    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 */
    017
    018package org.apache.commons.io.input;
    019
    020import java.io.BufferedInputStream;
    021import java.io.IOException;
    022import java.io.InputStream;
    023
    024import org.apache.commons.io.IOUtils;
    025import org.apache.commons.io.build.AbstractStreamBuilder;
    026
    027/**
    028 * An unsynchronized version of {@link BufferedInputStream}, not thread-safe.
    029 * <p>
    030 * Wraps an existing {@link InputStream} and <em>buffers</em> the input. Expensive interaction with the underlying input stream is minimized, since most
    031 * (smaller) requests can be satisfied by accessing the buffer alone. The drawback is that some extra space is required to hold the buffer and that copying
    032 * takes place when filling that buffer, but this is usually outweighed by the performance benefits.
    033 * </p>
    034 * <p>
    035 * To build an instance, use {@link Builder}.
    036 * </p>
    037 * <p>
    038 * A typical application pattern for the class looks like this:
    039 * </p>
    040 *
    041 * <pre>
    042 * UnsynchronizedBufferedInputStream s = new UnsynchronizedBufferedInputStream.Builder().
    043 *   .setInputStream(new FileInputStream(&quot;file.java&quot;))
    044 *   .setBufferSize(8192)
    045 *   .get();
    046 * </pre>
    047 * <p>
    048 * Provenance: Apache Harmony and modified.
    049 * </p>
    050 *
    051 * @see Builder
    052 * @see BufferedInputStream
    053 * @since 2.12.0
    054 */
    055//@NotThreadSafe
    056public final class UnsynchronizedBufferedInputStream extends UnsynchronizedFilterInputStream {
    057
    058    // @formatter:off
    059    /**
    060     * Builds a new {@link UnsynchronizedBufferedInputStream}.
    061     *
    062     * <p>
    063     * Using File IO:
    064     * </p>
    065     * <pre>{@code
    066     * UnsynchronizedBufferedInputStream s = UnsynchronizedBufferedInputStream.builder()
    067     *   .setFile(file)
    068     *   .setBufferSize(8192)
    069     *   .get();}
    070     * </pre>
    071     * <p>
    072     * Using NIO Path:
    073     * </p>
    074     * <pre>{@code
    075     * UnsynchronizedBufferedInputStream s = UnsynchronizedBufferedInputStream.builder()
    076     *   .setPath(path)
    077     *   .setBufferSize(8192)
    078     *   .get();}
    079     * </pre>
    080     *
    081     * @see #get()
    082     */
    083    // @formatter:on
    084    public static class Builder extends AbstractStreamBuilder<UnsynchronizedBufferedInputStream, Builder> {
    085
    086        /**
    087         * Constructs a builder of {@link UnsynchronizedBufferedInputStream}.
    088         */
    089        public Builder() {
    090            // empty
    091        }
    092
    093        /**
    094         * Builds a new {@link UnsynchronizedBufferedInputStream}.
    095         * <p>
    096         * You must set an aspect that supports {@link #getInputStream()} on this builder, otherwise, this method throws an exception.
    097         * </p>
    098         * <p>
    099         * This builder uses the following aspects:
    100         * </p>
    101         * <ul>
    102         * <li>{@link #getInputStream()}</li>
    103         * <li>{@link #getBufferSize()}</li>
    104         * </ul>
    105         *
    106         * @return a new instance.
    107         * @throws IllegalStateException         if the {@code origin} is {@code null}.
    108         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
    109         * @throws IOException                   if an I/O error occurs converting to an {@link InputStream} using {@link #getInputStream()}.
    110         * @see #getInputStream()
    111         * @see #getBufferSize()
    112         * @see #getUnchecked()
    113         */
    114        @Override
    115        public UnsynchronizedBufferedInputStream get() throws IOException {
    116            return new UnsynchronizedBufferedInputStream(this);
    117        }
    118
    119    }
    120
    121    /**
    122     * The buffer containing the current bytes read from the target InputStream.
    123     */
    124    protected volatile byte[] buffer;
    125
    126    /**
    127     * The total number of bytes inside the byte array {@code buffer}.
