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diff --git a/svl/source/notify/broadcast.cxx b/svl/source/notify/broadcast.cxx
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+/* -*- 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/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <svl/broadcast.hxx>
+#include <svl/listener.hxx>
+#include <svl/hint.hxx>
+#include <o3tl/safeint.hxx>
+#include <cassert>
+#include <algorithm>
+
+/**
+ Design Notes
+ -------------------------------
+
+ This class is extremely heavily used - we can have millions of broadcasters and listeners and we can also
+ have a broadcaster that has a million listeners.
+
+ So we do a number of things
+ (*) use a cache-dense listener list (std::vector) because caching effects dominate a lot of operations
+ (*) use a sorted list to speed up find operations
+ (*) only sort the list when we absolutely have to, to speed up sequential add/remove operations
+ (*) defer removing items from the list by (ab)using the last bit of the pointer
+
+ Also we have some complications around destruction because
+ (*) we broadcast a message to indicate that we are destructing
+ (*) which can trigger arbitrality complicated behaviour, including
+ (*) adding a removing things from the in-destruction object!
+
+*/
+
+static bool isDeletedPtr(SvtListener* p)
+{
+    /** mark deleted entries by toggling the last bit,which is effectively unused, since the struct we point
+     * to is at least 16-bit aligned. This allows the binary search to continue working even when we have
+     * deleted entries */
+#if SAL_TYPES_SIZEOFPOINTER == 4
+    return (reinterpret_cast<sal_uInt32>(p) & 0x01) == 0x01;
+#else
+    return (reinterpret_cast<sal_uInt64>(p) & 0x01) == 0x01;
+#endif
+}
+
+static void markDeletedPtr(SvtListener*& rp)
+{
+#if SAL_TYPES_SIZEOFPOINTER == 4
+    reinterpret_cast<sal_uInt32&>(rp) |= 0x01;
+#else
+    reinterpret_cast<sal_uInt64&>(rp) |= 0x01;
+#endif
+}
+
+static void sortListeners(std::vector<SvtListener*>& listeners, size_t firstUnsorted)
+{
+    // Add() only appends new values, so often the container will be sorted expect for one
+    // or few last items. For larger containers it is much more efficient to just handle
+    // the unsorted part.
+    auto sortedEnd = firstUnsorted == 0
+        ? std::is_sorted_until(listeners.begin(),listeners.end())
+        : listeners.begin() + firstUnsorted;
+    if( listeners.end() - sortedEnd == 1 )
+    {   // Just one item, insert it in the right place.
+        SvtListener* item = listeners.back();
+        listeners.pop_back();
+        listeners.insert( std::upper_bound( listeners.begin(), listeners.end(), item ), item );
+    }
+    else if( o3tl::make_unsigned( sortedEnd - listeners.begin()) > listeners.size() * 3 / 4 )
+    {   // Sort the unsorted part and then merge.
+        std::sort( sortedEnd, listeners.end());
+        std::inplace_merge( listeners.begin(), sortedEnd, listeners.end());
+    }
+    else
+    {
+        std::sort(listeners.begin(), listeners.end());
+    }
+}
+
+void SvtBroadcaster::Normalize() const
+{
+    // clear empty slots first, because then we often have to do very little sorting
+    if (mnEmptySlots)
+    {
+        maListeners.erase(
+            std::remove_if(maListeners.begin(), maListeners.end(), [] (SvtListener* p) { return isDeletedPtr(p); }),
+            maListeners.end());
+        mnEmptySlots = 0;
+    }
+
+    if (mnListenersFirstUnsorted != static_cast<sal_Int32>(maListeners.size()))
+    {
+        sortListeners(maListeners, mnListenersFirstUnsorted);
+        mnListenersFirstUnsorted = maListeners.size();
+    }
+
+    if (!mbDestNormalized)
+    {
+        sortListeners(maDestructedListeners, 0);
+        mbDestNormalized = true;
+    }
+}
+
+void SvtBroadcaster::Add( SvtListener* p )
+{
+    assert(!mbDisposing && "called inside my own destructor?");
+    assert(!mbAboutToDie && "called after PrepareForDestruction()?");
+    if (mbDisposing || mbAboutToDie)
+        return;
+    // Avoid normalizing if the item appended keeps the container sorted.
