ShapesFileWriter.h

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#ifndef CASACORE_SHAPES_FILE_WRITER_H_
#define CASACORE_SHAPES_FILE_WRITER_H_
 
#include <fstream>
 
#include <casacore/casa/Arrays/IPosition.h>
 
#include "Deflate.h"
 
namespace casacore {
 
class ShapesFileWriter {
 public:
  ShapesFileWriter(const std::string& filename) : compressor_(9), file_(filename) {}
 
  ~ShapesFileWriter() {
    if (!buffer_.empty()) Flush();
  }
 
  void Write(const IPosition& position) {
    buffer_.emplace_back(position.size());
    if (buffer_.size() == kMaxBufferSize) Flush();
    for (ssize_t value : position) {
      buffer_.emplace_back(value);
      if (buffer_.size() == kMaxBufferSize) Flush();
    }
  }
 
 private:
  void Flush() {
    const uint32_t uncompressed_size = buffer_.size() * sizeof(uint64_t);
    compressed_buffer_.resize(compressor_.CompressBound(uncompressed_size));
    std::span input(reinterpret_cast<const std::byte*>(buffer_.data()), uncompressed_size);
    const uint32_t compressed_size = compressor_.Compress(input, compressed_buffer_);
    file_.write(reinterpret_cast<const char*>(&uncompressed_size), sizeof(uint32_t));
    file_.write(reinterpret_cast<const char*>(&compressed_size), sizeof(uint32_t));
    file_.write(reinterpret_cast<const char*>(compressed_buffer_.data()), compressed_size);
    buffer_.clear();
  }
 
  static constexpr size_t kMaxBufferSize = 1024 * 10 * 128;
  std::vector<uint64_t> buffer_;
  std::vector<std::byte> compressed_buffer_;
  deflate::Compressor compressor_;
  std::ofstream file_;
};
 
}  // namespace casacore
 
#endif