    128     */
    129    protected int count;
    130
    131    /**
    132     * The current limit, which when passed, invalidates the current mark.
    133     */
    134    protected int markLimit;
    135
    136    /**
    137     * The currently marked position. -1 indicates no mark has been set or the mark has been invalidated.
    138     */
    139    protected int markPos = IOUtils.EOF;
    140
    141    /**
    142     * The current position within the byte array {@code buffer}.
    143     */
    144    protected int pos;
    145
    146    /**
    147     * Constructs a new {@code BufferedInputStream} on the {@link InputStream} {@code in}. The buffer size is specified by the parameter {@code size} and all
    148     * reads are now filtered through this stream.
    149     *
    150     * @param builder   A builder providing the input stream and buffer size.
    151     * @throws IOException if an I/O error occurs.
    152     * @throws IllegalArgumentException if {@code size < 0}.
    153     */
    154    @SuppressWarnings("resource")
    155    private UnsynchronizedBufferedInputStream(final Builder builder) throws IOException {
    156        super(builder.getInputStream());
    157        final int bufferSize = builder.getBufferSize();
    158        if (bufferSize <= 0) {
    159            throw new IllegalArgumentException("Size must be > 0");
    160        }
    161        buffer = new byte[bufferSize];
    162    }
    163
    164    /**
    165     * Returns the number of bytes that are available before this stream will block. This method returns the number of bytes available in the buffer plus those
    166     * available in the source stream.
    167     *
    168     * @return the number of bytes available before blocking.
    169     * @throws IOException if this stream is closed.
    170     */
    171    @Override
    172    public int available() throws IOException {
    173        final InputStream localIn = inputStream; // 'in' could be invalidated by close()
    174        if (buffer == null || localIn == null) {
    175            throw new IOException("Stream is closed");
    176        }
    177        return count - pos + localIn.available();
    178    }
    179
    180    /**
    181     * Closes this stream. The source stream is closed and any resources associated with it are released.
    182     *
    183     * @throws IOException if an error occurs while closing this stream.
    184     */
    185    @Override
    186    public void close() throws IOException {
    187        buffer = null;
    188        final InputStream localIn = inputStream;
    189        inputStream = null;
    190        if (localIn != null) {
    191            localIn.close();
    192        }
    193    }
    194
    195    private int fillBuffer(final InputStream localIn, byte[] localBuf) throws IOException {
    196        if (markPos == IOUtils.EOF || pos - markPos >= markLimit) {
    197            /* Mark position not set or exceeded readLimit */
    198            final int result = localIn.read(localBuf);
    199            if (result > 0) {
    200                markPos = IOUtils.EOF;
    201                pos = 0;
    202                count = result;
    203            }
    204            return result;
    205        }
    206        if (markPos == 0 && markLimit > localBuf.length) {
    207            /* Increase buffer size to accommodate the readLimit */
    208            int newLength = localBuf.length * 2;
    209            if (newLength > markLimit) {
    210                newLength = markLimit;
    211            }
    212            final byte[] newbuf = new byte[newLength];
    213            System.arraycopy(localBuf, 0, newbuf, 0, localBuf.length);
    214            // Reassign buffer, which will invalidate any local references
    215            // FIXME: what if buffer was null?
    216            localBuf = buffer = newbuf;
    217        } else if (markPos > 0) {
    218            System.arraycopy(localBuf, markPos, localBuf, 0, localBuf.length - markPos);
    219        }
    220        // Set the new position and mark position
    221        pos -= markPos;
    222        count = markPos = 0;
    223        final int bytesread = localIn.read(localBuf, pos, localBuf.length - pos);
    224        count = bytesread <= 0 ? pos : pos + bytesread;
    225        return bytesread;
    226    }
    227
    228    byte[] getBuffer() {
    229        return buffer;
    230    }
    231
    232    /**
    233     * Sets a mark position in this stream. The parameter {@code readLimit} indicates how many bytes can be read before a mark is invalidated. Calling
    234     * {@code reset()} will reposition the stream back to the marked position if {@code readLimit} has not been surpassed. The underlying buffer may be
    235     * increased in size to allow {@code readLimit} number of bytes to be supported.
