user: 请显示与下面列出的汇编代码相匹配的C语言实现：

```asm
<uudecode>:
  endbr64
  push   %r15
  mov    %rdx,%r15
  push   %r14
  push   %r13
  mov    %rdi,%r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rsi,0x8(%rsp)
  mov    %fs:0x28,%rax
  mov    %rax,0x38(%rsp)
  xor    %eax,%eax
  test   %rcx,%rcx
  jne    L191
  mov    %rdx,%rdi
  call   <strlen@plt>
  mov    %rax,%rcx
L191:
  lea    0x34(%rsp),%rax
  xor    %r14d,%r14d
  xor    %r12d,%r12d
  mov    %rax,0x18(%rsp)
  nopl   (%rax)
L199:
  cmp    %r14,0x8(%rsp)
  seta   %al
L31:
  cmp    %rcx,%r12
  jae    L217
  test   %al,%al
  je     L217
  add    $0x1,%r12
  movzbl -0x1(%r15,%r12,1),%edx
  cmp    $0x1f,%dl
  jle    L31
  lea    -0x20(%rdx),%eax
  and    $0x3f,%eax
  mov    %rax,0x10(%rsp)
  sete   %al
  cmp    %rcx,%r12
  setae  %dl
  or     %dl,%al
  jne    L217
  xor    %r11d,%r11d
  jmp    L201
  nopl   0x0(%rax)
L36:
  mov    %rax,%r11
  mov    %rbp,%r14
  mov    %rbx,%r12
L201:
  mov    0x18(%rsp),%rdi
  xor    %esi,%esi
  mov    $0x4,%edx
  mov    %rcx,0x28(%rsp)
  mov    %r11,0x20(%rsp)
  call   <memset@plt>
  mov    0x28(%rsp),%rcx
  mov    0x20(%rsp),%r11
  cmp    %r12,%rcx
  jbe    L50
  movzbl (%r15,%r12,1),%edx
  lea    0x1(%r12),%rbx
  lea    -0x20(%rdx),%eax
  cmp    $0x1f,%dl
  cmovbe %edx,%eax
  mov    %al,0x34(%rsp)
  cmp    %rbx,%rcx
  jbe    L281
  movzbl 0x1(%r15,%r12,1),%edx
  lea    0x2(%r12),%rbx
  lea    -0x20(%rdx),%eax
  cmp    $0x1f,%dl
  cmovbe %edx,%eax
  mov    %al,0x35(%rsp)
  cmp    %rcx,%rbx
  jae    L281
  movzbl 0x2(%r15,%r12,1),%edx
  lea    0x3(%r12),%rbx
  lea    -0x20(%rdx),%eax
  cmp    $0x1f,%dl
  cmovbe %edx,%eax
  mov    %al,0x36(%rsp)
  cmp    %rbx,%rcx
  jbe    L281
  movzbl 0x3(%r15,%r12,1),%eax
  lea    0x4(%r12),%rbx
  lea    -0x20(%rax),%edx
  cmp    $0x20,%al
  cmovae %edx,%eax
  cmp    %rbx,%rcx
  seta   %dl
  mov    %al,0x37(%rsp)
L72:
  movzbl 0x35(%rsp),%edi
  movzbl 0x34(%rsp),%esi
  lea    0x3(%r14),%rbp
  mov    %edi,%eax
  shl    $0x2,%esi
  sar    $0x4,%eax
  shl    $0x4,%edi
  and    $0x3,%eax
  or     %esi,%eax
  movzbl 0x36(%rsp),%esi
  mov    %al,0x0(%r13,%r14,1)
  mov    %esi,%eax
  shl    $0x6,%esi
  sar    $0x2,%eax
  and    $0xf,%eax
  or     %edi,%eax
  mov    %al,0x1(%r13,%r14,1)
  movzbl 0x37(%rsp),%eax
  and    $0x3f,%eax
  or     %esi,%eax
  mov    %al,-0x1(%r13,%rbp,1)
  lea    0x3(%r11),%rax
  cmp    %rax,0x10(%rsp)
  seta   %dil
  cmp    %rbp,0x8(%rsp)
  seta   %sil
  test   %sil,%dil
  je     L18
  test   %dl,%dl
  je     L18
  cmp    %r12,%rcx
  ja     L36
  sub    %r14,%r11
  mov    %r11,%r12
  jmp    L187
  nopw   0x0(%rax,%rax,1)
L189:
