xref: /frameworks/base/core/java/com/android/internal/util/FastPrintWriter.java

/*
 * Copyright (C) 2013 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.util;

import android.util.Log;
import android.util.Printer;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;

public class FastPrintWriter extends PrintWriter {
    private static class DummyWriter extends Writer {
        @Override
        public void close() throws IOException {
            UnsupportedOperationException ex
                    = new UnsupportedOperationException("Shouldn't be here");
            throw ex;
        }

        @Override
        public void flush() throws IOException {
            close();
        }

        @Override
        public void write(char[] buf, int offset, int count) throws IOException {
            close();
        }
    };

    private final int mBufferLen;
    private final char[] mText;
    private int mPos;

    final private OutputStream mOutputStream;
    final private boolean mAutoFlush;
    final private String mSeparator;

    final private Writer mWriter;
    final private Printer mPrinter;

    private CharsetEncoder mCharset;
    final private ByteBuffer mBytes;

    private boolean mIoError;

    /**
     * Constructs a new {@code PrintWriter} with {@code out} as its target
     * stream. By default, the new print writer does not automatically flush its
     * contents to the target stream when a newline is encountered.
     *
     * @param out
     *            the target output stream.
     * @throws NullPointerException
     *             if {@code out} is {@code null}.
     */
    public FastPrintWriter(OutputStream out) {
        this(out, false, 8192);
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code out} as its target
     * stream. The parameter {@code autoFlush} determines if the print writer
     * automatically flushes its contents to the target stream when a newline is
     * encountered.
     *
     * @param out
     *            the target output stream.
     * @param autoFlush
     *            indicates whether contents are flushed upon encountering a
     *            newline sequence.
     * @throws NullPointerException
     *             if {@code out} is {@code null}.
     */
    public FastPrintWriter(OutputStream out, boolean autoFlush) {
        this(out, autoFlush, 8192);
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code out} as its target
     * stream and a custom buffer size. The parameter {@code autoFlush} determines
     * if the print writer automatically flushes its contents to the target stream
     * when a newline is encountered.
     *
     * @param out
     *            the target output stream.
     * @param autoFlush
     *            indicates whether contents are flushed upon encountering a
     *            newline sequence.
     * @param bufferLen
     *            specifies the size of the FastPrintWriter's internal buffer; the
     *            default is 8192.
     * @throws NullPointerException
     *             if {@code out} is {@code null}.
     */
    public FastPrintWriter(OutputStream out, boolean autoFlush, int bufferLen) {
        super(new DummyWriter(), autoFlush);
        if (out == null) {
            throw new NullPointerException("out is null");
        }
        mBufferLen = bufferLen;
        mText = new char[bufferLen];
        mBytes = ByteBuffer.allocate(mBufferLen);
        mOutputStream = out;
        mWriter = null;
        mPrinter = null;
        mAutoFlush = autoFlush;
        mSeparator = System.lineSeparator();
        initDefaultEncoder();
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code wr} as its target
     * writer. By default, the new print writer does not automatically flush its
     * contents to the target writer when a newline is encountered.
     *
     * <p>NOTE: Unlike PrintWriter, this version will still do buffering inside of
     * FastPrintWriter before sending data to the Writer.  This means you must call
     * flush() before retrieving any data from the Writer.</p>
     *
     * @param wr
     *            the target writer.
     * @throws NullPointerException
     *             if {@code wr} is {@code null}.
     */
    public FastPrintWriter(Writer wr) {
        this(wr, false, 8192);
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code wr} as its target
     * writer. The parameter {@code autoFlush} determines if the print writer
     * automatically flushes its contents to the target writer when a newline is
     * encountered.
     *
     * @param wr
     *            the target writer.
     * @param autoFlush
     *            indicates whether to flush contents upon encountering a
     *            newline sequence.
     * @throws NullPointerException
     *             if {@code out} is {@code null}.
     */
    public FastPrintWriter(Writer wr, boolean autoFlush) {
        this(wr, autoFlush, 8192);
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code wr} as its target
     * writer and a custom buffer size. The parameter {@code autoFlush} determines
     * if the print writer automatically flushes its contents to the target writer
     * when a newline is encountered.
     *
     * @param wr
     *            the target writer.
     * @param autoFlush
     *            indicates whether to flush contents upon encountering a
     *            newline sequence.
     * @param bufferLen
     *            specifies the size of the FastPrintWriter's internal buffer; the
     *            default is 8192.
     * @throws NullPointerException
     *             if {@code wr} is {@code null}.
     */
    public FastPrintWriter(Writer wr, boolean autoFlush, int bufferLen) {
        super(new DummyWriter(), autoFlush);
        if (wr == null) {
            throw new NullPointerException("wr is null");
        }
        mBufferLen = bufferLen;
        mText = new char[bufferLen];
        mBytes = null;
        mOutputStream = null;
        mWriter = wr;
        mPrinter = null;
        mAutoFlush = autoFlush;
        mSeparator = System.lineSeparator();
        initDefaultEncoder();
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code pr} as its target
     * printer and the default buffer size.  Because a {@link Printer} is line-base,
     * autoflush is always enabled.
     *
     * @param pr
     *            the target writer.
     * @throws NullPointerException
     *             if {@code pr} is {@code null}.
     */
    public FastPrintWriter(Printer pr) {
        this(pr, 512);
    }