+    auto nRealSize = static_cast<sal_Int32>(maListeners.size() - mnEmptySlots);
+    auto bSorted = mnListenersFirstUnsorted == nRealSize;
+    if (maListeners.empty() || (bSorted && maListeners.back() <= p))
+    {
+        ++mnListenersFirstUnsorted;
+        maListeners.push_back(p);
+        return;
+    }
+    // see if we can stuff it into an empty slot, which succeeds surprisingly often in
+    // some calc workloads where it removes and then re-adds the same listener
+    if (mnEmptySlots && bSorted)
+    {
+        auto it = std::lower_bound(maListeners.begin(), maListeners.end(), p);
+        if (it != maListeners.end() && isDeletedPtr(*it))
+        {
+            *it = p;
+            ++mnListenersFirstUnsorted;
+            --mnEmptySlots;
+            return;
+        }
+    }
+    maListeners.push_back(p);
+}
+
+void SvtBroadcaster::Remove( SvtListener* p )
+{
+    if (mbDisposing)
+        return;
+
+    if (mbAboutToDie)
+    {
+        // only reset mbDestNormalized if we are going to become unsorted
+        if (!maDestructedListeners.empty() && maDestructedListeners.back() > p)
+            mbDestNormalized = false;
+        maDestructedListeners.push_back(p);
+        return;
+    }
+
+    // We only need to fully normalize if one or more Add()s have been performed that make the array unsorted.
+    auto nRealSize = static_cast<sal_Int32>(maListeners.size() - mnEmptySlots);
+    if (mnListenersFirstUnsorted != nRealSize || (maListeners.size() > 1024 && maListeners.size() / nRealSize > 16))
+        Normalize();
+
+    auto it = std::lower_bound(maListeners.begin(), maListeners.end(), p);
+    assert (it != maListeners.end() && *it == p);
+    if (it != maListeners.end() && *it == p)
+    {
+        markDeletedPtr(*it);
+        ++mnEmptySlots;
+        --mnListenersFirstUnsorted;
+    }
+
+    if (!HasListeners())
+        ListenersGone();
+}
+
+SvtBroadcaster::SvtBroadcaster( const SvtBroadcaster &rBC ) :
+    mnEmptySlots(0), mnListenersFirstUnsorted(0),
+    mbAboutToDie(false), mbDisposing(false),
+    mbDestNormalized(true)
+{
+    assert(!rBC.mbAboutToDie && "copying an object marked with PrepareForDestruction()?");
+    assert(!rBC.mbDisposing && "copying an object that is in its destructor?");
+
+    rBC.Normalize(); // so that insert into ourself is in-order, and therefore we do not need to Normalize()
+    maListeners.reserve(rBC.maListeners.size());
+    for (SvtListener* p : rBC.maListeners)
+         p->StartListening(*this); // this will call back into this->Add()
+}
+
+SvtBroadcaster::~SvtBroadcaster()
+{
+    mbDisposing = true;
+    Broadcast( SfxHint(SfxHintId::Dying) );
+
+    Normalize();
+
+    // now when both lists are sorted, we can linearly unregister all
+    // listeners, with the exception of those that already asked to be removed
+    // during their own destruction
+    ListenersType::const_iterator dest(maDestructedListeners.begin());
+    for (auto& rpListener : maListeners)
+    {
+        // skip the destructed ones
+        while (dest != maDestructedListeners.end() && (*dest < rpListener))
+            ++dest;
+
+        if (dest == maDestructedListeners.end() || *dest != rpListener)
+            rpListener->BroadcasterDying(*this);
+    }
+}
+
+void SvtBroadcaster::Broadcast( const SfxHint &rHint )
+{
+    Normalize();
+
+    ListenersType::const_iterator dest(maDestructedListeners.begin());
+    ListenersType aListeners(maListeners); // this copy is important to avoid erasing entries while iterating
+    for (auto& rpListener : aListeners)
+    {
+        // skip the destructed ones
+        while (dest != maDestructedListeners.end() && (*dest < rpListener))
+            ++dest;
+
+        if (dest == maDestructedListeners.end() || *dest != rpListener)
+            rpListener->Notify(rHint);
+    }
+}
+
+void SvtBroadcaster::ListenersGone() {}
+
+SvtBroadcaster::ListenersType& SvtBroadcaster::GetAllListeners()
+{
+    Normalize();
+    return maListeners;
+}
+
+const SvtBroadcaster::ListenersType& SvtBroadcaster::GetAllListeners() const
+{
+    Normalize();
+    return maListeners;
+}
+
+void SvtBroadcaster::PrepareForDestruction()
+{
+    mbAboutToDie = true;
+    // the reserve() serves two purpose (1) performance (2) makes sure our iterators do not become invalid
+    maDestructedListeners.reserve(maListeners.size());
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */