Avoid COW overhead using css::uno::Sequence

The scenarios are:

1. Calling sequence's begin() and end() in pairs to pass to algorithms
(both calls use getArray(), which does the COW checks)
2. In addition to #1, calling end() again when checking result of find
algorithms, and/or begin() to calculate result's distance
3. Using non-const sequences in range-based for loops, which internally
do #1
4. Assigning sequence to another sequence variable, and then modifying
one of them

In many cases, the sequences could be made const, or treated as const
for the purposes of the algorithms (using std::as_const, std::cbegin,
and std::cend). Where algorithm modifies the sequence, it was changed
to only call getArray() once. For that, css::uno::toNonConstRange was
introduced, which returns a struct (sublclass of std::pair) with two
iterators [begin, end], that are calculated using one call to begin()
and one call to getLength().

To handle #4, css::uno::Sequence::swap was introduced, that swaps the
internal pointer to uno_Sequence. So when a local Sequence variable
should be assigned to another variable, and the latter will be modified
further, it's now possible to use swap instead, so the two sequences
are kept independent.

The modified places were found by temporarily removing non-const end().

Change-Id: I8fe2787f200eecb70744e8b77fbdf7a49653f628
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/123542
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

4 files changed, 17 insertions, 16 deletions

diff --git a/stoc/source/implementationregistration/implreg.cxx b/stoc/source/implementationregistration/implreg.cxx
index 90c9d462db71..bfd19ccd07e4 100644
--- a/stoc/source/implementationregistration/implreg.cxx
+++ b/stoc/source/implementationregistration/implreg.cxx
@@ -254,7 +254,7 @@ OUString searchLinkTargetForImpl(const Reference < XRegistryKey >& xRootKey,
 
     if (xKey.is())
     {
-        Sequence< Reference < XRegistryKey > > subKeys = xKey->openKeys();
+        const Sequence< Reference < XRegistryKey > > subKeys = xKey->openKeys();
 
         OUString qualifiedLinkName( slash_UNO + linkName );
 
@@ -283,7 +283,7 @@ void createUniqueSubEntry(const Reference < XRegistryKey > & xSuperKey,
 
     if (xSuperKey->getValueType() == RegistryValueType_ASCIILIST)
     {
-        Sequence<OUString> implEntries = xSuperKey->getAsciiListValue();
+        const Sequence<OUString> implEntries = xSuperKey->getAsciiListValue();
         sal_Int32 length = implEntries.getLength();
 
         bool bReady = comphelper::findValue(implEntries, value) != -1;
@@ -320,7 +320,7 @@ bool deleteSubEntry(const Reference < XRegistryKey >& xSuperKey, const OUString&
 {
     if (xSuperKey->getValueType() == RegistryValueType_ASCIILIST)
     {
-        Sequence<OUString> implEntries = xSuperKey->getAsciiListValue();
+        const Sequence<OUString> implEntries = xSuperKey->getAsciiListValue();
         sal_Int32 length = implEntries.getLength();
         sal_Int32 equals = static_cast<sal_Int32>(std::count(implEntries.begin(), implEntries.end(), value));
         bool hasNoImplementations = false;
@@ -423,7 +423,7 @@ void deleteUserLink(const Reference < XRegistryKey >& xRootKey,
     {
         if (xOldKey->getValueType() == RegistryValueType_ASCIILIST)
         {
-            Sequence<OUString> implEntries = xOldKey->getAsciiListValue();
+            const Sequence<OUString> implEntries = xOldKey->getAsciiListValue();
             sal_Int32 length = implEntries.getLength();
             sal_Int32 equals = static_cast<sal_Int32>(std::count(implEntries.begin(), implEntries.end(), implName));
             bool hasNoImplementations = false;
@@ -438,20 +438,21 @@ void deleteUserLink(const Reference < XRegistryKey >& xRootKey,
                 if (length > equals + 1)
                 {
                     Sequence<OUString> implEntriesNew(length - equals - 1);
+                    auto pNewArray = implEntriesNew.getArray();
 
                     sal_Int32 j = 0;
                     bool first = true;
                     for (sal_Int32 i = 0; i < length; i++)
                     {
-                        if (implEntries.getConstArray()[i] != implName)
+                        if (implEntries[i] != implName)
                         {
                             if (first)
                             {
-                                oldImpl = implEntries.getConstArray()[i];
+                                oldImpl = implEntries[i];
                                 first = false;
                             } else
                             {
-                                implEntriesNew.getArray()[j++] = implEntries.getConstArray()[i];
+                                pNewArray[j++] = implEntries[i];
                             }
                         }
                     }
@@ -459,7 +460,7 @@ void deleteUserLink(const Reference < XRegistryKey >& xRootKey,
                     xOldKey->setAsciiListValue(implEntriesNew);
                 } else
                 {
-                    oldImpl = implEntries.getConstArray()[0];
+                    oldImpl = implEntries[0];
                     OUString path(xOldKey->getKeyName());
                     xOldKey->closeKey();
                     xRootKey->deleteKey(path);
@@ -727,7 +728,7 @@ void deleteAllServiceEntries(    const Reference < XSimpleRegistry >& xReg,
         {
             if (xServiceKey->getValueType() == RegistryValueType_ASCIILIST)
             {
-                Sequence<OUString> implEntries = xServiceKey->getAsciiListValue();
+                const Sequence<OUString> implEntries = xServiceKey->getAsciiListValue();
                 sal_Int32 length = implEntries.getLength();
                 sal_Int32 equals = static_cast<sal_Int32>(std::count(implEntries.begin(), implEntries.end(), implName));
 
