    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.commons.configuration2;
    018
    019import java.io.BufferedReader;
    020import java.io.IOException;
    021import java.io.PrintWriter;
    022import java.io.Reader;
    023import java.io.Writer;
    024import java.util.LinkedHashMap;
    025import java.util.LinkedHashSet;
    026import java.util.List;
    027import java.util.Map;
    028import java.util.Set;
    029import java.util.stream.Collectors;
    030
    031import org.apache.commons.configuration2.convert.ListDelimiterHandler;
    032import org.apache.commons.configuration2.ex.ConfigurationException;
    033import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    034import org.apache.commons.configuration2.tree.ImmutableNode;
    035import org.apache.commons.configuration2.tree.InMemoryNodeModel;
    036import org.apache.commons.configuration2.tree.InMemoryNodeModelSupport;
    037import org.apache.commons.configuration2.tree.NodeHandler;
    038import org.apache.commons.configuration2.tree.NodeHandlerDecorator;
    039import org.apache.commons.configuration2.tree.NodeSelector;
    040import org.apache.commons.configuration2.tree.TrackedNodeModel;
    041
    042/**
    043 * <p>
    044 * A specialized hierarchical configuration implementation for parsing ini files.
    045 * </p>
    046 * <p>
    047 * An initialization or ini file is a configuration file typically found on Microsoft's Windows operating system and
    048 * contains data for Windows based applications.
    049 * </p>
    050 * <p>
    051 * Although popularized by Windows, ini files can be used on any system or platform due to the fact that they are merely
    052 * text files that can easily be parsed and modified by both humans and computers.
    053 * </p>
    054 * <p>
    055 * A typical ini file could look something like:
    056 * </p>
    057 *
    058 * <pre>
    059 * [section1]
    060 * ; this is a comment!
    061 * var1 = foo
    062 * var2 = bar
    063 *
    064 * [section2]
    065 * var1 = doo
    066 * </pre>
    067 * <p>
    068 * The format of ini files is fairly straight forward and is composed of three components:
    069 * </p>
    070 * <ul>
    071 * <li><b>Sections:</b> Ini files are split into sections, each section starting with a section declaration. A section
    072 * declaration starts with a '[' and ends with a ']'. Sections occur on one line only.</li>
    073 * <li><b>Parameters:</b> Items in a section are known as parameters. Parameters have a typical {@code key = value}
    074 * format.</li>
    075 * <li><b>Comments:</b> Lines starting with a ';' are assumed to be comments.</li>
    076 * </ul>
    077 * <p>
    078 * There are various implementations of the ini file format by various vendors which has caused a number of differences
    079 * to appear. As far as possible this configuration tries to be lenient and support most of the differences.
    080 * </p>
    081 * <p>
    082 * Some of the differences supported are as follows:
    083 * </p>
    084 * <ul>
    085 * <li><b>Comments:</b> The '#' character is also accepted as a comment signifier.</li>
    086 * <li><b>Key value separator:</b> The ':' character is also accepted in place of '=' to separate keys and values in
    087 * parameters, for example {@code var1 : foo}.</li>
    088 * <li><b>Duplicate sections:</b> Typically duplicate sections are not allowed, this configuration does however support
    089 * this feature. In the event of a duplicate section, the two section's values are merged so that there is only a single
    090 * section. <strong>Note</strong>: This also affects the internal data of the configuration. If it is saved, only a
    091 * single section is written!</li>
    092 * <li><b>Duplicate parameters:</b> Typically duplicate parameters are only allowed if they are in two different
    093 * sections, thus they are local to sections; this configuration simply merges duplicates; if a section has a duplicate
    094 * parameter the values are then added to the key as a list.</li>
    095 * </ul>
    096 * <p>
    097 * Global parameters are also allowed; any parameters declared before a section is declared are added to a global
    098 * section. It is important to note that this global section does not have a name.
    099 * </p>
    100 * <p>
    101 * In all instances, a parameter's key is prepended with its section name and a '.' (period). Thus a parameter named
    102 * "var1" in "section1" will have the key {@code section1.var1} in this configuration. (This is the default behavior.
    103 * Because this is a hierarchical configuration you can change this by setting a different
    104 * {@link org.apache.commons.configuration2.tree.ExpressionEngine}.)
