Source/WebCore/storage/StorageMap.cpp

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#include "config.h"
#include "StorageMap.h"

#include <wtf/CheckedArithmetic.h>
#include <wtf/SetForScope.h>

namespace WebCore {

StorageMap::StorageMap(unsigned quota)
    : m_impl(Impl::create())
    , m_quotaSize(quota) // quota measured in bytes
{
}

void StorageMap::invalidateIterator()
{
    m_impl->iterator = m_impl->map.end();
    m_impl->iteratorIndex = UINT_MAX;
}

void StorageMap::setIteratorToIndex(unsigned index)
{
    // FIXME: Once we have bidirectional iterators for HashMap we can be more intelligent about this.
    // The requested index will be closest to begin(), our current iterator, or end(), and we
    // can take the shortest route.
    // Until that mechanism is available, we'll always increment our iterator from begin() or current.

    if (m_impl->iteratorIndex == index)
        return;

    if (index < m_impl->iteratorIndex) {
        m_impl->iteratorIndex = 0;
        m_impl->iterator = m_impl->map.begin();
        ASSERT(m_impl->iterator != m_impl->map.end());
    }

    while (m_impl->iteratorIndex < index) {
        ++m_impl->iteratorIndex;
        ++m_impl->iterator;
        ASSERT(m_impl->iterator != m_impl->map.end());
    }
}

unsigned StorageMap::length() const
{
    return m_impl->map.size();
}

String StorageMap::key(unsigned index)
{
    if (index >= length())
        return String();

    setIteratorToIndex(index);
    return m_impl->iterator->key;
}

String StorageMap::getItem(const String& key) const
{
    return m_impl->map.get(key);
}

void StorageMap::setItem(const String& key, const String& value, String& oldValue, bool& quotaException)
{
    ASSERT(!value.isNull());
    quotaException = false;

    // Implement copy-on-write semantics.
    if (m_impl->refCount() > 1)
        m_impl = m_impl->copy();

    oldValue = m_impl->map.get(key);

    // Quota tracking. This is done in a couple of steps to keep the overflow tracking simple.
    CheckedUint32 newSize = m_impl->currentSize;
    newSize -= oldValue.sizeInBytes();
    newSize += value.sizeInBytes();
    if (oldValue.isNull())
        newSize += key.sizeInBytes();
    if (m_quotaSize != noQuota && (newSize.hasOverflowed() || newSize > m_quotaSize)) {
        quotaException = true;
        return;
    }
    m_impl->currentSize = newSize;

    HashMap<String, String>::AddResult addResult = m_impl->map.add(key, value);
    if (!addResult.isNewEntry)
        addResult.iterator->value = value;

    invalidateIterator();
}

void StorageMap::setItemIgnoringQuota(const String& key, const String& value)
{
    SetForScope<unsigned> quotaSizeChange(m_quotaSize, noQuota);

    String oldValue;
    bool quotaException;
    setItem(key, value, oldValue, quotaException);
    ASSERT(!quotaException);
}

void StorageMap::removeItem(const String& key, String& oldValue)
{
    // Implement copy-on-write semantics.
    if (m_impl->refCount() > 1)
        m_impl = m_impl->copy();

    oldValue = m_impl->map.take(key);
    if (oldValue.isNull())
        return;

    invalidateIterator();
    ASSERT(m_impl->currentSize - key.sizeInBytes() <= m_impl->currentSize);
    m_impl->currentSize -= key.sizeInBytes();
    ASSERT(m_impl->currentSize - oldValue.sizeInBytes() <= m_impl->currentSize);
    m_impl->currentSize -= oldValue.sizeInBytes();
}

void StorageMap::clear()
{
    if (m_impl->refCount() > 1 && length()) {
        m_impl = Impl::create();
        return;
    }
    m_impl->map.clear();
    m_impl->currentSize = 0;
    invalidateIterator();
}

bool StorageMap::contains(const String& key) const
{
    return m_impl->map.contains(key);
}

void StorageMap::importItems(HashMap<String, String>&& items)
{
    if (m_impl->map.isEmpty()) {
        // Fast path.
        m_impl->map = WTFMove(items);
        for (auto& pair : m_impl->map) {
            ASSERT(m_impl->currentSize + pair.key.sizeInBytes() + pair.value.sizeInBytes() >= m_impl->currentSize);
            m_impl->currentSize += (pair.key.sizeInBytes() + pair.value.sizeInBytes());
        }
        return;
    }

    for (auto& item : items) {
        auto& key = item.key;
        auto& value = item.value;

        ASSERT(m_impl->currentSize + key.sizeInBytes() + value.sizeInBytes() >= m_impl->currentSize);
        m_impl->currentSize += (key.sizeInBytes() + value.sizeInBytes());

        auto result = m_impl->map.add(WTFMove(key), WTFMove(value));
        ASSERT_UNUSED(result, result.isNewEntry); // True if the key didn't exist previously.
    }
}

Ref<StorageMap::Impl> StorageMap::Impl::copy() const
{
    auto copy = Impl::create();
    copy->map = map;
    copy->currentSize = currentSize;
    return copy;
}

}