Merge pull request #1079 from Holt59/moinfo-improvements

ModInfo improvements

14 files changed, 274 insertions, 94 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 6625e4b6..f1f54cbc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -186,6 +186,7 @@ add_filter(NAME src/utilities GROUPS
 	shared/util
 	usvfsconnector
 	shared/windows_error
+	thread_utils
 	json
 )
 
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index b5beb229..de4a6b39 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -3061,8 +3061,6 @@ void MainWindow::ignoreMissingData_clicked()
     for (QModelIndex idx : selection->selectedRows()) {
       int row_idx = idx.data(Qt::UserRole + 1).toInt();
       ModInfo::Ptr info = ModInfo::getByIndex(row_idx);
-      //QDir(info->absolutePath()).mkdir("textures");
-      info->testValid();
       info->markValidated(true);
       connect(this, SIGNAL(modListDataChanged(QModelIndex, QModelIndex)), m_OrganizerCore.modList(), SIGNAL(dataChanged(QModelIndex, QModelIndex)));
 
@@ -3070,8 +3068,6 @@ void MainWindow::ignoreMissingData_clicked()
     }
   } else {
     ModInfo::Ptr info = ModInfo::getByIndex(m_ContextRow);
-    //QDir(info->absolutePath()).mkdir("textures");
-    info->testValid();
     info->markValidated(true);
     connect(this, SIGNAL(modListDataChanged(QModelIndex, QModelIndex)), m_OrganizerCore.modList(), SIGNAL(dataChanged(QModelIndex, QModelIndex)));
 
diff --git a/src/modinfo.cpp b/src/modinfo.cpp
index 379fa071..15fa71da 100644
--- a/src/modinfo.cpp
+++ b/src/modinfo.cpp
@@ -29,6 +29,7 @@ along with Mod Organizer.  If not, see <http://www.gnu.org/licenses/>.
 #include "modinfodialog.h"
 #include "overwriteinfodialog.h"
 #include "versioninfo.h"
+#include "thread_utils.h"
 
 #include <iplugingame.h>
 #include <versioninfo.h>
@@ -249,6 +250,7 @@ void ModInfo::updateFromDisc(const QString &modDirectory,
                              DirectoryEntry **directoryStructure,
                              PluginContainer *pluginContainer,
                              bool displayForeign,
+                             std::size_t refreshThreadCount,
                              MOBase::IPluginGame const *game)
 {
   TimeThis tt("ModInfo::updateFromDisc()");
@@ -285,8 +287,11 @@ void ModInfo::updateFromDisc(const QString &modDirectory,
   createFromOverwrite(pluginContainer, game, directoryStructure);
 
   std::sort(s_Collection.begin(), s_Collection.end(), ModInfo::ByName);
+  
+  parallelMap(std::begin(s_Collection), std::end(s_Collection), &ModInfo::prefetch, refreshThreadCount);
 
   updateIndices();
+
 }
 
 
@@ -306,7 +311,7 @@ void ModInfo::updateIndices()
 
 
 ModInfo::ModInfo(PluginContainer *pluginContainer)
-  : m_Valid(false), m_PrimaryCategory(-1)
+  : m_PrimaryCategory(-1)
 {
 }
 
@@ -528,11 +533,6 @@ bool ModInfo::categorySet(int categoryID) const
   return false;
 }
 
-void ModInfo::testValid()
-{
-  m_Valid = doTestValid();
-}
-
 QUrl ModInfo::parseCustomURL() const
 {
   if (!hasCustomURL() || getCustomURL().isEmpty()) {
diff --git a/src/modinfo.h b/src/modinfo.h
index f582cc32..29e6124d 100644
--- a/src/modinfo.h
+++ b/src/modinfo.h
@@ -142,6 +142,7 @@ public:
                              MOShared::DirectoryEntry **directoryStructure,
                              PluginContainer *pluginContainer,
                              bool displayForeign,
+                             std::size_t refreshThreadCount,
                              MOBase::IPluginGame const *game);
 
   static void clear() { s_Collection.clear(); s_ModsByName.clear(); s_ModsByModID.clear(); }
@@ -702,7 +703,7 @@ public:
   /**
    * @return true if this mod is considered "valid", that is: it contains data used by the game
    **/
-  virtual bool isValid() const { return m_Valid; }
+  virtual bool isValid() const = 0;
 