    105 * </p>
    106 * <p>
    107 * <strong>Implementation Details:</strong> Consider the following ini file:
    108 * </p>
    109 * <pre>
    110 *  default = ok
    111 *
    112 *  [section1]
    113 *  var1 = foo
    114 *  var2 = doodle
    115 *
    116 *  [section2]
    117 *  ; a comment
    118 *  var1 = baz
    119 *  var2 = shoodle
    120 *  bad =
    121 *  = worse
    122 *
    123 *  [section3]
    124 *  # another comment
    125 *  var1 : foo
    126 *  var2 : bar
    127 *  var5 : test1
    128 *
    129 *  [section3]
    130 *  var3 = foo
    131 *  var4 = bar
    132 *  var5 = test2
    133 *
    134 *  [sectionSeparators]
    135 *  passwd : abc=def
    136 *  a:b = "value"
    137 *
    138 *  []
    139 *  var = emptySection
    140 * </pre>
    141 * <p>
    142 * This ini file will be parsed without error. Note:
    143 * </p>
    144 * <ul>
    145 * <li>The parameter named "default" is added to the global section, it's value is accessed simply using
    146 * {@code getProperty("default")}.</li>
    147 * <li>Section 1's parameters can be accessed using {@code getProperty("section1.var1")}.</li>
    148 * <li>The parameter named "bad" simply adds the parameter with an empty value.</li>
    149 * <li>The empty key with value "= worse" is added using a key consisting of a single space character. This key is still
    150 * added to section 2 and the value can be accessed using {@code getProperty("section2. ")}, notice the period '.' and
    151 * the space following the section name.</li>
    152 * <li>Section three uses both '=' and ':' to separate keys and values.</li>
    153 * <li>Section 3 has a duplicate key named "var5". The value for this key is [test1, test2], and is represented as a
    154 * List.</li>
    155 * <li>The section called <em>sectionSeparators</em> demonstrates how the configuration deals with multiple occurrences
    156 * of separator characters. Per default the first separator character in a line is detected and used to split the key
    157 * from the value. Therefore the first property definition in this section has the key {@code passwd} and the value
    158 * {@code abc=def}. This default behavior can be changed by using quotes. If there is a separator character before the
    159 * first quote character (ignoring whitespace), this character is used as separator. Thus the second property definition
    160 * in the section has the key {@code a:b} and the value {@code value}.</li>
    161 * <li>The empty section is added using a key consisting of a single space character. The parameters can be accessed
    162 * using {@code getProperty(" .var")}</li>
    163 * </ul>
    164 * <p>
    165 * Internally, this configuration maps the content of the represented ini file to its node structure in the following
    166 * way:
    167 * </p>
    168 * <ul>
    169 * <li>Sections are represented by direct child nodes of the root node.</li>
    170 * <li>For the content of a section, corresponding nodes are created as children of the section node.</li>
    171 * </ul>
    172 * <p>
    173 * This explains how the keys for the properties can be constructed. You can also use other methods of
    174 * {@link HierarchicalConfiguration} for querying or manipulating the hierarchy of configuration nodes, for instance the
    175 * {@code configurationAt()} method for obtaining the data of a specific section. However, be careful that the storage
    176 * scheme described above is not violated (e.g. by adding multiple levels of nodes or inserting duplicate section
    177 * nodes). Otherwise, the special methods for ini configurations may not work correctly!
    178 * </p>
    179 * <p>
    180 * The set of sections in this configuration can be retrieved using the {@code getSections()} method. For obtaining a
    181 * {@code SubnodeConfiguration} with the content of a specific section the {@code getSection()} method can be used.
    182 * </p>
    183 * <p>
    184 * Like other {@code Configuration} implementations, this class uses a {@code Synchronizer} object to control concurrent
    185 * access. By choosing a suitable implementation of the {@code Synchronizer} interface, an instance can be made
    186 * thread-safe or not. Note that access to most of the properties typically set through a builder is not protected by
    187 * the {@code Synchronizer}. The intended usage is that these properties are set once at construction time through the
    188 * builder and after that remain constant. If you wish to change such properties during life time of an instance, you
    189 * have to use the {@code lock()} and {@code unlock()} methods manually to ensure that other threads see your changes.
    190 * </p>
    191 * <p>
    192 * As this class extends {@link AbstractConfiguration}, all basic features like variable interpolation, list handling,
    193 * or data type conversions are available as well. This is described in the chapter
    194 * <a href="https://commons.apache.org/proper/commons-configuration/userguide/howto_basicfeatures.html"> Basic features
    195 * and AbstractConfiguration</a> of the user's guide.
    196 * </p>
    197 * <p>
    198 * Note that this configuration does not support properties with null values. Such properties are considered to be
    199 * section nodes.
    200 * </p>
    201 *
    202 * @since 1.6
    203 */
    204public class INIConfiguration extends BaseHierarchicalConfiguration implements FileBasedConfiguration {
    205
    206    /**
    207     * Builds instances of INIConfiguration.