@@ -779,7 +780,7 @@ bool is_supported_service(
 {
     if (xService_td->getName() == service_name)
         return true;
-    Sequence< Reference< reflection::XServiceTypeDescription > > seq(
+    const Sequence< Reference< reflection::XServiceTypeDescription > > seq(
         xService_td->getMandatoryServices() );
     return std::any_of(seq.begin(), seq.end(), [&service_name](const auto& rService) {
         return is_supported_service( service_name, rService ); });
diff --git a/stoc/source/inspect/introspection.cxx b/stoc/source/inspect/introspection.cxx
index d07cb9c906d5..aa1440bb4b7d 100644
--- a/stoc/source/inspect/introspection.cxx
+++ b/stoc/source/inspect/introspection.cxx
@@ -92,7 +92,7 @@ typedef WeakImplHelper< XIntrospectionAccess, XMaterialHolder, XExactName,
 // Method to assert, if a class is derived from another class
 bool isDerivedFrom( const Reference<XIdlClass>& xToTestClass, const Reference<XIdlClass>& xDerivedFromClass )
 {
-    Sequence< Reference<XIdlClass> > aClassesSeq = xToTestClass->getSuperclasses();
+    const Sequence< Reference<XIdlClass> > aClassesSeq = xToTestClass->getSuperclasses();
 
     return std::any_of(aClassesSeq.begin(), aClassesSeq.end(),
         [&xDerivedFromClass](const Reference<XIdlClass>& rxClass) {
@@ -2275,7 +2275,7 @@ css::uno::Reference<css::beans::XIntrospectionAccess> Implementation::inspect(
 
                             // Option 1: Search for parameters for a listener class
                             // Disadvantage: Superclasses should be searched recursively
-                            Sequence< Reference<XIdlClass> > aParams = rxMethod->getParameterTypes();
+                            const Sequence< Reference<XIdlClass> > aParams = rxMethod->getParameterTypes();
 
                             css::uno::Reference<css::reflection::XIdlClass>
                                 xEventListenerClass(
diff --git a/stoc/source/invocation/invocation.cxx b/stoc/source/invocation/invocation.cxx
index 4874c20750ce..6d4db16effe3 100644
--- a/stoc/source/invocation/invocation.cxx
+++ b/stoc/source/invocation/invocation.cxx
@@ -669,7 +669,7 @@ Any Invocation_Impl::invoke( const OUString& FunctionName, const Sequence<Any>&
         OutIndices.realloc( nOutIndex );
         OutParams.realloc( nOutIndex );
 
-        std::transform(OutIndices.begin(), OutIndices.end(), OutParams.begin(),
+        std::transform(std::cbegin(OutIndices), std::cend(OutIndices), OutParams.begin(),
             [&pInvokeParams](const sal_Int16 nIndex) -> Any { return pInvokeParams[nIndex]; });
 
         return aRet;
diff --git a/stoc/source/servicemanager/servicemanager.cxx b/stoc/source/servicemanager/servicemanager.cxx
index e38b9db609ae..3e50aed3953a 100644
--- a/stoc/source/servicemanager/servicemanager.cxx
+++ b/stoc/source/servicemanager/servicemanager.cxx
@@ -81,7 +81,7 @@ Sequence< OUString > retrieveAsciiValueList(
             xEnum->nextElement() >>= xTempReg;
             if( xTempReg.is() )
             {
-                Sequence< OUString > seq2 = retrieveAsciiValueList( xTempReg, keyName );
+                const Sequence< OUString > seq2 = retrieveAsciiValueList( xTempReg, keyName );
 
                 if( seq2.hasElements() )
                 {
@@ -194,7 +194,7 @@ beans::Property PropertySetInfo_Impl::getPropertyByName( OUString const & name )
 
 sal_Bool PropertySetInfo_Impl::hasPropertyByName( OUString const & name )
 {
-    return std::any_of(m_properties.begin(), m_properties.end(),
+    return std::any_of(std::cbegin(m_properties), std::cend(m_properties),
         [&name](const beans::Property& rProp) { return rProp.Name == name; });
 }
 
@@ -1327,7 +1327,7 @@ void ORegistryServiceManager::fillAllNamesFromRegistry( HashSet_OWString & rSet
         if( xServicesKey.is() )
         {
             sal_Int32 nPrefix = xServicesKey->getKeyName().getLength() +1;
-            Sequence<Reference<XRegistryKey > > aKeys = xServicesKey->openKeys();
+            const Sequence<Reference<XRegistryKey > > aKeys = xServicesKey->openKeys();
             std::transform(aKeys.begin(), aKeys.end(), std::inserter(rSet, rSet.end()),
                 [nPrefix](const Reference<XRegistryKey>& rKey) -> OUString {
                     return rKey->getKeyName().copy( nPrefix ); });