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A library jar that provides APIs for Applications written for the Google Android Platform.
/*
* Copyright (C) 2006 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.util;
import android.os.DeadSystemException;
import com.android.internal.os.RuntimeInit;
import com.android.internal.util.FastPrintWriter;
import com.android.internal.util.LineBreakBufferedWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.net.UnknownHostException;
/**
* API for sending log output.
*
* Generally, use the Log.v() Log.d() Log.i() Log.w() and Log.e()
* methods.
*
*
The order in terms of verbosity, from least to most is
* ERROR, WARN, INFO, DEBUG, VERBOSE. Verbose should never be compiled
* into an application except during development. Debug logs are compiled
* in but stripped at runtime. Error, warning and info logs are always kept.
*
*
Tip: A good convention is to declare a TAG constant
* in your class:
*
*
private static final String TAG = "MyActivity";
*
* and use that in subsequent calls to the log methods.
*
*
* Tip: Don't forget that when you make a call like
*
Log.v(TAG, "index=" + i);
* that when you're building the string to pass into Log.d, the compiler uses a
* StringBuilder and at least three allocations occur: the StringBuilder
* itself, the buffer, and the String object. Realistically, there is also
* another buffer allocation and copy, and even more pressure on the gc.
* That means that if your log message is filtered out, you might be doing
* significant work and incurring significant overhead.
*/
public final class Log {
/**
* Priority constant for the println method; use Log.v.
*/
public static final int VERBOSE = 2;
/**
* Priority constant for the println method; use Log.d.
*/
public static final int DEBUG = 3;
/**
* Priority constant for the println method; use Log.i.
*/
public static final int INFO = 4;
/**
* Priority constant for the println method; use Log.w.
*/
public static final int WARN = 5;
/**
* Priority constant for the println method; use Log.e.
*/
public static final int ERROR = 6;
/**
* Priority constant for the println method.
*/
public static final int ASSERT = 7;
/**
* Exception class used to capture a stack trace in {@link #wtf}.
*/
private static class TerribleFailure extends Exception {
TerribleFailure(String msg, Throwable cause) { super(msg, cause); }
}
/**
* Interface to handle terrible failures from {@link #wtf}.
*
* @hide
*/
public interface TerribleFailureHandler {
void onTerribleFailure(String tag, TerribleFailure what, boolean system);
}
private static TerribleFailureHandler sWtfHandler = new TerribleFailureHandler() {
public void onTerribleFailure(String tag, TerribleFailure what, boolean system) {
RuntimeInit.wtf(tag, what, system);
}
};
private Log() {
}
/**
* Send a {@link #VERBOSE} log message.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
*/
public static int v(String tag, String msg) {
return println_native(LOG_ID_MAIN, VERBOSE, tag, msg);
}
/**
* Send a {@link #VERBOSE} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @param tr An exception to log
*/
public static int v(String tag, String msg, Throwable tr) {
return printlns(LOG_ID_MAIN, VERBOSE, tag, msg, tr);
}
/**
* Send a {@link #DEBUG} log message.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
*/
public static int d(String tag, String msg) {
return println_native(LOG_ID_MAIN, DEBUG, tag, msg);
}
/**
* Send a {@link #DEBUG} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @param tr An exception to log
*/
public static int d(String tag, String msg, Throwable tr) {
return printlns(LOG_ID_MAIN, DEBUG, tag, msg, tr);
}
/**
* Send an {@link #INFO} log message.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
*/
public static int i(String tag, String msg) {
return println_native(LOG_ID_MAIN, INFO, tag, msg);
}
/**
* Send a {@link #INFO} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @param tr An exception to log
*/
public static int i(String tag, String msg, Throwable tr) {
return printlns(LOG_ID_MAIN, INFO, tag, msg, tr);
}
/**
* Send a {@link #WARN} log message.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
*/
public static int w(String tag, String msg) {
return println_native(LOG_ID_MAIN, WARN, tag, msg);
}
/**
* Send a {@link #WARN} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @param tr An exception to log
*/
public static int w(String tag, String msg, Throwable tr) {
return printlns(LOG_ID_MAIN, WARN, tag, msg, tr);
}
/**
* Checks to see whether or not a log for the specified tag is loggable at the specified level.
