  BasicWriter<Char>::prepare_int_buffer(
    unsigned num_digits, const Spec &spec,
    const char *prefix, unsigned prefix_size) {
  unsigned width = spec.width();
  Alignment align = spec.align();
  Char fill = internal::CharTraits<Char>::cast(spec.fill());
  if (spec.precision() > static_cast<int>(num_digits)) {
    // Octal prefix '0' is counted as a digit, so ignore it if precision
    // is specified.
    if (prefix_size > 0 && prefix[prefix_size - 1] == '0')
      --prefix_size;
    unsigned number_size =
        prefix_size + internal::to_unsigned(spec.precision());
    AlignSpec subspec(number_size, '0', ALIGN_NUMERIC);
    if (number_size >= width)
      return prepare_int_buffer(num_digits, subspec, prefix, prefix_size);
    buffer_.reserve(width);
    unsigned fill_size = width - number_size;
    if (align != ALIGN_LEFT) {
      CharPtr p = grow_buffer(fill_size);
      std::uninitialized_fill(p, p + fill_size, fill);
    }
    std::ptrdiff_t offset = get(prepare_int_buffer(
        num_digits, subspec, prefix, prefix_size)) - &buffer_[0];
    if (align == ALIGN_LEFT) {
      CharPtr p = grow_buffer(fill_size);
      std::uninitialized_fill(p, p + fill_size, fill);
    }
    return internal::make_ptr(&buffer_[0], buffer_.size()) + offset;
  }
  unsigned size = prefix_size + num_digits;
  if (width <= size) {
    CharPtr p = grow_buffer(size);
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    return p + size - 1;
  }
  CharPtr p = grow_buffer(width);
  CharPtr end = p + width;
  if (align == ALIGN_LEFT) {
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    p += size;
    std::uninitialized_fill(p, end, fill);
  } else if (align == ALIGN_CENTER) {
    p = fill_padding(p, width, size, fill);
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    p += size;
  } else {
    if (align == ALIGN_NUMERIC) {
      if (prefix_size != 0) {
        p = std::uninitialized_copy(prefix, prefix + prefix_size, p);
        size -= prefix_size;
      }
    } else {
      std::uninitialized_copy(prefix, prefix + prefix_size, end - size);
    }
    std::uninitialized_fill(p, end - size, fill);
    p = end;
  }
  return p - 1;
}
  BasicWriter<Char>::prepare_int_buffer(
    unsigned num_digits, const Spec &spec,
    const char *prefix, unsigned prefix_size) {
  unsigned width = spec.width();
  Alignment align = spec.align();
  Char fill = internal::CharTraits<Char>::cast(spec.fill());
  if (spec.precision() > static_cast<int>(num_digits)) {
     
     
    if (prefix_size > 0 && prefix[prefix_size - 1] == '0')
      --prefix_size;
    unsigned number_size =
        prefix_size + internal::to_unsigned(spec.precision());
    AlignSpec subspec(number_size, '0', ALIGN_NUMERIC);
    if (number_size >= width)
      return prepare_int_buffer(num_digits, subspec, prefix, prefix_size);
    buffer_.reserve(width);
    unsigned fill_size = width - number_size;
    if (align != ALIGN_LEFT) {
      CharPtr p = grow_buffer(fill_size);
      std::uninitialized_fill(p, p + fill_size, fill);
    }
    std::ptrdiff_t offset = get(prepare_int_buffer(
        num_digits, subspec, prefix, prefix_size)) - &buffer_[0];
    if (align == ALIGN_LEFT) {
      CharPtr p = grow_buffer(fill_size);
      std::uninitialized_fill(p, p + fill_size, fill);
    }
    return internal::make_ptr(&buffer_[0], buffer_.size()) + offset;
  }
  unsigned size = prefix_size + num_digits;
  if (width <= size) {
    CharPtr p = grow_buffer(size);
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    return p + size - 1;
  }
  CharPtr p = grow_buffer(width);
  CharPtr end = p + width;
  if (align == ALIGN_LEFT) {
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    p += size;
    std::uninitialized_fill(p, end, fill);
  } else if (align == ALIGN_CENTER) {
    p = fill_padding(p, width, size, fill);
    std::uninitialized_copy(prefix, prefix + prefix_size, p);
    p += size;
  } else {
    if (align == ALIGN_NUMERIC) {
      if (prefix_size != 0) {
        p = std::uninitialized_copy(prefix, prefix + prefix_size, p);
        size -= prefix_size;
      }
    } else {
      std::uninitialized_copy(prefix, prefix + prefix_size, end - size);
    }
    std::uninitialized_fill(p, end - size, fill);
    p = end;
  }
  return p - 1;
}