1 files changed, 46 insertions, 0 deletions
diff --git a/includes/image_io/base/istream_ref_data_source.h b/includes/image_io/base/istream_ref_data_source.h
new file mode 100644
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--- /dev/null
+++ b/includes/image_io/base/istream_ref_data_source.h
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+#ifndef IMAGE_IO_BASE_ISTREAM_REF_DATA_SOURCE_H_  // NOLINT
+#define IMAGE_IO_BASE_ISTREAM_REF_DATA_SOURCE_H_  // NOLINT
+
+#include <iostream>
+
+#include "image_io/base/data_source.h"
+
+namespace photos_editing_formats {
+namespace image_io {
+
+/// A DataSource that obtains data from an istream held as a reference.
+class IStreamRefDataSource : public DataSource {
+ public:
+  /// Constructs an IStreamDataSource using the given istream.
+  /// @param istream_ref The istream from which to read.
+  explicit IStreamRefDataSource(std::istream& istream_ref)
+      : istream_ref_(istream_ref) {}
+  IStreamRefDataSource(const IStreamRefDataSource&) = delete;
+  IStreamRefDataSource& operator=(const IStreamRefDataSource&) = delete;
+
+  void Reset() override;
+  std::shared_ptr<DataSegment> GetDataSegment(size_t begin,
+                                              size_t min_size) override;
+  TransferDataResult TransferData(const DataRange& data_range, size_t best_size,
+                                  DataDestination* data_destination) override;
+
+ private:
+  /// The worker function to create a DataSegment and fill it with the given
+  /// number of bytes read from the istream, starting at the given location.
+  /// @param begin The location in the istream at which to start reading.
+  /// @param count The number of bytes to read.
+  /// @return A DataSegment pointer, or nullptr if the read failed.
+  std::shared_ptr<DataSegment> Read(size_t begin, size_t count);
+
+ private:
+  /// The istream from which to read.
+  std::istream& istream_ref_;
+
+  /// The current data segment that was read in the GetDataSegment() function.
+  std::shared_ptr<DataSegment> current_data_segment_;
+};
+
+}  // namespace image_io
+}  // namespace photos_editing_formats
+
+#endif  // IMAGE_IO_BASE_ISTREAM_REF_DATA_SOURCE_H_  // NOLINT