From 6814dfcbfc5eee145e6201ebb86de729842952bf Mon Sep 17 00:00:00 2001
From: Sam Gondelman <samuel_gondelman@brown.edu>
Date: Sun, 17 Dec 2017 22:09:20 -0800
Subject: [PATCH] weak_ptr _cacheFile

---
 libraries/gpu/src/gpu/Texture.h       |  2 +-
 libraries/gpu/src/gpu/Texture_ktx.cpp | 22 +++++++++++++++++-----
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/libraries/gpu/src/gpu/Texture.h b/libraries/gpu/src/gpu/Texture.h
index 7c087fec2b..06208179e0 100755
--- a/libraries/gpu/src/gpu/Texture.h
+++ b/libraries/gpu/src/gpu/Texture.h
@@ -328,7 +328,7 @@ public:
         std::shared_ptr<storage::FileStorage> maybeOpenFile() const;
 
         mutable std::shared_ptr<std::mutex> _cacheFileMutex { std::make_shared<std::mutex>() };
-        mutable std::shared_ptr<storage::FileStorage> _cacheFile;
+        mutable std::weak_ptr<storage::FileStorage> _cacheFile;
 
         static std::vector<std::pair<std::shared_ptr<storage::FileStorage>, std::shared_ptr<std::mutex>>> _cachedKtxFiles;
         static std::mutex _cachedKtxFilesMutex;
diff --git a/libraries/gpu/src/gpu/Texture_ktx.cpp b/libraries/gpu/src/gpu/Texture_ktx.cpp
index 8b054816bb..883d9abf15 100644
--- a/libraries/gpu/src/gpu/Texture_ktx.cpp
+++ b/libraries/gpu/src/gpu/Texture_ktx.cpp
@@ -190,13 +190,25 @@ KtxStorage::KtxStorage(const std::string& filename) : _filename(filename) {
     }
 }
 
+// maybeOpenFile should be called with _cacheFileMutex already held to avoid modifying the file from multiple threads
 std::shared_ptr<storage::FileStorage> KtxStorage::maybeOpenFile() const {
-    if (!_cacheFile) {
-        _cacheFile = std::make_shared<storage::FileStorage>(_filename.c_str());
-        std::lock_guard<std::mutex> lock(_cachedKtxFilesMutex);
-        _cachedKtxFiles.emplace_back(_cacheFile, _cacheFileMutex);
+    // Try to get the shared_ptr
+    std::shared_ptr<storage::FileStorage> file = _cacheFile.lock();
+    if (file) {
+        return file;
     }
-    return _cacheFile;
+
+    // If the file isn't open, create it and save a weak_ptr to it
+    file = std::make_shared<storage::FileStorage>(_filename.c_str());
+    _cacheFile = file;
+
+    {
+        // Add the shared_ptr to the global list of open KTX files, to be released at the beginning of the next present thread frame
+        std::lock_guard<std::mutex> lock(_cachedKtxFilesMutex);
+        _cachedKtxFiles.emplace_back(file, _cacheFileMutex);
+    }
+
+    return file;
 }
 
 void KtxStorage::releaseOpenKtxFiles() {