user: Demonstrate the C code that generates the assembly output below:

```asm
<bureadupto>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x50,%rsp
  mov    %edi,-0x24(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    %edx,-0x28(%rbp)
  mov    %rcx,-0x38(%rbp)
  mov    %r8,-0x40(%rbp)
  mov    %r9,-0x48(%rbp)
  movl   $0x0,-0x14(%rbp)
  cmpq   $0x0,-0x30(%rbp)
  je     L155
  mov    -0x30(%rbp),%rax
  movl   $0x0,(%rax)
L155:
  cmpq   $0x0,-0x38(%rbp)
  je     L180
  mov    -0x38(%rbp),%rax
  movl   $0x0,(%rax)
L180:
  cmpq   $0x0,-0x40(%rbp)
  jne    L215
  mov    $0xffffffff,%eax
  jmp    L119
L215:
  cmpl   $0x1,-0x28(%rbp)
  jg     L146
  mov    -0x40(%rbp),%rax
  movb   $0x0,(%rax)
  mov    $0x0,%eax
  jmp    L119
L146:
  subl   $0x1,-0x28(%rbp)
  cmpl   $0x0,0x10(%rbp)
  jne    L169
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    %eax,0x10(%rbp)
L169:
  mov    -0x24(%rbp),%eax
  mov    %eax,%edi
  call   <jelio_buffer@plt>
  mov    %rax,-0x8(%rbp)
  cmpq   $0x0,-0x8(%rbp)
  jne    L0
  mov    $0xffffffff,%eax
  jmp    L119
L0:
  mov    -0x8(%rbp),%rax
  mov    %rax,%rdi
  call   <jelio_buffer_getc@plt>
  mov    %eax,-0xc(%rbp)
  cmpl   $0xffffffff,-0xc(%rbp)
  jne    L102
  cmpq   $0x0,-0x30(%rbp)
  je     L96
  mov    -0x30(%rbp),%rax
  movl   $0x1,(%rax)
  jmp    L96
L102:
  mov    -0x14(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  mov    -0xc(%rbp),%edx
  mov    %dl,(%rax)
  addl   $0x1,-0x14(%rbp)
  mov    -0x14(%rbp),%eax
  cmp    0x10(%rbp),%eax
  jl     L170
  mov    -0x14(%rbp),%eax
  cltq
  mov    0x10(%rbp),%edx
  movslq %edx,%rdx
  sub    %rdx,%rax
  mov    %rax,%rcx
  mov    -0x40(%rbp),%rax
  add    %rax,%rcx
  mov    -0x48(%rbp),%rax
  mov    0x10(%rbp),%edx
  mov    %rax,%rsi
  mov    %rcx,%rdi
  call   <memcmp@plt>
  test   %eax,%eax
  jne    L170
  cmpq   $0x0,-0x38(%rbp)
  je     L3
  mov    -0x38(%rbp),%rax
  movl   $0x1,(%rax)
  jmp    L3
L170:
  mov    -0x14(%rbp),%eax
  cmp    -0x28(%rbp),%eax
  jl     L0
  mov    0x10(%rbp),%eax
  cmp    -0x14(%rbp),%eax
  jl     L205
  mov    -0x14(%rbp),%eax
  sub    $0x1,%eax
  mov    %eax,0x10(%rbp)
L205:
  cmpl   $0x1,-0x14(%rbp)
  jle    L98
  mov    0x10(%rbp),%eax
  mov    %eax,-0x10(%rbp)
  jmp    L147
L57:
  mov    -0x14(%rbp),%eax
  cltq
  mov    -0x10(%rbp),%edx
  movslq %edx,%rdx
  sub    %rdx,%rax
  mov    %rax,%rcx
  mov    -0x40(%rbp),%rax
  add    %rax,%rcx
  mov    -0x10(%rbp),%edx
  mov    -0x48(%rbp),%rax
  mov    %rax,%rsi
  mov    %rcx,%rdi
  call   <memcmp@plt>
  test   %eax,%eax
  jne    L207
  mov    -0x14(%rbp),%eax
  cltq
  mov    -0x10(%rbp),%edx
  movslq %edx,%rdx
  sub    %rdx,%rax
  mov    %rax,%rcx
  mov    -0x40(%rbp),%rax
  add    %rax,%rcx
  mov    -0x10(%rbp),%edx
  mov    -0x8(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <jelio_buffer_ungetc@plt>
  mov    -0x10(%rbp),%eax
  sub    %eax,-0x14(%rbp)
L207:
  subl   $0x1,-0x10(%rbp)
L147:
  cmpl   $0x0,-0x10(%rbp)
  jg     L57
  jmp    L98
L96:
  nop
  jmp    L165
L3:
  nop
  jmp    L165
L98:
  nop
L165:
  mov    -0x14(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  movb   $0x0,(%rax)
  mov    -0x14(%rbp),%eax
L119:
  leave
  ret
```

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;
}
```