Function CopySegmentsBytesToBitfield

src/types/redis_bitmap.cc:734–768

Copy a range of bytes from entire bitmap and store them into ArrayBitfieldBitmap.

// Copy a range of bytes from entire bitmap and store them into ArrayBitfieldBitmap.
static rocksdb::Status CopySegmentsBytesToBitfield(engine::Context &ctx, Bitmap::SegmentCacheStore &store,
                                                   uint32_t byte_offset, uint32_t bytes,
                                                   ArrayBitfieldBitmap *bitfield) {
  bitfield->SetByteOffset(byte_offset);
  bitfield->Reset();

  uint32_t segment_index = byte_offset / kBitmapSegmentBytes;
  int64_t remain_bytes = bytes;
  // the byte_offset in current segment.
  auto segment_byte_offset = static_cast<int>(byte_offset % kBitmapSegmentBytes);
  for (; remain_bytes > 0; ++segment_index) {
    const std::string *cache = nullptr;
    auto cache_status = store.Get(ctx, segment_index, &cache);
    if (!cache_status.ok()) {
      return cache_status;
    }

    auto cache_size = static_cast<int>(cache->size());
    auto copyable = std::max(0, cache_size - segment_byte_offset);
    auto copy_count = std::min(static_cast<int>(remain_bytes), copyable);
    auto src = reinterpret_cast<const uint8_t *>(cache->data() + segment_byte_offset);
    auto status = bitfield->Set(byte_offset, copy_count, src);
    if (!status) {
      return rocksdb::Status::InvalidArgument();
    }

    // next segment will copy from its front.
    byte_offset = (segment_index + 1) * kBitmapSegmentBytes;
    // maybe negative, but still correct.
    remain_bytes -= kBitmapSegmentBytes - segment_byte_offset;
    segment_byte_offset = 0;
  }

  return rocksdb::Status::OK();
}

static rocksdb::Status GetBitfieldInteger(const ArrayBitfieldBitmap &bitfield, uint32_t bit_offset,
                                          BitfieldEncoding enc, uint64_t *res) {