1 files changed, 95 insertions, 0 deletions
diff --git a/image/decoders/EXIF.h b/image/decoders/EXIF.h
new file mode 100644
index 0000000000..eb23f8d537
--- /dev/null
+++ b/image/decoders/EXIF.h
@@ -0,0 +1,95 @@
+/* -*- 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"
+#include "mozilla/Maybe.h"
+#include "mozilla/image/Resolution.h"
+#include "mozilla/gfx/Point.h"
+
+namespace mozilla::image {
+
+enum class ByteOrder : uint8_t { Unknown, LittleEndian, BigEndian };
+
+struct EXIFData {
+  const Orientation orientation = Orientation();
+  const Resolution resolution = Resolution();
+};
+
+struct ParsedEXIFData;
+
+enum class ResolutionUnit : uint8_t {
+  Dpi,
+  Dpcm,
+};
+
+class EXIFParser {
+ public:
+  static EXIFData Parse(const uint8_t* aData, const uint32_t aLength,
+                        const gfx::IntSize& aRealImageSize) {
+    EXIFParser parser;
+    return parser.ParseEXIF(aData, aLength, aRealImageSize);
+  }
+
+ private:
+  EXIFParser()
+      : mStart(nullptr),
+        mCurrent(nullptr),
+        mLength(0),
+        mRemainingLength(0),
+        mByteOrder(ByteOrder::Unknown) {}
+
+  EXIFData ParseEXIF(const uint8_t* aData, const uint32_t aLength,
+                     const gfx::IntSize& aRealImageSize);
+  bool ParseEXIFHeader();
+  bool ParseTIFFHeader(uint32_t& aIFD0OffsetOut);
+
+  void ParseIFD(ParsedEXIFData&, uint32_t aDepth = 0);
+  bool ParseOrientation(uint16_t aType, uint32_t aCount, Orientation&);
+  bool ParseResolution(uint16_t aType, uint32_t aCount, Maybe<float>&);
+  bool ParseResolutionUnit(uint16_t aType, uint32_t aCount,
+                           Maybe<ResolutionUnit>&);
+  bool ParseDimension(uint16_t aType, uint32_t aCount, Maybe<uint32_t>&);
+
+  bool Initialize(const uint8_t* aData, const uint32_t aLength);
+  void Advance(const uint32_t aDistance);
+  void JumpTo(const uint32_t aOffset);
+
+  uint32_t CurrentOffset() const { return mCurrent - mStart; }
+
+  class ScopedJump {
+    EXIFParser& mParser;
+    uint32_t mOldOffset;
+
+   public:
+    ScopedJump(EXIFParser& aParser, uint32_t aOffset)
+        : mParser(aParser), mOldOffset(aParser.CurrentOffset()) {
+      mParser.JumpTo(aOffset);
+    }
+
+    ~ScopedJump() { mParser.JumpTo(mOldOffset); }
+  };
+
+  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);
+  bool ReadRational(float& aOut);
+
+  const uint8_t* mStart;
+  const uint8_t* mCurrent;
+  uint32_t mLength;
+  uint32_t mRemainingLength;
+  ByteOrder mByteOrder;
+};
+
+}  // namespace mozilla::image
+
+#endif  // mozilla_image_decoders_EXIF_h