   /**
    * @return true if the file has been endorsed on nexus
@@ -715,11 +716,6 @@ public:
   virtual ETrackedState trackedState() const { return TRACKED_FALSE; }
 
   /**
-   * @brief updates the valid-flag for this mod
-   */
-  void testValid();
-
-  /**
    * @brief updates the mod to flag it as converted in order to ignore the alternate game warning
    */
   virtual void markConverted(bool) {}
@@ -801,6 +797,13 @@ public:
    **/
   QUrl parseCustomURL() const;
 
+public slots:
+
+  /**
+   * @brief Notify this mod that the content of the disk may have changed.
+   */
+  virtual void diskContentModified() = 0;
+
 signals:
 
   /**
@@ -812,17 +815,22 @@ signals:
 
 protected:
 
+  /**
+   *
+   */
   ModInfo(PluginContainer *pluginContainer);
 
-  static void updateIndices();
-  static bool ByName(const ModInfo::Ptr &LHS, const ModInfo::Ptr &RHS);
-
   /**
-   * @brief check if the content of this mod is valid.
+   * @brief Prefetch content for this mod.
    *
-   * @return true if the content is valid, false otherwize.
-   **/
-  virtual bool doTestValid() const = 0;
+   * This method can be used to prefetch content from the mod, e.g., for isValid()
+   * or getContents(). This method will only be called when first creating the mod
+   * using multiple threads for all the mods.
+   */
+  virtual void prefetch() = 0;
+
+  static void updateIndices();
+  static bool ByName(const ModInfo::Ptr &LHS, const ModInfo::Ptr &RHS);
 
 private:
 
@@ -848,8 +856,6 @@ private:
   static std::map<std::pair<QString, int>, std::vector<unsigned int> > s_ModsByModID;
   static int s_NextID;
 
-  bool m_Valid;
-
 };
 
 
diff --git a/src/modinfooverwrite.cpp b/src/modinfooverwrite.cpp
index 3b914134..8aad6209 100644
--- a/src/modinfooverwrite.cpp
+++ b/src/modinfooverwrite.cpp
@@ -9,7 +9,6 @@
 ModInfoOverwrite::ModInfoOverwrite(PluginContainer *pluginContainer, const MOBase::IPluginGame *game, MOShared::DirectoryEntry **directoryStructure) 
   : ModInfoWithConflictInfo(pluginContainer, game, directoryStructure)
 {
-  testValid();
 }
 
 bool ModInfoOverwrite::isEmpty() const
diff --git a/src/modinforegular.cpp b/src/modinforegular.cpp
index d89716da..a1f1a04d 100644
--- a/src/modinforegular.cpp
+++ b/src/modinforegular.cpp
@@ -38,7 +38,6 @@ ModInfoRegular::ModInfoRegular(PluginContainer *pluginContainer, const IPluginGa
   , m_TrackedState(TRACKED_UNKNOWN)
   , m_NexusBridge(pluginContainer)
 {
-  testValid();
   m_CreationTime = QFileInfo(path.absolutePath()).birthTime();
   // read out the meta-file for information
   readMeta();
@@ -654,61 +653,60 @@ std::vector<ModInfo::EFlag> ModInfoRegular::getFlags() const
 }
 
 
-std::vector<ModInfo::EContent> ModInfoRegular::getContents() const
+std::vector<ModInfo::EContent> ModInfoRegular::doGetContents() const
 {
-  QTime now = QTime::currentTime();
-  if (m_LastContentCheck.isNull() || (m_LastContentCheck.secsTo(now) > 60)) {
-    m_CachedContent.clear();
-    QDir dir(absolutePath());
-    if (dir.entryList(QStringList() << "*.esp" << "*.esm" << "*.esl").size() > 0) {
-      m_CachedContent.push_back(CONTENT_PLUGIN);
-    }
-    if (dir.entryList(QStringList() << "*.bsa" << "*.ba2").size() > 0) {
-      m_CachedContent.push_back(CONTENT_BSA);
-    }
-    //use >1 for ini files since there is meta.ini in all mods already.
-    if (dir.entryList(QStringList() << "*.ini").size() > 1) {
-      m_CachedContent.push_back(CONTENT_INI);
-    }
+  auto tree = contentFileTree();
+  std::vector<ModInfo::EContent> contents;
 
