user: 下面的汇编指令对应的C源代码是什么：

```asm
<http_base64decode>:
  endbr64
  sub    $0x118,%rsp
  mov    %rdx,%r9
  mov    %fs:0x28,%rax
  mov    %rax,0x108(%rsp)
  xor    %eax,%eax
  movq   $0xffffffffffffffff,(%rsp)
  movq   $0xffffffffffffffff,0x8(%rsp)
  movq   $0xffffffffffffffff,0x10(%rsp)
  movq   $0xffffffffffffffff,0x18(%rsp)
  mov    $0xffffffffffffffff,%rax
  movabs $0x3fffffff3effffff,%rdx
  mov    %rax,0x20(%rsp)
  mov    %rdx,0x28(%rsp)
  movabs $0x3b3a393837363534,%rax
  movabs $0xffff00ffffff3d3c,%rdx
  mov    %rax,0x30(%rsp)
  mov    %rdx,0x38(%rsp)
  movabs $0x6050403020100ff,%rax
  movabs $0xe0d0c0b0a090807,%rdx
  mov    %rax,0x40(%rsp)
  mov    %rdx,0x48(%rsp)
  movabs $0x161514131211100f,%rax
  mov    $0xffffffffff191817,%rdx
  mov    %rax,0x50(%rsp)
  mov    %rdx,0x58(%rsp)
  movabs $0x201f1e1d1c1b1aff,%rax
  movabs $0x2827262524232221,%rdx
  mov    %rax,0x60(%rsp)
  mov    %rdx,0x68(%rsp)
  movabs $0x302f2e2d2c2b2a29,%rax
  mov    $0xffffffffff333231,%rdx
  mov    %rax,0x70(%rsp)
  mov    %rdx,0x78(%rsp)
  movq   $0xffffffffffffffff,0x80(%rsp)
  movq   $0xffffffffffffffff,0x88(%rsp)
  movq   $0xffffffffffffffff,0x90(%rsp)
  movq   $0xffffffffffffffff,0x98(%rsp)
  movq   $0xffffffffffffffff,0xa0(%rsp)
  movq   $0xffffffffffffffff,0xa8(%rsp)
  movq   $0xffffffffffffffff,0xb0(%rsp)
  movq   $0xffffffffffffffff,0xb8(%rsp)
  movq   $0xffffffffffffffff,0xc0(%rsp)
  movq   $0xffffffffffffffff,0xc8(%rsp)
  movq   $0xffffffffffffffff,0xd0(%rsp)
  movq   $0xffffffffffffffff,0xd8(%rsp)
  movq   $0xffffffffffffffff,0xe0(%rsp)
  movq   $0xffffffffffffffff,0xe8(%rsp)
  movq   $0xffffffffffffffff,0xf0(%rsp)
  movq   $0xffffffffffffffff,0xf8(%rsp)
  test   %esi,%esi
  jle    L32
  mov    %rdi,%rax
  mov    %r9,%rcx
  lea    -0x1(%rsi),%r8d
  shr    $0x2,%r8d
  mov    %r8d,%edx
  lea    0x4(%rdi,%rdx,4),%rdi
L26:
  movzbl (%rax),%edx
  movsbl (%rsp,%rdx,1),%esi
  shl    $0x2,%esi
  movzbl 0x1(%rax),%edx
  movzbl (%rsp,%rdx,1),%edx
  sar    $0x4,%dl
  or     %esi,%edx
  mov    %dl,(%rcx)
  movzbl 0x1(%rax),%edx
  movsbl (%rsp,%rdx,1),%esi
  shl    $0x4,%esi
  movzbl 0x2(%rax),%edx
  movzbl (%rsp,%rdx,1),%edx
  sar    $0x2,%dl
  or     %esi,%edx
  mov    %dl,0x1(%rcx)
  movzbl 0x2(%rax),%edx
  movsbl (%rsp,%rdx,1),%edx
  shl    $0x6,%edx
  movzbl 0x3(%rax),%esi
  or     (%rsp,%rsi,1),%dl
  mov    %dl,0x2(%rcx)
  add    $0x4,%rax
  add    $0x3,%rcx
  cmp    %rdi,%rax
  jne    L26
  lea    0x3(%r8,%r8,2),%eax
L38:
  movslq %eax,%rdx
  movb   $0x0,(%r9,%rdx,1)
  mov    0x108(%rsp),%rdx
  sub    %fs:0x28,%rdx
  jne    L12
  add    $0x118,%rsp
  ret
L32:
  mov    $0x0,%eax
  jmp    L38
L12:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int http_base64decode(unsigned char *src, int src_len, unsigned char *dst) {
  int i = 0, j = 0;
  char base64_decode_map[256] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 0, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255, 255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255};
  for (; i < src_len; i += 4) {
    dst[j++] = (base64_decode_map[src[i]] << 2) | (base64_decode_map[src[i + 1]] >> 4);
    dst[j++] = (base64_decode_map[src[i + 1]] << 4) | (base64_decode_map[src[i + 2]] >> 2);
    dst[j++] = (base64_decode_map[src[i + 2]] << 6) | (base64_decode_map[src[i + 3]]);
  }
  dst[j] = '\0';
  return j;
}
```