Consolidate SkCodec functions for handling rewind

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 453 matching lines @@
     fSwizzler.reset(SkSwizzler::CreateSwizzler(fSrcConfig, colors, requestedInfo,
             options.fZeroInitialized));
     if (!fSwizzler) {
         // FIXME: CreateSwizzler could fail for another reason.
         return kUnimplemented;
     }
     return kSuccess;
 }
 
 
-bool SkPngCodec::handleRewind() {
-    switch (this->rewindIfNeeded()) {
-        case kNoRewindNecessary_RewindState:
-            return true;
-        case kCouldNotRewind_RewindState:
-            return false;
-        case kRewound_RewindState: {
-            // This sets fPng_ptr and fInfo_ptr to NULL. If read_header
-            // succeeds, they will be repopulated, and if it fails, they will
-            // remain NULL. Any future accesses to fPng_ptr and fInfo_ptr will
-            // come through this function which will rewind and again attempt
-            // to reinitialize them.
-            this->destroyReadStruct();
-            png_structp png_ptr;
-            png_infop info_ptr;
-            if (read_header(this->stream(), &png_ptr, &info_ptr, NULL, NULL)) {
-                fPng_ptr = png_ptr;
-                fInfo_ptr = info_ptr;
-                return true;
-            }
-            return false;
-        }
-        default:
-            SkASSERT(false);
-            return false;
+bool SkPngCodec::onRewind() {
+    // This sets fPng_ptr and fInfo_ptr to NULL. If read_header
+    // succeeds, they will be repopulated, and if it fails, they will
+    // remain NULL. Any future accesses to fPng_ptr and fInfo_ptr will
+    // come through this function which will rewind and again attempt
+    // to reinitialize them.
+    this->destroyReadStruct();
+
+    png_structp png_ptr;
+    png_infop info_ptr;
+    if (!read_header(this->stream(), &png_ptr, &info_ptr, NULL, NULL)) {
+        return false;
     }
+
+    fPng_ptr = png_ptr;
+    fInfo_ptr = info_ptr;
+    return true;
 }
 
 SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void* dst,
                                         size_t dstRowBytes, const Options& options,
                                         SkPMColor ctable[], int* ctableCount) {
     if (!conversion_possible(requestedInfo, this->getInfo())) {
         return kInvalidConversion;
     }
     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }
     if (requestedInfo.dimensions() != this->getInfo().dimensions()) {
         return kInvalidScale;
     }
-    if (!this->handleRewind()) {
+    if (!this->rewindIfNeeded()) {
         return kCouldNotRewind;
     }
 
     // Note that ctable and ctableCount may be modified if there is a color table
     const Result result = this->initializeSwizzler(requestedInfo, options,
                                                    ctable, ctableCount);
     if (result != kSuccess) {
         return result;
     }
     // FIXME: Could we use the return value of setjmp to specify the type of
@@ skipping 60 matching lines @@
     SkPngScanlineDecoder(const SkImageInfo& srcInfo, SkPngCodec* codec)
         : INHERITED(srcInfo)
         , fCodec(codec)
         , fHasAlpha(false)
     {}
 
     SkCodec::Result onStart(const SkImageInfo& dstInfo,
                             const SkCodec::Options& options,
                             SkPMColor ctable[], int* ctableCount) override
     {
-        if (!fCodec->handleRewind()) {
+        if (!fCodec->rewindIfNeeded()) {
             return SkCodec::kCouldNotRewind;
         }
 
         if (!conversion_possible(dstInfo, this->getInfo())) {
             return SkCodec::kInvalidConversion;
         }
 
         // Check to see if scaling was requested.
         if (dstInfo.dimensions() != this->getInfo().dimensions()) {
             return SkCodec::kInvalidScale;
@@ skipping 63 matching lines @@
         , fHasAlpha(false)
         , fCurrentRow(0)
         , fHeight(srcInfo.height())
         , fCanSkipRewind(false)
     {}
 
     SkCodec::Result onStart(const SkImageInfo& dstInfo,
                             const SkCodec::Options& options,
                             SkPMColor ctable[], int* ctableCount) override
     {
-        if (!fCodec->handleRewind()) {
+        if (!fCodec->rewindIfNeeded()) {
             return SkCodec::kCouldNotRewind;
         }
 
         if (!conversion_possible(dstInfo, this->getInfo())) {
             return SkCodec::kInvalidConversion;
         }
 
         // Check to see if scaling was requested.
         if (dstInfo.dimensions() != this->getInfo().dimensions()) {
             return SkCodec::kInvalidScale;
@@ skipping 16 matching lines @@
         return SkCodec::kSuccess;
     }
 
     SkCodec::Result onGetScanlines(void* dst, int count, size_t dstRowBytes) override {
         // rewind stream if have previously called onGetScanlines,
         // since we need entire progressive image to get scanlines
         if (fCanSkipRewind) {
             // We already rewound in onStart, so there is no reason to rewind.
             // Next time onGetScanlines is called, we will need to rewind.
             fCanSkipRewind = false;
-        } else if (!fCodec->handleRewind()) {
+        } else if (!fCodec->rewindIfNeeded()) {
             return SkCodec::kCouldNotRewind;
         }
 
         if (setjmp(png_jmpbuf(fCodec->fPng_ptr))) {
             SkCodecPrintf("setjmp long jump!\n");
             return SkCodec::kInvalidInput;
         }
         const int number_passes = png_set_interlace_handling(fCodec->fPng_ptr);
         SkAutoMalloc storage(count * fSrcRowBytes);
         uint8_t* storagePtr = static_cast<uint8_t*>(storage.get());
@@ skipping 66 matching lines @@
 
     const SkImageInfo& srcInfo = codec->getInfo();
     if (codec->fNumberPasses > 1) {
         // interlaced image
         return SkNEW_ARGS(SkPngInterlacedScanlineDecoder, (srcInfo, codec.detach()));
     }
 
     return SkNEW_ARGS(SkPngScanlineDecoder, (srcInfo, codec.detach()));
 }