    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 *      https://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 static org.apache.commons.io.IOUtils.EOF;
    020
    021import java.io.IOException;
    022import java.io.InputStream;
    023import java.io.OutputStream;
    024import java.io.SequenceInputStream;
    025import java.io.UnsupportedEncodingException;
    026import java.nio.charset.Charset;
    027import java.util.ArrayList;
    028import java.util.Collections;
    029import java.util.List;
    030
    031import org.apache.commons.io.Charsets;
    032import org.apache.commons.io.IOUtils;
    033import org.apache.commons.io.input.ClosedInputStream;
    034
    035/**
    036 * This is the base class for implementing an output stream in which the data
    037 * is written into a byte array. The buffer automatically grows as data
    038 * is written to it.
    039 * <p>
    040 * The data can be retrieved using {@code toByteArray()} and
    041 * {@code toString()}.
    042 * Closing an {@link AbstractByteArrayOutputStream} has no effect. The methods in
    043 * this class can be called after the stream has been closed without
    044 * generating an {@link IOException}.
    045 * </p>
    046 * <p>
    047 * This is the base for an alternative implementation of the
    048 * {@link java.io.ByteArrayOutputStream} class. The original implementation
    049 * only allocates 32 bytes at the beginning. As this class is designed for
    050 * heavy duty it starts at {@value #DEFAULT_SIZE} bytes. In contrast to the original it doesn't
    051 * reallocate the whole memory block but allocates additional buffers. This
    052 * way no buffers need to be garbage collected and the contents don't have
    053 * to be copied to the new buffer. This class is designed to behave exactly
    054 * like the original. The only exception is the deprecated
    055 * {@link java.io.ByteArrayOutputStream#toString(int)} method that has been
    056 * ignored.
    057 * </p>
    058 *
    059 * @param <T> The AbstractByteArrayOutputStream subclass.
    060 * @since 2.7
    061 */
    062public abstract class AbstractByteArrayOutputStream<T extends AbstractByteArrayOutputStream<T>> extends OutputStream {
    063
    064    /**
    065     * Constructor for an InputStream subclass.
    066     *
    067     * @param <T> the type of the InputStream.
    068     */
    069    @FunctionalInterface
    070    protected interface InputStreamConstructor<T extends InputStream> {
    071
    072        /**
    073         * Constructs an InputStream subclass.
    074         *
    075         * @param buffer the buffer.
    076         * @param offset the offset into the buffer.
    077         * @param length the length of the buffer.
    078         * @return the InputStream subclass.
    079         */
    080        T construct(byte[] buffer, int offset, int length);
    081    }
    082
    083    static final int DEFAULT_SIZE = 1024;
    084
    085    /** The list of buffers, which grows and never reduces. */
    086    private final List<byte[]> buffers = new ArrayList<>();
    087
    088    /** The total count of bytes written. */
    089    protected int count;
    090
    091    /** The current buffer. */
    092    private byte[] currentBuffer;
    093
    094    /** The index of the current buffer. */
    095    private int currentBufferIndex = -1;
    096
    097    /** The total count of bytes in all the filled buffers. */
    098    private int filledBufferSum;
    099
    100    /** Flag to indicate if the buffers can be reused after reset */
    101    private boolean reuseBuffers = true;
    102
    103    /**
    104     * Constructs a new instance for subclasses.
    105     */
    106    public AbstractByteArrayOutputStream() {
    107        // empty
    108    }
    109
    110    /**
    111     * Returns this instance typed to {@code T}.
    112     *
    113     * @return {@code this} instance.
    114     */
    115    @SuppressWarnings("unchecked")
    116    protected T asThis() {
    117        return (T) this;
    118    }
    119
    120    /**
    121     * Does nothing.
    122     *
    123     * The methods in this class can be called after the stream has been closed without generating an {@link IOException}.
    124     *
    125     * @throws IOException never (this method should not declare this exception but it has to now due to backwards
    126     *         compatibility).
