util/zip/InflaterInputStream.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package java.util.zip;

import java.io.EOFException;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import libcore.base.Streams;

/**
 * This class provides an implementation of {@code FilterInputStream} that
 * decompresses data that was compressed using the <i>DEFLATE</i> algorithm
 * (see <a href="http://www.gzip.org/algorithm.txt">specification</a>).
 * Basically it wraps the {@code Inflater} class and takes care of the
 * buffering.
 *
 * @see Inflater
 * @see DeflaterOutputStream
 */
public class InflaterInputStream extends FilterInputStream {

    /**
     * The inflater used for this stream.
     */
    protected Inflater inf;

    /**
     * The input buffer used for decompression.
     */
    protected byte[] buf;

    /**
     * The length of the buffer.
     */
    protected int len;

    boolean closed;

    /**
     * True if this stream's last byte has been returned to the user. This
     * could be because the underlying stream has been exhausted, or if errors
     * were encountered while inflating that stream.
     */
    boolean eof;

    static final int BUF_SIZE = 512;

    int nativeEndBufSize = 0; // android-only

    /**
     * This is the most basic constructor. You only need to pass the {@code
     * InputStream} from which the compressed data is to be read from. Default
     * settings for the {@code Inflater} and internal buffer are be used. In
     * particular the Inflater expects a ZLIB header from the input stream.
     *
     * @param is
     *            the {@code InputStream} to read data from.
     */
    public InflaterInputStream(InputStream is) {
        this(is, new Inflater(), BUF_SIZE);
    }

    /**
     * This constructor lets you pass a specifically initialized Inflater,
     * for example one that expects no ZLIB header.
     *
     * @param is
     *            the {@code InputStream} to read data from.
     * @param inflater
     *            the specific {@code Inflater} for decompressing data.
     */
    public InflaterInputStream(InputStream is, Inflater inflater) {
        this(is, inflater, BUF_SIZE);
    }

    /**
     * This constructor lets you specify both the {@code Inflater} as well as
     * the internal buffer size to be used.
     *
     * @param is
     *            the {@code InputStream} to read data from.
     * @param inflater
     *            the specific {@code Inflater} for decompressing data.
     * @param bsize
     *            the size to be used for the internal buffer.
     */
    public InflaterInputStream(InputStream is, Inflater inflater, int bsize) {
        super(is);
        if (is == null || inflater == null) {
            throw new NullPointerException();
        }
        if (bsize <= 0) {
            throw new IllegalArgumentException();
        }
        this.inf = inflater;
        // BEGIN android-only
        if (is instanceof ZipFile.RAFStream) {
            nativeEndBufSize = bsize;
        } else {
            buf = new byte[bsize];
        }
        // END android-only
    }

    /**
     * Reads a single byte of decompressed data.
     *
     * @return the byte read.
     * @throws IOException
     *             if an error occurs reading the byte.
     */
    @Override
    public int read() throws IOException {
        byte[] b = new byte[1];
        if (read(b, 0, 1) == -1) {
            return -1;
        }
        return b[0] & 0xff;
    }

    /**
     * Reads up to {@code byteCount} bytes of decompressed data and stores it in
     * {@code buffer} starting at {@code offset}.
     *
     * @return Number of uncompressed bytes read
     */
    @Override
    public int read(byte[] buffer, int offset, int byteCount) throws IOException {
        checkClosed();
        Arrays.checkOffsetAndCount(buffer.length, offset, byteCount);

        if (byteCount == 0) {
            return 0;
        }

        if (eof) {
            return -1;
        }

        do {
            if (inf.needsInput()) {
                fill();
            }
            // Invariant: if reading returns -1 or throws, eof must be true.
            // It may also be true if the next read() should return -1.
            try {
                int result = inf.inflate(buffer, offset, byteCount);
                eof = inf.finished();
                if (result > 0) {
                    return result;
                } else if (eof) {
                    return -1;
                } else if (inf.needsDictionary()) {
                    eof = true;
                    return -1;
                } else if (len == -1) {
                    eof = true;
                    throw new EOFException();
                    // If result == 0, fill() and try again
                }
            } catch (DataFormatException e) {
                eof = true;
                if (len == -1) {
                    throw new EOFException();
                }
                throw (IOException) (new IOException().initCause(e));
            }
        } while (true);
    }

    /**
     * Fills the input buffer with data to be decompressed.
     *
     * @throws IOException
     *             if an {@code IOException} occurs.
     */
    protected void fill() throws IOException {
        checkClosed();
        // BEGIN android-only
        if (nativeEndBufSize > 0) {
            ZipFile.RAFStream is = (ZipFile.RAFStream)in;
            synchronized (is.mSharedRaf) {
                long len = is.mLength - is.mOffset;
                if (len > nativeEndBufSize) len = nativeEndBufSize;
                int cnt = inf.setFileInput(is.mSharedRaf.getFD(), is.mOffset, (int)nativeEndBufSize);
                is.skip(cnt);
            }
        } else {
            if ((len = in.read(buf)) > 0) {
                inf.setInput(buf, 0, len);
            }
        }
        // END android-only
    }

    /**
     * Skips up to {@code byteCount} bytes of uncompressed data.
     *
     * @param byteCount the number of bytes to skip.
     * @return the number of uncompressed bytes skipped.
     * @throws IllegalArgumentException if {@code byteCount < 0}.
     * @throws IOException if an error occurs skipping.
     */
    @Override
    public long skip(long byteCount) throws IOException {
        if (byteCount < 0) {
            throw new IllegalArgumentException("byteCount < 0");
        }
        return Streams.skipByReading(this, byteCount);
    }

    /**
     * Returns 0 when when this stream has exhausted its input; and 1 otherwise.
     * A result of 1 does not guarantee that further bytes can be returned,
     * with or without blocking.
     *
     * <p>Although consistent with the RI, this behavior is inconsistent with
     * {@link InputStream#available()}, and violates the <a
     * href="http://en.wikipedia.org/wiki/Liskov_substitution_principle">Liskov
     * Substitution Principle</a>. This method should not be used.
     *
     * @return 0 if no further bytes are available. Otherwise returns 1,
     *         which suggests (but does not guarantee) that additional bytes are
     *         available.
     * @throws IOException if this stream is closed or an error occurs
     */
    @Override
    public int available() throws IOException {
        checkClosed();
        if (eof) {
            return 0;
        }
        return 1;
    }

    /**
     * Closes the input stream.
     *
     * @throws IOException
     *             If an error occurs closing the input stream.
     */
    @Override
    public void close() throws IOException {
        if (!closed) {
            inf.end();
            closed = true;
            eof = true;
            super.close();
        }
    }

    /**
     * Marks the current position in the stream. This implementation overrides
     * the super type implementation to do nothing at all.
     *
     * @param readlimit
     *            of no use.
     */
    @Override
    public void mark(int readlimit) {
        // do nothing
    }

    /**
     * Reset the position of the stream to the last marked position. This
     * implementation overrides the supertype implementation and always throws
     * an {@link IOException IOException} when called.
     *
     * @throws IOException
     *             if the method is called
     */
    @Override
    public void reset() throws IOException {
        throw new IOException();
    }

    /**
     * Returns whether the receiver implements {@code mark} semantics. This type
     * does not support {@code mark()}, so always responds {@code false}.
     *
     * @return false, always
     */
    @Override
    public boolean markSupported() {
        return false;
    }

    private void checkClosed() throws IOException {
        if (closed) {
            throw new IOException("Stream is closed");
        }
    }
}