From 4dc141503517d6f629d49d4593cb1d9c1f19cce3 Mon Sep 17 00:00:00 2001
From: Hans-Christoph Steiner <hans@eds.org>
Date: Tue, 16 Aug 2016 16:50:04 +0200
Subject: [PATCH] document processes in CleanCacheService

This breaks out each separate process into its own utility method, and adds
javadoc to describe them.
---
 .../org/fdroid/fdroid/CleanCacheService.java  | 21 +++++++++++++++++--
 .../java/org/fdroid/fdroid/Preferences.java   |  2 +-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/app/src/main/java/org/fdroid/fdroid/CleanCacheService.java b/app/src/main/java/org/fdroid/fdroid/CleanCacheService.java
index 9089b12c6..9fca46e7d 100644
--- a/app/src/main/java/org/fdroid/fdroid/CleanCacheService.java
+++ b/app/src/main/java/org/fdroid/fdroid/CleanCacheService.java
@@ -23,7 +23,14 @@ import java.util.concurrent.TimeUnit;
  * Handles cleaning up caches files that are not going to be used, and do not
  * block the operation of the app itself.  For things that must happen before
  * F-Droid starts normal operation, that should go into
- * {@link FDroidApp#onCreate()}
+ * {@link FDroidApp#onCreate()}.
+ * <p>
+ * These files should only be deleted when they are at least an hour-ish old,
+ * in case they are actively in use while {@code CleanCacheService} is running.
+ * {@link #clearOldFiles(File, long)} checks the file age using access time from
+ * {@link StructStat#st_atime} on {@link android.os.Build.VERSION_CODES#LOLLIPOP}
+ * and newer.  On older Android, last modified time from {@link File#lastModified()}
+ * is used.
  */
 public class CleanCacheService extends IntentService {
 
@@ -58,12 +65,22 @@ public class CleanCacheService extends IntentService {
             return;
         }
         Process.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
-        clearOldFiles(ApkCache.getApkCacheDir(getBaseContext()), Preferences.get().getKeepCacheTime());
+        deleteExpiredApksFromCache();
         deleteStrayIndexFiles();
         deleteOldInstallerFiles();
         deleteOldIcons();
     }
 
+    /**
+     * All downloaded APKs will be cached for a certain amount of time, which is
+     * specified by the user in the "Keep Cache Time" preference.  This removes
+     * any APK in the cache that is older than that preference specifies.
+     */
+    private void deleteExpiredApksFromCache() {
+        File cacheDir = ApkCache.getApkCacheDir(getBaseContext());
+        clearOldFiles(cacheDir, Preferences.get().getKeepCacheTime());
+    }
+
     /**
      * {@link org.fdroid.fdroid.installer.Installer} instances copy the APK into
      * a safe place before installing.  It doesn't clean up them reliably yet.
diff --git a/app/src/main/java/org/fdroid/fdroid/Preferences.java b/app/src/main/java/org/fdroid/fdroid/Preferences.java
index 3216f4c87..626b44182 100644
--- a/app/src/main/java/org/fdroid/fdroid/Preferences.java
+++ b/app/src/main/java/org/fdroid/fdroid/Preferences.java
@@ -71,7 +71,7 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
     private static final int DEFAULT_UPD_HISTORY = 14;
     private static final boolean DEFAULT_PRIVILEGED_INSTALLER = false;
     //private static final boolean DEFAULT_LOCAL_REPO_BONJOUR = true;
-    private static final long DEFAULT_KEEP_CACHE_TIME = TimeUnit.DAYS.toMillis(1);  // one day
+    private static final long DEFAULT_KEEP_CACHE_TIME = TimeUnit.DAYS.toMillis(1);
     private static final boolean DEFAULT_UNSTABLE_UPDATES = false;
     //private static final boolean DEFAULT_LOCAL_REPO_HTTPS = false;
     private static final boolean DEFAULT_INCOMP_VER = false;