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.logging.log4j.util;
018
019import java.util.Map.Entry;
020
021import static java.lang.Character.toLowerCase;
022
023/**
024 * <em>Consider this class private.</em>
025 */
026public final class StringBuilders {
027    private StringBuilders() {
028    }
029
030    /**
031     * Appends in the following format: double quoted value.
032     *
033     * @param sb a string builder
034     * @param value a value
035     * @return {@code "value"}
036     */
037    public static StringBuilder appendDqValue(final StringBuilder sb, final Object value) {
038        return sb.append(Chars.DQUOTE).append(value).append(Chars.DQUOTE);
039    }
040
041    /**
042     * Appends in the following format: key=double quoted value.
043     *
044     * @param sb a string builder
045     * @param entry a map entry
046     * @return {@code key="value"}
047     */
048    public static StringBuilder appendKeyDqValue(final StringBuilder sb, final Entry<String, String> entry) {
049        return appendKeyDqValue(sb, entry.getKey(), entry.getValue());
050    }
051
052    /**
053     * Appends in the following format: key=double quoted value.
054     *
055     * @param sb a string builder
056     * @param key a key
057     * @param value a value
058     * @return the specified StringBuilder
059     */
060    public static StringBuilder appendKeyDqValue(final StringBuilder sb, final String key, final Object value) {
061        return sb.append(key).append(Chars.EQ).append(Chars.DQUOTE).append(value).append(Chars.DQUOTE);
062    }
063
064    /**
065     * Appends a text representation of the specified object to the specified StringBuilder,
066     * if possible without allocating temporary objects.
067     *
068     * @param stringBuilder the StringBuilder to append the value to
069     * @param obj the object whose text representation to append to the StringBuilder
070     */
071    public static void appendValue(final StringBuilder stringBuilder, final Object obj) {
072        if (!appendSpecificTypes(stringBuilder, obj)) {
073            stringBuilder.append(obj);
074        }
075    }
076
077    public static boolean appendSpecificTypes(final StringBuilder stringBuilder, final Object obj) {
078        if (obj == null || obj instanceof String) {
079            stringBuilder.append((String) obj);
080        } else if (obj instanceof StringBuilderFormattable) {
081            ((StringBuilderFormattable) obj).formatTo(stringBuilder);
082        } else if (obj instanceof CharSequence) {
083            stringBuilder.append((CharSequence) obj);
084        } else if (obj instanceof Integer) { // LOG4J2-1437 unbox auto-boxed primitives to avoid calling toString()
085            stringBuilder.append(((Integer) obj).intValue());
086        } else if (obj instanceof Long) {
087            stringBuilder.append(((Long) obj).longValue());
088        } else if (obj instanceof Double) {
089            stringBuilder.append(((Double) obj).doubleValue());
090        } else if (obj instanceof Boolean) {
091            stringBuilder.append(((Boolean) obj).booleanValue());
092        } else if (obj instanceof Character) {
093            stringBuilder.append(((Character) obj).charValue());
094        } else if (obj instanceof Short) {
095            stringBuilder.append(((Short) obj).shortValue());
096        } else if (obj instanceof Float) {
097            stringBuilder.append(((Float) obj).floatValue());
098        } else if (obj instanceof Byte) {
099            stringBuilder.append(((Byte) obj).byteValue());
100        } else {
101            return false;
102        }
103        return true;
104    }
105
106    /**
107     * Returns true if the specified section of the left CharSequence equals the specified section of the right
108     * CharSequence.
109     *
110     * @param left the left CharSequence
111     * @param leftOffset start index in the left CharSequence
112     * @param leftLength length of the section in the left CharSequence
113     * @param right the right CharSequence to compare a section of
114     * @param rightOffset start index in the right CharSequence
115     * @param rightLength length of the section in the right CharSequence
116     * @return true if equal, false otherwise
117     */
118    public static boolean equals(final CharSequence left, final int leftOffset, final int leftLength,
119                                    final CharSequence right, final int rightOffset, final int rightLength) {
120        if (leftLength == rightLength) {
121            for (int i = 0; i < rightLength; i++) {
122                if (left.charAt(i + leftOffset) != right.charAt(i + rightOffset)) {
123                    return false;
124                }
125            }
126            return true;
127        }
128        return false;
129    }
130
131    /**
132     * Returns true if the specified section of the left CharSequence equals, ignoring case, the specified section of
133     * the right CharSequence.
134     *
135     * @param left the left CharSequence
136     * @param leftOffset start index in the left CharSequence
137     * @param leftLength length of the section in the left CharSequence
138     * @param right the right CharSequence to compare a section of
139     * @param rightOffset start index in the right CharSequence
140     * @param rightLength length of the section in the right CharSequence
141     * @return true if equal ignoring case, false otherwise
142     */
143    public static boolean equalsIgnoreCase(final CharSequence left, final int leftOffset, final int leftLength,
144                                              final CharSequence right, final int rightOffset, final int rightLength) {
145        if (leftLength == rightLength) {
146            for (int i = 0; i < rightLength; i++) {
147                if (toLowerCase(left.charAt(i + leftOffset)) != toLowerCase(right.charAt(i + rightOffset))) {
148                    return false;
149                }
150            }
151            return true;
152        }
153        return false;
154    }
155
156    /**
157     * Ensures that the char[] array of the specified StringBuilder does not exceed the specified number of characters.
158     * This method is useful to ensure that excessively long char[] arrays are not kept in memory forever.