    127     */
    128    @Override
    129    public void close() throws IOException {
    130        //nop
    131    }
    132
    133    /**
    134     * Makes a new buffer available either by allocating
    135     * a new one or re-cycling an existing one.
    136     *
    137     * @param newCount  the size of the buffer if one is created.
    138     */
    139    protected void needNewBuffer(final int newCount) {
    140        if (currentBufferIndex < buffers.size() - 1) {
    141            // Recycling old buffer
    142            filledBufferSum += currentBuffer.length;
    143            currentBufferIndex++;
    144            currentBuffer = buffers.get(currentBufferIndex);
    145        } else {
    146            // Creating new buffer
    147            final int newBufferSize;
    148            if (currentBuffer == null) {
    149                // prevents 0 size buffers
    150                newBufferSize = newCount > 0 ? newCount : DEFAULT_SIZE;
    151                filledBufferSum = 0;
    152            } else {
    153                newBufferSize = Math.max(currentBuffer.length << 1, newCount - filledBufferSum);
    154                filledBufferSum += currentBuffer.length;
    155            }
    156            currentBufferIndex++;
    157            currentBuffer = IOUtils.byteArray(newBufferSize);
    158            buffers.add(currentBuffer);
    159        }
    160    }
    161
    162    /**
    163     * See {@link ByteArrayOutputStream#reset()}.
    164     *
    165     * @see ByteArrayOutputStream#reset()
    166     */
    167    public abstract void reset();
    168
    169    /**
    170     * Implements a default reset behavior.
    171     *
    172     * @see ByteArrayOutputStream#reset()
    173     */
    174    protected void resetImpl() {
    175        count = 0;
    176        filledBufferSum = 0;
    177        currentBufferIndex = 0;
    178        if (reuseBuffers) {
    179            currentBuffer = buffers.get(currentBufferIndex);
    180        } else {
    181            //Throw away old buffers
    182            currentBuffer = null;
    183            final int size = buffers.get(0).length;
    184            buffers.clear();
    185            needNewBuffer(size);
    186            reuseBuffers = true;
    187        }
    188    }
    189
    190    /**
    191     * Returns the current size of the byte array.
    192     *
    193     * @return the current size of the byte array.
    194     */
    195    public abstract int size();
    196
    197    /**
    198     * Gets the current contents of this byte stream as a byte array.
    199     * The result is independent of this stream.
    200     *
    201     * @return the current contents of this output stream, as a byte array.
    202     * @see java.io.ByteArrayOutputStream#toByteArray()
    203     */
    204    public abstract byte[] toByteArray();
    205
    206    /**
    207     * Gets the current contents of this byte stream as a byte array.
    208     * The result is independent of this stream.
    209     *
    210     * @return the current contents of this output stream, as a byte array.
    211     * @see java.io.ByteArrayOutputStream#toByteArray()
    212     */
    213    protected byte[] toByteArrayImpl() {
    214        int remaining = count;
    215        if (remaining == 0) {
    216            return IOUtils.EMPTY_BYTE_ARRAY;
    217        }
    218        final byte[] newBuf = IOUtils.byteArray(remaining);
    219        int pos = 0;
    220        for (final byte[] buf : buffers) {
    221            final int c = Math.min(buf.length, remaining);
    222            System.arraycopy(buf, 0, newBuf, pos, c);
    223            pos += c;
    224            remaining -= c;
    225            if (remaining == 0) {
    226                break;
    227            }
    228        }
    229        return newBuf;
    230    }
    231
    232    /**
    233     * Gets the current contents of this byte stream as an Input Stream. The
    234     * returned stream is backed by buffers of {@code this} stream,
    235     * avoiding memory allocation and copy, thus saving space and time.
    236     *
    237     * @return the current contents of this output stream.
