Function forEncode

pj_datastore/src/encoding.cpp:174–217

// ---------------------------------------------------------------------------

FrameOfReferenceEncoded forEncode(
    Span<const uint8_t> data, StorageKind kind, std::size_t count, int64_t min_val, int64_t max_val) {
  FrameOfReferenceEncoded result;
  result.reference = min_val;
  result.count = count;

  const auto range = static_cast<uint64_t>(max_val - min_val);
  result.offset_bytes = offsetBytesFor(range);

  const std::size_t esize = storageKindSize(kind);
  result.offsets.reserve(count * result.offset_bytes);

  for (std::size_t i = 0; i < count; ++i) {
    int64_t val{};
    if (kind == StorageKind::kInt32) {
      int32_t tmp{};
      std::memcpy(&tmp, data.data() + i * esize, sizeof(tmp));
      val = tmp;  // sign-extend
    } else {
      std::memcpy(&val, data.data() + i * esize, sizeof(val));
    }
    const auto offset = static_cast<uint64_t>(val - min_val);

    switch (result.offset_bytes) {
      case 1: {
        auto v = static_cast<uint8_t>(offset);
        result.offsets.append(&v, sizeof(v));
        break;
      }
      case 2: {
        auto v = static_cast<uint16_t>(offset);
        result.offsets.append(&v, sizeof(v));
        break;
      }
      default: {
        auto v = static_cast<uint32_t>(offset);
        result.offsets.append(&v, sizeof(v));
        break;
      }
    }
  }

  return result;
}

namespace {