Rewrite SyncStorageEngine to use flat files and in-memory data structures.

The previous implementation used a database for storing all of its state, which could cause
a significant amount of IO activity as its tables were updated through the stages of a sync.
This new implementation replaces that in-memory data structures, with hand-written code
for writing them to persistent storage.

There are now 4 files associated with this class, holding various pieces of its state that
should be consistent.  These are everything from a main XML file of account information that
must always be retained, to a binary file of per-day statistics that can be thrown away at
any time.  Writes of these files as scheduled at various times based on their importance of
the frequency at which they change.

Because the database no longer exists, there needs to be a new explicit interface for
interacting with the sync manager database.  This is provided by new APIs on IContentService,
with a hidden method on ContentResolver to retrieve the IContentService so that various
system entities can use it.  Other changes in other projects are required to update to the
new API.

The goal here is to have as little an impact on the code and functionality outside of
SyncStorageEngine, though due to the necessary change in API it is still somewhat extensive.

1 files changed, 153 insertions, 0 deletions

diff --git a/core/java/com/android/internal/os/AtomicFile.java b/core/java/com/android/internal/os/AtomicFile.java
new file mode 100644
index 0000000..ca0345f
--- /dev/null
+++ b/core/java/com/android/internal/os/AtomicFile.java
@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.internal.os;
+
+import android.os.FileUtils;
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * Helper class for performing atomic operations on a file, by creating a
+ * backup file until a write has successfully completed.
+ */
+public class AtomicFile {
+    private final File mBaseName;
+    private final File mBackupName;
+    
+    public AtomicFile(File baseName) {
+        mBaseName = baseName;
+        mBackupName = new File(baseName.getPath() + ".bak");
+    }
+    
+    public File getBaseFile() {
+        return mBaseName;
+    }
+    
+    public FileOutputStream startWrite() throws IOException {
+        // Rename the current file so it may be used as a backup during the next read
+        if (mBaseName.exists()) {
+            if (!mBaseName.renameTo(mBackupName)) {
+                mBackupName.delete();
+                if (!mBaseName.renameTo(mBackupName)) {
+                    Log.w("AtomicFile", "Couldn't rename file " + mBaseName
+                            + " to backup file " + mBackupName);
+                }
+            }
+        }
+        FileOutputStream str = null;
+        try {
+            str = new FileOutputStream(mBaseName);
+        } catch (FileNotFoundException e) {
+            File parent = mBaseName.getParentFile();
+            if (!parent.mkdir()) {
+                throw new IOException("Couldn't create directory " + mBaseName);
+            }
+            FileUtils.setPermissions(
+                parent.getPath(),
+                FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
+                -1, -1);
+            try {
+                str = new FileOutputStream(mBaseName);
+            } catch (FileNotFoundException e2) {
+                throw new IOException("Couldn't create " + mBaseName);
+            }
+        }
+        return str;
+    }
+    
+    public void finishWrite(FileOutputStream str) {
+        if (str != null) {
+            try {
+                str.close();
+                mBackupName.delete();
+            } catch (IOException e) {
+                Log.w("AtomicFile", "finishWrite: Got exception:", e);
+            }
+        }
+    }
+    
+    public void failWrite(FileOutputStream str) {
+        if (str != null) {
+            try {
+                str.close();
+                mBaseName.delete();
+                mBackupName.renameTo(mBaseName);
+            } catch (IOException e) {
+                Log.w("AtomicFile", "failWrite: Got exception:", e);
+            }
+        }
+    }
+    
+    public FileOutputStream openAppend() throws IOException {
+        try {
+            return new FileOutputStream(mBaseName, true);
+        } catch (FileNotFoundException e) {
+            throw new IOException("Couldn't append " + mBaseName);
+        }
+    }
+    
+    public void truncate() throws IOException {
+        try {
+            FileOutputStream fos = new FileOutputStream(mBaseName);
+            fos.close();
+        } catch (FileNotFoundException e) {
+            throw new IOException("Couldn't append " + mBaseName);
+        } catch (IOException e) {
+        }
+    }
+    
+    public FileInputStream openRead() throws FileNotFoundException {
+        if (mBackupName.exists()) {
+            mBaseName.delete();
+            mBackupName.renameTo(mBaseName);
+        }
+        return new FileInputStream(mBaseName);
+    }
+    
+    public byte[] readFully() throws IOException {
+        FileInputStream stream = openRead();
+        try {
+            int pos = 0;
+            int avail = stream.available();
+            byte[] data = new byte[avail];
+            while (true) {
+                int amt = stream.read(data, pos, data.length-pos);
+                //Log.i("foo", "Read " + amt + " bytes at " + pos
+                //        + " of avail " + data.length);
+                if (amt <= 0) {
+                    //Log.i("foo", "**** FINISHED READING: pos=" + pos
+                    //        + " len=" + data.length);
+                    return data;
+                }
+                pos += amt;
+                avail = stream.available();
+                if (avail > data.length-pos) {
+                    byte[] newData = new byte[pos+avail];
+                    System.arraycopy(data, 0, newData, 0, pos);
+                    data = newData;
+                }
+            }
+        } finally {
+            stream.close();
+        }
+    }
+}