-    if (dir.entryList(QStringList() << "*.modgroups").size() > 0) {
-      m_CachedContent.push_back(CONTENT_MODGROUP);
+  for (auto e : *tree) {
+    if (e->isFile()) {
+      auto suffix = e->suffix().toLower();
+      if (suffix == "esp" || suffix == "esm" || suffix == "esl") {
+        contents.push_back(CONTENT_PLUGIN);
+      }
+      else if (suffix == "bsa" || suffix == "ba2") {
+        contents.push_back(CONTENT_BSA);
+      }
+      else if (suffix == "ini" && e->compare("meta.ini") != 0) {
+        contents.push_back(CONTENT_INI);
+      }
+      else if (suffix == "modgroups") {
+        contents.push_back(CONTENT_MODGROUP);
+      }
     }
+    else {
+      if (e->compare("textures") == 0 || e->compare("icons") == 0 || e->compare("bookart") == 0)
+        contents.push_back(CONTENT_TEXTURE);
+      if (e->compare("meshes") == 0)
+        contents.push_back(CONTENT_MESH);
+      if (e->compare("interface") == 0 || e->compare("menus") == 0)
+        contents.push_back(CONTENT_INTERFACE);
+      if (e->compare("music") == 0 || e->compare("sound") == 0)
+        contents.push_back(CONTENT_SOUND);
+      if (e->compare("scripts") == 0)
+        contents.push_back(CONTENT_SCRIPT);
+      if (e->compare("SkyProc Patchers") == 0)
+        contents.push_back(CONTENT_SKYPROC);
+      if (e->compare("MCM") == 0)
+        contents.push_back(CONTENT_MCM);
+    }
+  }
 
-    ScriptExtender *extender = qApp->property("managed_game")
-                                   .value<IPluginGame *>()
-                                   ->feature<ScriptExtender>();
-
-    if (extender != nullptr) {
-      QString sePluginPath = extender->PluginPath();
-      if (dir.exists(sePluginPath)) {
-        m_CachedContent.push_back(CONTENT_SKSEFILES);
-        QDir sePluginDir(absolutePath() + "/" + sePluginPath);
-        if (sePluginDir.entryList(QStringList() << "*.dll").size() > 0) {
-          m_CachedContent.push_back(CONTENT_SKSE);
+  ScriptExtender* extender = m_GamePlugin->feature<ScriptExtender>();
+  if (extender != nullptr) {
+    auto e = tree->findDirectory(extender->PluginPath());
+    if (e) {
+      contents.push_back(CONTENT_SKSEFILES);
+      for (auto f : *e) {
+        if (f->hasSuffix("dll")) {
+          contents.push_back(CONTENT_SKSE);
+          break;
         }
       }
     }
-    if (dir.exists("textures") || dir.exists("icons") || dir.exists("bookart"))
-      m_CachedContent.push_back(CONTENT_TEXTURE);
-    if (dir.exists("meshes"))
-      m_CachedContent.push_back(CONTENT_MESH);
-    if (dir.exists("interface") || dir.exists("menus"))
-      m_CachedContent.push_back(CONTENT_INTERFACE);
-    if (dir.exists("music") || dir.exists("sound"))
-      m_CachedContent.push_back(CONTENT_SOUND);
-    if (dir.exists("scripts"))
-      m_CachedContent.push_back(CONTENT_SCRIPT);
-    if (dir.exists("SkyProc Patchers"))
-      m_CachedContent.push_back(CONTENT_SKYPROC);
-    if (dir.exists("MCM"))
-      m_CachedContent.push_back(CONTENT_MCM);
-
-    m_LastContentCheck = QTime::currentTime();
   }
 
-  return m_CachedContent;
-
+  return contents;
 }
 
 
diff --git a/src/modinforegular.h b/src/modinforegular.h
index 0f22b6cb..e63e7570 100644
--- a/src/modinforegular.h
+++ b/src/modinforegular.h
@@ -289,8 +289,6 @@ public:
    */
   virtual std::vector<EFlag> getFlags() const override;
 
-  virtual std::vector<EContent> getContents() const override;
-
   /**
    * @return an indicator if and how this mod should be highlighted by the UI
    */
@@ -418,6 +416,8 @@ private slots:
 
 protected:
 
