gecko-dev/image/decoders/EXIF.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_image_decoders_EXIF_h
#define mozilla_image_decoders_EXIF_h

#include <stdint.h>
#include "nsDebug.h"

#include "Orientation.h"

namespace mozilla {
namespace image {

enum class ByteOrder : uint8_t { Unknown, LittleEndian, BigEndian };

struct EXIFData {
  EXIFData() {}
  explicit EXIFData(Orientation aOrientation) : orientation(aOrientation) {}

  const Orientation orientation;
};

class EXIFParser {
 public:
  static EXIFData Parse(const uint8_t* aData, const uint32_t aLength) {
    EXIFParser parser;
    return parser.ParseEXIF(aData, aLength);
  }

 private:
  EXIFParser()
      : mStart(nullptr),
        mCurrent(nullptr),
        mLength(0),
        mRemainingLength(0),
        mByteOrder(ByteOrder::Unknown) {}

  EXIFData ParseEXIF(const uint8_t* aData, const uint32_t aLength);
  bool ParseEXIFHeader();
  bool ParseTIFFHeader(uint32_t& aIFD0OffsetOut);
  bool ParseIFD0(Orientation& aOrientationOut);
  bool ParseOrientation(uint16_t aType, uint32_t aCount, Orientation& aOut);

  bool Initialize(const uint8_t* aData, const uint32_t aLength);
  void Advance(const uint32_t aDistance);
  void JumpTo(const uint32_t aOffset);

  bool MatchString(const char* aString, const uint32_t aLength);
  bool MatchUInt16(const uint16_t aValue);
  bool ReadUInt16(uint16_t& aOut);
  bool ReadUInt32(uint32_t& aOut);

  const uint8_t* mStart;
  const uint8_t* mCurrent;
  uint32_t mLength;
  uint32_t mRemainingLength;
  ByteOrder mByteOrder;
};

}  // namespace image
}  // namespace mozilla

#endif  // mozilla_image_decoders_EXIF_h