159     *
160     * @param stringBuilder the StringBuilder to check
161     * @param maxSize the maximum number of characters the StringBuilder is allowed to have
162     * @since 2.9
163     */
164    public static void trimToMaxSize(final StringBuilder stringBuilder, final int maxSize) {
165        if (stringBuilder != null && stringBuilder.capacity() > maxSize) {
166            stringBuilder.setLength(maxSize);
167            stringBuilder.trimToSize();
168        }
169    }
170
171    public static void escapeJson(final StringBuilder toAppendTo, final int start) {
172        int escapeCount = 0;
173        for (int i = start; i < toAppendTo.length(); i++) {
174            final char c = toAppendTo.charAt(i);
175            switch (c) {
176                case '\b':
177                case '\t':
178                case '\f':
179                case '\n':
180                case '\r':
181                case '"':
182                case '\\':
183                    escapeCount++;
184                    break;
185                default:
186                    if (Character.isISOControl(c)) {
187                        escapeCount += 5;
188                    }
189            }
190        }
191
192        int lastChar = toAppendTo.length() - 1;
193        toAppendTo.setLength(toAppendTo.length() + escapeCount);
194        int lastPos = toAppendTo.length() - 1;
195
196        for (int i = lastChar; lastPos > i; i--) {
197            final char c = toAppendTo.charAt(i);
198            switch (c) {
199                case '\b':
200                    lastPos = escapeAndDecrement(toAppendTo, lastPos, 'b');
201                    break;
202
203                case '\t':
204                    lastPos = escapeAndDecrement(toAppendTo, lastPos, 't');
205                    break;
206
207                case '\f':
208                    lastPos = escapeAndDecrement(toAppendTo, lastPos, 'f');
209                    break;
210
211                case '\n':
212                    lastPos = escapeAndDecrement(toAppendTo, lastPos, 'n');
213                    break;
214
215                case '\r':
216                    lastPos = escapeAndDecrement(toAppendTo, lastPos, 'r');
217                    break;
218
219                case '"':
220                case '\\':
221                    lastPos = escapeAndDecrement(toAppendTo, lastPos, c);
222                    break;
223
224                default:
225                    if (Character.isISOControl(c)) {
226                        // all iso control characters are in U+00xx, JSON output format is "\\u00XX"
227                        toAppendTo.setCharAt(lastPos--, Chars.getUpperCaseHex(c & 0xF));
228                        toAppendTo.setCharAt(lastPos--, Chars.getUpperCaseHex((c & 0xF0) >> 4));
229                        toAppendTo.setCharAt(lastPos--, '0');
230                        toAppendTo.setCharAt(lastPos--, '0');
231                        toAppendTo.setCharAt(lastPos--, 'u');
232                        toAppendTo.setCharAt(lastPos--, '\\');
233                    } else {
234                        toAppendTo.setCharAt(lastPos, c);
235                        lastPos--;
236                    }
237            }
238        }
239    }
240
241    private static int escapeAndDecrement(StringBuilder toAppendTo, int lastPos, char c) {
242        toAppendTo.setCharAt(lastPos--, c);
243        toAppendTo.setCharAt(lastPos--, '\\');
244        return lastPos;
245    }
246
247    public static void escapeXml(final StringBuilder toAppendTo, final int start) {
248        int escapeCount = 0;
249        for (int i = start; i < toAppendTo.length(); i++) {
250            final char c = toAppendTo.charAt(i);
251            switch (c) {
252                case '&':
253                    escapeCount += 4;
254                    break;
255                case '<':
256                case '>':
257                    escapeCount += 3;
258                    break;
259                case '"':
260                case '\'':
261                    escapeCount += 5;
262            }
263        }
264
265        int lastChar = toAppendTo.length() - 1;
266        toAppendTo.setLength(toAppendTo.length() + escapeCount);
267        int lastPos = toAppendTo.length() - 1;
268
269        for (int i = lastChar; lastPos > i; i--) {
270            final char c = toAppendTo.charAt(i);
271            switch (c) {
272                case '&':
273                    toAppendTo.setCharAt(lastPos--, ';');
274                    toAppendTo.setCharAt(lastPos--, 'p');
275                    toAppendTo.setCharAt(lastPos--, 'm');
276                    toAppendTo.setCharAt(lastPos--, 'a');
277                    toAppendTo.setCharAt(lastPos--, '&');
278                    break;
279                case '<':
280                    toAppendTo.setCharAt(lastPos--, ';');
281                    toAppendTo.setCharAt(lastPos--, 't');
282                    toAppendTo.setCharAt(lastPos--, 'l');
283                    toAppendTo.setCharAt(lastPos--, '&');
284                    break;
285                case '>':
286                    toAppendTo.setCharAt(lastPos--, ';');
287                    toAppendTo.setCharAt(lastPos--, 't');
288                    toAppendTo.setCharAt(lastPos--, 'g');
289                    toAppendTo.setCharAt(lastPos--, '&');
290                    break;
291                case '"':
292                    toAppendTo.setCharAt(lastPos--, ';');
293                    toAppendTo.setCharAt(lastPos--, 't');
294                    toAppendTo.setCharAt(lastPos--, 'o');
295                    toAppendTo.setCharAt(lastPos--, 'u');
296                    toAppendTo.setCharAt(lastPos--, 'q');
297                    toAppendTo.setCharAt(lastPos--, '&');
298                    break;
299                case '\'':
300                    toAppendTo.setCharAt(lastPos--, ';');
301                    toAppendTo.setCharAt(lastPos--, 's');
302                    toAppendTo.setCharAt(lastPos--, 'o');
303                    toAppendTo.setCharAt(lastPos--, 'p');
304                    toAppendTo.setCharAt(lastPos--, 'a');
305                    toAppendTo.setCharAt(lastPos--, '&');
306                    break;
307                default:
308                    toAppendTo.setCharAt(lastPos--, c);
309            }
310        }
311    }
312}