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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QtWidgets/qfiledialog.h>
#include <QtWidgets/qapplication.h>
#include <QtCore/qmimedatabase.h>
#include <QtCore/qelapsedtimer.h>
#include <QtConcurrent/qtconcurrentmap.h>
typedef QMap<QString, int> WordCount;
void printHighestResult(const WordCount &, qsizetype);
QStringList findFiles(const QString &);
// Single threaded word counter function.
WordCount singleThreadedWordCount(const QStringList &files)
{
WordCount wordCount;
for (const QString &file : files) {
QFile f(file);
f.open(QIODevice::ReadOnly);
QTextStream textStream(&f);
while (!textStream.atEnd()) {
const auto words = textStream.readLine().split(' ', Qt::SkipEmptyParts);
for (const QString &word : words)
wordCount[word] += 1;
}
}
return wordCount;
}
// countWords counts the words in a single file. This function is
// called in parallel by several threads and must be thread
// safe.
WordCount countWords(const QString &file)
{
QFile f(file);
f.open(QIODevice::ReadOnly);
QTextStream textStream(&f);
WordCount wordCount;
while (!textStream.atEnd()) {
const auto words = textStream.readLine().split(' ', Qt::SkipEmptyParts);
for (const QString &word : words)
wordCount[word] += 1;
}
return wordCount;
}
// reduce adds the results from map to the final
// result. This functor will only be called by one thread
// at a time.
void reduce(WordCount &result, const WordCount &w)
{
for (auto i = w.begin(), end = w.end(); i != end; ++i)
result[i.key()] += i.value();
}
int main(int argc, char** argv)
{
QApplication app(argc, argv);
app.setOrganizationName("QtProject");
app.setApplicationName(QCoreApplication::translate("main", "Word Count"));
QFileDialog fileDialog;
fileDialog.setOption(QFileDialog::ReadOnly);
// Grab the directory path from the dialog
auto dirPath = QFileDialog::getExistingDirectory(nullptr,
QCoreApplication::translate("main","Select a Folder"),
QDir::currentPath());
QStringList files = findFiles(dirPath);
qDebug() << QCoreApplication::translate("main", "Indexing %1 files in %2")
.arg(files.size()).arg(dirPath);
// Start the single threaded operation
qint64 singleThreadTime;
{
QElapsedTimer timer;
timer.start();
//! [1]
WordCount total = singleThreadedWordCount(files);
//! [1]
singleThreadTime = timer.elapsed();
qDebug() << QCoreApplication::translate("main", "Single threaded scanning took %1 ms")
.arg(singleThreadTime);
}
// Start the multithreaded mappedReduced operation.
qint64 mapReduceTime;
{
QElapsedTimer timer;
timer.start();
//! [2]
WordCount total = QtConcurrent::mappedReduced(files, countWords, reduce).result();
//! [2]
mapReduceTime = timer.elapsed();
qDebug() << QCoreApplication::translate("main", "MapReduce scanning took %1 ms")
.arg(mapReduceTime);
qDebug() << QCoreApplication::translate("main", "MapReduce speedup: %1")
.arg(((double)singleThreadTime - (double)mapReduceTime) / (double)mapReduceTime + 1);
printHighestResult(total, 10);
}
}
// Utility function that recursively searches for text files.
QStringList findFiles(const QString &startDir)
{
QStringList names;
QDir dir(startDir);
static const QMimeDatabase db;
const auto files = dir.entryList(QDir::Files);
for (const QString &file : files) {
const auto path = startDir + QDir::separator() + file;
const QMimeType mime = db.mimeTypeForFile(QFileInfo(path));
const auto mimeTypesForFile = mime.parentMimeTypes();
for (const auto &i : mimeTypesForFile) {
if (i.contains("text", Qt::CaseInsensitive)
|| mime.comment().contains("text", Qt::CaseInsensitive)) {
names += startDir + QDir::separator() + file;
}
}
}
const auto subdirs = dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot);
for (const QString &subdir : subdirs) {
if (names.length() >= 20000) {
qDebug() << QCoreApplication::translate("main", "Too many files! Aborting ...");
exit(-1);
}
names += findFiles(startDir + QDir::separator() + subdir);
}
return names;
}
// Utility function that prints the results of the map in decreasing order based on the value.
void printHighestResult(const WordCount &countedWords, qsizetype nResults)
{
using pair = QPair<QString, int>;
QList<pair> vec;
std::copy(countedWords.keyValueBegin(), countedWords.keyValueEnd(),
std::back_inserter<QList<pair>>(vec));
std::sort(vec.begin(), vec.end(),
[](const pair &l, const pair &r) { return l.second > r.second; });
qDebug() << QCoreApplication::translate("main", "Most occurring words are:");
for (qsizetype i = 0; i < qMin(vec.size(), nResults); ++i)
qDebug() << vec[i].first << " : " << vec[i].second;
}
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