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 */
017
018package org.apache.commons.codec.binary;
019
020import static org.apache.commons.codec.binary.BaseNCodec.EOF;
021
022import java.io.FilterInputStream;
023import java.io.IOException;
024import java.io.InputStream;
025import java.util.Objects;
026
027import org.apache.commons.codec.binary.BaseNCodec.Context;
028
029/**
030 * Abstract superclass for Base-N input streams.
031 *
032 * @since 1.5
033 */
034public class BaseNCodecInputStream extends FilterInputStream {
035
036    private final BaseNCodec baseNCodec;
037
038    private final boolean doEncode;
039
040    private final byte[] singleByte = new byte[1];
041
042    private final byte[] buf;
043
044    private final Context context = new Context();
045
046    /**
047     * Create an instance.
048     *
049     * @param inputStream the input stream
050     * @param baseNCodec the codec
051     * @param doEncode set to true to perform encoding, else decoding
052     */
053    protected BaseNCodecInputStream(final InputStream inputStream, final BaseNCodec baseNCodec, final boolean doEncode) {
054        super(inputStream);
055        this.doEncode = doEncode;
056        this.baseNCodec = baseNCodec;
057        this.buf = new byte[doEncode ? 4096 : 8192];
058    }
059
060    /**
061     * {@inheritDoc}
062     *
063     * @return {@code 0} if the {@link InputStream} has reached {@code EOF},
064     * {@code 1} otherwise
065     * @since 1.7
066     */
067    @Override
068    public int available() throws IOException {
069        // Note: the logic is similar to the InflaterInputStream:
070        //       as long as we have not reached EOF, indicate that there is more
071        //       data available. As we do not know for sure how much data is left,
072        //       just return 1 as a safe guess.
073
074        return context.eof ? 0 : 1;
075    }
076
077    /**
078     * Returns true if decoding behavior is strict. Decoding will raise an
079     * {@link IllegalArgumentException} if trailing bits are not part of a valid encoding.
080     *
081     * <p>
082     * The default is false for lenient encoding. Decoding will compose trailing bits
083     * into 8-bit bytes and discard the remainder.
084     * </p>
085     *
086     * @return true if using strict decoding
087     * @since 1.15
088     */
089    public boolean isStrictDecoding() {
090        return baseNCodec.isStrictDecoding();
091    }
092
093    /**
094     * Marks the current position in this input stream.
095     * <p>
096     * The {@link #mark} method of {@link BaseNCodecInputStream} does nothing.
097     * </p>
098     *
099     * @param readLimit the maximum limit of bytes that can be read before the mark position becomes invalid.
100     * @see #markSupported()
101     * @since 1.7
102     */
103    @Override
104    public synchronized void mark(final int readLimit) {
105        // noop
106    }
107
108    /**
109     * {@inheritDoc}
110     *
111     * @return Always returns {@code false}
112     */
113    @Override
114    public boolean markSupported() {
115        return false; // not an easy job to support marks
116    }
117
118    /**
119     * Reads one {@code byte} from this input stream.
120     *
121     * @return the byte as an integer in the range 0 to 255. Returns -1 if EOF has been reached.
122     * @throws IOException
123     *             if an I/O error occurs.
124     */
125    @Override
126    public int read() throws IOException {
127        int r = read(singleByte, 0, 1);
128        while (r == 0) {
129            r = read(singleByte, 0, 1);
130        }
131        if (r > 0) {
132            final byte b = singleByte[0];
133            return b < 0 ? 256 + b : b;
134        }
135        return EOF;
136    }
137
138    /**
139     * Attempts to read {@code len} bytes into the specified {@code b} array starting at {@code offset}
140     * from this InputStream.
141     *
142     * @param array
143     *            destination byte array
144     * @param offset
145     *            where to start writing the bytes
146     * @param len
147     *            maximum number of bytes to read
148     *
149     * @return number of bytes read
150     * @throws IOException
151     *             if an I/O error occurs.
152     * @throws NullPointerException
153     *             if the byte array parameter is null
154     * @throws IndexOutOfBoundsException
155     *             if offset, len or buffer size are invalid
156     */
157    @Override
158    public int read(final byte[] array, final int offset, final int len) throws IOException {
159        Objects.requireNonNull(array, "array");
160        if (offset < 0 || len < 0) {
161            throw new IndexOutOfBoundsException();
162        }
163        if (offset > array.length || offset + len > array.length) {
164            throw new IndexOutOfBoundsException();
165        }
166        if (len == 0) {
167            return 0;
168        }
169        int readLen = 0;
170        /*
171         Rationale for while-loop on (readLen == 0):
172         -----
173         Base32.readResults() usually returns > 0 or EOF (-1).  In the
174         rare case where it returns 0, we just keep trying.
175
176         This is essentially an undocumented contract for InputStream
177         implementors that want their code to work properly with
178         java.io.InputStreamReader, since the latter hates it when
179         InputStream.read(byte[]) returns a zero.  Unfortunately our
180         readResults() call must return 0 if a large amount of the data
181         being decoded was non-base32, so this while-loop enables proper
182         interop with InputStreamReader for that scenario.
183         -----
184         This is a fix for CODEC-101
185        */
186        // Attempt to read the request length
187        while (readLen < len) {
188            if (!baseNCodec.hasData(context)) {
189                // Obtain more data.
190                // buf is reused across calls to read to avoid repeated allocations
191                final int c = in.read(buf);
192                if (doEncode) {
193                    baseNCodec.encode(buf, 0, c, context);
194                } else {
195                    baseNCodec.decode(buf, 0, c, context);
196                }
197            }
198            final int read = baseNCodec.readResults(array, offset + readLen, len - readLen, context);
199            if (read < 0) {
200                // Return the amount read or EOF
201                return readLen != 0 ? readLen : -1;
202            }
203            readLen += read;
204        }
205        return readLen;
206    }
207
208    /**
209     * Repositions this stream to the position at the time the mark method was last called on this input stream.
210     * <p>
211     * The {@link #reset} method of {@link BaseNCodecInputStream} does nothing except throw an {@link IOException}.
212     *
213     * @throws IOException if this method is invoked
214     * @since 1.7
215     */
216    @Override
217    public synchronized void reset() throws IOException {
218        throw new IOException("mark/reset not supported");
219    }
220
221    /**
222     * {@inheritDoc}
223     *
224     * @throws IllegalArgumentException if the provided skip length is negative
225     * @since 1.7
226     */
227    @Override
228    public long skip(final long n) throws IOException {
229        if (n < 0) {
230            throw new IllegalArgumentException("Negative skip length: " + n);
231        }
232
233        // skip in chunks of 512 bytes
234        final byte[] b = new byte[512];
235        long todo = n;
236
237        while (todo > 0) {
238            int len = (int) Math.min(b.length, todo);
239            len = this.read(b, 0, len);
240            if (len == EOF) {
241                break;
242            }
243            todo -= len;
244        }
245
246        return n - todo;
247    }
248}