+  virtual std::vector<EContent> doGetContents() const override;
+
   ModInfoRegular(PluginContainer *pluginContainer, const MOBase::IPluginGame *game, const QDir &path, MOShared::DirectoryEntry **directoryStructure);
 
 private:
@@ -462,9 +462,6 @@ private:
 
   NexusBridge m_NexusBridge;
 
-  mutable std::vector<ModInfo::EContent> m_CachedContent;
-  mutable QTime m_LastContentCheck;
-
   bool needsDescriptionUpdate() const;
 };
 
diff --git a/src/modinfoseparator.h b/src/modinfoseparator.h
index 4cfb9ea0..a7a6cb5f 100644
--- a/src/modinfoseparator.h
+++ b/src/modinfoseparator.h
@@ -49,7 +49,7 @@ public:
   virtual void addInstalledFile(int /*modId*/, int /*fileId*/) override { }
 
 protected:
-  virtual bool doTestValid() const override { return true; }
+  virtual bool doIsValid() const override { return true; }
 
 private:
 
diff --git a/src/modinfowithconflictinfo.cpp b/src/modinfowithconflictinfo.cpp
index 0c67b4f7..b0edf581 100644
--- a/src/modinfowithconflictinfo.cpp
+++ b/src/modinfowithconflictinfo.cpp
@@ -14,7 +14,11 @@ namespace fs = std::filesystem;
 
 ModInfoWithConflictInfo::ModInfoWithConflictInfo(
   PluginContainer *pluginContainer, const MOBase::IPluginGame* gamePlugin, DirectoryEntry **directoryStructure)
-  : ModInfo(pluginContainer), m_GamePlugin(gamePlugin), m_DirectoryStructure(directoryStructure), m_HasLooseOverwrite(false), m_HasHiddenFiles(false) {}
+  : ModInfo(pluginContainer), m_GamePlugin(gamePlugin), 
+  m_FileTree([this]() { return QDirFileTree::makeTree(absolutePath()); }),
+  m_Valid([this]() { return doIsValid(); }),
+  m_Contents([this]() { return doGetContents(); }),
+  m_DirectoryStructure(directoryStructure), m_HasLooseOverwrite(false), m_HasHiddenFiles(false) {}
 
 void ModInfoWithConflictInfo::clearCaches()
 {
@@ -296,14 +300,37 @@ bool ModInfoWithConflictInfo::hasHiddenFiles() const
   return m_HasHiddenFiles;
 }
 
+void ModInfoWithConflictInfo::diskContentModified() {
+  m_FileTree.invalidate();
+  m_Valid.invalidate();
+  m_Contents.invalidate();
+}
+
+void ModInfoWithConflictInfo::prefetch() {
+  // Populating the tree to 1-depth (IFileTree is lazy, so size() forces the
+  // tree to populate the first level):
+  contentFileTree()->size();
+}
 
-bool ModInfoWithConflictInfo::doTestValid() const {
+bool ModInfoWithConflictInfo::doIsValid() const {
   auto mdc = m_GamePlugin->feature<ModDataChecker>();
 
   if (mdc) {
-    auto qdirfiletree = QDirFileTree::makeTree(absolutePath());
+    auto qdirfiletree = contentFileTree();
     return mdc->dataLooksValid(qdirfiletree);
   }
 
   return true;
 }
+
+std::shared_ptr<const IFileTree> ModInfoWithConflictInfo::contentFileTree() const {
+  return m_FileTree.value();
+}
+
+bool ModInfoWithConflictInfo::isValid() const {
+  return m_Valid.value();
+}
+
+std::vector<ModInfo::EContent> ModInfoWithConflictInfo::getContents() const {
+  return m_Contents.value();
+}
diff --git a/src/modinfowithconflictinfo.h b/src/modinfowithconflictinfo.h
index 94a61c62..abc9f223 100644
--- a/src/modinfowithconflictinfo.h
+++ b/src/modinfowithconflictinfo.h
@@ -1,6 +1,9 @@
 #ifndef MODINFOWITHCONFLICTINFO_H
 #define MODINFOWITHCONFLICTINFO_H
 
+#include <ifiletree.h>
+
+#include "thread_utils.h"
 #include "modinfo.h"
 
 #include <QTime>
@@ -14,6 +17,16 @@ public:
   virtual std::vector<ModInfo::EFlag> getFlags() const override;
 