    236     *
    237     * @param readLimit the number of bytes that can be read before the mark is invalidated.
    238     * @see #reset()
    239     */
    240    @Override
    241    public void mark(final int readLimit) {
    242        markLimit = readLimit;
    243        markPos = pos;
    244    }
    245
    246    /**
    247     * Indicates whether {@code BufferedInputStream} supports the {@code mark()} and {@code reset()} methods.
    248     *
    249     * @return {@code true} for BufferedInputStreams.
    250     * @see #mark(int)
    251     * @see #reset()
    252     */
    253    @Override
    254    public boolean markSupported() {
    255        return true;
    256    }
    257
    258    /**
    259     * Reads a single byte from this stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of the source string has been
    260     * reached. If the internal buffer does not contain any available bytes then it is filled from the source stream and the first byte is returned.
    261     *
    262     * @return the byte read or -1 if the end of the source stream has been reached.
    263     * @throws IOException if this stream is closed or another IOException occurs.
    264     */
    265    @Override
    266    public int read() throws IOException {
    267        // Use local refs since buf and in may be invalidated by an
    268        // unsynchronized close()
    269        byte[] localBuf = buffer;
    270        final InputStream localIn = inputStream;
    271        if (localBuf == null || localIn == null) {
    272            throw new IOException("Stream is closed");
    273        }
    274
    275        /* Are there buffered bytes available? */
    276        if (pos >= count && fillBuffer(localIn, localBuf) == IOUtils.EOF) {
    277            return IOUtils.EOF; /* no, fill buffer */
    278        }
    279        // localBuf may have been invalidated by fillbuf
    280        if (localBuf != buffer) {
    281            localBuf = buffer;
    282            if (localBuf == null) {
    283                throw new IOException("Stream is closed");
    284            }
    285        }
    286
    287        /* Did filling the buffer fail with -1 (EOF)? */
    288        if (count - pos > 0) {
    289            return localBuf[pos++] & 0xFF;
    290        }
    291        return IOUtils.EOF;
    292    }
    293
    294    /**
    295     * Reads at most {@code length} bytes from this stream and stores them in byte array {@code buffer} starting at offset {@code offset}. Returns the number of
    296     * bytes actually read or -1 if no bytes were read and the end of the stream was encountered. If all the buffered bytes have been used, a mark has not been
    297     * set and the requested number of bytes is larger than the receiver's buffer size, this implementation bypasses the buffer and simply places the results
    298     * directly into {@code buffer}.
    299     *
    300     * @param dest the byte array in which to store the bytes read.
    301     * @param offset the initial position in {@code buffer} to store the bytes read from this stream.
    302     * @param length the maximum number of bytes to store in {@code buffer}.
    303     * @return the number of bytes actually read or -1 if end of stream.
    304     * @throws IndexOutOfBoundsException if {@code offset < 0} or {@code length < 0}, or if {@code offset + length} is greater than the size of {@code buffer}.
    305     * @throws IOException               if the stream is already closed or another IOException occurs.
    306     */
    307    @Override
    308    public int read(final byte[] dest, int offset, final int length) throws IOException {
    309        // Use local ref since buf may be invalidated by an unsynchronized
    310        // close()
    311        byte[] localBuf = buffer;
    312        if (localBuf == null) {
    313            throw new IOException("Stream is closed");
    314        }
    315        // avoid int overflow
    316        if (offset > dest.length - length || offset < 0 || length < 0) {
    317            throw new IndexOutOfBoundsException();
    318        }
    319        if (length == 0) {
    320            return 0;
    321        }
    322        final InputStream localIn = inputStream;
    323        if (localIn == null) {
    324            throw new IOException("Stream is closed");
    325        }
    326
    327        int required;
    328        if (pos < count) {
    329            /* There are bytes available in the buffer. */
    330            final int copylength = count - pos >= length ? length : count - pos;
    331            System.arraycopy(localBuf, pos, dest, offset, copylength);
    332            pos += copylength;
    333            if (copylength == length || localIn.available() == 0) {
    334                return copylength;
    335            }
    336            offset += copylength;
    337            required = length - copylength;
    338        } else {
    339            required = length;
    340        }
    341
    342        while (true) {
    343            final int read;
    344            /*
    345             * If we're not marked and the required size is greater than the buffer, simply read the bytes directly bypassing the buffer.