    /**
     * Constructs a new {@code PrintWriter} with {@code pr} as its target
     * printer and a custom buffer size.  Because a {@link Printer} is line-base,
     * autoflush is always enabled.
     *
     * @param pr
     *            the target writer.
     * @param bufferLen
     *            specifies the size of the FastPrintWriter's internal buffer; the
     *            default is 512.
     * @throws NullPointerException
     *             if {@code pr} is {@code null}.
     */
    public FastPrintWriter(Printer pr, int bufferLen) {
        super(new DummyWriter(), true);
        if (pr == null) {
            throw new NullPointerException("pr is null");
        }
        mBufferLen = bufferLen;
        mText = new char[bufferLen];
        mBytes = null;
        mOutputStream = null;
        mWriter = null;
        mPrinter = pr;
        mAutoFlush = true;
        mSeparator = System.lineSeparator();
        initDefaultEncoder();
    }

    private final void initEncoder(String csn) throws UnsupportedEncodingException {
        try {
            mCharset = Charset.forName(csn).newEncoder();
        } catch (Exception e) {
            throw new UnsupportedEncodingException(csn);
        }
        mCharset.onMalformedInput(CodingErrorAction.REPLACE);
        mCharset.onUnmappableCharacter(CodingErrorAction.REPLACE);
    }

    /**
     * Flushes this writer and returns the value of the error flag.
     *
     * @return {@code true} if either an {@code IOException} has been thrown
     *         previously or if {@code setError()} has been called;
     *         {@code false} otherwise.
     * @see #setError()
     */
    public boolean checkError() {
        flush();
        synchronized (lock) {
            return mIoError;
        }
    }

    /**
     * Sets the error state of the stream to false.
     * @since 1.6
     */
    protected void clearError() {
        synchronized (lock) {
            mIoError = false;
        }
    }

    /**
     * Sets the error flag of this writer to true.
     */
    protected void setError() {
        synchronized (lock) {
            mIoError = true;
        }
    }

    private final void initDefaultEncoder() {
        mCharset = Charset.defaultCharset().newEncoder();
        mCharset.onMalformedInput(CodingErrorAction.REPLACE);
        mCharset.onUnmappableCharacter(CodingErrorAction.REPLACE);
    }

    private void appendLocked(char c) throws IOException {
        int pos = mPos;
        if (pos >= (mBufferLen-1)) {
            flushLocked();
            pos = mPos;
        }
        mText[pos] = c;
        mPos = pos+1;
    }

    private void appendLocked(String str, int i, final int length) throws IOException {
        final int BUFFER_LEN = mBufferLen;
        if (length > BUFFER_LEN) {
            final int end = i + length;
            while (i < end) {
                int next = i + BUFFER_LEN;
                appendLocked(str, i, next < end ? BUFFER_LEN : (end - i));
                i = next;
            }
            return;
        }
        int pos = mPos;
        if ((pos+length) > BUFFER_LEN) {
            flushLocked();
            pos = mPos;
        }
        str.getChars(i, i + length, mText, pos);
        mPos = pos + length;
    }

