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#include "image_io/jpeg/jpeg_scanner.h"
#include <sstream>
#include "image_io/base/message_handler.h"
#include "image_io/jpeg/jpeg_segment.h"
namespace photos_editing_formats {
namespace image_io {
using std::stringstream;
/// The minimum size for the DataSegments requested from the DataSource. Using
/// this value will guarentee that a JpegSegment will occupy at most two
/// DataSegments.
const size_t kMinBufferDataRequestSize = 0x10000;
void JpegScanner::Run(DataSource* data_source,
JpegSegmentProcessor* segment_processor) {
if (data_source_) {
// The Run() function is already active.
return;
}
data_source_ = data_source;
segment_processor_ = segment_processor;
current_location_ = 0;
done_ = false;
has_error_ = false;
data_source_->Reset();
current_segment_ = data_source_->GetDataSegment(current_location_,
kMinBufferDataRequestSize);
segment_processor_->Start(this);
FindAndProcessSegments();
segment_processor_->Finish(this);
data_source_ = nullptr;
segment_processor_ = nullptr;
current_segment_.reset();
next_segment_.reset();
}
void JpegScanner::FindAndProcessSegments() {
while (!IsDone() && !HasError()) {
size_t begin_segment_location =
current_segment_->Find(current_location_, JpegMarker::kStart);
if (begin_segment_location == current_segment_->GetEnd()) {
GetNextSegment();
if (next_segment_) {
current_location_ =
std::max(current_location_, next_segment_->GetBegin());
current_segment_ = next_segment_;
next_segment_.reset();
continue;
}
SetDone();
break;
}
size_t payload_size = 0;
JpegMarker marker(
GetByte(begin_segment_location + JpegMarker::kTypeOffset));
if (marker.IsValid() && !HasError()) {
payload_size = GetPayloadSize(marker, begin_segment_location);
if (marker.IsValid() && interesting_marker_flags_[marker.GetType()]) {
size_t end_segment_location =
begin_segment_location + JpegMarker::kLength + payload_size;
GetByte(end_segment_location - 1);
if (!HasError()) {
JpegSegment segment(begin_segment_location, end_segment_location,
current_segment_.get(), next_segment_.get());
segment_processor_->Process(this, segment);
}
}
}
current_location_ =
begin_segment_location + JpegMarker::kLength + payload_size;
}
}
size_t JpegScanner::GetPayloadSize(const JpegMarker& marker,
size_t begin_location) {
if (marker.HasVariablePayloadSize()) {
return (GetByte(begin_location + JpegMarker::kLength) << 8) |
GetByte(begin_location + JpegMarker::kLength + 1);
} else {
return 0;
}
}
ValidatedByte JpegScanner::GetValidatedByte(size_t location) {
if (current_segment_->Contains(location)) {
return current_segment_->GetValidatedByte(location);
}
GetNextSegment();
if (next_segment_ && next_segment_->Contains(location)) {
return next_segment_->GetValidatedByte(location);
}
if (message_handler_) {
stringstream sstream;
sstream << location;
message_handler_->ReportMessage(Message::kPrematureEndOfDataError,
sstream.str());
}
return InvalidByte();
}
Byte JpegScanner::GetByte(size_t location) {
ValidatedByte validated_byte = GetValidatedByte(location);
if (validated_byte.is_valid) {
return validated_byte.value;
}
has_error_ = true;
return 0;
}
void JpegScanner::GetNextSegment() {
if (!next_segment_ && current_segment_) {
next_segment_ = data_source_->GetDataSegment(current_segment_->GetEnd(),
kMinBufferDataRequestSize);
}
}
} // namespace image_io
} // namespace photos_editing_formats
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