    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.io.output;
    018
    019import java.io.IOException;
    020import java.io.OutputStream;
    021import java.io.Writer;
    022import java.nio.ByteBuffer;
    023import java.nio.CharBuffer;
    024import java.nio.charset.Charset;
    025import java.nio.charset.CharsetDecoder;
    026import java.nio.charset.CoderResult;
    027import java.nio.charset.CodingErrorAction;
    028import java.nio.charset.StandardCharsets;
    029
    030import org.apache.commons.io.Charsets;
    031import org.apache.commons.io.IOUtils;
    032import org.apache.commons.io.build.AbstractStreamBuilder;
    033import org.apache.commons.io.charset.CharsetDecoders;
    034
    035/**
    036 * {@link OutputStream} implementation that transforms a byte stream to a character stream using a specified charset encoding and writes the resulting stream to
    037 * a {@link Writer}. The stream is transformed using a {@link CharsetDecoder} object, guaranteeing that all charset encodings supported by the JRE are handled
    038 * correctly.
    039 * <p>
    040 * The output of the {@link CharsetDecoder} is buffered using a fixed size buffer. This implies that the data is written to the underlying {@link Writer} in
    041 * chunks that are no larger than the size of this buffer. By default, the buffer is flushed only when it overflows or when {@link #flush()} or {@link #close()}
    042 * is called. In general there is therefore no need to wrap the underlying {@link Writer} in a {@link java.io.BufferedWriter}. {@link WriterOutputStream} can
    043 * also be instructed to flush the buffer after each write operation. In this case, all available data is written immediately to the underlying {@link Writer},
    044 * implying that the current position of the {@link Writer} is correlated to the current position of the {@link WriterOutputStream}.
    045 * </p>
    046 * <p>
    047 * {@link WriterOutputStream} implements the inverse transformation of {@link java.io.OutputStreamWriter}; in the following example, writing to {@code out2}
    048 * would have the same result as writing to {@code out} directly (provided that the byte sequence is legal with respect to the charset encoding):
    049 * </p>
    050 * <p>
    051 * To build an instance, see {@link Builder}.
    052 * </p>
    053 * <pre>
    054 * OutputStream out = ...
    055 * Charset cs = ...
    056 * OutputStreamWriter writer = new OutputStreamWriter(out, cs);
    057 * WriterOutputStream out2 = WriterOutputStream.builder()
    058 *   .setWriter(writer)
    059 *   .setCharset(cs)
    060 *   .get();
    061 * </pre>
    062 * <p>
    063 * {@link WriterOutputStream} implements the same transformation as {@link java.io.InputStreamReader}, except that the control flow is reversed: both classes
    064 * transform a byte stream into a character stream, but {@link java.io.InputStreamReader} pulls data from the underlying stream, while
    065 * {@link WriterOutputStream} pushes it to the underlying stream.
    066 * </p>
    067 * <p>
    068 * Note that while there are use cases where there is no alternative to using this class, very often the need to use this class is an indication of a flaw in
    069 * the design of the code. This class is typically used in situations where an existing API only accepts an {@link OutputStream} object, but where the stream is
    070 * known to represent character data that must be decoded for further use.
    071 * </p>
    072 * <p>
    073 * Instances of {@link WriterOutputStream} are not thread safe.
    074 * </p>
    075 *
    076 * @see org.apache.commons.io.input.ReaderInputStream
    077 * @since 2.0
    078 */
    079public class WriterOutputStream extends OutputStream {
    080
    081    /**
    082     * Builds a new {@link WriterOutputStream} instance.
    083     * <p>
    084     * For example:
    085     * </p>
    086     * <pre>{@code
    087     * WriterOutputStream s = WriterOutputStream.builder()
    088     *   .setPath(path)
    089     *   .setBufferSize(8192)
    090     *   .setCharset(StandardCharsets.UTF_8)
    091     *   .setWriteImmediately(false)
    092     *   .get();}
    093     * </pre>
    094     *
    095     * @since 2.12.0
    096     */
    097    public static class Builder extends AbstractStreamBuilder<WriterOutputStream, Builder> {
    098
    099        private CharsetDecoder charsetDecoder;
    100        private boolean writeImmediately;
    101
    102        public Builder() {
    103            this.charsetDecoder = getCharset().newDecoder();
    104        }
    105
    106        /**
    107         * Constructs a new instance.
    108         * <p>
    109         * This builder use the aspect Writer, OpenOption[], Charset, CharsetDecoder, buffer size and writeImmediately.
