1 files changed, 151 insertions, 0 deletions
diff --git a/svl/source/misc/sharedstringpool.cxx b/svl/source/misc/sharedstringpool.cxx
new file mode 100644
index 000000000..e4bc873e5
--- /dev/null
+++ b/svl/source/misc/sharedstringpool.cxx
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <svl/sharedstringpool.hxx>
+#include <svl/sharedstring.hxx>
+#include <unotools/charclass.hxx>
+#include <osl/mutex.hxx>
+
+#include <unordered_map>
+#include <unordered_set>
+
+namespace svl {
+
+namespace {
+
+sal_Int32 getRefCount( const rtl_uString* p )
+{
+    return (p->refCount & 0x3FFFFFFF);
+}
+
+}
+
+struct SharedStringPool::Impl
+{
+    mutable osl::Mutex maMutex;
+    // We use this map for two purposes - to store lower->upper case mappings
+    // and to retrieve a shared uppercase object, so the management logic
+    // is quite complex.
+    std::unordered_map<OUString,OUString> maStrMap;
+    const CharClass& mrCharClass;
+
+    explicit Impl( const CharClass& rCharClass ) : mrCharClass(rCharClass) {}
+};
+
+SharedStringPool::SharedStringPool( const CharClass& rCharClass ) :
+    mpImpl(new Impl(rCharClass)) {}
+
+SharedStringPool::~SharedStringPool()
+{
+}
+
+SharedString SharedStringPool::intern( const OUString& rStr )
+{
+    osl::MutexGuard aGuard(&mpImpl->maMutex);
+
+    auto [mapIt,bInserted] = mpImpl->maStrMap.emplace(rStr, rStr);
+    if (!bInserted)
+        // there is already a mapping
+        return SharedString(mapIt->first.pData, mapIt->second.pData);
+
+    // This is a new string insertion. Establish mapping to upper-case variant.
+    OUString aUpper = mpImpl->mrCharClass.uppercase(rStr);
+    if (aUpper == rStr)
+        // no need to do anything more, because we inserted an upper->upper mapping
+        return SharedString(mapIt->first.pData, mapIt->second.pData);
+
+    // We need to insert a lower->upper mapping, so also insert
+    // an upper->upper mapping, which we can use both for when an upper string
+    // is interned, and to look up a shared upper string.
+    auto mapIt2 = mpImpl->maStrMap.find(aUpper);
+    if (mapIt2 != mpImpl->maStrMap.end())
+    {
+        // there is an already existing upper string
+        mapIt->second = mapIt2->first;
+        return SharedString(mapIt->first.pData, mapIt->second.pData);
+    }
+
+    // There is no already existing upper string.
+    // First, update using the iterator, can't do this later because
+    // the iterator will be invalid.
+    mapIt->second = aUpper;
+    mpImpl->maStrMap.emplace_hint(mapIt2, aUpper, aUpper);
+    return SharedString(rStr.pData, aUpper.pData);
+}
+
+void SharedStringPool::purge()
+{
+    osl::MutexGuard aGuard(&mpImpl->maMutex);
+
+    // Because we can have an uppercase entry mapped to itself,
+    // and then a bunch of lowercase entries mapped to that same
+    // upper-case entry, we need to scan the map twice - the first
+    // time to remove lowercase entries, and then only can we
+    // check for unused uppercase entries.
+
+    auto it = mpImpl->maStrMap.begin();
+    auto itEnd = mpImpl->maStrMap.end();
+    while (it != itEnd)
+    {
+        rtl_uString* p1 = it->first.pData;
+        rtl_uString* p2 = it->second.pData;
+        if (p1 != p2)
+        {
+            // normal case - lowercase mapped to uppercase, which
+            // means that the lowercase entry has one ref-counted
+            // entry as the key in the map
+            if (getRefCount(p1) == 1)
+            {
+                it = mpImpl->maStrMap.erase(it);
+                continue;
+            }
+        }
+        ++it;
+    }
+
+    it = mpImpl->maStrMap.begin();
+    itEnd = mpImpl->maStrMap.end();
+    while (it != itEnd)
+    {
+        rtl_uString* p1 = it->first.pData;
+        rtl_uString* p2 = it->second.pData;
+        if (p1 == p2)
+        {
+            // uppercase which is mapped to itself, which means
+            // one ref-counted entry as the key in the map, and
+            // one ref-counted entry in the value in the map
+            if (getRefCount(p1) == 2)
+            {
+                it = mpImpl->maStrMap.erase(it);
+                continue;
+            }
+        }
+        ++it;
+    }
+}
+
+size_t SharedStringPool::getCount() const
+{
+    osl::MutexGuard aGuard(&mpImpl->maMutex);
+    return mpImpl->maStrMap.size();
+}
+
+size_t SharedStringPool::getCountIgnoreCase() const
+{
+    osl::MutexGuard aGuard(&mpImpl->maMutex);
+    // this is only called from unit tests, so no need to be efficient
+    std::unordered_set<OUString> aUpperSet;
+    for (auto const & pair : mpImpl->maStrMap)
+        aUpperSet.insert(pair.second);
+    return aUpperSet.size();
+}
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */