Split SkBmpCodec into three separate classes

src/codec/SkBmpCodec.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 SkBmpCodec_DEFINED
+#define SkBmpCodec_DEFINED
 
 #include "SkCodec.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
 #include "SkMaskSwizzler.h"
 #include "SkStream.h"
 #include "SkSwizzler.h"
 #include "SkTypes.h"
 
-// TODO: rename SkCodec_libbmp files to SkBmpCodec
 /*
- *
- * This class implements the decoding for bmp images
- *
+ * This class enables code sharing between its bmp codec subclasses.  The
+ * subclasses actually do the work.
  */
 class SkBmpCodec : public SkCodec {
 public:
 
     /*
-     *
      * Describes if rows of the input start at the top or bottom of the image
-     *
      */
     enum RowOrder {
         kTopDown_RowOrder,
         kBottomUp_RowOrder
     };
 
     /*
-     *
      * Checks the start of the stream to see if the image is a bmp
-     *
      */
     static bool IsBmp(SkStream*);
 
     /*
-     *
      * Assumes IsBmp was called and returned true
      * Creates a bmp decoder
      * Reads enough of the stream to determine the image format
-     *
      */
     static SkCodec* NewFromStream(SkStream*);
 
     /*
-     *
      * Creates a bmp decoder for a bmp embedded in ico
      * Reads enough of the stream to determine the image format
-     *
      */
     static SkCodec* NewFromIco(SkStream*);
 
 protected:
 
-    /*
-     *
-     * Initiates the bmp decode
-     *
-     */
-    Result onGetPixels(const SkImageInfo& dstInfo, void* dst,
-                       size_t dstRowBytes, const Options&, SkPMColor*,
-                       int*) override;
+    SkBmpCodec(const SkImageInfo& info, SkStream* stream, uint16_t bitsPerPixel,
+            RowOrder rowOrder);
 
     SkEncodedFormat onGetEncodedFormat() const override { return kBMP_SkEncodedFormat; }
 
+    /*
+     * Read enough of the stream to initialize the SkBmpCodec. Returns a bool
+     * representing success or failure. If it returned true, and codecOut was
+     * not NULL, it will be set to a new SkBmpCodec.
+     * Does *not* take ownership of the passed in SkStream.
+     */
+    static bool ReadHeader(SkStream*, bool inIco, SkCodec** codecOut);
+
+    /*
+     * Rewinds the image stream if necessary
+     */
+    bool handleRewind(bool inIco);
+
+    /*
+     * Get the destination row to start filling from
+     * Used to fill the remainder of the image on incomplete input for bmps
+     * This is tricky since bmps may be kTopDown or kBottomUp.  For kTopDown,
+     * we start filling from where we left off, but for kBottomUp we start
+     * filling at the top of the image.
+     */
+    void* getDstStartRow(void* dst, size_t dstRowBytes, int32_t y) const;
+
+    /*
+     * Compute the number of colors in the color table
+     */
+    uint32_t computeNumColors(uint32_t numColors);
+
+    /*
+     * Accessors used by subclasses
+     */
+    uint16_t bitsPerPixel() const { return fBitsPerPixel; }
+    RowOrder rowOrder() const { return fRowOrder; }
+
 private:
 
     /*
-     *
-     * Used to define the input format of the bmp
-     *
-     */
-    enum BitmapInputFormat {
-        kStandard_BitmapInputFormat,
-        kRLE_BitmapInputFormat,
-        kBitMask_BitmapInputFormat,
-        kUnknown_BitmapInputFormat
-    };
-
-    /*
-     *
-     * Creates the color table
-     * Sets colorCount to the new color count if it is non-NULL
-     */
-     bool createColorTable(SkAlphaType alphaType, int* colorCount);
-
-    /*
-     *
      * Creates a bmp decoder
      * Reads enough of the stream to determine the image format
-     *
      */
-    static SkCodec* NewFromStream(SkStream*, bool isIco);
+    static SkCodec* NewFromStream(SkStream*, bool inIco);
 
-    /*
-     *
-     * Read enough of the stream to initialize the SkBmpCodec. Returns a bool
-     * representing success or failure. If it returned true, and codecOut was
-     * not NULL, it will be set to a new SkBmpCodec.
-     * Does *not* take ownership of the passed in SkStream.
-     *
-     */
-    static bool ReadHeader(SkStream*, bool isIco, SkCodec** codecOut);
-
-    /*
-     *
-     * Performs the bitmap decoding for bit masks input format
-     *
-     */
-    Result decodeMask(const SkImageInfo& dstInfo, void* dst,
-                      size_t dstRowBytes, const Options& opts);
-
-    /*
-     *
-     * Set an RLE pixel using the color table
-     *
-     */
-    void setRLEPixel(void* dst, size_t dstRowBytes,
-                     const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
-                     uint8_t index);
-    /*
-     *
-     * Set an RLE24 pixel from R, G, B values
-     *
-     */
-    void setRLE24Pixel(void* dst, size_t dstRowBytes,
-                       const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
-                       uint8_t red, uint8_t green, uint8_t blue);
-
-    /*
-     *
-     * Performs the bitmap decoding for RLE input format
-     *
-     */
-    Result decodeRLE(const SkImageInfo& dstInfo, void* dst,
-                     size_t dstRowBytes, const Options& opts);
-
-    /*
-     *
-     * Performs the bitmap decoding for standard input format
-     *
-     */
-    Result decode(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, const Options& opts);
-
-    /*
-     *
-     * Creates an instance of the decoder
-     * Called only by NewFromStream
-     *
-     * @param srcInfo contains the source width and height
-     * @param stream the stream of image data
-     * @param bitsPerPixel the number of bits used to store each pixel
-     * @param format the format of the bmp file
-     * @param masks optional color masks for certain bmp formats, passes
-                    ownership to SkBmpCodec
-     * @param numColors the number of colors in the color table
-     * @param bytesPerColor the number of bytes in the stream used to represent
-                            each color in the color table
-     * @param offset the offset of the image pixel data from the end of the
-     *               headers
-     * @param rowOrder indicates whether rows are ordered top-down or bottom-up
-     * @param RLEBytes used only for RLE decodes, as we must decode all
-     *                  of the data at once rather than row by row
-     *                  it indicates the amount of data left in the stream
-     *                  after decoding the headers
-     *
-     */
-    SkBmpCodec(const SkImageInfo& srcInfo, SkStream* stream,
-               uint16_t bitsPerPixel, BitmapInputFormat format,
-               SkMasks* masks, uint32_t numColors, uint32_t bytesPerColor,
-               uint32_t offset, RowOrder rowOrder, size_t RLEBytes,
-               bool isIco);
-
-    // Fields
-    const uint16_t                      fBitsPerPixel;
-    const BitmapInputFormat             fInputFormat;
-    SkAutoTDelete<SkMasks>              fMasks;          // owned
-    SkAutoTUnref<SkColorTable>          fColorTable;     // owned
-    uint32_t                            fNumColors;
-    const uint32_t                      fBytesPerColor;
-    const uint32_t                      fOffset;
-    const RowOrder                      fRowOrder;
-    const size_t                        fRLEBytes;
-    const bool                          fIsIco;
+    const uint16_t fBitsPerPixel;
+    const RowOrder fRowOrder;
 
     typedef SkCodec INHERITED;
 };
+
+#endif