user: 请从给定的汇编指令推导出C源代码:

```asm
<long_c2i>:
  endbr64
  sub    $0x18,%rsp
  mov    %fs:0x28,%rax
  mov    %rax,0x8(%rsp)
  xor    %eax,%eax
  cmp    $0x8,%edx
  jg     L234
  test   %edx,%edx
  je     L244
  movzbl (%rsi),%eax
  mov    %rsi,%rcx
  test   %al,%al
  js     L39
  test   %edx,%edx
  jle    L244
  cmp    $0x1,%edx
  je     L153
  movzbl 0x1(%rsi),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x2,%edx
  je     L153
  movzbl 0x2(%rcx),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x3,%edx
  je     L153
  movzbl 0x3(%rcx),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x4,%edx
  je     L153
  movzbl 0x4(%rcx),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x5,%edx
  je     L153
  movzbl 0x5(%rcx),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x6,%edx
  je     L153
  movzbl 0x6(%rcx),%esi
  shl    $0x8,%rax
  or     %rsi,%rax
  cmp    $0x8,%edx
  jne    L153
  movzbl 0x7(%rcx),%edx
  shl    $0x8,%rax
  or     %rdx,%rax
L153:
  mov    %rax,(%rsp)
L66:
  cmp    %rax,(%r9)
  je     L234
  mov    %rsp,%rsi
  mov    $0x8,%edx
  call   <memcpy@plt>
  mov    $0x1,%eax
L52:
  mov    0x8(%rsp),%rdx
  sub    %fs:0x28,%rdx
  jne    L232
  add    $0x18,%rsp
  ret
  nopl   0x0(%rax,%rax,1)
L234:
  mov    D4(%rip),%rax
  mov    (%rax),%edi
  call   <ASN1error@plt>
  xor    %eax,%eax
  jmp    L52
  nopw   0x0(%rax,%rax,1)
L244:
  movq   $0x0,(%rsp)
  xor    %eax,%eax
  jmp    L66
  nopl   0x0(%rax)
L39:
  test   %edx,%edx
  jle    L152
  not    %eax
  movzbl %al,%eax
  cmp    $0x1,%edx
  je     L157
  movzbl 0x1(%rsi),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x2,%edx
  je     L157
  movzbl 0x2(%rcx),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x3,%edx
  je     L157
  movzbl 0x3(%rcx),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x4,%edx
  je     L157
  movzbl 0x4(%rcx),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x5,%edx
  je     L157
  movzbl 0x5(%rcx),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x6,%edx
  je     L157
  movzbl 0x6(%rcx),%esi
  shl    $0x8,%rax
  not    %esi
  movzbl %sil,%esi
  or     %rsi,%rax
  cmp    $0x8,%edx
  jne    L157
  movzbl 0x7(%rcx),%edx
  shl    $0x8,%rax
  not    %edx
  movzbl %dl,%edx
  or     %rdx,%rax
L157:
  not    %rax
  jmp    L153
L152:
  mov    $0xffffffffffffffff,%rax
  jmp    L153
L232:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int long_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len, int utype, char *free_cont, const ASN1_ITEM *it) {
  int neg, i;
  long ltmp;
  unsigned long utmp = 0;
  char *cp = (char *)pval;
  if (len > (int)sizeof(long)) {
    ASN1error(ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);
    return 0;
  }
  if (len && (cont[0] & 0x80))
    neg = 1;
  else
    neg = 0;
  utmp = 0;
  for (i = 0; i < len; i++) {
    utmp <<= 8;
    if (neg)
      utmp |= cont[i] ^ 0xff;
    else
      utmp |= cont[i];
  }
  ltmp = (long)utmp;
  if (neg) {
    ltmp++;
    ltmp = -ltmp;
  }
  if (ltmp == it->size) {
    ASN1error(ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);
    return 0;
  }
  memcpy(cp, &ltmp, sizeof(long));
  return 1;
}
```