    110         * </p>
    111         * <p>
    112         * You must provide an origin that can be converted to a Writer by this builder, otherwise, this call will throw an
    113         * {@link UnsupportedOperationException}.
    114         * </p>
    115         *
    116         * @return a new instance.
    117         * @throws UnsupportedOperationException if the origin cannot provide a Writer.
    118         * @see #getWriter()
    119         */
    120        @SuppressWarnings("resource")
    121        @Override
    122        public WriterOutputStream get() throws IOException {
    123            return new WriterOutputStream(getWriter(), charsetDecoder, getBufferSize(), writeImmediately);
    124        }
    125
    126        @Override
    127        public Builder setCharset(final Charset charset) {
    128            super.setCharset(charset);
    129            this.charsetDecoder = getCharset().newDecoder();
    130            return this;
    131        }
    132
    133        @Override
    134        public Builder setCharset(final String charset) {
    135            super.setCharset(charset);
    136            this.charsetDecoder = getCharset().newDecoder();
    137            return this;
    138        }
    139
    140        /**
    141         * Sets the charset decoder.
    142         *
    143         * @param charsetDecoder the charset decoder.
    144         * @return this
    145         */
    146        public Builder setCharsetDecoder(final CharsetDecoder charsetDecoder) {
    147            this.charsetDecoder = charsetDecoder != null ? charsetDecoder : getCharsetDefault().newDecoder();
    148            super.setCharset(this.charsetDecoder.charset());
    149            return this;
    150        }
    151
    152        /**
    153         * Sets whether the output buffer will be flushed after each write operation ({@code true}), i.e. all available data will be written to the underlying
    154         * {@link Writer} immediately. If {@code false}, the output buffer will only be flushed when it overflows or when {@link #flush()} or {@link #close()}
    155         * is called.
    156         *
    157         * @param writeImmediately If {@code true} the output buffer will be flushed after each write operation, i.e. all available data will be written to the
    158         *                         underlying {@link Writer} immediately. If {@code false}, the output buffer will only be flushed when it overflows or when
    159         *                         {@link #flush()} or {@link #close()} is called.
    160         * @return this
    161         */
    162        public Builder setWriteImmediately(final boolean writeImmediately) {
    163            this.writeImmediately = writeImmediately;
    164            return this;
    165        }
    166
    167    }
    168
    169    private static final int BUFFER_SIZE = IOUtils.DEFAULT_BUFFER_SIZE;
    170
    171    /**
    172     * Constructs a new {@link Builder}.
    173     *
    174     * @return a new {@link Builder}.
    175     * @since 2.12.0
    176     */
    177    public static Builder builder() {
    178        return new Builder();
    179    }
    180
    181    /**
    182     * Checks if the JDK in use properly supports the given charset.
    183     *
    184     * @param charset the charset to check the support for
    185     */
    186    private static void checkIbmJdkWithBrokenUTF16(final Charset charset) {
    187        if (!StandardCharsets.UTF_16.name().equals(charset.name())) {
    188            return;
    189        }
    190        final String TEST_STRING_2 = "v\u00e9s";
    191        final byte[] bytes = TEST_STRING_2.getBytes(charset);
    192
    193        final CharsetDecoder charsetDecoder2 = charset.newDecoder();
    194        final ByteBuffer bb2 = ByteBuffer.allocate(16);
    195        final CharBuffer cb2 = CharBuffer.allocate(TEST_STRING_2.length());
    196        final int len = bytes.length;
    197        for (int i = 0; i < len; i++) {
    198            bb2.put(bytes[i]);
    199            bb2.flip();
    200            try {
    201                charsetDecoder2.decode(bb2, cb2, i == len - 1);
    202            } catch (final IllegalArgumentException e) {
    203                throw new UnsupportedOperationException("UTF-16 requested when running on an IBM JDK with broken UTF-16 support. "
    204                        + "Please find a JDK that supports UTF-16 if you intend to use UF-16 with WriterOutputStream");
    205            }
    206            bb2.compact();
    207        }
    208        cb2.rewind();
    209        if (!TEST_STRING_2.equals(cb2.toString())) {
    210            throw new UnsupportedOperationException("UTF-16 requested when running on an IBM JDK with broken UTF-16 support. "
    211                    + "Please find a JDK that supports UTF-16 if you intend to use UF-16 with WriterOutputStream");
    212        }
    213
    214    }
    215
    216    private final Writer writer;
    217    private final CharsetDecoder decoder;
    218
    219    private final boolean writeImmediately;
    220
    221    /**
    222     * ByteBuffer used as input for the decoder. This buffer can be small as it is used only to transfer the received data to the decoder.
