user: 请显示与下面列出的汇编代码相匹配的C语言实现:

```asm
<str_decode>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x250,%rsp
  mov    %rdi,-0x248(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x8(%rbp)
  xor    %eax,%eax
  mov    -0x248(%rbp),%rax
  mov    %rax,-0x230(%rbp)
  lea    -0x210(%rbp),%rax
  mov    %rax,-0x228(%rbp)
  movl   $0x0,-0x238(%rbp)
  jmp    L10
L25:
  mov    -0x230(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3d,%al
  je     L259
  mov    -0x230(%rbp),%rax
  mov    %rax,-0x220(%rbp)
  jmp    L48
L232:
  addq   $0x1,-0x220(%rbp)
L48:
  cmpl   $0x0,-0x238(%rbp)
  je     L151
  mov    -0x220(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L151
  mov    -0x220(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  mov    %eax,%edi
  call   <isspace@plt>
  test   %eax,%eax
  jne    L232
L151:
  cmpl   $0x0,-0x238(%rbp)
  je     L56
  mov    -0x220(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3d,%al
  jne    L56
  movl   $0x0,-0x238(%rbp)
  mov    -0x220(%rbp),%rax
  mov    %rax,-0x230(%rbp)
  jmp    L10
L56:
  mov    -0x230(%rbp),%rdx
  lea    0x1(%rdx),%rax
  mov    %rax,-0x230(%rbp)
  mov    -0x228(%rbp),%rax
  lea    0x1(%rax),%rcx
  mov    %rcx,-0x228(%rbp)
  movzbl (%rdx),%edx
  mov    %dl,(%rax)
  jmp    L10
L259:
  mov    -0x230(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x218(%rbp)
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3f,%al
  jne    L79
  addq   $0x1,-0x218(%rbp)
  jmp    L105
L3:
  addq   $0x1,-0x218(%rbp)
L105:
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L206
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3f,%al
  jne    L3
L206:
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L79
  mov    -0x218(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L79
  mov    -0x218(%rbp),%rax
  add    $0x2,%rax
  movzbl (%rax),%eax
  cmp    $0x3f,%al
  jne    L79
  mov    -0x218(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  mov    -0x218(%rbp),%rdx
  lea    0x3(%rdx),%rcx
  mov    -0x228(%rbp),%rdx
  mov    %eax,%esi
  mov    %rcx,%rdi
  mov    $0x0,%eax
  call   <mmdecode_header@plt>
  mov    %eax,-0x234(%rbp)
  cmpl   $0x0,-0x234(%rbp)
  js     L79
  addq   $0x3,-0x218(%rbp)
  nop
L164:
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L168
  mov    -0x218(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x218(%rbp)
  movzbl (%rax),%eax
  cmp    $0x3f,%al
  jne    L164
L168:
  mov    -0x218(%rbp),%rax
  movzbl (%rax),%eax
  cmp    $0x3d,%al
  jne    L235
  addq   $0x1,-0x218(%rbp)
L235:
  mov    -0x218(%rbp),%rax
  mov    %rax,-0x230(%rbp)
  mov    -0x234(%rbp),%eax
  cltq
  add    %rax,-0x228(%rbp)
  movl   $0x1,-0x238(%rbp)
  jmp    L79
L11:
  mov    -0x230(%rbp),%rdx
  lea    0x1(%rdx),%rax
  mov    %rax,-0x230(%rbp)
  mov    -0x228(%rbp),%rax
  lea    0x1(%rax),%rcx
  mov    %rcx,-0x228(%rbp)
  movzbl (%rdx),%edx
  mov    %dl,(%rax)
L79:
  mov    -0x230(%rbp),%rax
  cmp    -0x218(%rbp),%rax
  jne    L11
L10:
  mov    -0x230(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  je     L67
  lea    -0x210(%rbp),%rdx
  mov    -0x228(%rbp),%rax
  sub    %rdx,%rax
  cmp    $0x1fe,%rax
  jbe    L25
L67:
  mov    -0x228(%rbp),%rax
  movb   $0x0,(%rax)
  lea    -0x210(%rbp),%rdx
  mov    -0x248(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcpy@plt>
  nop
  mov    -0x8(%rbp),%rax
  sub    %fs:0x28,%rax
  je     L226
  call   <__stack_chk_fail@plt>
L226:
  leave
  ret
```

assistant: ```c
void str_decode(str) unsigned char *str;
{
  int adj;
  unsigned char *src, *dst;
  unsigned char buf[512];
  src = str;
  dst = buf;
  adj = 0;
  while (*src && (dst - buf) < sizeof(buf) - 1) {
    if (*src != '=') {
      unsigned char *tmp = src;
      while (adj && *tmp && isspace(*tmp))
        tmp++;
      if (adj && *tmp == '=') {
        adj = 0;
        src = tmp;
      } else
        *dst++ = *src++;
    } else {
      unsigned char *tmp = src + 1;
      if (*tmp == '?') {
        tmp++;
        while (*tmp && *tmp != '?')
          tmp++;
        if (*tmp && tmp[1] && tmp[2] == '?') {
          int i = mmdecode_header(tmp + 3, tmp[1], dst);
          if (i >= 0) {
            tmp += 3;
            while (*tmp && *tmp++ != '?')
              ;
            if (*tmp == '=')
              tmp++;
            src = tmp;
            dst += i;
            adj = 1;
          }
        }
      }
      while (src != tmp)
        *dst++ = *src++;
    }
  }
  *dst = 0;
  strcpy(str, buf);
}
```