created disk manager class

This is a singleton class that will manage the disk cache to ensure the size
stays at sane levels.

app/render/diskmanager.cpp

@@ -0,0 +1,121 @@
+#include "diskmanager.h"
+
+#include <QDataStream>
+#include <QDateTime>
+#include <QDir>
+#include <QFile>
+
+#include "common/filefunctions.h"
+#include "config/config.h"
+
+DiskManager* DiskManager::instance_ = nullptr;
+
+DiskManager::DiskManager() :
+  consumption_(0)
+{
+
+  // Try to load any current cache index from file
+  QFile cache_index_file(QDir(GetMediaCacheLocation()).filePath("index"));
+
+  if (cache_index_file.open(QFile::ReadOnly)) {
+    QDataStream ds(&cache_index_file);
+
+    while (!cache_index_file.atEnd()) {
+      HashTime h;
+
+      ds >> h.file_name;
+      ds >> h.hash;
+      ds >> h.access_time;
+      ds >> h.file_size;
+
+      disk_data_.append(h);
+    }
+  } else {
+    qWarning() << "Failed to read cache index";
+  }
+
+}
+
+DiskManager::~DiskManager()
+{
+  // Save current cache index
+  QFile cache_index_file(QDir(GetMediaCacheLocation()).filePath("index"));
+
+  if (cache_index_file.open(QFile::WriteOnly)) {
+    QDataStream ds(&cache_index_file);
+
+    foreach (const HashTime& h, disk_data_) {
+      ds << h.file_name;
+      ds << h.hash;
+      ds << h.access_time;
+      ds << h.file_size;
+    }
+  } else {
+    qWarning() << "Failed to write cache index";
+  }
+}
+
+void DiskManager::CreateInstance()
+{
+  instance_ = new DiskManager();
+}
+
+void DiskManager::DestroyInstance()
+{
+  delete instance_;
+  instance_ = nullptr;
+}
+
+DiskManager *DiskManager::instance()
+{
+  return instance_;
+}
+
+void DiskManager::Accessed(const QByteArray &hash)
+{
+  for (int i=disk_data_.size()-1;i>=0;i--) {
+    const HashTime& h = disk_data_.at(i);
+
+    if (h.hash == hash) {
+      HashTime moved_hash = h;
+
+      moved_hash.access_time = QDateTime::currentMSecsSinceEpoch();
+
+      disk_data_.removeAt(i);
+      disk_data_.append(moved_hash);
+      break;
+    }
+  }
+}
+
+void DiskManager::CreatedFile(const QString &file_name, const QByteArray &hash)
+{
+  qint64 file_size = QFile(file_name).size();
+
+  disk_data_.append({file_name, hash, QDateTime::currentMSecsSinceEpoch(), });
+
+  consumption_ += file_size;
+
+  while (consumption_ > DiskLimit()) {
+    DeleteLeastRecent();
+  }
+}
+
+void DiskManager::DeleteLeastRecent()
+{
+  HashTime h = disk_data_.takeFirst();
+
+  QFile::remove(h.file_name);
+
+  consumption_ -= h.file_size;
+
+  emit DeletedFrame(h.hash);
+}
+
+qint64 DiskManager::DiskLimit()
+{
+  double gigabytes = Config::Current()["DiskCacheSize"].toDouble();
+
+  // Convert gigabytes to bytes
+  return qRound64(gigabytes * 1073741824);
+}