Destroy SkScanlineDecoder in the SkCodec subclass destructors

src/codec/SkCodec_libpng.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec_libpng.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
@@ skipping 354 matching lines @@
                        png_structp png_ptr, png_infop info_ptr)
     : INHERITED(info, stream)
     , fPng_ptr(png_ptr)
     , fInfo_ptr(info_ptr)
     , fSrcConfig(SkSwizzler::kUnknown)
     , fNumberPasses(INVALID_NUMBER_PASSES)
     , fReallyHasAlpha(false)
 {}
 
 SkPngCodec::~SkPngCodec() {
+    // First, ensure that the scanline decoder is left in a finished state.
+    SkAutoTDelete<SkScanlineDecoder> decoder(this->detachScanlineDecoder());
+    if (NULL != decoder) {
+        this->finish();
+    }
+
     this->destroyReadStruct();
 }
 
 void SkPngCodec::destroyReadStruct() {
     if (fPng_ptr) {
         // We will never have a NULL fInfo_ptr with a non-NULL fPng_ptr
         SkASSERT(fInfo_ptr);
         png_destroy_read_struct(&fPng_ptr, &fInfo_ptr, png_infopp_NULL);
         fPng_ptr = NULL;
         fInfo_ptr = NULL;
@@ skipping 122 matching lines @@
         }
         default:
             SkASSERT(false);
             return false;
     }
 }
 
 SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void* dst,
                                         size_t rowBytes, const Options& options,
                                         SkPMColor ctable[], int* ctableCount) {
+    // Do not allow a regular decode if the caller has asked for a scanline decoder
+    if (NULL != this->scanlineDecoder()) {
+        SkCodecPrintf("cannot getPixels() if a scanline decoder has been created\n");
+        return kInvalidParameters;
+    }
+
     if (!this->handleRewind()) {
         return kCouldNotRewind;
     }
     if (requestedInfo.dimensions() != this->getInfo().dimensions()) {
         return kInvalidScale;
     }
     if (!conversion_possible(requestedInfo, this->getInfo())) {
         return kInvalidConversion;
     }
 
@@ skipping 99 matching lines @@
         }
         //there is a potential tradeoff of memory vs speed created by putting this in a loop. 
         //calling png_read_rows in a loop is insignificantly slower than calling it once with count 
         //as png_read_rows has it's own loop which calls png_read_row count times.
         for (int i = 0; i < count; i++) {
             png_read_rows(fCodec->fPng_ptr, &fSrcRow, png_bytepp_NULL, 1);
         }
         return SkImageGenerator::kSuccess;
     }
 
-    void onFinish() override {
-        fCodec->finish();
-    }
-
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
 private:
     SkPngCodec*         fCodec;     // Unowned.
     bool                fHasAlpha;
     SkAutoMalloc        fStorage;
     uint8_t*            fSrcRow;
 
     typedef SkScanlineDecoder INHERITED;
 };
@@ skipping 59 matching lines @@
         fCurrentRow += count;
         return SkImageGenerator::kSuccess;
     }
 
     SkImageGenerator::Result onSkipScanlines(int count) override {
         //when ongetScanlines is called it will skip to fCurrentRow
         fCurrentRow += count;
         return SkImageGenerator::kSuccess;
     }
 
-    void onFinish() override {
-        fCodec->finish();
-    }
-
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
 private:
     SkPngCodec*         fCodec;     // Unowned.
     bool                fHasAlpha;
     int                 fCurrentRow;
     int                 fHeight;
     size_t              fSrcRowBytes;
     bool                fRewindNeeded;
     SkAutoMalloc        fGarbageRow;
     uint8_t*            fGarbageRowPtr;
     
     
     
-    
 
+
     typedef SkScanlineDecoder INHERITED;
 };
 
 
 SkScanlineDecoder* SkPngCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
         const Options& options, SkPMColor ctable[], int* ctableCount) {
     if (!this->handleRewind()) {
         return NULL;
     }
 
@@ skipping 18 matching lines @@
 
     SkASSERT(fNumberPasses != INVALID_NUMBER_PASSES);
     if (fNumberPasses > 1) {
         // interlaced image
         return SkNEW_ARGS(SkPngInterlacedScanlineDecoder, (dstInfo, this));
     }
 
     return SkNEW_ARGS(SkPngScanlineDecoder, (dstInfo, this));
 }