Scanline decoding for jpeg

src/codec/SkJpegCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkJpegCodec_DEFINED
 #define SkJpegCodec_DEFINED
 
@@ skipping 38 matching lines @@
     /*
      * Initiates the jpeg decode
      */
     Result onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, const Options&,
             SkPMColor*, int*) override;
 
     SkEncodedFormat onGetEncodedFormat() const override {
         return kJPEG_SkEncodedFormat;
     }
 
+    SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo, const Options& options,
+            SkPMColor ctable[], int* ctableCount) override;
+
 private:
 
     /*
      * Read enough of the stream to initialize the SkJpegCodec.
      * Returns a bool representing success or failure.
      *
      * @param codecOut
      * If this returns true, and codecOut was not NULL,
      * codecOut will be set to a new SkJpegCodec.
      *
@@ skipping 15 matching lines @@
      * Creates an instance of the decoder
      * Called only by NewFromStream
      *
      * @param srcInfo contains the source width and height
      * @param stream the encoded image data
      * @param decoderMgr holds decompress struct, src manager, and error manager
      *                   takes ownership
      */
     SkJpegCodec(const SkImageInfo& srcInfo, SkStream* stream, JpegDecoderMgr* decoderMgr);
 
+    /*
+     * Handles rewinding the input stream if it is necessary
+     */
+    bool handleRewind();
+
+    /*
+     * Checks if we can scale to the requested dimensions and performs the scaling

[scroggo, 2015/04/24 13:14:28]

This doesn't actually scale, right? It just sets up the jpeg_decompress_struct
to scale in the future.

[msarett, 2015/04/24 15:08:44]

Yes this is unclear.  I changed the function name and comments.

+     */
+    bool handleScaling(const SkImageInfo& dstInfo);
+
+    /*
+     * Create the swizzler based on the encoded format
+     */
+    void initializeSwizzler(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
+            const Options& options);
+
     SkAutoTDelete<JpegDecoderMgr> fDecoderMgr;
+    SkAutoTDelete<SkSwizzler>     fSwizzler;
+    size_t                        fSrcRowBytes;
+
+    friend class SkJpegScanlineDecoder;
 
     typedef SkCodec INHERITED;
 };
 
 #endif