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Commit 7dfbaf52 authored by Christopher Tate's avatar Christopher Tate Committed by Christopher Tate
Browse files

Make archive metadata idempotent 

We want to make sure that the manifest and widget metadata
blocks are identical, including their in-stream headers, if
we regenerate the archive without underlying filesystem changes.

Bug 15968355

Change-Id: I828b264545d19e1d865d98d5723915d02fafc012
parent 0615026b

services/backup/java/com/android/server/backup/BackupManagerService.java

+11 −0
Original line number Diff line number Diff line
@@ -3151,6 +3151,13 @@ public class BackupManagerService extends IBackupManager.Stub { 
            FileOutputStream outstream = new FileOutputStream(manifestFile);

            outstream.write(builder.toString().getBytes());

            outstream.close();



            // We want the manifest block in the archive stream to be idempotent:

            // each time we generate a backup stream for the app, we want the manifest

            // block to be identical.  The underlying tar mechanism sees it as a file,

            // though, and will propagate its mtime, causing the tar header to vary.

            // Avoid this problem by pinning the mtime to zero.

            manifestFile.setLastModified(0);

        }



        // Widget metadata format. All header entries are strings ending in LF:
@@ -3188,6 +3195,10 @@ public class BackupManagerService extends IBackupManager.Stub { 
            }

            bout.flush();

            out.close();



            // As with the manifest file, guarantee idempotence of the archive metadata

            // for the widget block by using a fixed mtime on the transient file.

            destination.setLastModified(0);

        }



        private void tearDown(PackageInfo pkg) {