1 files changed, 135 insertions, 0 deletions
diff --git a/src/qmldom/qqmldomfilewriter.cpp b/src/qmldom/qqmldomfilewriter.cpp
new file mode 100644
index 0000000000..82f2aca496
--- /dev/null
+++ b/src/qmldom/qqmldomfilewriter.cpp
@@ -0,0 +1,135 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "qqmldomfilewriter_p.h"
+#include <QtCore/QRandomGenerator>
+#include <QtCore/QScopeGuard>
+
+QT_BEGIN_NAMESPACE
+namespace QQmlJS {
+namespace Dom {
+
+FileWriter::Status FileWriter::write(const QString &tFile, function_ref<bool(QTextStream &)> write,
+                                     int nBk)
+{
+    if (shouldRemoveTempFile)
+        tempFile.remove();
+    tempFile.close();
+    shouldRemoveTempFile = false;
+    Q_ASSERT(status != Status::ShouldWrite);
+    status = Status::ShouldWrite;
+    targetFile = tFile;
+    newBkFiles.clear();
+    warnings.clear();
+
+    int i = 0;
+    const int maxAttempts = 20;
+    for (; i < maxAttempts; ++i) {
+        tempFile.setFileName(targetFile
+                             + QString::number(QRandomGenerator::global()->generate(), 16).mid(0, 8)
+                             + QStringLiteral(u".tmp"));
+        if (tempFile.open(QIODevice::ReadWrite | QIODevice::NewOnly))
+            break;
+    }
+    if (i == maxAttempts) {
+        warnings.append(tr("Could not create temp file for %1").arg(targetFile));
+        status = FileWriter::Status::SkippedDueToFailure;
+        return status;
+    }
+    shouldRemoveTempFile = true;
+    bool success = false;
+    QTextStream inF(&tempFile);
+    QT_TRY
+    {
+        auto cleanup = qScopeGuard([this, &inF, &success, nBk] {
+            inF.flush();
+            tempFile.flush();
+            tempFile.close();
+            if (success) {
+                if (QFile::exists(targetFile)) {
+                    // compareFiles
+                    if (tempFile.open(QIODevice::ReadOnly)) {
+                        auto closeTmpF = qScopeGuard([this] { tempFile.close(); });
+                        QFile oldF(targetFile);
+                        if (oldF.open(QIODevice::ReadOnly)) {
+                            bool same = true;
+                            while (!tempFile.atEnd() && !oldF.atEnd()) {
+                                QByteArray l1 = tempFile.readLine();
+                                QByteArray l2 = oldF.readLine();
+                                if (l1 != l2)
+                                    same = false;
+                            }
+                            if (tempFile.atEnd() && oldF.atEnd() && same) {
+                                tempFile.remove();
+                                shouldRemoveTempFile = false;
+                                status = Status::SkippedEqual;
+                                return;
+                            }
+                        }
+                    }
+                }
+                // move to target
+                int i = 0;
+                const int maxAttempts = 10;
+                for (; i < maxAttempts; ++i) {
+                    if (QFile::exists(targetFile)) {
+                        // make place for targetFile
+                        QString bkFileName;
+                        if (nBk < 1) {
+                            QFile::remove(targetFile);
+                        } else if (nBk == 1) {
+                            QString bkFileName = targetFile + QStringLiteral(u"~");
+                            QFile::remove(bkFileName);
+                            QFile::rename(targetFile, bkFileName);
+                        } else {
+                            // f~ is the oldest, further backups at f1~ .. f<nBk>~
+                            // keeping an empty place for the "next" backup
+                            // f~ is never overwritten
+                            int iBk = 0;
+                            QString bkFileName = targetFile + QStringLiteral(u"~");
+                            while (++iBk < nBk) {
+                                if (QFile::exists(bkFileName))
+                                    bkFileName = targetFile + QString::number(iBk)
+                                            + QStringLiteral(u"~");
+                            }
+                            if (iBk == nBk)
+                                QFile::remove(targetFile + QStringLiteral(u"1~"));
+                            else
+                                QFile::remove(targetFile + QString::number(++iBk)
+                                              + QStringLiteral(u"~"));
+                            QFile::remove(bkFileName);
+                            QFile::rename(targetFile, bkFileName);
+                        }
+                        if (!bkFileName.isEmpty() && QFile::rename(targetFile, bkFileName))
+                            newBkFiles.append(bkFileName);
+                    }
+                    if (tempFile.rename(targetFile)) {
+                        status = Status::DidWrite;
+                        shouldRemoveTempFile = false;
+                        return;
+                    }
+                }
+                warnings.append(
+                        tr("Rename of file %1 to %2 failed").arg(tempFile.fileName(), targetFile));
+                status = Status::SkippedDueToFailure;
+            } else {
+                warnings.append(tr("Error while writing"));
+            }
+        });
+        success = write(inF);
+    }
+    QT_CATCH(...)
+    {
+        warnings.append(tr("Exception trying to write file %1").arg(targetFile));
+        status = FileWriter::Status::SkippedDueToFailure;
+    }
+    if (status == Status::ShouldWrite)
+        status = Status::SkippedDueToFailure;
+    return status;
+}
+
+} // namespace Dom
+} // namespace QQmlJS
+QT_END_NAMESPACE
+
+#include "moc_qqmldomfilewriter_p.cpp"