1 files changed, 262 insertions, 0 deletions
diff --git a/chromium/third_party/WebKit/Source/platform/PurgeableVector.cpp b/chromium/third_party/WebKit/Source/platform/PurgeableVector.cpp
new file mode 100644
index 00000000000..d3efe15687d
--- /dev/null
+++ b/chromium/third_party/WebKit/Source/platform/PurgeableVector.cpp
@@ -0,0 +1,262 @@
+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "platform/PurgeableVector.h"
+
+#include "public/platform/Platform.h"
+#include "public/platform/WebDiscardableMemory.h"
+#include "wtf/Assertions.h"
+#include "wtf/OwnPtr.h"
+#include "wtf/PassOwnPtr.h"
+
+#include <cstring>
+
+namespace WebCore {
+
+// WebDiscardableMemory allocations are expensive and page-grained. We only use
+// them when there's a reasonable amount of memory to be saved by the OS
+// discarding the memory.
+static const size_t minimumDiscardableAllocationSize = 4 * 4096;
+
+PurgeableVector::PurgeableVector(PurgeableOption purgeable)
+    : m_discardableCapacity(0)
+    , m_discardableSize(0)
+    , m_isPurgeable(purgeable == Purgeable)
+    , m_locksCount(1) // The buffer is locked at creation.
+{
+}
+
+PurgeableVector::~PurgeableVector()
+{
+}
+
+void PurgeableVector::reserveCapacity(size_t capacity)
+{
+    ASSERT(isLocked());
+
+    if (m_isPurgeable) {
+        if (reservePurgeableCapacity(capacity, UseExactCapacity))
+            return;
+        // Fallback to non-purgeable buffer allocation in case discardable memory allocation failed.
+    }
+
+    if (!m_vector.capacity()) {
+        // Using reserveInitialCapacity() on the underlying vector ensures that the vector uses the
+        // exact specified capacity to avoid consuming too much memory for small resources.
+        m_vector.reserveInitialCapacity(capacity);
+    } else {
+        m_vector.reserveCapacity(capacity);
+    }
+
+    moveDataFromDiscardableToVector();
+}
+
+void PurgeableVector::moveDataFromDiscardableToVector()
+{
+    if (m_discardable) {
+        m_vector.append(static_cast<const char*>(m_discardable->data()), m_discardableSize);
+        clearDiscardable();
+    }
+}
+
+void PurgeableVector::clearDiscardable()
+{
+    m_discardable.clear();
+    m_discardableCapacity = 0;
+    m_discardableSize = 0;
+}
+
+void PurgeableVector::append(const char* data, size_t length)
+{
+    ASSERT(isLocked());
+
+    if (!m_isPurgeable) {
+        m_vector.append(data, length);
+        return;
+    }
+
+    const size_t currentSize = m_discardable ? m_discardableSize : m_vector.size();
+    const size_t newBufferSize = currentSize + length;
+
+    if (!reservePurgeableCapacity(newBufferSize, UseExponentialGrowth)) {
+        moveDataFromDiscardableToVector();
+        m_vector.append(data, length);
+        return;
+    }
+
+    ASSERT(m_discardableSize + length <= m_discardableCapacity);
+    memcpy(static_cast<char*>(m_discardable->data()) + m_discardableSize, data, length);
+    m_discardableSize += length;
+}
+
+void PurgeableVector::grow(size_t newSize)
+{
+    ASSERT(newSize >= size());
+
+    if (m_isPurgeable) {
+        if (reservePurgeableCapacity(newSize, UseExponentialGrowth)) {
+            m_discardableSize = newSize;
+            return;
+        }
+        moveDataFromDiscardableToVector();
+    }
+
+    m_vector.resize(newSize);
+}
+
+void PurgeableVector::clear()
+{
+    clearDiscardable();
+    m_vector.clear();
+}
+
+char* PurgeableVector::data()
+{
+    ASSERT(isLocked());
+    return m_discardable ? static_cast<char*>(m_discardable->data()) : m_vector.data();
+}
+
+size_t PurgeableVector::size() const
+{
+    return m_discardable ? m_discardableSize : m_vector.size();
+}
+
+void PurgeableVector::adopt(Vector<char>& other)
+{
+    if (size() > 0)
+        clear();
+
+    if (!m_isPurgeable) {
+        m_vector.swap(other);
+        return;
+    }
+
+    if (other.isEmpty())
+        return;
+
+    append(other.data(), other.size());
+    other.clear();
+}
+
+bool PurgeableVector::lock()
+{
+    ++m_locksCount;
+    if (m_locksCount > 1)
+        return true;
+
+    ASSERT(m_locksCount == 1);
+    if (!m_discardable)
+        return true;
+
+    return m_discardable->lock();
+}
+
+void PurgeableVector::unlock()
+{
+    ASSERT(isLocked());
+    --m_locksCount;
+    if (m_locksCount > 0)
+        return;
+
+    if (!m_vector.isEmpty()) {
+        ASSERT(!m_discardable);
+        m_isPurgeable = true;
+        if (!reservePurgeableCapacity(m_vector.size(), UseExactCapacity))
+            return;
+    }
+
+    if (m_discardable)
+        m_discardable->unlock();
+}
+
+bool PurgeableVector::isLocked() const
+{
+    ASSERT(m_locksCount >= 0);
+    return m_locksCount > 0;
+}
+
+bool PurgeableVector::reservePurgeableCapacity(size_t capacity, PurgeableAllocationStrategy allocationStrategy)
+{
+    ASSERT(m_isPurgeable);
+
+    if (m_discardable && m_discardableCapacity >= capacity) {
+        ASSERT(!m_vector.capacity());
+        return true;
+    }
+
+    if (capacity < minimumDiscardableAllocationSize)
+        return false;
+
+    if (allocationStrategy == UseExponentialGrowth)
+        capacity = adjustPurgeableCapacity(capacity);
+
+    OwnPtr<blink::WebDiscardableMemory> discardable = adoptPtr(
+        blink::Platform::current()->allocateAndLockDiscardableMemory(capacity));
+    if (!discardable) {
+        // Discardable memory is not supported.
+        m_isPurgeable = false;
+        return false;
+    }
+
+    m_discardableCapacity = capacity;
+    // Copy the data that was either in the previous purgeable buffer or in the vector to the new
+    // purgeable buffer.
+    if (m_discardable) {
+        memcpy(discardable->data(), m_discardable->data(), m_discardableSize);
+    } else {
+        memcpy(discardable->data(), m_vector.data(), m_vector.size());
+        m_discardableSize = m_vector.size();
+        m_vector.clear();
+    }
+
+    m_discardable.swap(discardable);
+    ASSERT(!m_vector.capacity());
+    return true;
+}
+
+size_t PurgeableVector::adjustPurgeableCapacity(size_t capacity) const
+{
+    ASSERT(capacity >= minimumDiscardableAllocationSize);
+
+    const float growthFactor = 1.5;
+    size_t newCapacity = std::max(capacity, static_cast<size_t>(m_discardableCapacity * growthFactor));
+
+    // Discardable memory has page-granularity so align to the next page here to minimize
+    // fragmentation.
+    // Since the page size is only used below to minimize fragmentation it's still safe to use it
+    // even if it gets out of sync (e.g. due to the use of huge pages).
+    const size_t kPageSize = 4096;
+    newCapacity = (newCapacity + kPageSize - 1) & ~(kPageSize - 1);
+
+    return std::max(capacity, newCapacity); // Overflow check.
+}
+
+} // namespace WebCore