    223     */
    224    private final ByteBuffer decoderIn = ByteBuffer.allocate(128);
    225
    226    /**
    227     * CharBuffer used as output for the decoder. It should be somewhat larger as we write from this buffer to the underlying Writer.
    228     */
    229    private final CharBuffer decoderOut;
    230
    231    /**
    232     * Constructs a new {@link WriterOutputStream} that uses the default character encoding and with a default output buffer size of {@value #BUFFER_SIZE}
    233     * characters. The output buffer will only be flushed when it overflows or when {@link #flush()} or {@link #close()} is called.
    234     *
    235     * @param writer the target {@link Writer}
    236     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    237     */
    238    @Deprecated
    239    public WriterOutputStream(final Writer writer) {
    240        this(writer, Charset.defaultCharset(), BUFFER_SIZE, false);
    241    }
    242
    243    /**
    244     * Constructs a new {@link WriterOutputStream} with a default output buffer size of {@value #BUFFER_SIZE} characters. The output buffer will only be flushed
    245     * when it overflows or when {@link #flush()} or {@link #close()} is called.
    246     *
    247     * @param writer  the target {@link Writer}
    248     * @param charset the charset encoding
    249     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    250     */
    251    @Deprecated
    252    public WriterOutputStream(final Writer writer, final Charset charset) {
    253        this(writer, charset, BUFFER_SIZE, false);
    254    }
    255
    256    /**
    257     * Constructs a new {@link WriterOutputStream}.
    258     *
    259     * @param writer           the target {@link Writer}
    260     * @param charset          the charset encoding
    261     * @param bufferSize       the size of the output buffer in number of characters
    262     * @param writeImmediately If {@code true} the output buffer will be flushed after each write operation, i.e. all available data will be written to the
    263     *                         underlying {@link Writer} immediately. If {@code false}, the output buffer will only be flushed when it overflows or when
    264     *                         {@link #flush()} or {@link #close()} is called.
    265     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    266     */
    267    @Deprecated
    268    public WriterOutputStream(final Writer writer, final Charset charset, final int bufferSize, final boolean writeImmediately) {
    269        // @formatter:off
    270        this(writer,
    271            Charsets.toCharset(charset).newDecoder()
    272                    .onMalformedInput(CodingErrorAction.REPLACE)
    273                    .onUnmappableCharacter(CodingErrorAction.REPLACE)
    274                    .replaceWith("?"),
    275             bufferSize,
    276             writeImmediately);
    277        // @formatter:on
    278    }
    279
    280    /**
    281     * Constructs a new {@link WriterOutputStream} with a default output buffer size of {@value #BUFFER_SIZE} characters. The output buffer will only be flushed
    282     * when it overflows or when {@link #flush()} or {@link #close()} is called.
    283     *
    284     * @param writer  the target {@link Writer}
    285     * @param decoder the charset decoder
    286     * @since 2.1
    287     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    288     */
    289    @Deprecated
    290    public WriterOutputStream(final Writer writer, final CharsetDecoder decoder) {
    291        this(writer, decoder, BUFFER_SIZE, false);
    292    }
    293
    294    /**
    295     * Constructs a new {@link WriterOutputStream}.
    296     *
    297     * @param writer           the target {@link Writer}
    298     * @param decoder          the charset decoder
    299     * @param bufferSize       the size of the output buffer in number of characters
    300     * @param writeImmediately If {@code true} the output buffer will be flushed after each write operation, i.e. all available data will be written to the
    301     *                         underlying {@link Writer} immediately. If {@code false}, the output buffer will only be flushed when it overflows or when
    302     *                         {@link #flush()} or {@link #close()} is called.
    303     * @since 2.1
    304     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    305     */
    306    @Deprecated
    307    public WriterOutputStream(final Writer writer, final CharsetDecoder decoder, final int bufferSize, final boolean writeImmediately) {
    308        checkIbmJdkWithBrokenUTF16(CharsetDecoders.toCharsetDecoder(decoder).charset());
    309        this.writer = writer;
    310        this.decoder = CharsetDecoders.toCharsetDecoder(decoder);
    311        this.writeImmediately = writeImmediately;
    312        this.decoderOut = CharBuffer.allocate(bufferSize);
    313    }
    314
    315    /**
    316     * Constructs a new {@link WriterOutputStream} with a default output buffer size of {@value #BUFFER_SIZE} characters. The output buffer will only be flushed
    317     * when it overflows or when {@link #flush()} or {@link #close()} is called.
