Add thread-safe RiaStringPool utility and unit tests

Introduce RiaStringPool for efficient shared string storage and retrieval by index, with thread-safe access using shared mutex. Pre-allocate empty string at index 0. Add comprehensive unit tests covering core functionality, concurrency, edge cases, and realistic usage.

Author: magnesj

ApplicationLibCode/Application/CMakeLists_files.cmake

@@ -23,6 +23,7 @@ set(SOURCE_GROUP_HEADER_FILES
     ${CMAKE_CURRENT_LIST_DIR}/RiaEclipseFileNameTools.h
     ${CMAKE_CURRENT_LIST_DIR}/RiaFeatureCommandContext.h
     ${CMAKE_CURRENT_LIST_DIR}/RiaStringListSerializer.h
+    ${CMAKE_CURRENT_LIST_DIR}/RiaStringPool.h
     ${CMAKE_CURRENT_LIST_DIR}/RiaNncDefines.h
     ${CMAKE_CURRENT_LIST_DIR}/RiaPlotDefines.h
     ${CMAKE_CURRENT_LIST_DIR}/RiaStimPlanModelDefines.h
@@ -67,6 +68,7 @@ set(SOURCE_GROUP_SOURCE_FILES
     ${CMAKE_CURRENT_LIST_DIR}/RiaEclipseFileNameTools.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaFeatureCommandContext.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaStringListSerializer.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/RiaStringPool.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaNncDefines.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaPlotDefines.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaStimPlanModelDefines.cpp

ApplicationLibCode/Application/RiaStringPool.cpp

@@ -0,0 +1,87 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (C) 2026     Equinor ASA
+//
+//  ResInsight is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
+//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.
+//
+//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
+//  for more details.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#include "RiaStringPool.h"
+
+#include <mutex>
+#include <stdexcept>
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+RiaStringPool& RiaStringPool::instance()
+{
+    static RiaStringPool pool;
+    return pool;
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+RiaStringPool::RiaStringPool()
+{
+    // Pre-allocate empty string at index 0
+    m_strings.push_back( "" );
+    m_stringToIndex[""] = 0;
+    m_emptyIndex        = 0;
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+RiaStringPool::IndexType RiaStringPool::getIndex( const std::string& str )
+{
+    // First try with shared lock for reading
+    {
+        std::shared_lock<std::shared_mutex> lock( m_mutex );
+        auto                                it = m_stringToIndex.find( str );
+        if ( it != m_stringToIndex.end() )
+        {
+            return it->second;
+        }
+    }
+
+    // Need to insert, acquire exclusive lock
+    std::unique_lock<std::shared_mutex> lock( m_mutex );
+
+    // Double-check after acquiring exclusive lock (another thread might have inserted it)
+    auto it = m_stringToIndex.find( str );
+    if ( it != m_stringToIndex.end() )
+    {
+        return it->second;
+    }
+
+    IndexType newIndex = static_cast<IndexType>( m_strings.size() );
+    m_strings.push_back( str );
+    m_stringToIndex[m_strings.back()] = newIndex;
+    return newIndex;
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+const std::string& RiaStringPool::getString( IndexType index ) const
+{
+    std::shared_lock<std::shared_mutex> lock( m_mutex );
+
+    if ( index >= m_strings.size() )
+    {
+        throw std::out_of_range( "String pool index out of range" );
+    }
+    return m_strings[index];
+}

ApplicationLibCode/Application/RiaStringPool.h

@@ -0,0 +1,57 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (C) 2026     Equinor ASA
+//
+//  ResInsight is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
+//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.
+//
+//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
+//  for more details.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include <cstdint>
+#include <shared_mutex>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+//==================================================================================================
+/// String pool for memory-efficient storage of shared strings
+/// Stores strings once and returns indices for lookups
+//==================================================================================================
+class RiaStringPool
+{
+public:
+    using IndexType                          = uint32_t;
+    static constexpr IndexType INVALID_INDEX = static_cast<IndexType>( -1 );
+
+    static RiaStringPool& instance();
+
+    // Get or create an index for a string
+    IndexType getIndex( const std::string& str );
+
+    // Get string by index
+    const std::string& getString( IndexType index ) const;
+
+    // Get empty string index
+    IndexType getEmptyIndex() const { return m_emptyIndex; }
+
+private:
+    RiaStringPool();
+    RiaStringPool( const RiaStringPool& )            = delete;
+    RiaStringPool& operator=( const RiaStringPool& ) = delete;
+
+    mutable std::shared_mutex                  m_mutex;
+    std::vector<std::string>                   m_strings;
+    std::unordered_map<std::string, IndexType> m_stringToIndex;
+    IndexType                                  m_emptyIndex;
+};

ApplicationLibCode/UnitTests/CMakeLists.txt

@@ -69,6 +69,7 @@ set(SOURCE_UNITTEST_FILES
     ${CMAKE_CURRENT_LIST_DIR}/RifCsvDataTableFormatter-Test.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaSummaryAddressAnalyzer-Test.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaStdStringTools-Test.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/RiaStringPool-Test.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaInterpolationTools-Test.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RifWellMeasurementReader-Test.cpp
     ${CMAKE_CURRENT_LIST_DIR}/RiaDateStringParser-Test.cpp