    private void appendLocked(char[] buf, int i, final int length) throws IOException {
        final int BUFFER_LEN = mBufferLen;
        if (length > BUFFER_LEN) {
            final int end = i + length;
            while (i < end) {
                int next = i + BUFFER_LEN;
                appendLocked(buf, i, next < end ? BUFFER_LEN : (end - i));
                i = next;
            }
            return;
        }
        int pos = mPos;
        if ((pos+length) > BUFFER_LEN) {
            flushLocked();
            pos = mPos;
        }
        System.arraycopy(buf, i, mText, pos, length);
        mPos = pos + length;
    }

    private void flushBytesLocked() throws IOException {
        if (!mIoError) {
            int position;
            if ((position = mBytes.position()) > 0) {
                mBytes.flip();
                mOutputStream.write(mBytes.array(), 0, position);
                mBytes.clear();
            }
        }
    }

    private void flushLocked() throws IOException {
        //Log.i("PackageManager", "flush mPos=" + mPos);
        if (mPos > 0) {
            if (mOutputStream != null) {
                CharBuffer charBuffer = CharBuffer.wrap(mText, 0, mPos);
                CoderResult result = mCharset.encode(charBuffer, mBytes, true);
                while (!mIoError) {
                    if (result.isError()) {
                        throw new IOException(result.toString());
                    } else if (result.isOverflow()) {
                        flushBytesLocked();
                        result = mCharset.encode(charBuffer, mBytes, true);
                        continue;
                    }
                    break;
                }
                if (!mIoError) {
                    flushBytesLocked();
                    mOutputStream.flush();
                }
            } else if (mWriter != null) {
                if (!mIoError) {
                    mWriter.write(mText, 0, mPos);
                    mWriter.flush();
                }
            } else {
                int nonEolOff = 0;
                final int sepLen = mSeparator.length();
                final int len = sepLen < mPos ? sepLen : mPos;
                while (nonEolOff < len && mText[mPos-1-nonEolOff]
                        == mSeparator.charAt(mSeparator.length()-1-nonEolOff)) {
                    nonEolOff++;
                }
                if (nonEolOff >= mPos) {
                    mPrinter.println("");
                } else {
                    mPrinter.println(new String(mText, 0, mPos-nonEolOff));
                }
            }
            mPos = 0;
        }
    }

    /**
     * Ensures that all pending data is sent out to the target. It also
     * flushes the target. If an I/O error occurs, this writer's error
     * state is set to {@code true}.
     */
    @Override
    public void flush() {
        synchronized (lock) {
            try {
                flushLocked();
                if (!mIoError) {
                    if (mOutputStream != null) {
                        mOutputStream.flush();
                    } else if (mWriter != null) {
                        mWriter.flush();
                    }
                }
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    @Override
    public void close() {
        synchronized (lock) {
            try {
                flushLocked();
                if (mOutputStream != null) {
                    mOutputStream.close();
                } else if (mWriter != null) {
                    mWriter.close();
                }
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Prints the string representation of the specified character array
     * to the target.
     *
     * @param charArray
     *            the character array to print to the target.
     * @see #print(String)
     */
    public void print(char[] charArray) {
        synchronized (lock) {
            try {
                appendLocked(charArray, 0, charArray.length);
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Prints the string representation of the specified character to the
     * target.
     *
     * @param ch
     *            the character to print to the target.
     * @see #print(String)
     */
    public void print(char ch) {
        synchronized (lock) {
            try {
                appendLocked(ch);
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Prints a string to the target. The string is converted to an array of
     * bytes using the encoding chosen during the construction of this writer.
     * The bytes are then written to the target with {@code write(int)}.
     * <p>
     * If an I/O error occurs, this writer's error flag is set to {@code true}.
     *
     * @param str
     *            the string to print to the target.
     * @see #write(int)
     */
    public void print(String str) {
        if (str == null) {
            str = String.valueOf((Object) null);
        }
        synchronized (lock) {
            try {
                appendLocked(str, 0, str.length());
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }


    @Override
    public void print(int inum) {
        if (inum == 0) {
            print("0");
        } else {
            super.print(inum);
        }
    }

