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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/.
*/
#include <svl/sharedstringpool.hxx>
#include <svl/sharedstring.hxx>
#include <unotools/charclass.hxx>
#include <mutex>
#include <unordered_map>
#include <unordered_set>
/** create a key class that caches the hashcode */
namespace
{
struct StringWithHash
{
OUString str;
sal_Int32 hashCode;
StringWithHash(OUString s)
: str(s)
, hashCode(s.hashCode())
{
}
bool operator==(StringWithHash const& rhs) const
{
if (hashCode != rhs.hashCode)
return false;
return str == rhs.str;
}
};
}
namespace std
{
template <> struct hash<StringWithHash>
{
std::size_t operator()(const StringWithHash& k) const { return k.hashCode; }
};
}
namespace svl
{
namespace
{
sal_Int32 getRefCount(const rtl_uString* p) { return (p->refCount & 0x3FFFFFFF); }
}
struct SharedStringPool::Impl
{
mutable std::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<StringWithHash, OUString> maStrMap;
const CharClass& mrCharClass;
explicit Impl(const CharClass& rCharClass)
: mrCharClass(rCharClass)
{
}
};
SharedStringPool::SharedStringPool(const CharClass& rCharClass)
: mpImpl(new Impl(rCharClass))
{
// make sure the one empty string instance is shared in this pool as well
intern(OUString());
assert(intern(OUString()) == SharedString::getEmptyString());
}
SharedStringPool::~SharedStringPool() {}
SharedString SharedStringPool::intern(const OUString& rStr)
{
StringWithHash aStrWithHash(rStr);
std::scoped_lock<std::mutex> aGuard(mpImpl->maMutex);
auto[mapIt, bInserted] = mpImpl->maStrMap.emplace(aStrWithHash, rStr);
if (!bInserted)
// there is already a mapping
return SharedString(mapIt->first.str.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.str.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.
StringWithHash aUpperWithHash(aUpper);
auto mapIt2 = mpImpl->maStrMap.find(aUpperWithHash);
if (mapIt2 != mpImpl->maStrMap.end())
{
// there is an already existing upper string
mapIt->second = mapIt2->first.str;
return SharedString(mapIt->first.str.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, aUpperWithHash, aUpper);
return SharedString(rStr.pData, aUpper.pData);
}
void SharedStringPool::purge()
{
std::scoped_lock<std::mutex> 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.str.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.str.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
{
std::scoped_lock<std::mutex> aGuard(mpImpl->maMutex);
return mpImpl->maStrMap.size();
}
size_t SharedStringPool::getCountIgnoreCase() const
{
std::scoped_lock<std::mutex> 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: */
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