*
* The default level of any tag is set to INFO. This means that any level above and including
* INFO will be logged. Before you make any calls to a logging method you should check to see
* if your tag should be logged. You can change the default level by setting a system property:
* 'setprop log.tag.<YOUR_LOG_TAG> <LEVEL>'
* Where level is either VERBOSE, DEBUG, INFO, WARN, ERROR, ASSERT, or SUPPRESS. SUPPRESS will
* turn off all logging for your tag. You can also create a local.prop file that with the
* following in it:
* 'log.tag.<YOUR_LOG_TAG>=<LEVEL>'
* and place that in /data/local.prop.
*
* @param tag The tag to check.
* @param level The level to check.
* @return Whether or not that this is allowed to be logged.
* @throws IllegalArgumentException is thrown if the tag.length() > 23
* for Nougat (7.0) releases (API <= 23) and prior, there is no
* tag limit of concern after this API level.
*/
public static native boolean isLoggable(String tag, int level);
/*
* Send a {@link #WARN} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param tr An exception to log
*/
public static int w(String tag, Throwable tr) {
return printlns(LOG_ID_MAIN, WARN, tag, "", tr);
}
/**
* Send an {@link #ERROR} log message.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
*/
public static int e(String tag, String msg) {
return println_native(LOG_ID_MAIN, ERROR, tag, msg);
}
/**
* Send a {@link #ERROR} log message and log the exception.
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @param tr An exception to log
*/
public static int e(String tag, String msg, Throwable tr) {
return printlns(LOG_ID_MAIN, ERROR, tag, msg, tr);
}
/**
* What a Terrible Failure: Report a condition that should never happen.
* The error will always be logged at level ASSERT with the call stack.
* Depending on system configuration, a report may be added to the
* {@link android.os.DropBoxManager} and/or the process may be terminated
* immediately with an error dialog.
* @param tag Used to identify the source of a log message.
* @param msg The message you would like logged.
*/
public static int wtf(String tag, String msg) {
return wtf(LOG_ID_MAIN, tag, msg, null, false, false);
}
/**
* Like {@link #wtf(String, String)}, but also writes to the log the full
* call stack.
* @hide
*/
public static int wtfStack(String tag, String msg) {
return wtf(LOG_ID_MAIN, tag, msg, null, true, false);
}
/**
* What a Terrible Failure: Report an exception that should never happen.
* Similar to {@link #wtf(String, String)}, with an exception to log.
* @param tag Used to identify the source of a log message.
* @param tr An exception to log.
*/
public static int wtf(String tag, Throwable tr) {
return wtf(LOG_ID_MAIN, tag, tr.getMessage(), tr, false, false);
}
/**
* What a Terrible Failure: Report an exception that should never happen.
* Similar to {@link #wtf(String, Throwable)}, with a message as well.
* @param tag Used to identify the source of a log message.
* @param msg The message you would like logged.
* @param tr An exception to log. May be null.
*/
public static int wtf(String tag, String msg, Throwable tr) {
return wtf(LOG_ID_MAIN, tag, msg, tr, false, false);
}
static int wtf(int logId, String tag, String msg, Throwable tr, boolean localStack,
boolean system) {
TerribleFailure what = new TerribleFailure(msg, tr);
// Only mark this as ERROR, do not use ASSERT since that should be
// reserved for cases where the system is guaranteed to abort.
// The onTerribleFailure call does not always cause a crash.
int bytes = printlns(logId, ERROR, tag, msg, localStack ? what : tr);
sWtfHandler.onTerribleFailure(tag, what, system);
return bytes;
}
static void wtfQuiet(int logId, String tag, String msg, boolean system) {
TerribleFailure what = new TerribleFailure(msg, null);
sWtfHandler.onTerribleFailure(tag, what, system);
}
/**
* Sets the terrible failure handler, for testing.
*
* @return the old handler
*
* @hide
*/
public static TerribleFailureHandler setWtfHandler(TerribleFailureHandler handler) {
if (handler == null) {
throw new NullPointerException("handler == null");
}
TerribleFailureHandler oldHandler = sWtfHandler;
sWtfHandler = handler;
return oldHandler;
}
/**
* Handy function to get a loggable stack trace from a Throwable
* @param tr An exception to log
*/
public static String getStackTraceString(Throwable tr) {
if (tr == null) {
return "";
}
// This is to reduce the amount of log spew that apps do in the non-error
// condition of the network being unavailable.
