user: 请显示与下面列出的汇编代码相匹配的C语言实现:

```asm
<decode64>:
  endbr64
  movzbl (%rdi),%eax
  mov    %rdi,%rdx
  cmp    $0x3d,%al
  je     L133
  xor    %r8d,%r8d
  xor    %ecx,%ecx
  cmp    $0x20,%al
  jle    L133
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  cmp    $0x3d,%al
  je     L409
  nop
L270:
  movsbl %al,%esi
  lea    0x1(%rcx),%ebp
  lea    -0x41(%rsi),%edi
  cmp    $0x19,%edi
  jbe    L493
  lea    -0x61(%rsi),%edi
  cmp    $0x19,%edi
  jbe    L411
  sub    $0x30,%esi
  cmp    $0x9,%esi
  jbe    L230
  cmp    $0x2b,%al
  je     L34
  cmp    $0x2f,%al
  je     L148
  nopw   0x0(%rax,%rax,1)
L419:
  lea    0x0(,%r10,4),%edi
L190:
  movslq %ebp,%rax
  add    %rdx,%rax
  movzbl (%rax),%esi
  cmp    $0x3d,%sil
  je     L115
L505:
  movsbl %sil,%eax
  lea    0x2(%rcx),%ebp
  lea    -0x41(%rax),%r12d
  cmp    $0x19,%r12d
  jbe    L203
  lea    -0x61(%rax),%r12d
  cmp    $0x19,%r12d
  jbe    L324
  lea    -0x30(%rax),%r12d
  cmp    $0x9,%r12d
  jbe    L151
  cmp    $0x2b,%eax
  je     L368
  cmp    $0x2f,%eax
  je     L44
  xchg   %ax,%ax
L423:
  mov    %r9d,%r13d
  sar    $0x4,%r13b
L401:
  movslq %ebp,%rax
  add    %rdx,%rax
  movzbl (%rax),%esi
  cmp    $0x3d,%sil
  je     L271
L136:
  movsbl %sil,%eax
  lea    0x3(%rcx),%ebp
  lea    -0x41(%rax),%r12d
  cmp    $0x19,%r12d
  jbe    L187
  lea    -0x61(%rax),%r12d
  cmp    $0x19,%r12d
  jbe    L71
  lea    -0x30(%rax),%r12d
  cmp    $0x9,%r12d
  jbe    L263
  cmp    $0x2b,%eax
  je     L139
  cmp    $0x2f,%eax
  je     L507
  nopl   (%rax)
L80:
  mov    %r11d,%r12d
  sar    $0x2,%r12b
L113:
  movslq %ebp,%rax
  add    %rdx,%rax
  movzbl (%rax),%esi
  cmp    $0x3d,%sil
  je     L108
L138:
  add    $0x4,%ecx
  movsbl %sil,%ebp
  movslq %ecx,%rax
  lea    -0x41(%rbp),%r14d
  add    %rdx,%rax
  cmp    $0x19,%r14d
  jbe    L116
  lea    -0x61(%rbp),%r14d
  cmp    $0x19,%r14d
  jbe    L280
  lea    -0x30(%rbp),%r14d
  cmp    $0x9,%r14d
  jbe    L350
  cmp    $0x2b,%ebp
  je     L448
  cmp    $0x2f,%ebp
  mov    $0x3f,%esi
  mov    $0x4,%ebp
  cmove  %esi,%ebx
  nopw   0x0(%rax,%rax,1)
L229:
  or     %r13d,%edi
  lea    0x2(%r8),%r13d
  movslq %r8d,%rsi
  mov    %dil,(%rdx,%rsi,1)
  mov    %r9d,%edi
  lea    0x1(%r8),%esi
  shl    $0x4,%edi
  movslq %esi,%rsi
  or     %r12d,%edi
  mov    %dil,(%rdx,%rsi,1)
  cmp    $0x4,%ebp
  je     L342
  mov    %r13d,%r8d
L169:
  movzbl (%rax),%eax
  cmp    $0x20,%al
  jle    L364
  cmp    $0x3d,%al
  jne    L270
L364:
  movslq %r8d,%rax
  pop    %rbx
  pop    %rbp
  add    %rax,%rdx
  pop    %r12
  mov    %r8d,%eax
  pop    %r13
  movb   $0x0,(%rdx)
  pop    %r14
  ret
  nopw   0x0(%rax,%rax,1)
L493:
  lea    -0x41(%rax),%r10d
  jmp    L419
  nopl   0x0(%rax)
L203:
  lea    -0x41(%rsi),%r9d
  jmp    L423
  nopl   0x0(%rax)
L187:
  lea    -0x41(%rsi),%r11d
  jmp    L80
  nopl   0x0(%rax)
L116:
  lea    -0x41(%rsi),%ebx
  mov    $0x4,%ebp
  jmp    L229
  nopl   (%rax)
L411:
  lea    -0x47(%rax),%r10d
