Android content shell bringup.

content/public/android/java/org/chromium/content/browser/LibraryLoader.java

Index: content/public/android/java/org/chromium/content/browser/LibraryLoader.java
diff --git a/content/public/android/java/org/chromium/content/browser/LibraryLoader.java b/content/public/android/java/org/chromium/content/browser/LibraryLoader.java
new file mode 100644
index 0000000000000000000000000000000000000000..ee9b35886111c4164c28b7aa0c64ec1c04c92e12
--- /dev/null
+++ b/content/public/android/java/org/chromium/content/browser/LibraryLoader.java
@@ -0,0 +1,239 @@
+// Copyright (c) 2012 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.content.browser;
+
+import android.os.AsyncTask;
+import android.os.Handler;
+import android.text.TextUtils;
+import android.util.Log;
+
+// This class provides functionality to:
+// - synchronously load and register the native library. This is used by callers
+// that can't do anything useful without the native side.
+// - asynchronously load and register the native library. This is used by callers
+// that can do more work in the java-side, and let a separate thread do all the
+// file IO and library loading.
+public class LibraryLoader {
+    private static final String TAG = "LibraryLoader";
+
+    /* TODO(jrg): resolve up and downstream discrepancy; there is no
+     * upstream libchromeview.so */
+    private static String sLibrary = "chromeview";
+
+    private static boolean sLoaded = false;
+
+    private static boolean sInitialized = false;
+
+    private static AsyncTask<Void, Void, Boolean> sAsyncLoader;
+
+    /**
+     * Callback for handling loading of the native library.
+     *
+     * <p> The callback methods will always be triggered on the UI thread.
+     */
+    public static interface Callback {
+        /**
+         * Called when loading the native library is successful.
+         */
+        void onSuccess();
+
+        /**
+         * Called when loading the native library fails.
+         */
+        void onFailure();
+    }
+
+    /**
+     * Sets the library name that is to be loaded.  This must be called prior to the library being
+     * loaded the first time.
+     *
+     * @param library The name of the library to be loaded (without the lib prefix).
+     */
+    public static void setLibraryToLoad(String library) {
+        if (TextUtils.equals(sLibrary, library)) return;
+
+        assert !sLoaded : "Setting the library must happen before load is called.";
+        sLibrary = library;
+    }
+
+    /**
+     *  This method blocks until the library is fully loaded and initialized;
+     *  must be called on the thread that the native will call its "main" thread.
+     */
+    public static void loadAndInitSync() {
+        checkThreadUsage();
+        if (sInitialized) {
+            // Already initialized, nothing to do.
+            return;
+        }
+        if (sAsyncLoader != null) {
+            // Async initialization in progress, wait.
+            waitForAsyncInitialized();
+            return;
+        }
+        loadNow();
+        initializeOnMainThread();
+    }
+
+    /**
+     *  Block until the library is fully initialized.
+     *  Must be called on the thread that the native will call its "main" thread.
+     */
+    private static void waitForAsyncInitialized() {
+        checkThreadUsage();
+        if (sInitialized) {
+            // Already initialized.
+            return;
+        }
+        synchronized(LibraryLoader.class) {
+            try {
+                while (!sLoaded) {
+                    LibraryLoader.class.wait();
+                }
+                // If the UI thread blocked waiting for the task it will already
+                // have handled the library load completion, so don't duplicate that work here.
+            } catch (InterruptedException e) {
+            }
+        }
+        initializeOnMainThread();
+    }
+
+    /**
+     *  Kicks off an asynchronous library load, and will asynchronously initialize the
+     *  library when that completes.
+     *  Must be called on the thread that the native will call its "main" thread.
+     */
+    public static void loadAndInitAsync(final Callback onLoadedListener) {
+        checkThreadUsage();
+        if (sInitialized) {
+            // Already initialized, post our Runnable if needed.
