android.media.MiniThumbFile Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of android-all Show documentation
Show all versions of android-all Show documentation
A library jar that provides APIs for Applications written for the Google Android Platform.
/*
* 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 android.media;
import android.net.Uri;
import android.os.Environment;
import android.util.Log;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.Hashtable;
/**
* This class handles the mini-thumb file. A mini-thumb file consists
* of blocks, indexed by id. Each block has BYTES_PER_MINTHUMB bytes in the
* following format:
*
* 1 byte status (0 = empty, 1 = mini-thumb available)
* 8 bytes magic (a magic number to match what's in the database)
* 4 bytes data length (LEN)
* LEN bytes jpeg data
* (the remaining bytes are unused)
*
* @hide This file is shared between MediaStore and MediaProvider and should remained internal use
* only.
*/
public class MiniThumbFile {
private static final String TAG = "MiniThumbFile";
private static final int MINI_THUMB_DATA_FILE_VERSION = 3;
public static final int BYTES_PER_MINTHUMB = 10000;
private static final int HEADER_SIZE = 1 + 8 + 4;
private Uri mUri;
private RandomAccessFile mMiniThumbFile;
private FileChannel mChannel;
private ByteBuffer mBuffer;
private static final Hashtable sThumbFiles =
new Hashtable();
/**
* We store different types of thumbnails in different files. To remain backward compatibility,
* we should hashcode of content://media/external/images/media remains the same.
*/
public static synchronized void reset() {
for (MiniThumbFile file : sThumbFiles.values()) {
file.deactivate();
}
sThumbFiles.clear();
}
public static synchronized MiniThumbFile instance(Uri uri) {
String type = uri.getPathSegments().get(1);
MiniThumbFile file = sThumbFiles.get(type);
// Log.v(TAG, "get minithumbfile for type: "+type);
if (file == null) {
file = new MiniThumbFile(
Uri.parse("content://media/external/" + type + "/media"));
sThumbFiles.put(type, file);
}
return file;
}
private String randomAccessFilePath(int version) {
String directoryName =
Environment.getExternalStorageDirectory().toString()
+ "/DCIM/.thumbnails";
return directoryName + "/.thumbdata" + version + "-" + mUri.hashCode();
}
private void removeOldFile() {
String oldPath = randomAccessFilePath(MINI_THUMB_DATA_FILE_VERSION - 1);
File oldFile = new File(oldPath);
if (oldFile.exists()) {
try {
oldFile.delete();
} catch (SecurityException ex) {
// ignore
}
}
}
private RandomAccessFile miniThumbDataFile() {
if (mMiniThumbFile == null) {
removeOldFile();
String path = randomAccessFilePath(MINI_THUMB_DATA_FILE_VERSION);
File directory = new File(path).getParentFile();
if (!directory.isDirectory()) {
if (!directory.mkdirs()) {
Log.e(TAG, "Unable to create .thumbnails directory "
+ directory.toString());
}
}
File f = new File(path);
try {
mMiniThumbFile = new RandomAccessFile(f, "rw");
} catch (IOException ex) {
// Open as read-only so we can at least read the existing
// thumbnails.
try {
mMiniThumbFile = new RandomAccessFile(f, "r");
} catch (IOException ex2) {
// ignore exception
}
}
if (mMiniThumbFile != null) {
mChannel = mMiniThumbFile.getChannel();
}
}
return mMiniThumbFile;
}
public MiniThumbFile(Uri uri) {
mUri = uri;
mBuffer = ByteBuffer.allocateDirect(BYTES_PER_MINTHUMB);
}
public synchronized void deactivate() {
if (mMiniThumbFile != null) {
try {
mMiniThumbFile.close();
mMiniThumbFile = null;
} catch (IOException ex) {
// ignore exception
}
}
}
// Get the magic number for the specified id in the mini-thumb file.
// Returns 0 if the magic is not available.
public synchronized long getMagic(long id) {
// check the mini thumb file for the right data. Right is
// defined as having the right magic number at the offset
// reserved for this "id".
RandomAccessFile r = miniThumbDataFile();
if (r != null) {
long pos = id * BYTES_PER_MINTHUMB;
FileLock lock = null;
try {
mBuffer.clear();
mBuffer.limit(1 + 8);
lock = mChannel.lock(pos, 1 + 8, true);
// check that we can read the following 9 bytes
// (1 for the "status" and 8 for the long)
if (mChannel.read(mBuffer, pos) == 9) {
mBuffer.position(0);
if (mBuffer.get() == 1) {
return mBuffer.getLong();
}
}
} catch (IOException ex) {
Log.v(TAG, "Got exception checking file magic: ", ex);
} catch (RuntimeException ex) {
// Other NIO related exception like disk full, read only channel..etc
Log.e(TAG, "Got exception when reading magic, id = " + id +
", disk full or mount read-only? " + ex.getClass());
} finally {
try {
if (lock != null) lock.release();
}
catch (IOException ex) {
// ignore it.
}
}
}
return 0;
}
public synchronized void saveMiniThumbToFile(byte[] data, long id, long magic)
throws IOException {
RandomAccessFile r = miniThumbDataFile();
if (r == null) return;
long pos = id * BYTES_PER_MINTHUMB;
FileLock lock = null;
try {
if (data != null) {
if (data.length > BYTES_PER_MINTHUMB - HEADER_SIZE) {
// not enough space to store it.
return;
}
mBuffer.clear();
mBuffer.put((byte) 1);
mBuffer.putLong(magic);
mBuffer.putInt(data.length);
mBuffer.put(data);
mBuffer.flip();
lock = mChannel.lock(pos, BYTES_PER_MINTHUMB, false);
mChannel.write(mBuffer, pos);
}
} catch (IOException ex) {
Log.e(TAG, "couldn't save mini thumbnail data for "
+ id + "; ", ex);
throw ex;
} catch (RuntimeException ex) {
// Other NIO related exception like disk full, read only channel..etc
Log.e(TAG, "couldn't save mini thumbnail data for "
+ id + "; disk full or mount read-only? " + ex.getClass());
} finally {
try {
if (lock != null) lock.release();
}
catch (IOException ex) {
// ignore it.
}
}
}
/**
* Gallery app can use this method to retrieve mini-thumbnail. Full size
* images share the same IDs with their corresponding thumbnails.
*
* @param id the ID of the image (same of full size image).
* @param data the buffer to store mini-thumbnail.
*/
public synchronized byte [] getMiniThumbFromFile(long id, byte [] data) {
RandomAccessFile r = miniThumbDataFile();
if (r == null) return null;
long pos = id * BYTES_PER_MINTHUMB;
FileLock lock = null;
try {
mBuffer.clear();
lock = mChannel.lock(pos, BYTES_PER_MINTHUMB, true);
int size = mChannel.read(mBuffer, pos);
if (size > 1 + 8 + 4) { // flag, magic, length
mBuffer.position(0);
byte flag = mBuffer.get();
long magic = mBuffer.getLong();
int length = mBuffer.getInt();
if (size >= 1 + 8 + 4 + length && length != 0 && magic != 0 && flag == 1 &&
data.length >= length) {
mBuffer.get(data, 0, length);
return data;
}
}
} catch (IOException ex) {
Log.w(TAG, "got exception when reading thumbnail id=" + id + ", exception: " + ex);
} catch (RuntimeException ex) {
// Other NIO related exception like disk full, read only channel..etc
Log.e(TAG, "Got exception when reading thumbnail, id = " + id +
", disk full or mount read-only? " + ex.getClass());
} finally {
try {
if (lock != null) lock.release();
}
catch (IOException ex) {
// ignore it.
}
}
return null;
}
}