Move deleteOlderFiles() to framework, tests.

Supports both age and count based constraints.  Added light docs and
tests to verify behavior.

Bug: 8387555
Change-Id: If4d0dac8bc54ce705c2a339bc09a60ea748728b8

1 files changed, 44 insertions, 1 deletions

diff --git a/core/java/android/os/FileUtils.java b/core/java/android/os/FileUtils.java
index 2bec1c176905..9666d9af8cc4 100644
--- a/core/java/android/os/FileUtils.java
+++ b/core/java/android/os/FileUtils.java
@@ -16,6 +16,8 @@
 
 package android.os;
 
+import android.util.Log;
+
 import java.io.BufferedInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
@@ -25,6 +27,8 @@ import java.io.FileOutputStream;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.Arrays;
+import java.util.Comparator;
 import java.util.regex.Pattern;
 import java.util.zip.CRC32;
 import java.util.zip.CheckedInputStream;
@@ -34,6 +38,8 @@ import java.util.zip.CheckedInputStream;
  * @hide
  */
 public class FileUtils {
+    private static final String TAG = "FileUtils";
+
     public static final int S_IRWXU = 00700;
     public static final int S_IRUSR = 00400;
     public static final int S_IWUSR = 00200;
@@ -161,7 +167,8 @@ public class FileUtils {
             } else if (max < 0) {  // "tail" mode: keep the last N
                 int len;
                 boolean rolled = false;
-                byte[] last = null, data = null;
+                byte[] last = null;
+                byte[] data = null;
                 do {
                     if (last != null) rolled = true;
                     byte[] tmp = last; last = data; data = tmp;
@@ -237,4 +244,40 @@ public class FileUtils {
             }
         }
     }
+
+    /**
+     * Delete older files in a directory until only those matching the given
+     * constraints remain.
+     *
+     * @param minCount Always keep at least this many files.
+     * @param minAge Always keep files younger than this age.
+     */
+    public static void deleteOlderFiles(File dir, int minCount, long minAge) {
+        if (minCount < 0 || minAge < 0) {
+            throw new IllegalArgumentException("Constraints must be positive or 0");
+        }
+
+        final File[] files = dir.listFiles();
+        if (files == null) return;
+
+        // Sort with newest files first
+        Arrays.sort(files, new Comparator<File>() {
+            @Override
+            public int compare(File lhs, File rhs) {
+                return (int) (rhs.lastModified() - lhs.lastModified());
+            }
+        });
+
+        // Keep at least minCount files
+        for (int i = minCount; i < files.length; i++) {
+            final File file = files[i];
+
+            // Keep files newer than minAge
+            final long age = System.currentTimeMillis() - file.lastModified();
+            if (age > minAge) {
+                Log.d(TAG, "Deleting old file " + file);
+                file.delete();
+            }
+        }
+    }
 }