    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.net;
    019
    020import java.nio.ByteBuffer;
    021import java.util.BitSet;
    022
    023import org.apache.commons.codec.BinaryDecoder;
    024import org.apache.commons.codec.BinaryEncoder;
    025import org.apache.commons.codec.DecoderException;
    026import org.apache.commons.codec.EncoderException;
    027
    028/**
    029 * Implements the Percent-Encoding scheme, as described in HTTP 1.1 specification. For extensibility, an array of
    030 * special US-ASCII characters can be specified in order to perform proper URI encoding for the different parts
    031 * of the URI.
    032 * <p>
    033 * This class is immutable. It is also thread-safe besides using BitSet which is not thread-safe, but its public
    034 * interface only call the access
    035 * </p>
    036 *
    037 * @see <a href="https://tools.ietf.org/html/rfc3986#section-2.1">Percent-Encoding</a>
    038 * @since 1.12
    039 */
    040public class PercentCodec implements BinaryEncoder, BinaryDecoder {
    041
    042    /**
    043     * The escape character used by the Percent-Encoding in order to introduce an encoded character.
    044     */
    045
    046    private static final byte ESCAPE_CHAR = '%';
    047
    048    /**
    049     * The bit set used to store the character that should be always encoded
    050     */
    051    private final BitSet alwaysEncodeChars = new BitSet();
    052
    053    /**
    054     * The flag defining if the space character should be encoded as '+'
    055     */
    056    private final boolean plusForSpace;
    057
    058    /**
    059     * The minimum and maximum code of the bytes that is inserted in the bit set, used to prevent look-ups
    060     */
    061    private int alwaysEncodeCharsMin = Integer.MAX_VALUE, alwaysEncodeCharsMax = Integer.MIN_VALUE;
    062
    063    /**
    064     * Constructs a Percent coded that will encode all the non US-ASCII characters using the Percent-Encoding
    065     * while it will not encode all the US-ASCII characters, except for character '%' that is used as escape
    066     * character for Percent-Encoding.
    067     */
    068    public PercentCodec() {
    069        this.plusForSpace = false;
    070        insertAlwaysEncodeChar(ESCAPE_CHAR);
    071    }
    072
    073    /**
    074     * Constructs a Percent codec by specifying the characters that belong to US-ASCII that should
    075     * always be encoded. The rest US-ASCII characters will not be encoded, except for character '%' that
    076     * is used as escape character for Percent-Encoding.
    077     *
    078     * @param alwaysEncodeChars the unsafe characters that should always be encoded
    079     * @param plusForSpace      the flag defining if the space character should be encoded as '+'
    080     */
    081    public PercentCodec(final byte[] alwaysEncodeChars, final boolean plusForSpace) {
    082        this.plusForSpace = plusForSpace;
    083        insertAlwaysEncodeChars(alwaysEncodeChars);
    084    }
    085
    086    /**
    087     * Adds the byte array into a BitSet for faster lookup
    088     *
    089     * @param alwaysEncodeCharsArray
    090     */
    091    private void insertAlwaysEncodeChars(final byte[] alwaysEncodeCharsArray) {
    092        if (alwaysEncodeCharsArray != null) {
    093            for (final byte b : alwaysEncodeCharsArray) {
    094                insertAlwaysEncodeChar(b);
    095            }
    096        }
    097        insertAlwaysEncodeChar(ESCAPE_CHAR);
    098    }
    099
    100    /**
    101     * Inserts a single character into a BitSet and maintains the min and max of the characters of the
    102     * {@code BitSet alwaysEncodeChars} in order to avoid look-ups when a byte is out of this range.
    103     *
    104     * @param b the byte that is candidate for min and max limit
    105     */
    106    private void insertAlwaysEncodeChar(final byte b) {
    107        this.alwaysEncodeChars.set(b);
    108        if (b < alwaysEncodeCharsMin) {
    109            alwaysEncodeCharsMin = b;
    110        }
    111        if (b > alwaysEncodeCharsMax) {
    112            alwaysEncodeCharsMax = b;
    113        }
    114    }
    115
    116    /**
    117     * Percent-Encoding based on RFC 3986. The non US-ASCII characters are encoded, as well as the
    118     * US-ASCII characters that are configured to be always encoded.
