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Commit de310dba authored by Hugo Benichi's avatar Hugo Benichi
Browse files

Better LocalLog 

This patch fixes the following issues in LocalLog:
  - reverseDump() uses a descending iterator with linear complexity
    instead of a quadratic loop using get(index) on a linked list.
  - reverseDump() is added to ReadOnlyLocalLog.
  - synchronized section in log() is restricted to mutation of internal
    list.
  - formatting of the log message does not create an internal
    StringBuilder.
  - the instance variable mNow is removed: it was only used inside log()
    as a local variable.
  - remaining instance variables are qualified with final.
  - the linked list is replaced by a fixed capacity array-backed queue.

Test: added unit tests
Change-Id: I1a54f0ad26dd35448d3297ea24df1fd626d20ef3
parent 9cf75061

core/java/android/util/LocalLog.java

+26 −18
Original line number Diff line number Diff line
@@ -20,44 +20,49 @@ import java.io.FileDescriptor; 
import java.io.PrintWriter;

import java.util.Calendar;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.Deque;

import java.util.ArrayDeque;



/**

 * @hide

 */

public final class LocalLog {



    private LinkedList<String> mLog;

    private int mMaxLines;

    private long mNow;

    private final Deque<String> mLog;

    private final int mMaxLines;



    public LocalLog(int maxLines) {

        mLog = new LinkedList<String>();

        mMaxLines = maxLines;

        mMaxLines = Math.max(0, maxLines);

        mLog = new ArrayDeque<>(mMaxLines);

    }



    public synchronized void log(String msg) {

        if (mMaxLines > 0) {

            mNow = System.currentTimeMillis();

            StringBuilder sb = new StringBuilder();

    public void log(String msg) {

        if (mMaxLines <= 0) {

            return;

        }

        Calendar c = Calendar.getInstance();

            c.setTimeInMillis(mNow);

            sb.append(String.format("%tm-%td %tH:%tM:%tS.%tL", c, c, c, c, c, c));

            mLog.add(sb.toString() + " - " + msg);

            while (mLog.size() > mMaxLines) mLog.remove();

        c.setTimeInMillis(System.currentTimeMillis());

        append(String.format("%tm-%td %tH:%tM:%tS.%tL - %s", c, c, c, c, c, c, msg));

    }



    private synchronized void append(String logLine) {

        while (mLog.size() >= mMaxLines) {

            mLog.remove();

        }

        mLog.add(logLine);

    }



    public synchronized void dump(FileDescriptor fd, PrintWriter pw, String[] args) {

        Iterator<String> itr = mLog.listIterator(0);

        Iterator<String> itr = mLog.iterator();

        while (itr.hasNext()) {

            pw.println(itr.next());

        }

    }



    public synchronized void reverseDump(FileDescriptor fd, PrintWriter pw, String[] args) {

        for (int i = mLog.size() - 1; i >= 0; i--) {

            pw.println(mLog.get(i));

        Iterator<String> itr = mLog.descendingIterator();

        while (itr.hasNext()) {

            pw.println(itr.next());

        }

    }
@@ -69,6 +74,9 @@ public final class LocalLog { 
        public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {

            mLog.dump(fd, pw, args);

        }

        public void reverseDump(FileDescriptor fd, PrintWriter pw, String[] args) {

            mLog.reverseDump(fd, pw, args);

        }

    }



    public ReadOnlyLocalLog readOnlyLocalLog() {

core/tests/coretests/src/android/util/LocalLogTest.java

0 → 100644
+110 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2016 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 junit.framework.TestCase;



import java.io.PrintWriter;

import java.io.StringWriter;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;





public class LocalLogTest extends TestCase {



    public void testA() {

        String[] lines = {

            "foo",

            "bar",

            "baz"

        };

        String[] want = lines;

        testcase(new LocalLog(10), lines, want);

    }



    public void testB() {

        String[] lines = {

            "foo",

            "bar",

            "baz"

        };

        String[] want = {};

        testcase(new LocalLog(0), lines, want);

    }



    public void testC() {

        String[] lines = {

            "dropped",

            "dropped",

            "dropped",

            "dropped",

            "dropped",

            "dropped",

            "foo",

            "bar",

            "baz",

        };

        String[] want = {

            "foo",

            "bar",

            "baz",

        };

        testcase(new LocalLog(3), lines, want);

    }



    void testcase(LocalLog logger, String[] input, String[] want) {

        for (String l : input) {

            logger.log(l);

        }

        verifyAllLines(want, dump(logger).split("\n"));

        verifyAllLines(reverse(want), reverseDump(logger).split("\n"));

    }



    void verifyAllLines(String[] wantLines, String[] gotLines) {

        for (int i = 0; i < wantLines.length; i++) {

            String want = wantLines[i];

            String got = gotLines[i];

            String msg = String.format("%s did not contain %s", quote(got), quote(want));

            assertTrue(msg, got.contains(want));

        }

    }



    static String dump(LocalLog logger) {

        StringWriter buffer = new StringWriter();

        PrintWriter writer = new PrintWriter(buffer);

        logger.dump(null, writer, new String[0]);

        return buffer.toString();

    }



    static String reverseDump(LocalLog logger) {

        StringWriter buffer = new StringWriter();

        PrintWriter writer = new PrintWriter(buffer);

        logger.reverseDump(null, writer, new String[0]);

        return buffer.toString();

    }



    static String quote(String s) {

        return '"' + s + '"';

    }



    static String[] reverse(String[] ary) {

        List<String> ls = Arrays.asList(ary);

        Collections.reverse(ls);

        return  ls.toArray(new String[ary.length]);

    }

}