GN: Side-load dex files as well as native code in incremental installs

build/android/incremental_install/java/org/chromium/incrementalinstall/LockFile.java

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.incrementalinstall;
+
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.channels.FileLock;
+import java.util.concurrent.Callable;
+
+/**
+ * Helpers for dealing with .lock files used during install / first run.
+ */
+final class LockFile {
+    private static final String TAG = "cr.incrementalinstall";
+
+    private final File mFile;
+    private final FileOutputStream mOutputStream;
+    private final FileLock mFileLock;
+
+    private LockFile(File file, FileOutputStream outputStream, FileLock fileLock) {
+        mFile = file;
+        mOutputStream = outputStream;
+        mFileLock = fileLock;
+    }
+
+    /**
+     * Clears the lock file by writing to it (making it non-zero in length);
+     */
+    static void clearInstallerLock(File lockFile) throws IOException {
+        Log.i(TAG, "Clearing " + lockFile);
+        // On Android M, we can't delete files in /data/local/tmp, so we write to it instead.

[nyquist, 2015/09/16 06:30:46]

Nit: Should this be "Android M+"?

[agrieve, 2015/09/16 14:59:59]

Done.

+        FileOutputStream os = new FileOutputStream(lockFile);
+        os.write(1);
+        os.close();
+    }
+
+    /**
+     * Waits for the given file to be non-zero in length.
+     */
+    static void waitForInstallerLock(final File file, long timeoutMs) {
+        pollingWait(new Callable<Boolean>() {
+            @Override public Boolean call() {
+                return !installerLockExists(file);
+            }
+        }, file, timeoutMs);
+    }
+
+    /**
+     * Waits for the given file to be non-zero in length.
+     */
+    private static void pollingWait(Callable<Boolean> func, File file, long timeoutMs) {
+        final long pollIntervalMs = 200;

[nyquist, 2015/09/16 06:30:46]

Nit: Unnecessary final

[agrieve, 2015/09/16 14:59:59]

Done.

+        for (int i = 0; i < timeoutMs / pollIntervalMs; i++) {
+            try {
+                if (func.call()) {
+                    if (i > 0) {
+                        Log.i(TAG, "Finished waiting on lock file: " + file);
+                    }
+                    return;
+                } else if (i == 0) {
+                    Log.i(TAG, "Waiting on lock file: " + file);
+                }
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+            try {
+                Thread.sleep(pollIntervalMs);
+            } catch (InterruptedException e) {
+                // Should never happen.
+            }
+        }
+        throw new RuntimeException("Timed out waiting for lock file: " + file);
+    }
+
+    /**
+     * Returns whether the given lock file is missing or is in the locked state.
+     */
+    static boolean installerLockExists(File file) {
+        return !file.exists() || file.length() == 0;
+    }
+
+    /**
+     * Attempts to acquire a lock for the given file.
+     * @return Returns the FileLock if it was acquired, or null otherwise.
+     */
+    static LockFile acquireRuntimeLock(final File file) {

[nyquist, 2015/09/16 06:30:46]

Nit: Unnecessary final

[agrieve, 2015/09/16 14:59:59]

Done.

+        try {
+            FileOutputStream outputStream = new FileOutputStream(file);
+            FileLock lock = outputStream.getChannel().tryLock();
+            if (lock != null) {
+                Log.i(TAG, "Created lock file: " + file);
+                return new LockFile(file, outputStream, lock);
+            }
+            outputStream.close();
+        } catch (IOException e) {
+            // Do nothing. We didn't get the lock.
+        }
+        return null;
+    }
+
+    /**
+     * Waits for the given file to not exist.
+     */
+    static void waitForRuntimeLock(final File file, long timeoutMs) {
+        pollingWait(new Callable<Boolean>() {
+            @Override public Boolean call() {
+                return !file.exists();
+            }
+        }, file, timeoutMs);
+    }
+
+    /**
+     * Releases and deletes the lock file.
+     */
+    void release() throws IOException {
+        Log.i(TAG, "Deleting lock file: " + mFile);
+        mFileLock.release();
+        mOutputStream.close();
+        mFile.delete();

[nyquist, 2015/09/16 06:30:46]

Nit: Do we need to do anything special if this operation fails? Log something?

[agrieve, 2015/09/16 14:59:59]

Done.

+    }
+}