Bug 1184996 (Part 4) - Forbid instantiation of decoders except via DecoderFactory. r=tn

image/Decoder.cpp

@@ -424,7 +424,6 @@ Decoder::SetSizeOnImage()
  */
 
 void Decoder::InitInternal() { }
-void Decoder::WriteInternal(const char* aBuffer, uint32_t aCount) { }
 void Decoder::FinishInternal() { }
 void Decoder::FinishWithErrorInternal() { }
 

image/Decoder.h

@@ -285,7 +285,7 @@ protected:
    * only these methods.
    */
   virtual void InitInternal();
-  virtual void WriteInternal(const char* aBuffer, uint32_t aCount);
+  virtual void WriteInternal(const char* aBuffer, uint32_t aCount) = 0;
   virtual void FinishInternal();
   virtual void FinishWithErrorInternal();
 

image/DecoderFactory.cpp

@@ -67,10 +67,10 @@ DecoderFactory::GetDecoderType(const char* aMimeType)
   return type;
 }
 
-static already_AddRefed<Decoder>
-GetDecoder(DecoderType aType,
-           RasterImage* aImage,
-           bool aIsRedecode)
+/* static */ already_AddRefed<Decoder>
+DecoderFactory::GetDecoder(DecoderType aType,
+                           RasterImage* aImage,
+                           bool aIsRedecode)
 {
   nsRefPtr<Decoder> decoder;
 

image/DecoderFactory.h

@@ -91,6 +91,13 @@ public:
 
 private:
   virtual ~DecoderFactory() = 0;
+
+  /**
+   * An internal method which allocates a new decoder of the requested @aType.
+   */
+  static already_AddRefed<Decoder> GetDecoder(DecoderType aType,
+                                              RasterImage* aImage,
+                                              bool aIsRedecode);
 };
 
 } // namespace image

image/decoders/nsBMPDecoder.h

@@ -22,8 +22,6 @@ class RasterImage;
 class nsBMPDecoder : public Decoder
 {
 public:
-
-    explicit nsBMPDecoder(RasterImage* aImage);
     ~nsBMPDecoder();
 
     // Specifies whether or not the BMP file will contain alpha data
@@ -55,6 +53,12 @@ public:
     virtual void FinishInternal() override;
 
 private:
+    friend class DecoderFactory;
+    friend class nsICODecoder;
+
+    // Decoders should only be instantiated via DecoderFactory.
+    // XXX(seth): nsICODecoder is temporarily an exception to this rule.
+    explicit nsBMPDecoder(RasterImage* aImage);
 
     /// Calculates the red-, green- and blueshift in mBitFields using
     /// the bitmasks from mBitFields

image/decoders/nsGIFDecoder2.h

@@ -22,8 +22,6 @@ class RasterImage;
 class nsGIFDecoder2 : public Decoder
 {
 public:
-
-  explicit nsGIFDecoder2(RasterImage* aImage);
   ~nsGIFDecoder2();
 
   virtual void WriteInternal(const char* aBuffer, uint32_t aCount) override;
@@ -31,9 +29,13 @@ public:
   virtual Telemetry::ID SpeedHistogram() override;
 
 private:
+  friend class DecoderFactory;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  explicit nsGIFDecoder2(RasterImage* aImage);
+
   // These functions will be called when the decoder has a decoded row,
   // frame size information, etc.
-
   void      BeginGIF();
   nsresult  BeginImageFrame(uint16_t aDepth);
   void      EndImageFrame();

image/decoders/nsICODecoder.h

@@ -22,8 +22,6 @@ class RasterImage;
 class nsICODecoder : public Decoder
 {
 public:
-
-  explicit nsICODecoder(RasterImage* aImage);
   virtual ~nsICODecoder();
 
   // Obtains the width of the icon directory entry
@@ -43,6 +41,11 @@ public:
   virtual void FinishWithErrorInternal() override;
 
 private:
+  friend class DecoderFactory;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  explicit nsICODecoder(RasterImage* aImage);
+
   // Writes to the contained decoder and sets the appropriate errors
   // Returns true if there are no errors.
   bool WriteToContainedDecoder(const char* aBuffer, uint32_t aCount);

image/decoders/nsIconDecoder.h

@@ -37,12 +37,17 @@ class RasterImage;
 class nsIconDecoder : public Decoder
 {
 public:
-
-  explicit nsIconDecoder(RasterImage* aImage);
   virtual ~nsIconDecoder();
 
   virtual void WriteInternal(const char* aBuffer, uint32_t aCount) override;
 
+private:
+  friend class DecoderFactory;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  explicit nsIconDecoder(RasterImage* aImage);
+
+public:
   uint8_t mWidth;
   uint8_t mHeight;
   uint32_t mPixBytesRead;

image/decoders/nsJPEGDecoder.h

@@ -53,7 +53,6 @@ struct Orientation;
 class nsJPEGDecoder : public Decoder
 {
 public:
-  nsJPEGDecoder(RasterImage* aImage, Decoder::DecodeStyle aDecodeStyle);
   virtual ~nsJPEGDecoder();
 
   virtual nsresult SetTargetSize(const nsIntSize& aSize) override;
@@ -71,6 +70,12 @@ protected:
 
   Maybe<Downscaler> mDownscaler;
 
+private:
+  friend class DecoderFactory;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  nsJPEGDecoder(RasterImage* aImage, Decoder::DecodeStyle aDecodeStyle);
+
 public:
   struct jpeg_decompress_struct mInfo;
   struct jpeg_source_mgr mSourceMgr;

image/decoders/nsPNGDecoder.h

@@ -24,7 +24,6 @@ class RasterImage;
 class nsPNGDecoder : public Decoder
 {
 public:
-  explicit nsPNGDecoder(RasterImage* aImage);
   virtual ~nsPNGDecoder();
 
   virtual void InitInternal() override;
@@ -67,6 +66,14 @@ public:
     }
   }
 
+private:
+  friend class DecoderFactory;
+  friend class nsICODecoder;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  // XXX(seth): nsICODecoder is temporarily an exception to this rule.
+  explicit nsPNGDecoder(RasterImage* aImage);
+
 public:
   png_structp mPNG;
   png_infop mInfo;