  lea    0x0(%rbp,%r12,1),%rax
  cmp    %rax,0x10(%rsp)
  jbe    L18
L187:
  mov    0x18(%rsp),%rdi
  xor    %esi,%esi
  mov    $0x4,%edx
  mov    %rcx,0x20(%rsp)
  call   <memset@plt>
  movzbl 0x35(%rsp),%edx
  movzbl 0x34(%rsp),%esi
  mov    0x20(%rsp),%rcx
  mov    %edx,%eax
  shl    $0x2,%esi
  sar    $0x4,%eax
  shl    $0x4,%edx
  and    $0x3,%eax
  or     %esi,%eax
  movzbl 0x36(%rsp),%esi
  mov    %al,0x0(%r13,%rbp,1)
  mov    %esi,%eax
  shl    $0x6,%esi
  sar    $0x2,%eax
  and    $0xf,%eax
  or     %edx,%eax
  mov    %al,0x1(%r13,%rbp,1)
  movzbl 0x37(%rsp),%eax
  add    $0x3,%rbp
  and    $0x3f,%eax
  or     %esi,%eax
  cmp    %rbp,0x8(%rsp)
  seta   %dl
  cmp    %rbx,%rcx
  mov    %al,-0x1(%r13,%rbp,1)
  seta   %al
  test   %al,%dl
  jne    L189
L18:
  cmp    %rbx,%rcx
  ja     L178
  jmp    L248
  nopl   (%rax)
L132:
  add    $0x1,%rbx
  cmp    %rcx,%rbx
  jae    L248
L178:
  cmpb   $0x20,(%r15,%rbx,1)
  jg     L132
  cmp    %rbx,%rcx
  ja     L113
  jmp    L248
  nopw   0x0(%rax,%rax,1)
L242:
  cmp    $0x20,%al
  jg     L248
  add    $0x1,%rbx
  cmp    %rcx,%rbx
  je     L248
L113:
  movzbl (%r15,%rbx,1),%eax
  test   %al,%al
  jne    L242
L248:
  mov    %rbp,%r14
  mov    %rbx,%r12
  jmp    L199
  nopl   0x0(%rax)
L281:
  xor    %edx,%edx
  jmp    L72
  nop
L50:
  xor    %edx,%edx
  mov    %r12,%rbx
  jmp    L72
L217:
  mov    %r14d,%eax
  mov    0x38(%rsp),%rdx
  sub    %fs:0x28,%rdx
  jne    L222
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L222:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int uudecode(char *target, size_t tlen, const char *source, size_t slen) {
  int i;
  char ch;
  size_t rd = 0;
  size_t wr = 0;
  size_t block;
  size_t len;
  unsigned char cell[4];
  if (slen == 0)
    slen = strlen(source);
  while (rd < slen && wr < tlen) {
    ch = source[rd++];
    if (ch < ' ')
      continue;
    len = (ch - ' ') & 0x3f;
    if (len <= 0 || rd >= slen)
      break;
    block = 0;
    while (block < len && wr < tlen && rd < slen) {
      memset(cell, 0, sizeof(cell));
      for (i = 0; i < sizeof(cell) && rd < slen; i++) {
        cell[i] = source[rd++];
        if (cell[i] >= ' ')
          cell[i] -= ' ';
      }
      target[wr] = (cell[0] & 0x3f) << 2;
      target[wr++] |= (cell[1] & 0x30) >> 4;
      target[wr] = (cell[1] & 0x0f) << 4;
      target[wr++] |= (cell[2] & 0x3c) >> 2;
      target[wr] = (cell[2] & 0x03) << 6;
      target[wr++] |= cell[3] & 0x3f;
      block += 3;
    }
    while (rd < slen && source[rd] > ' ')
      rd++;
    while (rd < slen && source[rd] != 0 && source[rd] <= ' ')
      rd++;
  }
  return (wr);
}
```