/*
* Copyright (C) 2007 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 libcore.util;
import android.system.ErrnoException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.FileChannel.MapMode;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.TimeZone;
import libcore.io.BufferIterator;
import libcore.io.IoUtils;
import libcore.io.MemoryMappedFile;
/**
* A class used to initialize the time zone database. This implementation uses the
* Olson tzdata as the source of time zone information. However, to conserve
* disk space (inodes) and reduce I/O, all the data is concatenated into a single file,
* with an index to indicate the starting position of each time zone record.
*
* @hide - used to implement TimeZone
*/
public final class ZoneInfoDB {
private static final TzData DATA =
new TzData(System.getenv("ANDROID_ROOT") + "/usr/share/zoneinfo/tzdata");
public static class TzData {
/**
* Rather than open, read, and close the big data file each time we look up a time zone,
* we map the big data file during startup, and then just use the MemoryMappedFile.
*
* At the moment, this "big" data file is about 500 KiB. At some point, that will be small
* enough that we could just keep the byte[] in memory, but using mmap(2) like this has the
* nice property that even if someone replaces the file under us (because multiple gservices
* updates have gone out, say), we still get a consistent (if outdated) view of the world.
*/
private MemoryMappedFile mappedFile;
private String version;
private String zoneTab;
/**
* The 'ids' array contains time zone ids sorted alphabetically, for binary searching.
* The other two arrays are in the same order. 'byteOffsets' gives the byte offset
* of each time zone, and 'rawUtcOffsetsCache' gives the time zone's raw UTC offset.
*/
private String[] ids;
private int[] byteOffsets;
private int[] rawUtcOffsetsCache; // Access this via getRawUtcOffsets instead.
/**
* ZoneInfo objects are worth caching because they are expensive to create.
* See http://b/8270865 for context.
*/
private final static int CACHE_SIZE = 1;
private final BasicLruCache<String, ZoneInfo> cache =
new BasicLruCache<String, ZoneInfo>(CACHE_SIZE) {
@Override
protected ZoneInfo create(String id) {
// Work out where in the big data file this time zone is.
int index = Arrays.binarySearch(ids, id);
if (index < 0) {
return null;
}
BufferIterator it = mappedFile.bigEndianIterator();
it.skip(byteOffsets[index]);
return ZoneInfo.makeTimeZone(id, it);
}
};
public TzData(String... paths) {
for (String path : paths) {
if (loadData(path)) {
return;
}
}
// We didn't find any usable tzdata on disk, so let's just hard-code knowledge of "GMT".
// This is actually implemented in TimeZone itself, so if this is the only time zone
// we report, we won't be asked any more questions.
System.logE("Couldn't find any tzdata!");
version = "missing";
zoneTab = "# Emergency fallback data.\n";
ids = new String[] { "GMT" };
byteOffsets = rawUtcOffsetsCache = new int[1];
}
private boolean loadData(String path) {
try {
mappedFile = MemoryMappedFile.mmapRO(path);
} catch (ErrnoException errnoException) {
return false;
}
try {
readHeader();
return true;
} catch (Exception ex) {
// Something's wrong with the file.
// Log the problem and return false so we try the next choice.
System.logE("tzdata file \"" + path + "\" was present but invalid!", ex);
return false;
}
}
private void readHeader() {
// byte[12] tzdata_version -- "tzdata2012f\0"
// int index_offset
// int data_offset
// int zonetab_offset
BufferIterator it = mappedFile.bigEndianIterator();
byte[] tzdata_version = new byte[12];
it.readByteArray(tzdata_version, 0, tzdata_version.length);
String magic = new String(tzdata_version, 0, 6, StandardCharsets.US_ASCII);
if (!magic.equals("tzdata") || tzdata_version[11] != 0) {
throw new RuntimeException("bad tzdata magic: " + Arrays.toString(tzdata_version));
}
version = new String(tzdata_version, 6, 5, StandardCharsets.US_ASCII);
int index_offset = it.readInt();
int data_offset = it.readInt();
int zonetab_offset = it.readInt();
readIndex(it, index_offset, data_offset);
readZoneTab(it, zonetab_offset, (int) mappedFile.size() - zonetab_offset);
}
private void readZoneTab(BufferIterator it, int zoneTabOffset, int zoneTabSize) {
byte[] bytes = new byte[zoneTabSize];
it.seek(zoneTabOffset);
it.readByteArray(bytes, 0, bytes.length);
zoneTab = new String(bytes, 0, bytes.length, StandardCharsets.US_ASCII);
}
private void readIndex(BufferIterator it, int indexOffset, int dataOffset) {
it.seek(indexOffset);
// The database reserves 40 bytes for each id.
