user: 下面的汇编指令对应的C源代码是什么:

```asm
<bureadupto>:
  endbr64
  push   %r15
  mov    %r9,%r15
  push   %r14
  push   %r13
  mov    %edi,%r13d
  push   %r12
  mov    %edx,%r12d
  push   %rbp
  mov    %r8,%rbp
  push   %rbx
  sub    $0x38,%rsp
  mov    %rsi,0x28(%rsp)
  mov    0x70(%rsp),%ebx
  mov    %rcx,0x20(%rsp)
  test   %rsi,%rsi
  je     L214
  movl   $0x0,(%rsi)
L214:
  mov    0x20(%rsp),%rax
  test   %rax,%rax
  je     L139
  movl   $0x0,(%rax)
L139:
  test   %rbp,%rbp
  je     L159
  cmp    $0x1,%r12d
  jle    L238
  test   %ebx,%ebx
  je     L2
L128:
  mov    %r13d,%edi
  call   <jelio_buffer@plt>
  mov    %rax,%r14
  test   %rax,%rax
  je     L159
  movslq %r12d,%rax
  mov    $0x1,%r12d
  mov    %rax,0x8(%rsp)
  movslq %ebx,%rax
  mov    %rax,0x18(%rsp)
  jmp    L103
  xchg   %ax,%ax
L166:
  add    $0x1,%r12
  cmp    %r12,0x8(%rsp)
  je     L120
L103:
  mov    %r14,%rdi
  lea    -0x1(%r12),%r13d
  call   <jelio_buffer_getc@plt>
  lea    -0x1(%r12),%r8
  cmp    $0xffffffff,%eax
  je     L152
  mov    %al,-0x1(%rbp,%r12,1)
  mov    %r12d,%r8d
  cmp    %r12d,%ebx
  jg     L166
  mov    %rbp,%rdi
  sub    0x18(%rsp),%rdi
  mov    %ebx,%edx
  mov    %r15,%rsi
  add    %r12,%rdi
  mov    %r12d,0x10(%rsp)
  call   <memcmp@plt>
  mov    0x10(%rsp),%r8d
  test   %eax,%eax
  jne    L166
  mov    0x20(%rsp),%rax
  test   %rax,%rax
  je     L25
  movl   $0x1,(%rax)
  mov    %r12,%r8
  mov    %r12d,%r13d
  jmp    L189
  nopw   0x0(%rax,%rax,1)
L2:
  mov    %r15,%rdi
  call   <strlen@plt>
  mov    %eax,%ebx
  jmp    L128
  nopw   0x0(%rax,%rax,1)
L152:
  mov    0x28(%rsp),%rax
  test   %rax,%rax
  je     L189
  movl   $0x1,(%rax)
L189:
  movb   $0x0,0x0(%rbp,%r8,1)
L56:
  add    $0x38,%rsp
  mov    %r13d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax,%rax,1)
L120:
  cmp    %r8d,%ebx
  cmovge %r13d,%ebx
  cmp    $0x1,%r8d
  je     L194
  movslq %r8d,%r9
  movslq %ebx,%rcx
  mov    %r9,%r13
  mov    %r9,%r8
  test   %ebx,%ebx
  jg     L172
  jmp    L189
  nopl   0x0(%rax,%rax,1)
L77:
  mov    %ebx,%edx
  mov    %r12,%rsi
  mov    %r14,%rdi
  sub    %ebx,%r13d
  call   <jelio_buffer_ungetc@plt>
  movslq %r13d,%r9
  mov    0x8(%rsp),%rcx
  mov    %r9,%r8
L0:
  sub    $0x1,%rcx
  sub    $0x1,%ebx
  je     L189
L172:
  mov    %r9,%r12
  mov    %ebx,%edx
  mov    %r15,%rsi
  mov    %r9,0x18(%rsp)
  sub    %rcx,%r12
  mov    %r9,0x10(%rsp)
  add    %rbp,%r12
  mov    %rcx,0x8(%rsp)
  mov    %r12,%rdi
  call   <memcmp@plt>
  mov    0x8(%rsp),%rcx
  mov    0x10(%rsp),%r9
  test   %eax,%eax
  mov    0x18(%rsp),%r8
  jne    L0
  jmp    L77
  cs nopw 0x0(%rax,%rax,1)
L238:
  movb   $0x0,0x0(%rbp)
  xor    %r13d,%r13d
  jmp    L56
  nopl   0x0(%rax)
L194:
  mov    $0x1,%r13d
  mov    $0x1,%r8d
  jmp    L189
L25:
  mov    %r12,%r8
  mov    %r12d,%r13d
  jmp    L189
L159:
  mov    $0xffffffff,%r13d
  jmp    L56
```

assistant: ```c
int bureadupto(int fd, int *opt_eof, int maxlen, int *opt_complete, char *rbuf, char *upto, int upto_len) {
  int count = 0;
  int buf;
  struct jelio_buf *jb;
  if (opt_eof)
    *opt_eof = 0;
  if (opt_complete)
    *opt_complete = 0;
  if (!rbuf)
    return -1;
  if (maxlen < 2) {
    *rbuf = 0;
    return 0;
  }
  maxlen--;
  if (upto_len == 0)
    upto_len = strlen(upto);
  jb = jelio_buffer(fd);
  if (!jb)
    return -1;
  while (1) {
    buf = jelio_buffer_getc(jb);
    if (buf == -1) {
      if (opt_eof)
        *opt_eof = 1;
      break;
    }
    *(rbuf + count) = buf;
    count++;
    if (count >= upto_len)
      if (!memcmp(rbuf + count - upto_len, upto, upto_len)) {
        if (opt_complete)
          *opt_complete = 1;
        break;
      }
    if (count >= maxlen) {
      int i;
      if (upto_len >= count)
        upto_len = count - 1;
      if (count > 1)
        for (i = upto_len; i > 0; i--)
          if (!memcmp(rbuf + count - i, upto, i)) {
            jelio_buffer_ungetc(jb, rbuf + count - i, i);
            count -= i;
          }
      break;
    }
  }
  *(rbuf + count) = 0;
  return count;
}
```