[Platform] Enable to get a partial data of SharedBuffer

third_party/WebKit/Source/platform/SharedBuffer.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 222 matching lines @@
         size_t segmentedSize = std::min(maxSegmentedSize, bytesLeft);
 
         size_t positionInSegment = offsetInSegment(position);
         someData = m_segments[segment] + positionInSegment;
         return segment == segments - 1 ? segmentedSize - position : kSegmentSize - positionInSegment;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
-bool SharedBuffer::getAsBytesInternal(void* dest, size_t byteLength) const
+bool SharedBuffer::getAsBytesInternal(void* dest, size_t loadPosition, size_t byteLength) const
 {
-    if (!dest || byteLength != size())
+    if (!dest)
         return false;
 
-    const char* segment = 0;
-    size_t position = 0;
-    while (size_t segmentSize = getSomeDataInternal(segment, position)) {
-        memcpy(static_cast<char*>(dest) + position, segment, segmentSize);
-        position += segmentSize;
+    const char* segment = nullptr;
+    size_t writePosition = 0;
+    while (byteLength > 0) {
+        size_t loadSize = getSomeDataInternal(segment, loadPosition);
+        if (loadSize == 0)
+            break;
+
+        if (byteLength < loadSize)
+            loadSize = byteLength;
+        memcpy(static_cast<char*>(dest) + writePosition, segment, loadSize);
+        loadPosition += loadSize;
+        writePosition += loadSize;
+        byteLength -= loadSize;
     }
 
-    if (position != byteLength) {
-        ASSERT_NOT_REACHED();
-        // Don't return the incomplete data.
-        return false;
-    }
-
-    return true;
+    return byteLength == 0;
 }
 
 sk_sp<SkData> SharedBuffer::getAsSkData() const
 {
     size_t bufferLength = size();
     sk_sp<SkData> data = SkData::MakeUninitialized(bufferLength);
     char* buffer = static_cast<char*>(data->writable_data());
     const char* segment = 0;
     size_t position = 0;
     while (size_t segmentSize = getSomeDataInternal(segment, position)) {
@@ skipping 33 matching lines @@
         // If there is data in the segments, then it should have been allocated
         // using fastMalloc.
         const String dataDumpName = dumpPrefix + "/segments";
         auto dump = memoryDump->createMemoryAllocatorDump(dataDumpName);
         dump->addScalar("size", "bytes", m_size);
         memoryDump->addSuballocation(dump->guid(), String(WTF::Partitions::kAllocatedObjectPoolName));
     }
 }
 
 } // namespace blink