  movslq %ebp,%rax
  add    %rdx,%rax
  lea    0x0(,%r10,4),%edi
  movzbl (%rax),%esi
  cmp    $0x3d,%sil
  jne    L505
L115:
  mov    %r9d,%r13d
  mov    %ebp,%ecx
  sar    $0x4,%r13b
  jmp    L293
  nopl   (%rax)
L324:
  movslq %ebp,%rax
  lea    -0x47(%rsi),%r9d
  add    %rdx,%rax
  mov    %r9d,%r13d
  movzbl (%rax),%esi
  sar    $0x4,%r13b
  cmp    $0x3d,%sil
  jne    L136
L271:
  mov    %ebp,%ecx
  jmp    L293
  nopl   (%rax)
L71:
  movslq %ebp,%rax
  lea    -0x47(%rsi),%r11d
  add    %rdx,%rax
  mov    %r11d,%r12d
  movzbl (%rax),%esi
  sar    $0x2,%r12b
  cmp    $0x3d,%sil
  jne    L138
L108:
  mov    %ebp,%ecx
  mov    $0x3,%ebp
  jmp    L229
  nopw   0x0(%rax,%rax,1)
L280:
  lea    -0x47(%rsi),%ebx
  mov    $0x4,%ebp
  jmp    L229
  nopl   (%rax)
L342:
  mov    %r11d,%esi
  movslq %r13d,%r13
  add    $0x3,%r8d
  shl    $0x6,%esi
  or     %ebx,%esi
  mov    %sil,(%rdx,%r13,1)
  jmp    L169
  nopl   0x0(%rax,%rax,1)
L230:
  lea    0x4(%rax),%r10d
  lea    0x0(,%r10,4),%edi
  jmp    L190
  nopl   0x0(%rax)
L151:
  lea    0x4(%rsi),%r9d
  mov    %r9d,%r13d
  sar    $0x4,%r13b
  jmp    L401
  nopl   0x0(%rax,%rax,1)
L263:
  lea    0x4(%rsi),%r11d
  mov    %r11d,%r12d
  sar    $0x2,%r12b
  jmp    L113
L350:
  lea    0x4(%rsi),%ebx
  mov    $0x4,%ebp
  jmp    L229
L148:
  mov    $0xfffffffc,%edi
  mov    $0x3f,%r10d
  jmp    L190
L44:
  mov    $0x3,%r13d
  mov    $0x3f,%r9d
  jmp    L401
L409:
  mov    %r9d,%r13d
  movslq %ecx,%rax
  lea    0x0(,%r10,4),%edi
  sar    $0x4,%r13b
  add    %rdx,%rax
L293:
  movslq %r8d,%rsi
  or     %edi,%r13d
  add    $0x1,%r8d
  mov    %r13b,(%rdx,%rsi,1)
  jmp    L169
L34:
  mov    $0xfffffff8,%edi
  mov    $0x3e,%r10d
  jmp    L190
L368:
  mov    $0x3,%r13d
  mov    $0x3e,%r9d
  jmp    L401
L139:
  mov    $0xf,%r12d
  mov    $0x3e,%r11d
  jmp    L113
L448:
  mov    $0x3e,%ebx
  mov    $0x4,%ebp
  jmp    L229
L507:
  mov    $0xf,%r12d
  mov    $0x3f,%r11d
  jmp    L113
L133:
  xor    %r8d,%r8d
  movb   $0x0,(%rdx)
  mov    %r8d,%eax
  ret
```

assistant: ```c
int decode64(char *buffer) {
  int car;
  char valcar[4];
  int i;
  int posorig;
  int posdest;
  posorig = 0;
  posdest = 0;
  while (buffer[posorig] > ' ' && buffer[posorig] != '=') {
    for (i = 0; i < 4 && buffer[posorig] != '='; i++) {
      car = buffer[posorig++];
      if ('A' <= car && car <= 'Z')
        valcar[i] = car - 'A';
      else if ('a' <= car && car <= 'z')
        valcar[i] = car + 26 - 'a';
      else if ('0' <= car && car <= '9')
        valcar[i] = car + 52 - '0';
      else if (car == '+')
        valcar[i] = 62;
      else if (car == '/')
        valcar[i] = 63;
    }
    buffer[posdest++] = (valcar[0] << 2) | (valcar[1] >> 4);
    if (i > 2) {
      buffer[posdest++] = (valcar[1] << 4) | (valcar[2] >> 2);
      if (i > 3)
        buffer[posdest++] = (valcar[2] << 6) | (valcar[3]);
    }
  }
  buffer[posdest] = '\0';
  return (posdest);
}
```