blob: 0ab048862a794960b36023ff9249c65f7790b538 [file] [log] [blame]
#include <memory>
#include "image_io/base/data_segment.h"
#include "image_io/base/data_source.h"
#include "image_io/jpeg/jpeg_marker.h"
#include "image_io/jpeg/jpeg_segment_processor.h"
namespace photos_editing_formats {
namespace image_io {
/// JpegScanner reads DataSegments from a DataSource, finds interesting
/// JpegSegments and passes them on to a JpegSegmentProcessor for further
/// examination.
class JpegScanner {
: data_source_(nullptr),
has_error_(false) {}
/// Called to start and run the scanner.
/// @param data_source The DataSource from which to obtain DataSegments.
/// @param segment_processor The processor of the JpegSegment instances.
void Run(DataSource* data_source, JpegSegmentProcessor* segment_processor);
/// If the JpegSegmentProcessor determines that it has seen enough JpegSegment
/// instances, it can call this function to terminate the scanner prematurely.
void SetDone() { done_ = true; }
/// @return True if the done flag was set by SetDone(), else false.
bool IsDone() const { return done_; }
/// @return True if the scanner encountered errors.
bool HasError() const { return has_error_; }
/// @return The DataSource from which DataSegments are being read.
DataSource* GetDataSource() const { return data_source_; }
/// JpegSegmentProcessor instances can call this function to inform the
/// scanner about the types of JpegSegment instances it is interested in.
/// The JpegScanner will not send any uninteresting segments to the processor.
void UpdateInterestingMarkerFlags(const JpegMarker::Flags& marker_flags) {
interesting_marker_flags_ = marker_flags;
/// Called from the Run() function to do the heavy lifting.
void FindAndProcessSegments();
/// @param marker The marker of the JpegSegment under construction.
/// @param begin_location The start of the JpegSegment under construction.
/// @return The size of the segment payload of given marker type that starts
/// at the specified location.
size_t GetPayloadSize(const JpegMarker& marker, size_t begin_location);
/// @return The validated byte value at the given location.
ValidatedByte GetValidatedByte(size_t location);
/// Calls GetValidatedByte() and returns its value if the byte is valid, else
/// sets the get_byte_error_ flag.
/// @return the byte value at the given location, or 0 if the byte is invalid.
Byte GetByte(size_t location);
/// Asks the DataSource for the next DataSegment.
void GetNextSegment();
/// The DataSource from which DataSegments are obtained.
DataSource* data_source_;
/// The JpegSegmentProcessor to which JpegSegments are sent.
JpegSegmentProcessor* segment_processor_;
/// The JpegSegment types of interest to the JpegSegmentProcessor.
JpegMarker::Flags interesting_marker_flags_;
/// Depending on the DataSource, a given JpegSegment may span up to two
/// DataSegments. These are they.
std::shared_ptr<DataSegment> current_segment_;
std::shared_ptr<DataSegment> next_segment_;
/// The current location of the scanner in the DataSource.
size_t current_location_;
/// A flag that indicates the scanner is done, naturally or prematurely.
bool done_;
/// A flag that indicates an error occurred while getting Byte data.
bool has_error_;
} // namespace image_io
} // namespace photos_editing_formats