+            if (onLoadedListener != null) {
+                new Handler().post(new Runnable() {
+                    @Override
+                    public void run() {
+                        onLoadedListener.onSuccess();
+                    }
+                });
+            }
+            return;
+        }
+        sAsyncLoader = new AsyncTask<Void, Void, Boolean>() {
+            @Override
+            public Boolean doInBackground(Void... voids) {
+                // We're loading the .so in a background thread. Potentially, this
+                // can break native code that relies on static initializers using
+                // thread local storage, as the library would normally load in the
+                // main thread. If do we hit such cases we should remove those static
+                // initializers, as we chrome has banned them.
+                // (Worst case, we can go back to just warming up the file in the system
+                // cache here and do the actual loading in onPostExecute().)
+                return loadNow();
+            }
+
+            @Override
+            protected void onPostExecute(Boolean result) {
+                if (result) {
+                    initializeOnMainThread();
+                    if (onLoadedListener != null) onLoadedListener.onSuccess();
+                } else {
+                    if (onLoadedListener != null) onLoadedListener.onFailure();
+                }
+
+            }
+        };
+        sAsyncLoader.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    }
+
+    /**
+     * @throws UnsatisfiedLinkError if the library is not yet initialized.
+     */
+    public static void checkIsReady() {
+        if (!sInitialized) {
+            throw new UnsatisfiedLinkError(sLibrary + " is not initialized");
+        }
+    }
+
+    /**
+     * Loads the library and blocks until the load completes. The caller is responsible
+     * for subsequently calling initialize().
+     * May be called on any thread, but should only be called once. Note the thread
+     * this is called on will be the thread that runs the native code's static initializers.
+     * See the comment in doInBackground() for more considerations on this.
+     *
+     * @return Whether the native library was successfully loaded.
+     */
+    static boolean loadNow() {
+        assert !sInitialized;
+        try {
+            Log.i(TAG, "loading: " + sLibrary);
+            System.loadLibrary(sLibrary);
+            Log.i(TAG, "loaded: " + sLibrary);
+            synchronized(LibraryLoader.class) {
+                sLoaded = true;
+                LibraryLoader.class.notifyAll();
+            }
+        } catch (UnsatisfiedLinkError e) {
+            Log.e(TAG, "error loading: " + sLibrary, e);
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * initializes the library here and now: must be called on the thread that the
+     * native will call its "main" thread. The library must have previously been
+     * loaded with loadNow.
+     * @param initCommandLine The command line arguments that native command line will
+     * be initialized with.
+     */
+    static void initializeOnMainThread(String[] initCommandLine) {
+        checkThreadUsage();
+        if (sInitialized) {
+            return;
+        }
+        if (!nativeLibraryLoadedOnMainThread(initCommandLine)) {
+            Log.e(TAG, "error calling nativeLibraryLoadedOnMainThread");
+            throw new UnsatisfiedLinkError();
+        }
+        // From this point on, native code is ready to use and checkIsReady()
+        // shouldn't complain from now on (and in fact, it's used by the
+        // following calls).
+        sInitialized = true;
+        CommandLine.enableNativeProxy();
+        TraceEvent.setEnabledToMatchNative();
+    }
+
+    static private void initializeOnMainThread() {
+        checkThreadUsage();
+        if (!sInitialized) {
+            initializeOnMainThread(CommandLine.getJavaSwitchesOrNull());
+        }
+    }
+
+    private LibraryLoader() {
+    }
+
+    // The public API of this class is meant to be used from a single
+    // thread. Internally, we may bounce to a separate thread to actually
+    // load the library.
+    private static Thread sMyThread;
+    private static void checkThreadUsage() {
+        Thread currentThread = java.lang.Thread.currentThread();
+        if (sMyThread == null) {
+            sMyThread = currentThread;
+        } else {
+            if (sMyThread != currentThread) {
+                Log.e(TAG, "Threading violation detected. My thread=" + sMyThread +
+                    " but I'm being accessed from thread=" + currentThread);
+                assert false;
+            }
+        }
+    }
+
+    // This is the only method that is registered during System.loadLibrary, as it
+    // happens on a different thread. We then call it on the main thread to register
+    // everything else.
+    private static native boolean nativeLibraryLoadedOnMainThread(String[] initCommandLine);
+}