user: 下面的汇编指令对应的C源代码是什么:

```asm
<css_decode>:
  endbr64
  test   %rdi,%rdi
  je     L187
  push   %r15
  push   %r14
  push   %r13
  mov    %rsi,%r13
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  mov    %rdi,%rbp
  push   %rbx
  sub    $0x18,%rsp
  test   %rsi,%rsi
  jle    L153
  xor    %ebx,%ebx
  jmp    L286
  nopl   0x0(%rax)
L264:
  mov    %al,0x0(%rbp)
  mov    %r14,%rbx
  add    $0x1,%rbp
L106:
  cmp    %r13,%rbx
  jge    L308
L286:
  movzbl (%r12,%rbx,1),%eax
  mov    %rbx,%r15
  lea    0x1(%rbx),%r14
  cmp    $0x5c,%al
  jne    L264
  cmp    %r13,%r14
  jl     L41
L308:
  mov    %ebp,%eax
  sub    %r12d,%eax
L10:
  movb   $0x0,0x0(%rbp)
  add    $0x18,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L41:
  lea    (%r12,%r14,1),%r8
  lea    0x2(%rbx),%rdx
  movzbl (%r8),%eax
  lea    -0x30(%rax),%ecx
  cmp    $0x9,%cl
  ja     L337
L175:
  cmp    %r13,%rdx
  jge    L46
  movzbl (%r12,%rdx,1),%eax
  lea    -0x30(%rax),%ecx
  cmp    $0x9,%cl
  ja     L26
L245:
  lea    0x3(%rbx),%rcx
  mov    %rcx,%rdx
  cmp    %rcx,%r13
  jle    L8
  movzbl 0x3(%r12,%rbx,1),%eax
  lea    -0x30(%rax),%esi
  cmp    $0x9,%sil
  ja     L236
L269:
  lea    0x4(%rbx),%rsi
  mov    %rsi,%rdx
  cmp    %rsi,%r13
  jle    L197
  movzbl 0x4(%r12,%rbx,1),%eax
  lea    -0x30(%rax),%edi
  cmp    $0x9,%dil
  ja     L117
L411:
  lea    0x5(%rbx),%rdx
  cmp    %rdx,%r13
  jle    L314
  movzbl 0x5(%r12,%rbx,1),%eax
  lea    -0x30(%rax),%edi
  cmp    $0x9,%dil
  ja     L206
L92:
  lea    0x6(%rbx),%rcx
  cmp    %rcx,%r13
  jle    L199
  movzbl 0x6(%r12,%rbx,1),%eax
  lea    -0x30(%rax),%edi
  cmp    $0x9,%dil
  jbe    L65
  and    $0xffffffdf,%eax
  sub    $0x41,%eax
  cmp    $0x5,%al
  ja     L199
L65:
  lea    (%r12,%rdx,1),%rdi
  mov    %r8,(%rsp)
  add    $0x7,%rbx
  call   <x2c@plt>
  mov    (%rsp),%r8
  mov    %al,0x0(%rbp)
  mov    %eax,%esi
  cmpb   $0x30,(%r8)
  je     L365
L220:
  add    $0x1,%rbp
  mov    $0x6,%r15d
  nopl   0x0(%rax,%rax,1)
L14:
  cmp    %rbx,%r13
  jle    L308
  movzbl (%r12,%rbx,1),%edi
  call   <isspace@plt>
  test   %rax,%rax
  je     L286
  lea    0x1(%r15,%r14,1),%rbx
  jmp    L106
  cs nopw 0x0(%rax,%rax,1)
L337:
  mov    %eax,%ecx
  and    $0xffffffdf,%ecx
  sub    $0x41,%ecx
  cmp    $0x5,%cl
  jbe    L175
  mov    %rdx,%rbx
  cmp    $0xa,%al
  je     L106
  mov    %al,0x0(%rbp)
  add    $0x1,%rbp
  jmp    L106
  nopl   0x0(%rax,%rax,1)
L26:
  and    $0xffffffdf,%eax
  sub    $0x41,%eax
  cmp    $0x5,%al
  jbe    L245
L46:
  mov    %r8,%rdi
  mov    %rdx,(%rsp)
  add    $0x1,%rbp
  mov    $0x1,%r15d
  call   <xsingle2c@plt>
  mov    (%rsp),%rbx
  mov    %al,-0x1(%rbp)
  jmp    L14
L236:
  and    $0xffffffdf,%eax
  sub    $0x41,%eax
  cmp    $0x5,%al
  jbe    L269
L8:
  mov    %rdx,%rbx
  mov    $0x2,%r15d
L276:
  lea    -0x2(%r12,%rdx,1),%rdi
  add    $0x1,%rbp
  call   <x2c@plt>
  mov    %al,-0x1(%rbp)
  jmp    L14
  nopl   (%rax)
L117:
  and    $0xffffffdf,%eax
  sub    $0x41,%eax
  cmp    $0x5,%al
  jbe    L411
L197:
  mov    %rdx,%rbx
  mov    $0x3,%r15d
  jmp    L276
  nopl   0x0(%rax)
L206:
  and    $0xffffffdf,%eax
