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}