Teach `File` how to change its encoding

If a `File` is in "text" mode, then it has an encoding.  This
encoding defaults to UTF-8; however, it can be set only at time of
construction (by using `fs.open`).

This modification allows the user to change the encoding on-the-fly
for "text" mode `File` instances.

See #11234 https://github.com/ariya/phantomjs/pull/11234
Spin off from #11168 https://github.com/ariya/phantomjs/pull/11168

src/filesystem.cpp

@@ -216,6 +216,49 @@ void File::close()
     deleteLater();
 }
 
+bool File::setEncoding(const QString &encoding) {
+    if (encoding.isEmpty() || encoding.isNull()) {
+        return false;
+    }
+
+    // "Binary" mode doesn't use/need text codecs
+    if ((QTextStream *)NULL == m_fileStream) {
+        // TODO: Should we switch to "text" mode?
+        return false;
+    }
+
+    // Since there can be multiple names for the same codec (i.e., "utf8" and
+    // "utf-8"), we need to get the codec in the system first and use its
+    // canonical name
+    QTextCodec *codec = QTextCodec::codecForName(encoding.toAscii());
+    if ((QTextCodec *)NULL == codec) {
+      return false;
+    }
+
+    // Check whether encoding actually needs to be changed
+    const QString encodingBeforeUpdate(m_fileStream->codec()->name());
+    if (0 == encodingBeforeUpdate.compare(QString(codec->name()), Qt::CaseInsensitive)) {
+        return false;
+    }
+
+    m_fileStream->setCodec(codec);
+
+    // Return whether update was successful
+    const QString encodingAfterUpdate(m_fileStream->codec()->name());
+    return 0 != encodingBeforeUpdate.compare(encodingAfterUpdate, Qt::CaseInsensitive);
+}
+
+QString File::getEncoding() const
+{
+    QString encoding;
+
+    if ((QTextStream *)NULL != m_fileStream) {
+        encoding = QString(m_fileStream->codec()->name());
+    }
+
+    return encoding;
+}
+
 // private:
 
 bool File::_isUnbuffered() const

src/filesystem.h

@@ -64,6 +64,9 @@ public slots:
     void flush();
     void close();
 
+    QString getEncoding() const;
+    bool setEncoding(const QString &encoding);
+
 private:
     bool _isUnbuffered() const;
 

test/fs-spec-01.js

@@ -59,6 +59,74 @@ describe("Basic Files API (read, write, remove, ...)", function() {
         expect(content).toEqual("hello\nworld\nasdf\n");
     });
 
+    it("should be able to get the encoding (default: UTF-8)", function() {
+        var encoding = "";
+        try {
+            var f = fs.open(FILENAME, "r");
+            encoding = f.getEncoding();
+            f.close();
+        } catch (e) {
+            console.log(e);
+        }
+        expect(encoding).toEqual("UTF-8");
+    });
+
+    it("should be able to set the encoding via options", function() {
+        var encoding = "";
+        try {
+            var f = fs.open(FILENAME, {
+              charset: "UTF-8"
+            , mode: "r"
+            });
+            encoding = f.getEncoding();
+            f.close();
+        } catch (e) {
+            console.log(e);
+        }
+        expect(encoding).toEqual("UTF-8");
+
+        try {
+            var f = fs.open(FILENAME, {
+              charset: "SJIS"
+            , mode: "r"
+            });
+            encoding = f.getEncoding();
+            f.close();
+        } catch (e) {
+            console.log(e);
+        }
+        expect(encoding).toEqual("Shift_JIS");
+    });
+
+    it("should be able to change the encoding", function() {
+        var encoding = "";
+        try {
+            var f = fs.open(FILENAME, {
+              charset: "UTF-8"
+            , mode: "r"
+            });
+            f.setEncoding("utf8");
+            encoding = f.getEncoding();
+            f.close();
+        } catch (e) {
+            console.log(e);
+        }
+        expect(encoding).toEqual("UTF-8");
+
+        try {
+            var f = fs.open(FILENAME, {
+              charset: "SJIS"
+            , mode: "r"
+            });
+            f.setEncoding("eucjp");
+            encoding = f.getEncoding();
+            f.close();
+        } catch (e) {
+            console.log(e);
+        }
+        expect(encoding).toEqual("EUC-JP");
+    });
+
     it("should be able to copy a file", function() {
         expect(fs.exists(FILENAME_COPY)).toBeFalsy();
         fs.copy(FILENAME, FILENAME_COPY);