refactor(registry): drop CancellationToken (#1820)

Replace the CancellationToken class with a plain
std::atomic_bool member in DocsetRegistry.

src/libs/registry/CMakeLists.txt

@@ -7,7 +7,6 @@ add_library(Registry STATIC
     searchquery.cpp
 
     # Show headers without .cpp in Qt Creator.
-    cancellationtoken.h
     itemdatarole.h
     searchresult.h
 )

src/libs/registry/cancellationtoken.h

@@ -1,29 +0,0 @@
-// Copyright (C) Oleg Shparber, et al. <https://zealdocs.org>
-// Copyright (C) 2015 Artur Spychaj
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-#ifndef ZEAL_REGISTRY_CANCELLATIONTOKEN_H
-#define ZEAL_REGISTRY_CANCELLATIONTOKEN_H
-
-#include <atomic>
-
-namespace Zeal::Registry {
-
-/// Token that stores whether cancel was called on it.
-/// In async code can be used to check if another thread called cancel.
-class CancellationToken
-{
-public:
-    inline bool isCanceled() const { return m_canceled; }
-
-    inline void cancel() { m_canceled = true; }
-
-    inline void reset() { m_canceled = false; }
-
-private:
-    std::atomic_bool m_canceled{false};
-};
-
-} // namespace Zeal::Registry
-
-#endif // ZEAL_REGISTRY_CANCELLATIONTOKEN_H

src/libs/registry/docset.cpp

@@ -4,7 +4,6 @@
 
 #include "docset.h"
 
-#include "cancellationtoken.h"
 #include "searchresult.h"
 
 #include <util/fuzzy.h>
@@ -310,7 +309,7 @@ const QMultiMap<QString, QUrl> &Docset::symbols(const QString &symbolType) const
     return m_symbols[symbolType];
 }
 
-QList<SearchResult> Docset::search(const QString &query, const CancellationToken &token) const
+QList<SearchResult> Docset::search(const QString &query, const std::atomic_bool &canceled) const
 {
     QString sql;
     if (m_type == Docset::Type::Dash) {
@@ -351,7 +350,7 @@ QList<SearchResult> Docset::search(const QString &query, const CancellationToken
     m_db->prepare(sql.arg(sanitizedQuery));
 
     QList<SearchResult> results;
-    while (m_db->next() && !token.isCanceled()) {
+    while (m_db->next() && !canceled.load(std::memory_order_relaxed)) {
         SearchResult result;
         result.name = m_db->value(0).toString();
         result.type = parseSymbolType(m_db->value(1).toString());

src/libs/registry/docset.h

@@ -11,6 +11,8 @@
 #include <QMultiMap>
 #include <QUrl>
 
+#include <atomic>
+
 namespace Zeal {
 
 namespace Util {
@@ -19,7 +21,6 @@ class SQLiteDatabase;
 
 namespace Registry {
 
-class CancellationToken;
 struct SearchResult;
 
 class Docset final
@@ -50,7 +51,7 @@ public:
 
     const QMultiMap<QString, QUrl> &symbols(const QString &symbolType) const;
 
-    QList<SearchResult> search(const QString &query, const CancellationToken &token) const;
+    QList<SearchResult> search(const QString &query, const std::atomic_bool &canceled) const;
     QList<SearchResult> relatedLinks(const QUrl &url) const;
 
     // FIXME: This a temporary solution to create URL on demand.

src/libs/registry/docsetregistry.cpp

@@ -18,7 +18,6 @@
 #include <QtConcurrent>
 
 #include <functional>
-#include <future>
 
 namespace Zeal::Registry {
 
@@ -200,7 +199,7 @@ QList<Docset *> DocsetRegistry::docsets() const
 
 void DocsetRegistry::search(const QString &query)
 {
-    m_cancellationToken.cancel();
+    m_cancelSearch.store(true, std::memory_order_relaxed);
 
     if (query.isEmpty()) {
         emit searchCompleted({});
@@ -212,7 +211,7 @@ void DocsetRegistry::search(const QString &query)
 
 void DocsetRegistry::_runQuery(const QString &query)
 {
-    m_cancellationToken.reset();
+    m_cancelSearch.store(false, std::memory_order_relaxed);
 
     QList<Docset *> enabledDocsets;
 
@@ -227,22 +226,22 @@ void DocsetRegistry::_runQuery(const QString &query)
         enabledDocsets = docsets();
     }
 
-    QFuture<QList<SearchResult>> queryResultsFuture = QtConcurrent::mappedReduced(enabledDocsets,
-                                                                                  std::bind(&Docset::search,
-                                                                                            std::placeholders::_1,
-                                                                                            searchQuery.query(),
-                                                                                            std::ref(
-                                                                                                m_cancellationToken)),
-                                                                                  &MergeQueryResults);
-    QList<SearchResult> results = queryResultsFuture.result();
+    const QString queryString = searchQuery.query();
+    QFuture<QList<SearchResult>> queryFuture = QtConcurrent::mappedReduced(enabledDocsets,
+                                                                           std::bind(&Docset::search,
+                                                                                     std::placeholders::_1,
+                                                                                     queryString,
+                                                                                     std::cref(m_cancelSearch)),
+                                                                           &MergeQueryResults);
+    QList<SearchResult> results = queryFuture.result();
 
-    if (m_cancellationToken.isCanceled()) {
+    if (m_cancelSearch.load(std::memory_order_relaxed)) {
         return;
     }
 
     std::sort(results.begin(), results.end());
 
-    if (m_cancellationToken.isCanceled()) {
+    if (m_cancelSearch.load(std::memory_order_relaxed)) {
         return;
     }
 

src/libs/registry/docsetregistry.h

@@ -5,12 +5,13 @@
 #ifndef ZEAL_REGISTRY_DOCSETREGISTRY_H
 #define ZEAL_REGISTRY_DOCSETREGISTRY_H
 
-#include "cancellationtoken.h"
 #include "searchresult.h"
 
 #include <QMap>
 #include <QObject>
 
+#include <atomic>
+
 class QAbstractItemModel;
 class QThread;
 
@@ -70,7 +71,7 @@ private:
     QThread *m_thread = nullptr;
     QMap<QString, Docset *> m_docsets;
 
-    CancellationToken m_cancellationToken;
+    std::atomic_bool m_cancelSearch{false};
 };
 
 } // namespace Zeal::Registry