    @Override
    public void print(long lnum) {
        if (lnum == 0) {
            print("0");
        } else {
            super.print(lnum);
        }
    }

    /**
     * Prints a newline. Flushes this writer if the autoFlush flag is set to {@code true}.
     */
    public void println() {
        synchronized (lock) {
            try {
                appendLocked(mSeparator, 0, mSeparator.length());
                if (mAutoFlush) {
                    flushLocked();
                }
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    @Override
    public void println(int inum) {
        if (inum == 0) {
            println("0");
        } else {
            super.println(inum);
        }
    }

    @Override
    public void println(long lnum) {
        if (lnum == 0) {
            println("0");
        } else {
            super.println(lnum);
        }
    }

    /**
     * Prints the string representation of the character array {@code chars} followed by a newline.
     * Flushes this writer if the autoFlush flag is set to {@code true}.
     */
    public void println(char[] chars) {
        print(chars);
        println();
    }

    /**
     * Prints the string representation of the char {@code c} followed by a newline.
     * Flushes this writer if the autoFlush flag is set to {@code true}.
     */
    public void println(char c) {
        print(c);
        println();
    }

    /**
     * Writes {@code count} characters from {@code buffer} starting at {@code
     * offset} to the target.
     * <p>
     * This writer's error flag is set to {@code true} if this writer is closed
     * or an I/O error occurs.
     *
     * @param buf
     *            the buffer to write to the target.
     * @param offset
     *            the index of the first character in {@code buffer} to write.
     * @param count
     *            the number of characters in {@code buffer} to write.
     * @throws IndexOutOfBoundsException
     *             if {@code offset < 0} or {@code count < 0}, or if {@code
     *             offset + count} is greater than the length of {@code buf}.
     */
    @Override
    public void write(char[] buf, int offset, int count) {
        synchronized (lock) {
            try {
                appendLocked(buf, offset, count);
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Writes one character to the target. Only the two least significant bytes
     * of the integer {@code oneChar} are written.
     * <p>
     * This writer's error flag is set to {@code true} if this writer is closed
     * or an I/O error occurs.
     *
     * @param oneChar
     *            the character to write to the target.
     */
    @Override
    public void write(int oneChar) {
        synchronized (lock) {
            try {
                appendLocked((char) oneChar);
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Writes the characters from the specified string to the target.
     *
     * @param str
     *            the non-null string containing the characters to write.
     */
    @Override
    public void write(String str) {
        synchronized (lock) {
            try {
                appendLocked(str, 0, str.length());
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Writes {@code count} characters from {@code str} starting at {@code
     * offset} to the target.
     *
     * @param str
     *            the non-null string containing the characters to write.
     * @param offset
     *            the index of the first character in {@code str} to write.
     * @param count
     *            the number of characters from {@code str} to write.
     * @throws IndexOutOfBoundsException
     *             if {@code offset < 0} or {@code count < 0}, or if {@code
     *             offset + count} is greater than the length of {@code str}.
     */
    @Override
    public void write(String str, int offset, int count) {
        synchronized (lock) {
            try {
                appendLocked(str, offset, count);
            } catch (IOException e) {
                Log.w("FastPrintWriter", "Write failure", e);
                setError();
            }
        }
    }

    /**
     * Appends a subsequence of the character sequence {@code csq} to the
     * target. This method works the same way as {@code
     * PrintWriter.print(csq.subsequence(start, end).toString())}. If {@code
     * csq} is {@code null}, then the specified subsequence of the string "null"
     * will be written to the target.
     *
     * @param csq
     *            the character sequence appended to the target.
     * @param start
     *            the index of the first char in the character sequence appended
     *            to the target.
     * @param end
     *            the index of the character following the last character of the
     *            subsequence appended to the target.
     * @return this writer.
     * @throws StringIndexOutOfBoundsException
     *             if {@code start > end}, {@code start < 0}, {@code end < 0} or
     *             either {@code start} or {@code end} are greater or equal than
     *             the length of {@code csq}.
     */
    @Override
    public PrintWriter append(CharSequence csq, int start, int end) {
        if (csq == null) {
            csq = "null";
        }
        String output = csq.subSequence(start, end).toString();
        write(output, 0, output.length());
        return this;
    }
}