    346             */
    347            if (markPos == IOUtils.EOF && required >= localBuf.length) {
    348                read = localIn.read(dest, offset, required);
    349                if (read == IOUtils.EOF) {
    350                    return required == length ? IOUtils.EOF : length - required;
    351                }
    352            } else {
    353                if (fillBuffer(localIn, localBuf) == IOUtils.EOF) {
    354                    return required == length ? IOUtils.EOF : length - required;
    355                }
    356                // localBuf may have been invalidated by fillBuffer()
    357                if (localBuf != buffer) {
    358                    localBuf = buffer;
    359                    if (localBuf == null) {
    360                        throw new IOException("Stream is closed");
    361                    }
    362                }
    363
    364                read = count - pos >= required ? required : count - pos;
    365                System.arraycopy(localBuf, pos, dest, offset, read);
    366                pos += read;
    367            }
    368            required -= read;
    369            if (required == 0) {
    370                return length;
    371            }
    372            if (localIn.available() == 0) {
    373                return length - required;
    374            }
    375            offset += read;
    376        }
    377    }
    378
    379    /**
    380     * Resets this stream to the last marked location.
    381     *
    382     * @throws IOException if this stream is closed, no mark has been set or the mark is no longer valid because more than {@code readLimit} bytes have been
    383     *                     read since setting the mark.
    384     * @see #mark(int)
    385     */
    386    @Override
    387    public void reset() throws IOException {
    388        if (buffer == null) {
    389            throw new IOException("Stream is closed");
    390        }
    391        if (IOUtils.EOF == markPos) {
    392            throw new IOException("Mark has been invalidated");
    393        }
    394        pos = markPos;
    395    }
    396
    397    /**
    398     * Skips {@code amount} number of bytes in this stream. Subsequent {@code read()}'s will not return these bytes unless {@code reset()} is used.
    399     *
    400     * @param amount the number of bytes to skip. {@code skip} does nothing and returns 0 if {@code amount} is less than zero.
    401     * @return the number of bytes actually skipped.
    402     * @throws IOException if this stream is closed or another IOException occurs.
    403     */
    404    @Override
    405    public long skip(final long amount) throws IOException {
    406        // Use local refs since buf and in may be invalidated by an
    407        // unsynchronized close()
    408        final byte[] localBuf = buffer;
    409        final InputStream localIn = inputStream;
    410        if (localBuf == null) {
    411            throw new IOException("Stream is closed");
    412        }
    413        if (amount < 1) {
    414            return 0;
    415        }
    416        if (localIn == null) {
    417            throw new IOException("Stream is closed");
    418        }
    419
    420        if (count - pos >= amount) {
    421            // (int count - int pos) here is always an int so amount is also in the int range if the above test is true.
    422            // We can safely cast to int and avoid static analysis warnings.
    423            pos += (int) amount;
    424            return amount;
    425        }
    426        int read = count - pos;
    427        pos = count;
    428
    429        if (markPos != IOUtils.EOF && amount <= markLimit) {
    430            if (fillBuffer(localIn, localBuf) == IOUtils.EOF) {
    431                return read;
    432            }
    433            if (count - pos >= amount - read) {
    434                // (int count - int pos) here is always an int so (amount - read) is also in the int range if the above test is true.
    435                // We can safely cast to int and avoid static analysis warnings.
    436                pos += (int) amount - read;
    437                return amount;
    438            }
    439            // Couldn't get all the bytes, skip what we read
    440            read += count - pos;
    441            pos = count;
    442            return read;
    443        }
    444        return read + localIn.skip(amount - read);
    445    }
    446}