  sub    $0x41,%eax
  cmp    $0x5,%al
  jbe    L92
L314:
  lea    (%r12,%rcx,1),%rdi
  mov    %rdx,(%rsp)
  mov    $0x4,%r15d
  call   <x2c@plt>
  mov    (%rsp),%rbx
  mov    %al,0x0(%rbp)
  mov    %eax,%esi
L201:
  lea    -0x1(%rsi),%eax
  cmp    $0x5d,%al
  ja     L362
  movzbl -0x3(%r12,%rbx,1),%eax
  and    $0xffffffdf,%eax
  cmp    $0x46,%al
  jne    L362
  movzbl -0x4(%r12,%rbx,1),%eax
  and    $0xffffffdf,%eax
  cmp    $0x46,%al
  jne    L362
  add    $0x20,%esi
  mov    %sil,0x0(%rbp)
  nopw   0x0(%rax,%rax,1)
L362:
  add    $0x1,%rbp
  jmp    L14
  nopl   0x0(%rax)
L153:
  xor    %eax,%eax
  jmp    L10
L199:
  lea    (%r12,%rsi,1),%rdi
  mov    %rcx,0x8(%rsp)
  mov    %r8,(%rsp)
  call   <x2c@plt>
  mov    (%rsp),%r8
  mov    0x8(%rsp),%rcx
  mov    %al,0x0(%rbp)
  mov    %eax,%esi
  cmpb   $0x30,(%r8)
  je     L339
  add    $0x1,%rbp
  mov    %rcx,%rbx
  mov    $0x5,%r15d
  jmp    L14
L339:
  mov    %rcx,%rbx
  mov    $0x5,%r15d
  jmp    L201
L365:
  cmpb   $0x30,0x2(%r12,%r15,1)
  jne    L220
  mov    $0x6,%r15d
  jmp    L201
L187:
  mov    $0xffffffff,%eax
  ret
```

assistant: ```c
int css_decode(unsigned char *input, long int input_len) {
  unsigned char *d = (unsigned char *)input;
  long int i, j, count;
  if (input == NULL)
    return -1;
  i = count = 0;
  while (i < input_len) {
    if (input[i] == '\\') {
      if (i + 1 < input_len) {
        i++;
        j = 0;
        while ((j < 6) && (i + j < input_len) && ((((input[i + j] >= '0') && (input[i + j] <= '9')) || ((input[i + j] >= 'a') && (input[i + j] <= 'f')) || ((input[i + j] >= 'A') && (input[i + j] <= 'F'))))) {
          j++;
        }
        if (j > 0) {
          int fullcheck = 0;
          switch (j) {
          case 1:
            *d++ = xsingle2c(&input[i]);
            break;
          case 2:
          case 3:
            *d++ = x2c(&input[i + j - 2]);
            break;
          case 4:
            *d = x2c(&input[i + j - 2]);
            fullcheck = 1;
            break;
          case 5:
            *d = x2c(&input[i + j - 2]);
            if (input[i] == '0') {
              fullcheck = 1;
            } else {
              d++;
            }
            break;
          case 6:
            *d = x2c(&input[i + j - 2]);
            if ((input[i] == '0') && (input[i + 1] == '0')) {
              fullcheck = 1;
            } else {
              d++;
            }
            break;
          }
          if (fullcheck) {
            if ((*d > 0x00) && (*d < 0x5f) && ((input[i + j - 3] == 'f') || (input[i + j - 3] == 'F')) && ((input[i + j - 4] == 'f') || (input[i + j - 4] == 'F'))) {
              (*d) += 0x20;
            }
            d++;
          }
          if ((i + j < input_len) && isspace(input[i + j])) {
            j++;
          }
          count++;
          i += j;
        } else if (input[i] == '\n') {
          i++;
        } else {
          *d++ = input[i++];
          count++;
        }
      } else {
        i++;
      }
    } else {
      *d++ = input[i++];
      count++;
    }
  }
  *d = '\0';
  return d - input;
}
```