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