    238     * @see java.io.ByteArrayOutputStream#toByteArray()
    239     * @see #reset()
    240     * @since 2.5
    241     */
    242    public abstract InputStream toInputStream();
    243
    244    /**
    245     * Gets the current contents of this byte stream as an Input Stream. The
    246     * returned stream is backed by buffers of {@code this} stream,
    247     * avoiding memory allocation and copy, thus saving space and time.
    248     *
    249     * @param <S> the type of the InputStream which makes up
    250     *            the {@link SequenceInputStream}.
    251     * @param isConstructor A constructor for an InputStream which makes
    252     *                     up the {@link SequenceInputStream}.
    253     *
    254     * @return the current contents of this output stream.
    255     * @see java.io.ByteArrayOutputStream#toByteArray()
    256     * @see #reset()
    257     * @since 2.7
    258     */
    259    @SuppressWarnings("resource") // The result InputStream MUST be managed by the call site.
    260    protected <S extends InputStream> InputStream toInputStream(final InputStreamConstructor<S> isConstructor) {
    261        int remaining = count;
    262        if (remaining == 0) {
    263            return ClosedInputStream.INSTANCE;
    264        }
    265        final List<S> list = new ArrayList<>(buffers.size());
    266        for (final byte[] buf : buffers) {
    267            final int c = Math.min(buf.length, remaining);
    268            list.add(isConstructor.construct(buf, 0, c));
    269            remaining -= c;
    270            if (remaining == 0) {
    271                break;
    272            }
    273        }
    274        reuseBuffers = false;
    275        return new SequenceInputStream(Collections.enumeration(list));
    276    }
    277
    278    /**
    279     * Gets the current contents of this byte stream as a string using the virtual machine's {@linkplain Charset#defaultCharset() default charset}.
    280     *
    281     * @return the contents of the byte array as a String.
    282     * @see java.io.ByteArrayOutputStream#toString()
    283     * @see Charset#defaultCharset()
    284     * @deprecated Use {@link #toString(String)} instead.
    285     */
    286    @Override
    287    @Deprecated
    288    public String toString() {
    289        // make explicit the use of the default charset
    290        return new String(toByteArray(), Charset.defaultCharset());
    291    }
    292
    293    /**
    294     * Gets the current contents of this byte stream as a string
    295     * using the specified encoding.
    296     *
    297     * @param charset  the character encoding.
    298     * @return the string converted from the byte array.
    299     * @see java.io.ByteArrayOutputStream#toString(String)
    300     * @since 2.5
    301     */
    302    public String toString(final Charset charset) {
    303        return new String(toByteArray(), charset);
    304    }
    305
    306    /**
    307     * Gets the current contents of this byte stream as a string
    308     * using the specified encoding.
    309     *
    310     * @param enc  the name of the character encoding.
    311     * @return the string converted from the byte array.
    312     * @throws UnsupportedEncodingException if the encoding is not supported.
    313     * @see java.io.ByteArrayOutputStream#toString(String)
    314     */
    315    public String toString(final String enc) throws UnsupportedEncodingException {
    316        return new String(toByteArray(), enc);
    317    }
    318
    319    /**
    320     * Writes {@code b.length} bytes from the given byte array to this output stream. This has same effect as {@code write(b, 0, b.length)}.
    321     *
    322     * @param b the data.
    323     * @see #write(byte[], int, int)
    324     * @since 2.19.0
    325     */
    326    @Override
    327    public void write(final byte b[]) {
    328        write(b, 0, b.length);
    329    }
    330
    331    @Override
    332    public abstract void write(byte[] b, int off, int len);
    333
    334    /**
    335     * Writes the bytes for given CharSequence encoded using a Charset.
    336     *
    337     * @param data    The String to convert to bytes. not null.
    338     * @param charset The {@link Charset} o encode the {@code String}, null means the default encoding.
    339     * @return {@code this} instance.
