From 3175e640bbc6d84935b3bd7c28cf5abcd8e1b3f7 Mon Sep 17 00:00:00 2001
From: Mathew Sutcliffe <oktal3700@gmail.com>
Date: Sat, 6 Feb 2016 18:25:04 +0000
Subject: [PATCH] refs #581, #592, #545 CAtomicFile can support ReadWrite mode
 by first copying the file.

---
 src/blackmisc/atomicfile.cpp | 10 +++++++---
 src/blackmisc/valuecache.cpp | 17 ++++++++---------
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/blackmisc/atomicfile.cpp b/src/blackmisc/atomicfile.cpp
index 55d7f2240..05cf29d4c 100644
--- a/src/blackmisc/atomicfile.cpp
+++ b/src/blackmisc/atomicfile.cpp
@@ -22,14 +22,18 @@ namespace BlackMisc
 
     bool CAtomicFile::open(CAtomicFile::OpenMode mode)
     {
-        Q_ASSERT_X(!(mode & (ReadOnly | Append)), Q_FUNC_INFO, "ReadOnly and Append flags are incompatible with CAtomicFile");
-
         m_originalFilename = fileName();
         QFileInfo fileInfo(fileName());
         setFileName(QFileInfo(fileInfo.dir(), ".tmp." + fileInfo.fileName() + "." + randomSuffix()).filePath());
         if (exists()) { remove(); }
 
-        bool ok = QFile::open(mode);
+        bool ok = true;
+        if (mode & ReadOnly)
+        {
+            if (exists(m_originalFilename) && ! copy(m_originalFilename, fileName())) { ok = false; }
+        }
+
+        if (ok && ! QFile::open(mode)) { ok = false; }
         if (! ok) { setFileName(m_originalFilename); }
         return ok;
     }
diff --git a/src/blackmisc/valuecache.cpp b/src/blackmisc/valuecache.cpp
index 227856a97..be2eeeb88 100644
--- a/src/blackmisc/valuecache.cpp
+++ b/src/blackmisc/valuecache.cpp
@@ -241,25 +241,24 @@ namespace BlackMisc
         }
         for (auto it = namespaces.cbegin(); it != namespaces.cend(); ++it)
         {
-            QFile readFile(dir + "/" + it.key() + ".json");
-            if (! readFile.open(QFile::ReadWrite | QFile::Text))
+            CAtomicFile file(dir + "/" + it.key() + ".json");
+            if (! file.open(QFile::ReadWrite | QFile::Text))
             {
-                return CLogMessage(this).error("Failed to open %1: %2") << readFile.fileName() << readFile.errorString();
+                return CLogMessage(this).error("Failed to open %1: %2") << file.fileName() << file.errorString();
             }
-            auto json = QJsonDocument::fromJson(readFile.readAll());
+            auto json = QJsonDocument::fromJson(file.readAll());
             if (json.isArray() || (json.isNull() && ! json.isEmpty()))
             {
-                return CLogMessage(this).error("Invalid JSON format in %1") << readFile.fileName();
+                return CLogMessage(this).error("Invalid JSON format in %1") << file.fileName();
             }
             CVariantMap storedValues;
             storedValues.convertFromJson(json.object());
             storedValues.insert(*it);
             json.setObject(storedValues.toJson());
-            readFile.close();
-            CAtomicFile writeFile(readFile.fileName());
-            if (! (writeFile.open(QFile::WriteOnly | QFile::Text) && writeFile.write(json.toJson()) > 0 && writeFile.checkedClose()))
+
+            if (! (file.seek(0) && file.resize(0) && file.write(json.toJson()) > 0 && file.checkedClose()))
             {
-                return CLogMessage(this).error("Failed to write to %1: %2") << writeFile.fileName() << writeFile.errorString();
+                return CLogMessage(this).error("Failed to write to %1: %2") << file.fileName() << file.errorString();
             }
         }
         return {};