Partially revert "Remove unused stringutils methods"

This partially reverts commit 0c1a5a5c97.

samples/blackmisc/samplesperformance.cpp

@@ -408,6 +408,13 @@ namespace BlackSample
         }
         out << "Remove from 100,000 strings all uppercase letters: (regex)           " << timer.elapsed() << "ms" << endl << Qt::endl;
 
+        timer.start();
+        {
+            auto lines = splitLines(bigString);
+            Q_UNUSED(lines);
+        }
+        out << "Split 100,000 line string into list of lines: (QStringList)          " << timer.elapsed() << "ms" << Qt::endl;
+
         timer.start();
         {
             auto lines = splitLinesRefs(bigString);

src/blackmisc/simulation/xplane/aircraftmodelloaderxplane.cpp

@@ -569,7 +569,7 @@ namespace BlackMisc::Simulation::XPlane
         {
             ++lineNum;
             QString line = in.readLine();
-            auto tokens = line.split(' ');
+            auto tokens = splitString(line, [](QChar c) { return c.isSpace(); });
             if (!tokens.empty())
             {
                 auto it = commands.find(tokens[0]);
@@ -615,7 +615,7 @@ namespace BlackMisc::Simulation::XPlane
             ++lineNum;
             QString line = in.readLine();
             if (line.isEmpty() || line[0] == '#') continue;
-            auto tokens = line.split(' ');
+            auto tokens = splitString(line, [](QChar c) { return c.isSpace(); });
             if (!tokens.empty())
             {
                 auto it = commands.find(tokens[0]);

src/blackmisc/stringutils.cpp

@@ -29,6 +29,11 @@ namespace BlackMisc
         return splitStringRefs(s, [](QChar c) { return c == '\n' || c == '\r'; });
     }
 
+    QStringList splitLines(const QString &s)
+    {
+        return splitString(s, [](QChar c) { return c == '\n' || c == '\r'; });
+    }
+
     QByteArray utfToPercentEncoding(const QString& s, const QByteArray &allow, char percent)
     {
         QByteArray result;

src/blackmisc/stringutils.h

@@ -12,6 +12,7 @@
 #define BLACKMISC_STRINGUTILS_H
 
 #include "blackmisc/blackmiscexport.h"
+#include "blackmisc/range.h"
 #include "blackmisc/typetraits.h"
 
 #include <QByteArray>
@@ -116,6 +117,15 @@ namespace BlackMisc
     //! It would be risky to call splitLinesRefs with an rvalue, so forbid it.
     void splitLinesRefs(const QString &&) = delete;
 
+    //! Split a string into multiple strings, using a predicate function to identify the split points.
+    template <class F> QStringList splitString(const QString &s, F predicate)
+    {
+        return makeRange(splitStringRefs(s, predicate)).transform([](QStringRef sr) { return sr.toString(); });
+    }
+
+    //! Split a string into multiple lines. Blank lines are skipped.
+    BLACKMISC_EXPORT QStringList splitLines(const QString &s);
+
     //! Extended percent encoding supporting UTF-16
     BLACKMISC_EXPORT QByteArray utfToPercentEncoding(const QString &s, const QByteArray &allow = {}, char percent = '%');
 

tests/blackmisc/teststringutils/teststringutils.cpp

@@ -33,6 +33,7 @@ namespace BlackMiscTest
         void testRemove();
         void testContains();
         void testIndexOf();
+        void testSplit();
         void testTimestampParsing();
         void testCodecs();
         void testSimplify();
@@ -60,6 +61,16 @@ namespace BlackMiscTest
         QVERIFY2(indexOfChar(s, [](QChar c) { return c.isNumber(); }) == -1, "Test not index of character by predicate");
     }
 
+    void CTestStringUtils::testSplit()
+    {
+        const QString s = "line one\nline two\r\nline three\n";
+        QStringList lines = splitLines(s);
+        QVERIFY2(lines.size() == 3, "Test split string into lines: correct number of lines");
+        QVERIFY2(lines[0] == "line one", "Test split string into lines: correct first line");
+        QVERIFY2(lines[1] == "line two", "Test split string into lines: correct second line");
+        QVERIFY2(lines[2] == "line three", "Test split string into lines: correct third line");
+    }
+
     void CTestStringUtils::testTimestampParsing()
     {
         const QStringList dts(