    340     * @since 2.19.0
    341     */
    342    public T write(final CharSequence data, final Charset charset) {
    343        write(data.toString().getBytes(Charsets.toCharset(charset)));
    344        return asThis();
    345    }
    346
    347    /**
    348     * Writes the entire contents of the specified input stream to this byte stream. Bytes from the input stream are read directly into the internal buffer of
    349     * this stream.
    350     *
    351     * @param in the input stream to read from.
    352     * @return total number of bytes read from the input stream (and written to this stream).
    353     * @throws IOException if an I/O error occurs while reading the input stream.
    354     * @since 1.4
    355     */
    356    public abstract int write(InputStream in) throws IOException;
    357
    358    @Override
    359    public abstract void write(int b);
    360
    361    /**
    362     * Writes the bytes to the byte array.
    363     *
    364     * @param b the bytes to write.
    365     * @param off The start offset.
    366     * @param len The number of bytes to write.
    367     */
    368    protected void writeImpl(final byte[] b, final int off, final int len) {
    369        final int newCount = count + len;
    370        int remaining = len;
    371        int inBufferPos = count - filledBufferSum;
    372        while (remaining > 0) {
    373            final int part = Math.min(remaining, currentBuffer.length - inBufferPos);
    374            System.arraycopy(b, off + len - remaining, currentBuffer, inBufferPos, part);
    375            remaining -= part;
    376            if (remaining > 0) {
    377                needNewBuffer(newCount);
    378                inBufferPos = 0;
    379            }
    380        }
    381        count = newCount;
    382    }
    383
    384    /**
    385     * Writes the entire contents of the specified input stream to this byte stream. Bytes from the input stream are read directly into the internal buffer of
    386     * this stream.
    387     *
    388     * @param in the input stream to read from.
    389     * @return total number of bytes read from the input stream (and written to this stream).
    390     * @throws IOException if an I/O error occurs while reading the input stream.
    391     * @since 2.7
    392     */
    393    protected int writeImpl(final InputStream in) throws IOException {
    394        int readCount = 0;
    395        int inBufferPos = count - filledBufferSum;
    396        int n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
    397        while (n != EOF) {
    398            readCount += n;
    399            inBufferPos += n;
    400            count += n;
    401            if (inBufferPos == currentBuffer.length) {
    402                needNewBuffer(currentBuffer.length);
    403                inBufferPos = 0;
    404            }
    405            n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
    406        }
    407        return readCount;
    408    }
    409
    410    /**
    411     * Writes a byte to byte array.
    412     *
    413     * @param b the byte to write.
    414     */
    415    protected void writeImpl(final int b) {
    416        int inBufferPos = count - filledBufferSum;
    417        if (inBufferPos == currentBuffer.length) {
    418            needNewBuffer(count + 1);
    419            inBufferPos = 0;
    420        }
    421        currentBuffer[inBufferPos] = (byte) b;
    422        count++;
    423    }
    424
    425    /**
    426     * Writes the entire contents of this byte stream to the specified output stream.
    427     *
    428     * @param out the output stream to write to.
    429     * @throws IOException if an I/O error occurs, such as if the stream is closed.
    430     * @see java.io.ByteArrayOutputStream#writeTo(OutputStream)
    431     */
    432    public abstract void writeTo(OutputStream out) throws IOException;
    433
    434    /**
    435     * Writes the entire contents of this byte stream to the specified output stream.
    436     *
    437     * @param out the output stream to write to.
    438     * @throws IOException if an I/O error occurs, such as if the stream is closed.
    439     * @see java.io.ByteArrayOutputStream#writeTo(OutputStream)
    440     */
    441    protected void writeToImpl(final OutputStream out) throws IOException {
    442        int remaining = count;
    443        for (final byte[] buf : buffers) {
    444            final int c = Math.min(buf.length, remaining);
    445            out.write(buf, 0, c);
    446            remaining -= c;
    447            if (remaining == 0) {
    448                break;
    449            }
    450        }
    451    }
    452
    453}