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

```asm
<scanexp>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x40,%rsp
  mov    %rdi,-0x28(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    %edx,-0x34(%rbp)
  movl   $0x0,-0xc(%rbp)
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <shgetc@plt>
  mov    %eax,-0x14(%rbp)
  cmpl   $0x2b,-0x14(%rbp)
  je     L105
  cmpl   $0x2d,-0x14(%rbp)
  jne    L48
L105:
  cmpl   $0x2d,-0x14(%rbp)
  sete   %al
  movzbl %al,%eax
  mov    %eax,-0xc(%rbp)
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <shgetc@plt>
  mov    %eax,-0x14(%rbp)
  mov    -0x14(%rbp),%eax
  sub    $0x30,%eax
  cmp    $0x9,%eax
  jbe    L48
  cmpl   $0x0,-0x34(%rbp)
  je     L48
  mov    -0x30(%rbp),%rax
  mov    %rax,%rdi
  call   <shunget@plt>
L48:
  mov    -0x14(%rbp),%eax
  sub    $0x30,%eax
  cmp    $0x9,%eax
  jbe    L81
  mov    -0x30(%rbp),%rax
  mov    %rax,%rdi
  call   <shunget@plt>
  mov    D0(%rip),%rax
  mov    (%rax),%rax
  jmp    L72
L81:
  movl   $0x0,-0x10(%rbp)
  jmp    L64
L122:
  mov    -0x10(%rbp),%edx
  mov    %edx,%eax
  shl    $0x2,%eax
  add    %edx,%eax
  add    %eax,%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  sub    $0x30,%eax
  mov    %eax,-0x10(%rbp)
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <shgetc@plt>
  mov    %eax,-0x14(%rbp)
L64:
  mov    -0x14(%rbp),%eax
  sub    $0x30,%eax
  cmp    $0x9,%eax
  ja     L34
  mov    D17(%rip),%rax
  mov    (%rax),%eax
  movslq %eax,%rdx
  imul   $0x66666667,%rdx,%rdx
  shr    $0x20,%rdx
  sar    $0x2,%edx
  sar    $0x1f,%eax
  mov    %eax,%ecx
  mov    %edx,%eax
  sub    %ecx,%eax
  cmp    %eax,-0x10(%rbp)
  jl     L122
L34:
  mov    -0x10(%rbp),%eax
  cltq
  mov    %rax,-0x8(%rbp)
  jmp    L36
L13:
  mov    -0x8(%rbp),%rdx
  mov    %rdx,%rax
  shl    $0x2,%rax
  add    %rdx,%rax
  add    %rax,%rax
  mov    %rax,%rdx
  mov    -0x14(%rbp),%eax
  cltq
  add    %rdx,%rax
  sub    $0x30,%rax
  mov    %rax,-0x8(%rbp)
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <shgetc@plt>
  mov    %eax,-0x14(%rbp)
L36:
  mov    -0x14(%rbp),%eax
  sub    $0x30,%eax
  cmp    $0x9,%eax
  ja     L123
  mov    D26(%rip),%rax
  mov    (%rax),%eax
  movslq %eax,%rdx
  imul   $0x51eb851f,%rdx,%rdx
  shr    $0x20,%rdx
  sar    $0x5,%edx
  sar    $0x1f,%eax
  mov    %eax,%ecx
  mov    %edx,%eax
  sub    %ecx,%eax
  cltq
  cmp    %rax,-0x8(%rbp)
  jl     L13
  jmp    L123
L40:
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <shgetc@plt>
  mov    %eax,-0x14(%rbp)
L123:
  mov    -0x14(%rbp),%eax
  sub    $0x30,%eax
  cmp    $0x9,%eax
  jbe    L40
  mov    -0x30(%rbp),%rax
  mov    %rax,%rdi
  call   <shunget@plt>
  cmpl   $0x0,-0xc(%rbp)
  je     L51
  mov    -0x8(%rbp),%rax
  neg    %rax
  jmp    L72
L51:
  mov    -0x8(%rbp),%rax
L72:
  leave
  ret
```

assistant: ```c
long long scanexp(char *input, int *index, int pok) {
  int c;
  int x;
  long long y;
  int neg = 0;
  c = shgetc(input, index);
  if (c == '+' || c == '-') {
    neg = (c == '-');
    c = shgetc(input, index);
    if ((unsigned)(c - '0') >= 10U && pok)
      shunget(index);
  }
  if ((unsigned)(c - '0') >= 10U) {
    shunget(index);
    return LLONG_MIN;
  }
  for (x = 0; (unsigned)(c - '0') < 10U && x < INT_MAX / 10; c = shgetc(input, index))
    x = 10 * x + c - '0';
  for (y = x; (unsigned)(c - '0') < 10U && y < LLONG_MAX / 100; c = shgetc(input, index))
    y = 10 * y + c - '0';
  for (; (unsigned)(c - '0') < 10U; c = shgetc(input, index))
    ;
  shunget(index);
  return neg ? -y : y;
}
```