From e0863aa50f3509b3102f33d694f7d129bc33fbcb Mon Sep 17 00:00:00 2001
From: Atlante45 <clement.brisset@gmail.com>
Date: Thu, 11 May 2017 11:15:36 -0700
Subject: [PATCH] Only open files for write if necessary

---
 libraries/shared/src/shared/Storage.cpp | 30 ++++++++++++++++++++++++-
 libraries/shared/src/shared/Storage.h   |  5 ++++-
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/libraries/shared/src/shared/Storage.cpp b/libraries/shared/src/shared/Storage.cpp
index aae1f8455f..943dad9f56 100644
--- a/libraries/shared/src/shared/Storage.cpp
+++ b/libraries/shared/src/shared/Storage.cpp
@@ -68,7 +68,7 @@ StoragePointer FileStorage::create(const QString& filename, size_t size, const u
 }
 
 FileStorage::FileStorage(const QString& filename) : _file(filename) {
-    if (_file.open(QFile::ReadWrite)) {
+    if (_file.open(QFile::ReadOnly)) {
         _mapped = _file.map(0, _file.size());
         if (_mapped) {
             _valid = true;
@@ -90,3 +90,31 @@ FileStorage::~FileStorage() {
         _file.close();
     }
 }
+
+void FileStorage::ensureWriteAccess() {
+    if (_hasWriteAccess) {
+        return;
+    }
+
+    if (_mapped) {
+        if (!_file.unmap(_mapped)) {
+            throw std::runtime_error("Unable to unmap file");
+        }
+    }
+    if (_file.isOpen()) {
+        _file.close();
+    }
+    _valid = false;
+
+    if (_file.open(QFile::ReadWrite)) {
+        _mapped = _file.map(0, _file.size());
+        if (_mapped) {
+            _valid = true;
+            _hasWriteAccess = true;
+        } else {
+            qCWarning(storagelogging) << "Failed to map file " << _file.fileName();
+        }
+    } else {
+        qCWarning(storagelogging) << "Failed to open file " << _file.fileName();
+    }
+}
\ No newline at end of file
diff --git a/libraries/shared/src/shared/Storage.h b/libraries/shared/src/shared/Storage.h
index da5b773d52..4cad9fa083 100644
--- a/libraries/shared/src/shared/Storage.h
+++ b/libraries/shared/src/shared/Storage.h
@@ -60,11 +60,14 @@ namespace storage {
         FileStorage& operator=(const FileStorage& other) = delete;
 
         const uint8_t* data() const override { return _mapped; }
-        uint8_t* mutableData() override { return _mapped; }
+        uint8_t* mutableData() override { ensureWriteAccess(); return _mapped; }
         size_t size() const override { return _file.size(); }
         operator bool() const override { return _valid; }
     private:
+        void ensureWriteAccess();
+
         bool _valid { false };
+        bool _hasWriteAccess { false };
         QFile _file;
         uint8_t* _mapped { nullptr };
     };