    318     *
    319     * @param writer      the target {@link Writer}
    320     * @param charsetName the name of the charset encoding
    321     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    322     */
    323    @Deprecated
    324    public WriterOutputStream(final Writer writer, final String charsetName) {
    325        this(writer, charsetName, BUFFER_SIZE, false);
    326    }
    327
    328    /**
    329     * Constructs a new {@link WriterOutputStream}.
    330     *
    331     * @param writer           the target {@link Writer}
    332     * @param charsetName      the name of the charset encoding
    333     * @param bufferSize       the size of the output buffer in number of characters
    334     * @param writeImmediately If {@code true} the output buffer will be flushed after each write operation, i.e. all available data will be written to the
    335     *                         underlying {@link Writer} immediately. If {@code false}, the output buffer will only be flushed when it overflows or when
    336     *                         {@link #flush()} or {@link #close()} is called.
    337     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    338     */
    339    @Deprecated
    340    public WriterOutputStream(final Writer writer, final String charsetName, final int bufferSize, final boolean writeImmediately) {
    341        this(writer, Charsets.toCharset(charsetName), bufferSize, writeImmediately);
    342    }
    343
    344    /**
    345     * Close the stream. Any remaining content accumulated in the output buffer will be written to the underlying {@link Writer}. After that
    346     * {@link Writer#close()} will be called.
    347     *
    348     * @throws IOException if an I/O error occurs.
    349     */
    350    @Override
    351    public void close() throws IOException {
    352        processInput(true);
    353        flushOutput();
    354        writer.close();
    355    }
    356
    357    /**
    358     * Flush the stream. Any remaining content accumulated in the output buffer will be written to the underlying {@link Writer}. After that
    359     * {@link Writer#flush()} will be called.
    360     *
    361     * @throws IOException if an I/O error occurs.
    362     */
    363    @Override
    364    public void flush() throws IOException {
    365        flushOutput();
    366        writer.flush();
    367    }
    368
    369    /**
    370     * Flush the output.
    371     *
    372     * @throws IOException if an I/O error occurs.
    373     */
    374    private void flushOutput() throws IOException {
    375        if (decoderOut.position() > 0) {
    376            writer.write(decoderOut.array(), 0, decoderOut.position());
    377            decoderOut.rewind();
    378        }
    379    }
    380
    381    /**
    382     * Decode the contents of the input ByteBuffer into a CharBuffer.
    383     *
    384     * @param endOfInput indicates end of input
    385     * @throws IOException if an I/O error occurs.
    386     */
    387    private void processInput(final boolean endOfInput) throws IOException {
    388        // Prepare decoderIn for reading
    389        decoderIn.flip();
    390        CoderResult coderResult;
    391        while (true) {
    392            coderResult = decoder.decode(decoderIn, decoderOut, endOfInput);
    393            if (coderResult.isOverflow()) {
    394                flushOutput();
    395            } else if (coderResult.isUnderflow()) {
    396                break;
    397            } else {
    398                // The decoder is configured to replace malformed input and unmappable characters,
    399                // so we should not get here.
    400                throw new IOException("Unexpected coder result");
    401            }
    402        }
    403        // Discard the bytes that have been read
    404        decoderIn.compact();
    405    }
    406
    407    /**
    408     * Write bytes from the specified byte array to the stream.
    409     *
    410     * @param b the byte array containing the bytes to write
    411     * @throws IOException if an I/O error occurs.
    412     */
    413    @Override
    414    public void write(final byte[] b) throws IOException {
    415        write(b, 0, b.length);
    416    }
    417
    418    /**
    419     * Write bytes from the specified byte array to the stream.
    420     *
    421     * @param b   the byte array containing the bytes to write
    422     * @param off the start offset in the byte array
    423     * @param len the number of bytes to write
    424     * @throws IOException if an I/O error occurs.
    425     */
    426    @Override
    427    public void write(final byte[] b, int off, int len) throws IOException {
    428        while (len > 0) {
    429            final int c = Math.min(len, decoderIn.remaining());
    430            decoderIn.put(b, off, c);
    431            processInput(false);
    432            len -= c;
    433            off += c;
    434        }
    435        if (writeImmediately) {
    436            flushOutput();
    437        }
    438    }
    439
    440    /**
    441     * Write a single byte to the stream.
    442     *
    443     * @param b the byte to write
    444     * @throws IOException if an I/O error occurs.
    445     */
    446    @Override
    447    public void write(final int b) throws IOException {
    448        write(new byte[] { (byte) b }, 0, 1);
    449    }
    450}