user: What is the c source code of the assembly code below?

```asm
<unmeng>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x38(%rbp)
  mov    %esi,-0x3c(%rbp)
  mov    %rdx,-0x48(%rbp)
  mov    %ecx,-0x40(%rbp)
  mov    -0x3c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x10(%rbp)
  mov    -0x48(%rbp),%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x40(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x48(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x8(%rbp)
  jmp    L53
L135:
  mov    -0x38(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  mov    %eax,-0x24(%rbp)
  cmpl   $0x7f,-0x24(%rbp)
  ja     L92
  mov    -0x24(%rbp),%eax
  and    $0xf,%eax
  not    %rax
  mov    %rax,%rdx
  mov    -0x20(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  cmp    -0x48(%rbp),%rax
  jae    L152
  mov    $0xffffffff,%eax
  jmp    L175
L152:
  mov    -0x24(%rbp),%eax
  shr    $0x4,%eax
  add    $0x3,%eax
  mov    %eax,-0x24(%rbp)
  addq   $0x1,-0x38(%rbp)
  jmp    L66
L92:
  mov    -0x24(%rbp),%eax
  and    $0xe0,%eax
  cmp    $0x80,%eax
  jne    L64
  mov    -0x24(%rbp),%eax
  and    $0x1f,%eax
  add    $0x1,%eax
  mov    %eax,-0x24(%rbp)
  addq   $0x1,-0x38(%rbp)
  mov    -0x38(%rbp),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x24(%rbp),%eax
  add    %rax,-0x38(%rbp)
  jmp    L66
L64:
  mov    -0x24(%rbp),%eax
  and    $0xc0,%eax
  cmp    $0xc0,%eax
  jne    L83
  mov    -0x24(%rbp),%eax
  and    $0x3f,%eax
  add    $0x4,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x38(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  not    %rax
  mov    %rax,%rdx
  mov    -0x20(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  cmp    -0x48(%rbp),%rax
  jae    L139
  mov    $0xffffffff,%eax
  jmp    L175
L139:
  addq   $0x2,-0x38(%rbp)
  jmp    L66
L83:
  mov    -0x24(%rbp),%eax
  and    $0xf0,%eax
  cmp    $0xa0,%eax
  jne    L143
  mov    -0x24(%rbp),%eax
  shl    $0x8,%eax
  and    $0xf00,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  or     %edx,%eax
  add    $0x20,%eax
  mov    %eax,-0x24(%rbp)
  addq   $0x2,-0x38(%rbp)
  mov    -0x38(%rbp),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x24(%rbp),%eax
  add    %rax,-0x38(%rbp)
  jmp    L66
L143:
  mov    -0x24(%rbp),%eax
  shl    $0x8,%eax
  and    $0xf00,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  or     %edx,%eax
  add    $0x6,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x38(%rbp),%rax
  add    $0x2,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  shl    $0x8,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x3,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  or     %edx,%eax
  cltq
  not    %rax
  mov    %rax,%rdx
  mov    -0x20(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  cmp    -0x48(%rbp),%rax
  jae    L61
  mov    $0xffffffff,%eax
  jmp    L175
L61:
  addq   $0x4,-0x38(%rbp)
  jmp    L66
L70:
  mov    -0x20(%rbp),%rax
  cmp    -0x8(%rbp),%rax
  jb     L121
  jmp    L53
L121:
  mov    -0x18(%rbp),%rdx
  lea    0x1(%rdx),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x20(%rbp),%rax
  lea    0x1(%rax),%rcx
  mov    %rcx,-0x20(%rbp)
  movzbl (%rdx),%edx
  mov    %dl,(%rax)
L66:
  mov    -0x24(%rbp),%eax
  lea    -0x1(%rax),%edx
  mov    %edx,-0x24(%rbp)
  test   %eax,%eax
  jne    L70
L53:
  mov    -0x38(%rbp),%rax
  cmp    -0x10(%rbp),%rax
  jae    L50
  mov    -0x20(%rbp),%rax
  cmp    -0x8(%rbp),%rax
  jb     L135
L50:
  mov    -0x20(%rbp),%rax
  sub    -0x48(%rbp),%rax
L175:
  pop    %rbp
  ret
```

assistant: ```c
int unmeng(unsigned char *in, int insz, unsigned char *out, int outsz) {
  unsigned a;
  unsigned char *o, *outl, *inl, *slide;
  inl = in + insz;
  o = out;
  outl = out + outsz;
  while ((in < inl) && (o < outl)) {
    a = in[0];
    if (a < 0x80) {
      slide = (o - (a & 0x0f)) - 1;
      if (slide < out)
        return (-1);
      a = (a >> 4) + 3;
      in++;
    } else if ((a & 0xe0) == 0x80) {
      a = (a & 0x1F) + 1;
      in++;
      slide = in;
      in += a;
    } else if ((a & 0xc0) == 0xc0) {
      a = (a & 0x3F) + 4;
      slide = (o - in[1]) - 1;
      if (slide < out)
        return (-1);
      in += 2;
    } else if ((a & 0xf0) == 0xa0) {
      a = (((a & 0x0F) << 8) | in[1]) + 32;
      in += 2;
      slide = in;
      in += a;
    } else {
      a = (((a & 0x0F) << 8) | in[1]) + 6;
      slide = (o - ((in[2] << 8) | in[3])) - 1;
      if (slide < out)
        return (-1);
      in += 4;
    }
    while (a--) {
      if (o >= outl)
        break;
      *o++ = *slide++;
    }
  }
  return (o - out);
}
```