   /**
+   * @return true if this mod is considered "valid", that is: it contains data used by the game
+   **/
+  virtual bool isValid() const override;
+
+  /**
+   * @return a list of content types contained in a mod
+   */
+  virtual std::vector<EContent> getContents() const override;
+
+  /**
    * @brief clear all caches held for this mod
    */
   virtual void clearCaches() override;
@@ -32,14 +45,39 @@ public:
 
   virtual void doConflictCheck() const override;
 
+public slots:
+
+  /**
+   * @brief Notify this mod that the content of the disk may have changed.
+   */
+  virtual void diskContentModified();
+
 protected:
 
   /**
-   * @brief check if the content of this mod is valid.
+   * @brief Check if the content of this mod is valid.
+   *
+   * @return true if the content is valid, false otherwise.
+   **/
+  virtual bool doIsValid() const;
+
+  /**
+   * @brief Compute the contents for this mod.
    *
-   * @return true if the content is valid, false otherwize.
+   * @return the contents for this mod.
    **/
-  virtual bool doTestValid() const;
+  virtual std::vector<EContent> doGetContents() const { return {}; }
+
+  /**
+   * @brief Retrieve a file tree corresponding to the underlying disk content
+   *     of this mod.
+   *
+   * The file tree should not be cached since it is already cached and updated when
+   * required.
+   *
+   * @return a file tree representing the content of this mod.
+   */
+  std::shared_ptr<const MOBase::IFileTree> contentFileTree() const;
 
   ModInfoWithConflictInfo(
     PluginContainer* pluginContainer,
@@ -81,10 +119,25 @@ private:
 
   bool hasHiddenFiles() const;
 
-private:
+protected:
+
+  /**
+   * @brief Prefetch content for this mod.
+   *
+   * This method can be used to prefetch content from the mod, e.g., for isValid()
+   * or getContents(). This method will only be called when first creating the mod
+   * using multiple threads for all the mods.
+   */
+  virtual void prefetch() override;
 
   // Current game plugin running in MO2:
-  MOBase::IPluginGame const* m_GamePlugin;
+  MOBase::IPluginGame const * const m_GamePlugin;
+
+private:
+
+  MOShared::MemoizedLocked<std::shared_ptr<const MOBase::IFileTree>> m_FileTree;
+  MOShared::MemoizedLocked<bool> m_Valid;
+  MOShared::MemoizedLocked<std::vector<EContent>> m_Contents;
 
   MOShared::DirectoryEntry **m_DirectoryStructure;
 
diff --git a/src/modlist.cpp b/src/modlist.cpp
index ea4aa2e3..e8c14434 100644
--- a/src/modlist.cpp
+++ b/src/modlist.cpp
@@ -849,7 +849,7 @@ void ModList::modInfoChanged(ModInfo::Ptr info)
     }
 
     int row = ModInfo::getIndex(info->name());
-    info->testValid();
+    info->diskContentModified();
     emit aboutToChangeData();
     emit dataChanged(index(row, 0), index(row, columnCount()));
     emit postDataChanged();
@@ -1076,7 +1076,7 @@ bool ModList::dropURLs(const QMimeData *mimeData, int row, const QModelIndex &pa
   }
 
   if (!modInfo->isValid()) {
-    modInfo->testValid();
+    modInfo->diskContentModified();
   }
 
   return true;
diff --git a/src/modlist.h b/src/modlist.h
index d8980dec..4d456a9a 100644
--- a/src/modlist.h
+++ b/src/modlist.h
@@ -276,8 +276,6 @@ protected:
 

 private:

 

-  bool testValid(const QString &modDir);

-

   QVariant getOverwriteData(int column, int role) const;

 

   QString getFlagText(ModInfo::EFlag flag, ModInfo::Ptr modInfo) const;

diff --git a/src/organizercore.cpp b/src/organizercore.cpp
index feab76a7..6e4b3fbf 100644
--- a/src/organizercore.cpp
+++ b/src/organizercore.cpp
@@ -208,7 +208,8 @@ void OrganizerCore::updateExecutablesList()
 void OrganizerCore::updateModInfoFromDisc() {
   ModInfo::updateFromDisc(
     m_Settings.paths().mods(), &m_DirectoryStructure,
-    m_PluginContainer, m_Settings.interface().displayForeign(), managedGame());
+    m_PluginContainer, m_Settings.interface().displayForeign(), 
+    m_Settings.refreshThreadCount(), managedGame());
 }
 
 void OrganizerCore::setUserInterface(IUserInterface* ui)
@@ -1097,7 +1098,8 @@ void OrganizerCore::refreshModList(bool saveChanges)
 
