df generation: single allocation with calloc

src/core/SkDistanceFieldGen.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDistanceFieldGen.h"
 #include "SkPoint.h"
 
@@ skipping 325 matching lines @@
     SkASSERT(copyPtr);
 
     // we expand our temp data by one more on each side to simplify
     // the scanning code -- will always be treated as infinitely far away
     int pad = SK_DistanceFieldPad + 1;
 
     // set params for distance field data
     int dataWidth = width + 2*pad;
     int dataHeight = height + 2*pad;
 
-    // create temp data
-    size_t dataSize = dataWidth*dataHeight*sizeof(DFData);
-    SkAutoSMalloc<1024> dfStorage(dataSize);
-    DFData* dataPtr = (DFData*) dfStorage.get();
-    sk_bzero(dataPtr, dataSize);
-
-    SkAutoSMalloc<1024> edgeStorage(dataWidth*dataHeight*sizeof(char));
-    unsigned char* edgePtr = (unsigned char*) edgeStorage.get();
-    sk_bzero(edgePtr, dataWidth*dataHeight*sizeof(char));
+    // create zeroed temp DFData+edge storage
+    SkAutoFree storage(sk_calloc_throw(dataWidth*dataHeight*(sizeof(DFData) + 1)));
+    DFData*        dataPtr = (DFData*)storage.get();
+    unsigned char* edgePtr = (unsigned char*)storage.get() + dataWidth*dataHeight*sizeof(DFData);
 
     // copy glyph into distance field storage
     init_glyph_data(dataPtr, edgePtr, copyPtr,
                     dataWidth, dataHeight,
                     width+2, height+2, SK_DistanceFieldPad);
 
     // create initial distance data, particularly at edges
     init_distances(dataPtr, edgePtr, dataWidth, dataHeight);
 
     // now perform Euclidean distance transform to propagate distances
@@ skipping 147 matching lines @@
                 *currDestPtr++ = (mask & (1 << i)) ? 0xff : 0;
             }
         }
         currSrcScanLine += rowBytes;
         *currDestPtr++ = 0;
     }
     sk_bzero(currDestPtr, (width+2)*sizeof(char));
 
     return generate_distance_field_from_image(distanceField, copyPtr, width, height);
 }