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Don't create temporary containers just to iterate over them

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Stops temporary containers being created needlessly due to API misuse.
For example, it’s common for developers to assume QHash::values() and
QHash::keys() are free and abuse them, failing to realize their
implementation internally actually iterates the whole container, allocates
memory, and fills a new QList.

Added a removeIf generic algorithm, similar to std ones. We can't use std
algorithms with Qt dictionaries because Qt iterators have different
behavior from the std ones.

Found using clazy.
This commit is contained in:
Luís Pereira 2018-03-06 14:50:10 +00:00 • committed by Vladimir Golovnev (Glassez)
parent e22946ef61
commit ac42ccb5e4
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GPG key ID: 52A2C7DEE2DFA6F7
14 changed files with 121 additions and 61 deletions
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44
src/webui/api/synccontroller.cpp
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@ -152,20 +152,22 @@ namespace
syncData.clear();
QVariantList removedItems;
foreach (QString key, data.keys()) {
for (auto i = data.cbegin(); i != data.cend(); ++i) {
const QString &key = i.key();
const QVariant &value = i.value();
removedItems.clear();
switch (static_cast<QMetaType::Type>(data[key].type())) {
switch (static_cast<QMetaType::Type>(value.type())) {
case QMetaType::QVariantMap: {
QVariantMap map;
processMap(prevData[key].toMap(), data[key].toMap(), map);
processMap(prevData[key].toMap(), value.toMap(), map);
if (!map.isEmpty())
syncData[key] = map;
}
break;
case QMetaType::QVariantHash: {
QVariantMap map;
processHash(prevData[key].toHash(), data[key].toHash(), map, removedItems);
processHash(prevData[key].toHash(), value.toHash(), map, removedItems);
if (!map.isEmpty())
syncData[key] = map;
if (!removedItems.isEmpty())
@ -174,7 +176,7 @@ namespace
break;
case QMetaType::QVariantList: {
QVariantList list;
processList(prevData[key].toList(), data[key].toList(), list, removedItems);
processList(prevData[key].toList(), value.toList(), list, removedItems);
if (!list.isEmpty())
syncData[key] = list;
if (!removedItems.isEmpty())
@ -190,13 +192,13 @@ namespace
case QMetaType::ULongLong:
case QMetaType::UInt:
case QMetaType::QDateTime:
if (prevData[key] != data[key])
syncData[key] = data[key];
if (prevData[key] != value)
syncData[key] = value;
break;
default:
Q_ASSERT_X(false, "processMap"
, QString("Unexpected type: %1")
.arg(QMetaType::typeName(static_cast<QMetaType::Type>(data[key].type())))
.arg(QMetaType::typeName(static_cast<QMetaType::Type>(value.type())))
.toUtf8().constData());
}
}
@ -213,25 +215,25 @@ namespace
if (prevData.isEmpty()) {
// If list was empty before, then difference is a whole new list.
foreach (QString key, data.keys())
syncData[key] = data[key];
for (auto i = data.cbegin(); i != data.cend(); ++i)
syncData[i.key()] = i.value();
}
else {
foreach (QString key, data.keys()) {
switch (data[key].type()) {
for (auto i = data.cbegin(); i != data.cend(); ++i) {
switch (i.value().type()) {
case QVariant::Map:
if (!prevData.contains(key)) {
if (!prevData.contains(i.key())) {
// new list item found - append it to syncData
syncData[key] = data[key];
syncData[i.key()] = i.value();
}
else {
QVariantMap map;
processMap(prevData[key].toMap(), data[key].toMap(), map);
processMap(prevData[i.key()].toMap(), i.value().toMap(), map);
// existing list item found - remove it from prevData
prevData.remove(key);
prevData.remove(i.key());
if (!map.isEmpty())
// changed list item found - append its changes to syncData
syncData[key] = map;
syncData[i.key()] = map;
}
break;
default:
@ -242,8 +244,8 @@ namespace
if (!prevData.isEmpty()) {
// prevData contains only items that are missing now -
// put them in removedItems
foreach (QString s, prevData.keys())
removedItems << s;
for (auto i = prevData.cbegin(); i != prevData.cend(); ++i)
removedItems << i.key();
}
}
}
@ -395,8 +397,8 @@ void SyncController::maindataAction()
data["torrents"] = torrents;
QVariantList categories;
foreach (const QString &category, session->categories().keys())
categories << category;
for (auto i = session->categories().cbegin(); i != session->categories().cend(); ++i)
categories << i.key();
data["categories"] = categories;