   ModInfo::updateFromDisc(
     m_Settings.paths().mods(), &m_DirectoryStructure,
-    m_PluginContainer, m_Settings.interface().displayForeign(), managedGame());
+    m_PluginContainer, m_Settings.interface().displayForeign(), 
+    m_Settings.refreshThreadCount(), managedGame());
 
   m_CurrentProfile->refreshModStatus();
 
@@ -1629,7 +1631,7 @@ void OrganizerCore::syncOverwrite()
                                  qApp->activeWindow());
   if (syncDialog.exec() == QDialog::Accepted) {
     syncDialog.apply(QDir::fromNativeSeparators(m_Settings.paths().mods()));
-    modInfo->testValid();
+    modInfo->diskContentModified();
     refreshDirectoryStructure();
   }
 }
diff --git a/src/thread_utils.h b/src/thread_utils.h
new file mode 100644
index 00000000..f0067b6a
--- /dev/null
+++ b/src/thread_utils.h
@@ -0,0 +1,103 @@
+#ifndef MO2_THREAD_UTILS_H
+#define MO2_THREAD_UTILS_H
+
+#include <functional>
+#include <mutex>
+#include <thread>
+
+namespace MOShared {
+
+/**
+ * Class that can be used to perform thread-safe memoization.
+ *
+ * Each instance hold a flag indicating if the current value is up-to-date
+ * or not. This flag can be reset using `invalidate()`. When the value is queried,
+ * the flag is checked, and if it is not up-to-date, the given callback is used
+ * to compute the value.
+ *
+ * The computation and update of the value is locked to avoid concurrent modifications.
+ *
+ * @tparam T Type of value ot memoized.
+ * @tparam Fn Type of the callback.
+ */
+template <class T, class Fn = std::function<T()>>
+struct MemoizedLocked {
+
+  template <class Callable>
+  MemoizedLocked(Callable &&callable, T value = {}) :
+    m_Fn{ std::forward<Callable>(callable) }, m_Value{ std::move(value) } { }
+  
+  template <class... Args>
+  T& value(Args&&... args) const {
+    if (m_NeedUpdating) {
+      std::scoped_lock lock(m_Mutex);
+      if (m_NeedUpdating) {
+        m_Value = std::invoke(m_Fn, std::forward<Args>(args)... );
+        m_NeedUpdating = false;
+      }
+    }
+    return m_Value;
+  }
+
+  void invalidate() {
+    m_NeedUpdating = true;
+  }
+
+private:
+  mutable std::mutex m_Mutex;
+  mutable std::atomic<bool> m_NeedUpdating{ true };
+
+  Fn m_Fn;
+  mutable T m_Value;
+};
+
+/**
+ * @brief Apply the given callable to each element between the two given iterators
+ *     in a parallel way.
+ *
+ * The callable should be independent, or properly synchronized, and the source of
+ * the range should not change during this call.
+ *
+ * @param start Beginning of the range.
+ * @param end End of the range.
+ * @param callable Callable to apply to every element of the range. See std::invoke
+ *     requirements. Must be copiable.
+ * @param nThreads Number of threads to use.
+ *
+ */
+template <class It, class Callable>
+void parallelMap(It begin, It end, Callable callable, std::size_t nThreads) 
+{
+  std::mutex m;
+  std::vector<std::thread> threads(nThreads);
+
+  // Create the thread:
+  //  - The mutex is only used to fetch/increment the iterator.
+  //  - The callable is copied in each thread to avoid conflicts.
+  for (auto &thread: threads) {
+    thread = std::thread([&m, &begin, end, callable]() {
+      while (true) {
+        decltype(begin) it;
+        {
+          std::scoped_lock lock(m);
+          if (begin == end) {
+            break;
+          }
+          it = begin++;
+        }
+        if (it != end) {
+          std::invoke(callable, *it);
+        }
+      }
+    });
+  }
+
+  // Join everything:
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+}
+
+#endif