Android example source code file (LoggingPrintStream.java)

This example Android source code file (LoggingPrintStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

assertionerror, bytebuffer, charsequence, charsetdecoder, coderresult, formatter, io, ioexception, locale, loggingprintstream, nio, object, override, printstream, string, stringbuilder, util

The LoggingPrintStream.java Android example source code

/*
 * Copyright (C) 2008 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 com.android.internal.os;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.util.Formatter;
import java.util.Locale;

/**
 * A print stream which logs output line by line.
 *
 * {@hide}
 */
abstract class LoggingPrintStream extends PrintStream {

    private final StringBuilder builder = new StringBuilder();

    /**
     * A buffer that is initialized when raw bytes are first written to this
     * stream. It may contain the leading bytes of multi-byte characters.
     * Between writes this buffer is always ready to receive data; ie. the
     * position is at the first unassigned byte and the limit is the capacity.
     */
    private ByteBuffer encodedBytes;

    /**
     * A buffer that is initialized when raw bytes are first written to this
     * stream. Between writes this buffer is always clear; ie. the position is
     * zero and the limit is the capacity.
     */
    private CharBuffer decodedChars;

    /**
     * Decodes bytes to characters using the system default charset. Initialized
     * when raw bytes are first written to this stream.
     */
    private CharsetDecoder decoder;

    protected LoggingPrintStream() {
        super(new OutputStream() {
            public void write(int oneByte) throws IOException {
                throw new AssertionError();
            }
        });
    }

    /**
     * Logs the given line.
     */
    protected abstract void log(String line);

    @Override
    public synchronized void flush() {
        flush(true);
    }

    /**
     * Searches buffer for line breaks and logs a message for each one.
     *
     * @param completely true if the ending chars should be treated as a line
     *  even though they don't end in a line break
     */
    private void flush(boolean completely) {
        int length = builder.length();

        int start = 0;
        int nextBreak;

        // Log one line for each line break.
        while (start < length
                && (nextBreak = builder.indexOf("\n", start)) != -1) {
            log(builder.substring(start, nextBreak));
            start = nextBreak + 1;
        }

        if (completely) {
            // Log the remainder of the buffer.
            if (start < length) {
                log(builder.substring(start));
            }
            builder.setLength(0);
        } else {
            // Delete characters leading up to the next starting point.
            builder.delete(0, start);
        }
    }

    public void write(int oneByte) {
        write(new byte[] { (byte) oneByte }, 0, 1);
    }

    @Override
    public void write(byte[] buffer) {
        write(buffer, 0, buffer.length);
    }

    @Override
    public synchronized void write(byte bytes[], int start, int count) {
        if (decoder == null) {
            encodedBytes = ByteBuffer.allocate(80);
            decodedChars = CharBuffer.allocate(80);
            decoder = Charset.defaultCharset().newDecoder()
                    .onMalformedInput(CodingErrorAction.REPLACE)
                    .onUnmappableCharacter(CodingErrorAction.REPLACE);
        }

        int end = start + count;
        while (start < end) {
            // copy some bytes from the array to the long-lived buffer. This
            // way, if we end with a partial character we don't lose it.
            int numBytes = Math.min(encodedBytes.remaining(), end - start);
            encodedBytes.put(bytes, start, numBytes);
            start += numBytes;

            encodedBytes.flip();
            CoderResult coderResult;
            do {
                // decode bytes from the byte buffer into the char buffer
                coderResult = decoder.decode(encodedBytes, decodedChars, false);

                // copy chars from the char buffer into our string builder
                decodedChars.flip();
                builder.append(decodedChars);
                decodedChars.clear();
            } while (coderResult.isOverflow());
            encodedBytes.compact();
        }
        flush(false);
    }

    /** Always returns false. */
    @Override
    public boolean checkError() {
        return false;
    }

    /** Ignored. */
    @Override
    protected void setError() { /* ignored */ }

    /** Ignored. */
    @Override
    public void close() { /* ignored */ }

    @Override
    public PrintStream format(String format, Object... args) {
        return format(Locale.getDefault(), format, args);
    }

    @Override
    public PrintStream printf(String format, Object... args) {
        return format(format, args);
    }

    @Override
    public PrintStream printf(Locale l, String format, Object... args) {
        return format(l, format, args);
    }

    private final Formatter formatter = new Formatter(builder, null);

    @Override
    public synchronized PrintStream format(
            Locale l, String format, Object... args) {
        if (format == null) {
            throw new NullPointerException("format");
        }

        formatter.format(l, format, args);
        flush(false);
        return this;
    }

    @Override
    public synchronized void print(char[] charArray) {
        builder.append(charArray);
        flush(false);
    }

    @Override
    public synchronized void print(char ch) {
        builder.append(ch);
        if (ch == '\n') {
            flush(false);
        }
    }

    @Override
    public synchronized void print(double dnum) {
        builder.append(dnum);
    }

    @Override
    public synchronized void print(float fnum) {
        builder.append(fnum);
    }

    @Override
    public synchronized void print(int inum) {
        builder.append(inum);
    }

    @Override
    public synchronized void print(long lnum) {
        builder.append(lnum);
    }

    @Override
    public synchronized void print(Object obj) {
        builder.append(obj);
        flush(false);
    }

    @Override
    public synchronized void print(String str) {
        builder.append(str);
        flush(false);
    }

    @Override
    public synchronized void print(boolean bool) {
        builder.append(bool);
    }

    @Override
    public synchronized void println() {
        flush(true);
    }

    @Override
    public synchronized void println(char[] charArray) {
        builder.append(charArray);
        flush(true);
    }

    @Override
    public synchronized void println(char ch) {
        builder.append(ch);
        flush(true);
    }

    @Override
    public synchronized void println(double dnum) {
        builder.append(dnum);
        flush(true);
    }

    @Override
    public synchronized void println(float fnum) {
        builder.append(fnum);
        flush(true);
    }

    @Override
    public synchronized void println(int inum) {
        builder.append(inum);
        flush(true);
    }

    @Override
    public synchronized void println(long lnum) {
        builder.append(lnum);
        flush(true);
    }

    @Override
    public synchronized void println(Object obj) {
        builder.append(obj);
        flush(true);
    }

    @Override
    public synchronized void println(String s) {
        if (builder.length() == 0) {
            // Optimization for a simple println.
            int length = s.length();

            int start = 0;
            int nextBreak;

            // Log one line for each line break.
            while (start < length
                    && (nextBreak = s.indexOf('\n', start)) != -1) {
                log(s.substring(start, nextBreak));
                start = nextBreak + 1;
            }

            if (start < length) {
                log(s.substring(start));
            }
        } else {
            builder.append(s);
            flush(true);
        }
    }

    @Override
    public synchronized void println(boolean bool) {
        builder.append(bool);
        flush(true);
    }

    @Override
    public synchronized PrintStream append(char c) {
        print(c);
        return this;
    }

    @Override
    public synchronized PrintStream append(CharSequence csq) {
        builder.append(csq);
        flush(false);
        return this;
    }

    @Override
    public synchronized PrintStream append(
            CharSequence csq, int start, int end) {
        builder.append(csq, start, end);
        flush(false);
        return this;
    }
}