final int SIZEOF_TZNAME = 40;
// The database uses 32-bit (4 byte) integers.
final int SIZEOF_TZINT = 4;
byte[] idBytes = new byte[SIZEOF_TZNAME];
int indexSize = (dataOffset - indexOffset);
int entryCount = indexSize / (SIZEOF_TZNAME + 3*SIZEOF_TZINT);
char[] idChars = new char[entryCount * SIZEOF_TZNAME];
int[] idEnd = new int[entryCount];
int idOffset = 0;
byteOffsets = new int[entryCount];
for (int i = 0; i < entryCount; i++) {
it.readByteArray(idBytes, 0, idBytes.length);
byteOffsets[i] = it.readInt();
byteOffsets[i] += dataOffset; // TODO: change the file format so this is included.
int length = it.readInt();
if (length < 44) {
throw new AssertionError("length in index file < sizeof(tzhead)");
}
it.skip(4); // Skip the unused 4 bytes that used to be the raw offset.
// Don't include null chars in the String
int len = idBytes.length;
for (int j = 0; j < len; j++) {
if (idBytes[j] == 0) {
break;
}
idChars[idOffset++] = (char) (idBytes[j] & 0xFF);
}
idEnd[i] = idOffset;
}
// We create one string containing all the ids, and then break that into substrings.
// This way, all ids share a single char[] on the heap.
String allIds = new String(idChars, 0, idOffset);
ids = new String[entryCount];
for (int i = 0; i < entryCount; i++) {
ids[i] = allIds.substring(i == 0 ? 0 : idEnd[i - 1], idEnd[i]);
}
}
public String[] getAvailableIDs() {
return ids.clone();
}
public String[] getAvailableIDs(int rawUtcOffset) {
List<String> matches = new ArrayList<String>();
int[] rawUtcOffsets = getRawUtcOffsets();
for (int i = 0; i < rawUtcOffsets.length; ++i) {
if (rawUtcOffsets[i] == rawUtcOffset) {
matches.add(ids[i]);
}
}
return matches.toArray(new String[matches.size()]);
}
private synchronized int[] getRawUtcOffsets() {
if (rawUtcOffsetsCache != null) {
return rawUtcOffsetsCache;
}
rawUtcOffsetsCache = new int[ids.length];
for (int i = 0; i < ids.length; ++i) {
// This creates a TimeZone, which is quite expensive. Hence the cache.
// Note that icu4c does the same (without the cache), so if you're
// switching this code over to icu4j you should check its performance.
// Telephony shouldn't care, but someone converting a bunch of calendar
// events might.
rawUtcOffsetsCache[i] = cache.get(ids[i]).getRawOffset();
}
return rawUtcOffsetsCache;
}
public String getVersion() {
return version;
}
public String getZoneTab() {
return zoneTab;
}
public ZoneInfo makeTimeZone(String id) throws IOException {
ZoneInfo zoneInfo = cache.get(id);
// The object from the cache is cloned because TimeZone / ZoneInfo are mutable.
return zoneInfo == null ? null : (ZoneInfo) zoneInfo.clone();
}
}
private ZoneInfoDB() {
}
public static TzData getInstance() {
return DATA;
}
}