    119     */
    120    @Override
    121    public byte[] encode(final byte[] bytes) throws EncoderException {
    122        if (bytes == null) {
    123            return null;
    124        }
    125
    126        final int expectedEncodingBytes = expectedEncodingBytes(bytes);
    127        final boolean willEncode = expectedEncodingBytes != bytes.length;
    128        if (willEncode || (plusForSpace && containsSpace(bytes))) {
    129            return doEncode(bytes, expectedEncodingBytes, willEncode);
    130        }
    131        return bytes;
    132    }
    133
    134    private byte[] doEncode(final byte[] bytes, final int expectedLength, final boolean willEncode) {
    135        final ByteBuffer buffer = ByteBuffer.allocate(expectedLength);
    136        for (final byte b : bytes) {
    137            if (willEncode && canEncode(b)) {
    138                byte bb = b;
    139                if (bb < 0) {
    140                    bb = (byte) (256 + bb);
    141                }
    142                final char hex1 = Utils.hexDigit(bb >> 4);
    143                final char hex2 = Utils.hexDigit(bb);
    144                buffer.put(ESCAPE_CHAR);
    145                buffer.put((byte) hex1);
    146                buffer.put((byte) hex2);
    147            } else if (plusForSpace && b == ' ') {
    148                buffer.put((byte) '+');
    149            } else {
    150                buffer.put(b);
    151            }
    152        }
    153        return buffer.array();
    154    }
    155
    156    private int expectedEncodingBytes(final byte[] bytes) {
    157        int byteCount = 0;
    158        for (final byte b : bytes) {
    159            byteCount += canEncode(b) ? 3: 1;
    160        }
    161        return byteCount;
    162    }
    163
    164    private boolean containsSpace(final byte[] bytes) {
    165        for (final byte b : bytes) {
    166            if (b == ' ') {
    167                return true;
    168            }
    169        }
    170        return false;
    171    }
    172
    173    private boolean canEncode(final byte c) {
    174        return !isAsciiChar(c) || (inAlwaysEncodeCharsRange(c) && alwaysEncodeChars.get(c));
    175    }
    176
    177    private boolean inAlwaysEncodeCharsRange(final byte c) {
    178        return c >= alwaysEncodeCharsMin && c <= alwaysEncodeCharsMax;
    179    }
    180
    181    private boolean isAsciiChar(final byte c) {
    182        return c >= 0;
    183    }
    184
    185    /**
    186     * Decode bytes encoded with Percent-Encoding based on RFC 3986. The reverse process is performed in order to
    187     * decode the encoded characters to Unicode.
    188     */
    189    @Override
    190    public byte[] decode(final byte[] bytes) throws DecoderException {
    191        if (bytes == null) {
    192            return null;
    193        }
    194
    195        final ByteBuffer buffer = ByteBuffer.allocate(expectedDecodingBytes(bytes));
    196        for (int i = 0; i < bytes.length; i++) {
    197            final byte b = bytes[i];
    198            if (b == ESCAPE_CHAR) {
    199                try {
    200                    final int u = Utils.digit16(bytes[++i]);
    201                    final int l = Utils.digit16(bytes[++i]);
    202                    buffer.put((byte) ((u << 4) + l));
    203                } catch (final ArrayIndexOutOfBoundsException e) {
    204                    throw new DecoderException("Invalid percent decoding: ", e);
    205                }
    206            } else if (plusForSpace && b == '+') {
    207                buffer.put((byte) ' ');
    208            } else {
    209                buffer.put(b);
    210            }
    211        }
    212        return buffer.array();
    213    }
    214
    215    private int expectedDecodingBytes(final byte[] bytes) {
    216        int byteCount = 0;
    217        for (int i = 0; i < bytes.length; ) {
    218            final byte b = bytes[i];
    219            i += b == ESCAPE_CHAR ? 3: 1;
    220            byteCount++;
    221        }
    222        return byteCount;
    223    }
    224
    225    /**
    226     * Encodes an object into using the Percent-Encoding. Only byte[] objects are accepted.
    227     *
    228     * @param obj the object to encode
    229     * @return the encoding result byte[] as Object
    230     * @throws EncoderException if the object is not a byte array
    231     */
    232    @Override
    233    public Object encode(final Object obj) throws EncoderException {
    234        if (obj == null) {
    235            return null;
    236        }
    237        if (obj instanceof byte[]) {
    238            return encode((byte[]) obj);
    239        }
    240        throw new EncoderException("Objects of type " + obj.getClass().getName() + " cannot be Percent encoded");
    241    }
    242
    243    /**
    244     * Decodes a byte[] Object, whose bytes are encoded with Percent-Encoding.
    245     *
    246     * @param obj the object to decode
    247     * @return the decoding result byte[] as Object
    248     * @throws DecoderException if the object is not a byte array
    249     */
    250    @Override
    251    public Object decode(final Object obj) throws DecoderException {
    252        if (obj == null) {
    253            return null;
    254        }
    255        if (obj instanceof byte[]) {
    256            return decode((byte[]) obj);
    257        }
    258        throw new DecoderException("Objects of type " + obj.getClass().getName() + " cannot be Percent decoded");
    259    }
    260}