
  mov    0x68(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L31
  mov    0x8(%rsp),%eax
  add    $0x78,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L49:
  add    $0x1,%rbp
  cmp    %r13,%rbp
  je     L13
L79:
  movsbl 0x0(%rbp),%esi
  cmp    $0x3d,%esi
  je     L21
  mov    %r12,%rdi
  call   <strchr@plt>
  test   %rax,%rax
  je     L49
  movslq %ebx,%rdx
  sub    %r12,%rax
  mov    %al,0x1b(%rsp,%rdx,1)
  lea    0x1(%rbx),%edx
  mov    %edx,%eax
  sar    $0x1f,%eax
  shr    $0x1e,%eax
  lea    (%rdx,%rax,1),%ebx
  and    $0x3,%ebx
  sub    %eax,%ebx
  test   $0x3,%dl
  jne    L49
  lea    0x1b(%rsp),%rdi
  mov    %r14d,%r8d
  mov    %r15d,%ecx
  mov    0xc(%rsp),%edx
  mov    (%rsp),%rsi
  call   <decodeblock@plt>
  mov    %eax,0x8(%rsp)
  add    $0x3,%r14d
  movb   $0x0,0x1e(%rsp)
  movb   $0x0,0x1d(%rsp)
  movb   $0x0,0x1c(%rsp)
  movb   $0x0,0x1b(%rsp)
  jmp    L49
L86:
  movl   $0x0,0x8(%rsp)
  jmp    L13
L31:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int Base64Decode(char *input, unsigned char *output, int oplen, int debug) {
  char *charval = 0;
  char decoderinput[4 + 1] = "";
  char encodingtable[63 + 1] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                               "abcdefghijklmnopqrstuvwxyz"
                               "0123456789"
                               "-_";
  ;
  int index = 0, asciival = 0, computeval = 0, iplen = 0, rc = 0, oindex = 3;
  iplen = (int)strlen(input);
  while (index < iplen) {
    asciival = (int)input[index];
    if (asciival == '=') {
      rc = decodeblock(decoderinput, output, oplen, debug, oindex);
      break;
    } else {
      charval = strchr(encodingtable, asciival);
      if (charval) {
        decoderinput[computeval] = charval - encodingtable;
        computeval = (computeval + 1) % 4;
        if (computeval == 0) {
          rc = decodeblock(decoderinput, output, oplen, debug, oindex);
          oindex = oindex + 3;
          decoderinput[0] = decoderinput[1] = decoderinput[2] = decoderinput[3] = 0;
        }
      }
    }
    index++;
  }
  return rc;
}
```