Throwable t = tr;
while (t != null) {
if (t instanceof UnknownHostException) {
return "";
}
t = t.getCause();
}
StringWriter sw = new StringWriter();
PrintWriter pw = new FastPrintWriter(sw, false, 256);
tr.printStackTrace(pw);
pw.flush();
return sw.toString();
}
/**
* Low-level logging call.
* @param priority The priority/type of this log message
* @param tag Used to identify the source of a log message. It usually identifies
* the class or activity where the log call occurs.
* @param msg The message you would like logged.
* @return The number of bytes written.
*/
public static int println(int priority, String tag, String msg) {
return println_native(LOG_ID_MAIN, priority, tag, msg);
}
/** @hide */ public static final int LOG_ID_MAIN = 0;
/** @hide */ public static final int LOG_ID_RADIO = 1;
/** @hide */ public static final int LOG_ID_EVENTS = 2;
/** @hide */ public static final int LOG_ID_SYSTEM = 3;
/** @hide */ public static final int LOG_ID_CRASH = 4;
/** @hide */ public static native int println_native(int bufID,
int priority, String tag, String msg);
/**
* Return the maximum payload the log daemon accepts without truncation.
* @return LOGGER_ENTRY_MAX_PAYLOAD.
*/
private static native int logger_entry_max_payload_native();
/**
* Helper function for long messages. Uses the LineBreakBufferedWriter to break
* up long messages and stacktraces along newlines, but tries to write in large
* chunks. This is to avoid truncation.
* @hide
*/
public static int printlns(int bufID, int priority, String tag, String msg,
Throwable tr) {
ImmediateLogWriter logWriter = new ImmediateLogWriter(bufID, priority, tag);
// Acceptable buffer size. Get the native buffer size, subtract two zero terminators,
// and the length of the tag.
// Note: we implicitly accept possible truncation for Modified-UTF8 differences. It
// is too expensive to compute that ahead of time.
int bufferSize = NoPreloadHolder.LOGGER_ENTRY_MAX_PAYLOAD // Base.
- 2 // Two terminators.
- (tag != null ? tag.length() : 0) // Tag length.
- 32; // Some slack.
// At least assume you can print *some* characters (tag is not too large).
bufferSize = Math.max(bufferSize, 100);
LineBreakBufferedWriter lbbw = new LineBreakBufferedWriter(logWriter, bufferSize);
lbbw.println(msg);
if (tr != null) {
// This is to reduce the amount of log spew that apps do in the non-error
// condition of the network being unavailable.
Throwable t = tr;
while (t != null) {
if (t instanceof UnknownHostException) {
break;
}
if (t instanceof DeadSystemException) {
lbbw.println("DeadSystemException: The system died; "
+ "earlier logs will point to the root cause");
break;
}
t = t.getCause();
}
if (t == null) {
tr.printStackTrace(lbbw);
}
}
lbbw.flush();
return logWriter.getWritten();
}
/**
* NoPreloadHelper class. Caches the LOGGER_ENTRY_MAX_PAYLOAD value to avoid
* a JNI call during logging.
*/
static class NoPreloadHolder {
public final static int LOGGER_ENTRY_MAX_PAYLOAD =
logger_entry_max_payload_native();
}
/**
* Helper class to write to the logcat. Different from LogWriter, this writes
* the whole given buffer and does not break along newlines.
*/
private static class ImmediateLogWriter extends Writer {
private int bufID;
private int priority;
private String tag;
private int written = 0;
/**
* Create a writer that immediately writes to the log, using the given
* parameters.
*/
public ImmediateLogWriter(int bufID, int priority, String tag) {
this.bufID = bufID;
this.priority = priority;
this.tag = tag;
}
public int getWritten() {
return written;
}
@Override
public void write(char[] cbuf, int off, int len) {
// Note: using String here has a bit of overhead as a Java object is created,
// but using the char[] directly is not easier, as it needs to be translated
// to a C char[] for logging.
written += println_native(bufID, priority, tag, new String(cbuf, off, len));
}
@Override
public void flush() {
// Ignored.
}
@Override
public void close() {
// Ignored.
}
}
}