SkData can allocate room for its contents in the same block

src/images/SkDecodingImageGenerator.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkDecodingImageGenerator.h"
 #include "SkImageDecoder.h"
@@ skipping 114 matching lines @@
 }
 
 DecodingImageGenerator::~DecodingImageGenerator() {
     SkSafeUnref(fData);
     fStream->unref();
 }
 
 SkData* DecodingImageGenerator::onRefEncodedData() {
     // This functionality is used in `gm --serialize`
     // Does not encode options.
-    if (fData != NULL) {
-        return SkSafeRef(fData);
+    if (NULL == fData) {
+        // TODO(halcanary): SkStreamRewindable needs a refData() function
+        // which returns a cheap copy of the underlying data.
+        if (!fStream->rewind()) {
+            return NULL;
+        }
+        size_t length = fStream->getLength();
+        if (0 == length) {
+            return NULL;
+        }
+        fData = SkData::NewUninitialized(length);
+        SkCheckResult(fStream->read(fData->writable_data(), length), length);
     }
-    // TODO(halcanary): SkStreamRewindable needs a refData() function
-    // which returns a cheap copy of the underlying data.
-    if (!fStream->rewind()) {
-        return NULL;
-    }
-    size_t length = fStream->getLength();
-    if (0 == length) {
-        return NULL;
-    }
-    void* buffer = sk_malloc_flags(length, 0);
-    SkCheckResult(fStream->read(buffer, length), length);
-    fData = SkData::NewFromMalloc(buffer, length);
-    return SkSafeRef(fData);
+    return SkRef(fData);
 }
 
 bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info,
                                          void* pixels, size_t rowBytes,
                                          SkPMColor ctableEntries[], int* ctableCount) {
     if (fInfo != info) {
         // The caller has specified a different info.  This is an
         // error for this kind of SkImageGenerator.  Use the Options
         // to change the settings.
         return false;
@@ skipping 116 matching lines @@
         SkStreamRewindable* stream,
         const SkDecodingImageGenerator::Options& opts) {
     SkASSERT(stream != NULL);
     SkASSERT(stream->unique());
     if ((stream == NULL) || !stream->unique()) {
         SkSafeUnref(stream);
         return NULL;
     }
     return CreateDecodingImageGenerator(NULL, stream, opts);
 }