user: 下面的汇编指令对应的C源代码是什么:

```asm
<base64_decode>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x28,%rsp
  mov    %rdi,%r15
  mov    %esi,%r14d
  mov    %fs:0x28,%rax
  mov    %rax,0x18(%rsp)
  xor    %eax,%eax
  lea    0x3(%rsi),%eax
  test   %esi,%esi
  cmovns %esi,%eax
  sar    $0x2,%eax
  lea    (%rax,%rax,2),%edx
  mov    %edx,%ebp
  movslq %esi,%rax
  cmpb   $0x3d,-0x1(%rdi,%rax,1)
  sete   %bl
  movzbl %bl,%ebx
  cmpb   $0x3d,-0x2(%rdi,%rax,1)
  je     L219
L125:
  cmpb   $0x3d,-0x3(%r15,%rax,1)
  je     L137
  cmp    $0x2,%ebx
  je     L1
L72:
  test   %ebx,%ebx
  je     L226
  cmp    $0x1,%ebx
  jne    L191
  lea    0x4(%rdx),%ebp
  jmp    L191
L219:
  add    $0x1,%ebx
  jmp    L125
L137:
  add    $0x1,%ebx
  cmp    $0x2,%ebx
  je     L1
  jle    L72
  lea    0x2(%rdx),%ebp
  jmp    L191
L226:
  lea    0x4(%rdx),%ebp
L191:
  mov    %ebp,%edi
  call   <malloc@plt>
  mov    %rax,0x8(%rsp)
  test   %rax,%rax
  je     L152
L93:
  mov    %ebp,%edx
  mov    $0x0,%esi
  mov    0x8(%rsp),%r12
  mov    %r12,%rdi
  call   <memset@plt>
  sub    %ebx,%r14d
  test   %r14d,%r14d
  jle    L84
  mov    $0x0,%r13d
  lea    0x15(%rsp),%rax
  mov    %rax,(%rsp)
  jmp    L71
L1:
  lea    0x3(%rdx),%ebp
  jmp    L191
L152:
  lea    D2(%rip),%rdi
  call   <printf@plt>
  mov    $0x0,%edi
  call   <exit@plt>
  jmp    L93
L160:
  cmp    %r14d,%r13d
  jge    L139
L71:
  mov    $0x4,%edx
  mov    $0x0,%esi
  mov    (%rsp),%rdi
  call   <memset@plt>
  cmp    %r13d,%r14d
  jle    L139
  add    $0x1,%r13d
  movslq %r13d,%rbx
  mov    $0x0,%eax
  mov    $0x0,%ebp
L133:
  shl    $0x6,%eax
  mov    %eax,%r13d
  movsbl -0x1(%r15,%rbx,1),%edi
  call   <find_pos@plt>
  or     %r13d,%eax
  mov    %ebp,%esi
  add    $0x1,%ebp
  mov    %ebx,%r13d
  cmp    $0x3,%ebp
  setg   %dl
  cmp    %ebx,%r14d
  setle  %cl
  add    $0x1,%rbx
  or     %cl,%dl
  je     L133
  mov    $0x4,%edx
  sub    %ebp,%edx
  lea    (%rdx,%rdx,2),%ecx
  add    %ecx,%ecx
  shl    %cl,%eax
  test   %ebp,%ebp
  je     L160
  mov    $0x10,%ecx
  mov    $0x0,%edx
L94:
  mov    %eax,%edi
  sar    %cl,%edi
  mov    %dil,(%r12)
  add    $0x1,%r12
  mov    %edx,%edi
  add    $0x1,%edx
  sub    $0x8,%ecx
  cmp    %edi,%esi
  je     L160
  cmp    $0x2,%edx
  jle    L94
  jmp    L160
L84:
  mov    0x8(%rsp),%r12
L139:
  movb   $0x0,(%r12)
  mov    0x18(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L31
  mov    0x8(%rsp),%rax
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L31:
  call   <__stack_chk_fail@plt>
```

tool_calls: name: extract_symbolic_data
arguments: data_tag: D2
type_infered: string

tool: D2: No enough memory.


assistant: ```c
char *base64_decode(const char *data, int data_len) {
  int ret_len = (data_len / 4) * 3;
  int equal_count = 0;
  char *ret = NULL;
  char *f = NULL;
  int tmp = 0;
  int temp = 0;
  char need[3];
  int prepare = 0;
  int i = 0;
  if (*(data + data_len - 1) == '=') {
    equal_count += 1;
  }
  if (*(data + data_len - 2) == '=') {
    equal_count += 1;
  }
  if (*(data + data_len - 3) == '=') {
    equal_count += 1;
  }
  switch (equal_count) {
  case 0:
    ret_len += 4;
    break;
  case 1:
    ret_len += 4;
    break;
  case 2:
    ret_len += 3;
    break;
  case 3:
    ret_len += 2;
    break;
  }
  ret = (char *)malloc(ret_len);
  if (ret == NULL) {
    printf("No enough memory.\n");
    exit(0);
  }
  memset(ret, 0, ret_len);
  f = ret;
  while (tmp < (data_len - equal_count)) {
    temp = 0;
    prepare = 0;
    memset(need, 0, 4);
    while (temp < 4) {
      if (tmp >= (data_len - equal_count)) {
        break;
      }
      prepare = (prepare << 6) | (find_pos(data[tmp]));
      temp++;
      tmp++;
    }
    prepare = prepare << ((4 - temp) * 6);
    for (i = 0; i < 3; i++) {
      if (i == temp) {
        break;
      }
      *f = (char)((prepare >> ((2 - i) * 8)) & 0xFF);
      f++;
    }
  }
  *f = '\0';
  return ret;
}
```