SkPngCodec clean-ups

src/codec/SkPngCodec.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 "SkCodecPriv.h"
 #include "SkColorPriv.h"
 #include "SkColorTable.h"
@@ skipping 460 matching lines @@
     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }
 
     // 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;
     }
+
+    const int width = requestedInfo.width();
+    const int height = requestedInfo.height();
+    const int bpp = SkSwizzler::BytesPerPixel(fSrcConfig);
+    const size_t srcRowBytes = width * bpp;
+
     // FIXME: Could we use the return value of setjmp to specify the type of
     // error?
     int row = 0;
     // This must be declared above the call to setjmp to avoid memory leaks on incomplete images.
     SkAutoTMalloc<uint8_t> storage;
     if (setjmp(png_jmpbuf(fPng_ptr))) {
         // Assume that any error that occurs while reading rows is caused by an incomplete input.
         if (fNumberPasses > 1) {
             // FIXME (msarett): Handle incomplete interlaced pngs.
-            return kInvalidInput;
+            return (row == height) ? kSuccess : kInvalidInput;
         }
         // FIXME: We do a poor job on incomplete pngs compared to other decoders (ex: Chromium,
         // Ubuntu Image Viewer).  This is because we use the default buffer size in libpng (8192
         // bytes), and if we can't fill the buffer, we immediately fail.
         // For example, if we try to read 8192 bytes, and the image (incorrectly) only contains
         // half that, which may have been enough to contain a non-zero number of lines, we fail
         // when we could have decoded a few more lines and then failed.
         // The read function that we provide for libpng has no way of indicating that we have
         // made a partial read.
         // Making our buffer size smaller improves our incomplete decodes, but what impact does
         // it have on regular decode performance?  Should we investigate using a different API
-        // instead of png_read_row(s)?  Chromium uses png_process_data.
+        // instead of png_read_row?  Chromium uses png_process_data.
         *rowsDecoded = row;
-        return kIncompleteInput;
+        return (row == height) ? kSuccess : kIncompleteInput;
     }
 
     // FIXME: We could split these out based on subclass.
     void* dstRow = dst;
     if (fNumberPasses > 1) {
-        const int width = requestedInfo.width();
-        const int height = requestedInfo.height();
-        const int bpp = SkSwizzler::BytesPerPixel(fSrcConfig);
-        const size_t srcRowBytes = width * bpp;
-
-        storage.reset(width * height * bpp);
+        storage.reset(height * srcRowBytes);
         uint8_t* const base = storage.get();
 
         for (int i = 0; i < fNumberPasses; i++) {
             uint8_t* srcRow = base;
             for (int y = 0; y < height; y++) {
-                uint8_t* bmRow = srcRow;
-                png_read_rows(fPng_ptr, &bmRow, nullptr, 1);
+                png_read_row(fPng_ptr, srcRow, nullptr);
                 srcRow += srcRowBytes;
             }
         }
 
         // Now swizzle it.
         uint8_t* srcRow = base;
-        for (int y = 0; y < height; y++) {
+        for (; row < height; row++) {
             fSwizzler->swizzle(dstRow, srcRow);
             dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
             srcRow += srcRowBytes;
         }
     } else {
-        storage.reset(requestedInfo.width() * SkSwizzler::BytesPerPixel(fSrcConfig));
+        storage.reset(srcRowBytes);
         uint8_t* srcRow = storage.get();
-        for (; row < requestedInfo.height(); row++) {
-            png_read_rows(fPng_ptr, &srcRow, nullptr, 1);
-            // FIXME: Only call IsOpaque once, outside the loop. Same for onGetScanlines.
+        for (; row < height; row++) {
+            png_read_row(fPng_ptr, srcRow, nullptr);
             fSwizzler->swizzle(dstRow, srcRow);
             dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
         }
     }
 
-    if (setjmp(png_jmpbuf(fPng_ptr))) {
-        // We've already read all the scanlines. This is a success.
-        return kSuccess;
-    }
-
     // read rest of file, and get additional comment and time chunks in info_ptr
     png_read_end(fPng_ptr, fInfo_ptr);
 
     return kSuccess;
 }
 
 uint32_t SkPngCodec::onGetFillValue(SkColorType colorType) const {
     const SkPMColor* colorPtr = get_color_ptr(fColorTable.get());
     if (colorPtr) {
         return get_color_table_fill_value(colorType, colorPtr, 0);
@@ skipping 31 matching lines @@
     int onGetScanlines(void* dst, int count, size_t rowBytes) override {
         // Assume that an error in libpng indicates an incomplete input.
         int row = 0;
         if (setjmp(png_jmpbuf(this->png_ptr()))) {
             SkCodecPrintf("setjmp long jump!\n");
             return row;
         }
 
         void* dstRow = dst;
         for (; row < count; row++) {
-            png_read_rows(this->png_ptr(), &fSrcRow, nullptr, 1);
+            png_read_row(this->png_ptr(), fSrcRow, nullptr);
             this->swizzler()->swizzle(dstRow, fSrcRow);
             dstRow = SkTAddOffset<void>(dstRow, rowBytes);
         }
 
         return row;
     }
 
     bool onSkipScanlines(int count) override {
         // Assume that an error in libpng indicates an incomplete input.
         if (setjmp(png_jmpbuf(this->png_ptr()))) {
             SkCodecPrintf("setjmp long jump!\n");
             return false;
         }
-        //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 row = 0; row < count; row++) {
-            png_read_rows(this->png_ptr(), &fSrcRow, nullptr, 1);
+            png_read_row(this->png_ptr(), fSrcRow, nullptr);
         }
         return true;
     }
 
 private:
     SkAutoTMalloc<uint8_t>      fStorage;
     uint8_t*                    fSrcRow;
 
     typedef SkPngCodec INHERITED;
 };
@@ skipping 63 matching lines @@
             // fail on the first pass, we can still report than some scanlines are initialized.
             return 0;
         }
         SkAutoTMalloc<uint8_t> storage(count * fSrcRowBytes);
         uint8_t* storagePtr = storage.get();
         uint8_t* srcRow;
         const int startRow = this->nextScanline();
         for (int i = 0; i < this->numberPasses(); i++) {
             // read rows we planned to skip into garbage row
             for (int y = 0; y < startRow; y++){
-                png_read_rows(this->png_ptr(), &fGarbageRowPtr, nullptr, 1);
+                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
             }
             // read rows we care about into buffer
             srcRow = storagePtr;
             for (int y = 0; y < count; y++) {
-                png_read_rows(this->png_ptr(), &srcRow, nullptr, 1);
+                png_read_row(this->png_ptr(), srcRow, nullptr);
                 srcRow += fSrcRowBytes;
             }
             // read rows we don't want into garbage buffer
             for (int y = 0; y < fHeight - startRow - count; y++) {
-                png_read_rows(this->png_ptr(), &fGarbageRowPtr, nullptr, 1);
+                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
             }
         }
         //swizzle the rows we care about
         srcRow = storagePtr;
         void* dstRow = dst;
         for (int y = 0; y < count; y++) {
             this->swizzler()->swizzle(dstRow, srcRow);
             dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
             srcRow += fSrcRowBytes;
         }
@@ skipping 42 matching lines @@
     }
 
     if (1 == numberPasses) {
         return new SkPngScanlineDecoder(imageInfo, streamDeleter.detach(), chunkReader,
                                         png_ptr, info_ptr, bitDepth);
     }
 
     return new SkPngInterlacedScanlineDecoder(imageInfo, streamDeleter.detach(), chunkReader,
                                               png_ptr, info_ptr, bitDepth, numberPasses);
 }