    208     *
    209     * @since 2.9.0
    210     */
    211    public static class Builder {
    212
    213        /**
    214         * The flag for decision, whether inline comments on the section line are allowed.
    215         */
    216        private boolean sectionInLineCommentsAllowed;
    217
    218        public INIConfiguration build() {
    219            return new INIConfiguration(sectionInLineCommentsAllowed);
    220        }
    221
    222        public Builder setSectionInLineCommentsAllowed(final boolean sectionInLineCommentsAllowed) {
    223            this.sectionInLineCommentsAllowed = sectionInLineCommentsAllowed;
    224            return this;
    225        }
    226
    227    }
    228
    229    /**
    230     * A specialized node model implementation for the sub configuration representing the global section of the INI file.
    231     * This is a regular {@code TrackedNodeModel} with one exception: The {@code NodeHandler} used by this model applies a
    232     * filter on the children of the root node so that only nodes are visible that are no sub sections.
    233     */
    234    private static final class GlobalSectionNodeModel extends TrackedNodeModel {
    235        /**
    236         * Creates a new instance of {@code GlobalSectionNodeModel} and initializes it with the given underlying model.
    237         *
    238         * @param modelSupport the underlying {@code InMemoryNodeModel}
    239         * @param selector the {@code NodeSelector}
    240         */
    241        public GlobalSectionNodeModel(final InMemoryNodeModelSupport modelSupport, final NodeSelector selector) {
    242            super(modelSupport, selector, true);
    243        }
    244
    245        @Override
    246        public NodeHandler<ImmutableNode> getNodeHandler() {
    247            return new NodeHandlerDecorator<ImmutableNode>() {
    248                /**
    249                 * Filters the child nodes of the global section. This method checks whether the passed in node is the root node of the
    250                 * configuration. If so, from the list of children all nodes are filtered which are section nodes.
    251                 *
    252                 * @param node the node in question
    253                 * @param children the children of this node
    254                 * @return a list with the filtered children
    255                 */
    256                private List<ImmutableNode> filterChildrenOfGlobalSection(final ImmutableNode node, final List<ImmutableNode> children) {
    257                    final List<ImmutableNode> filteredList;
    258                    if (node == getRootNode()) {
    259                        filteredList = children.stream().filter(child -> !isSectionNode(child)).collect(Collectors.toList());
    260                    } else {
    261                        filteredList = children;
    262                    }
    263
    264                    return filteredList;
    265                }
    266
    267                @Override
    268                public ImmutableNode getChild(final ImmutableNode node, final int index) {
    269                    final List<ImmutableNode> children = super.getChildren(node);
    270                    return filterChildrenOfGlobalSection(node, children).get(index);
    271                }
    272
    273                @Override
    274                public List<ImmutableNode> getChildren(final ImmutableNode node) {
    275                    final List<ImmutableNode> children = super.getChildren(node);
    276                    return filterChildrenOfGlobalSection(node, children);
    277                }
    278
    279                @Override
    280                public List<ImmutableNode> getChildren(final ImmutableNode node, final String name) {
    281                    final List<ImmutableNode> children = super.getChildren(node, name);
    282                    return filterChildrenOfGlobalSection(node, children);
    283                }
    284
    285                @Override
    286                public int getChildrenCount(final ImmutableNode node, final String name) {
    287                    final List<ImmutableNode> children = name != null ? super.getChildren(node, name) : super.getChildren(node);
    288                    return filterChildrenOfGlobalSection(node, children).size();
    289                }
    290
    291                @Override
    292                protected NodeHandler<ImmutableNode> getDecoratedNodeHandler() {
    293                    return GlobalSectionNodeModel.super.getNodeHandler();
    294                }
    295
    296                @Override
    297                public int indexOfChild(final ImmutableNode parent, final ImmutableNode child) {
    298                    final List<ImmutableNode> children = super.getChildren(parent);
    299                    return filterChildrenOfGlobalSection(parent, children).indexOf(child);
    300                }
    301            };
    302        }
    303    }
    304
    305    /**
    306     * The empty key.
    307     */
    308    private static final String EMPTY_KEY = " ";
    309
    310    /**
    311     * The default characters that signal the start of a comment line.
    312     */
    313    protected static final String COMMENT_CHARS = "#;";
    314
    315    /**
    316     * The default characters used to separate keys from values.
    317     */
    318    protected static final String SEPARATOR_CHARS = "=:";
    319
    320    /**
    321     * Constant for the line separator.
    322     */
    323    private static final String LINE_SEPARATOR = System.lineSeparator();
    324
    325    /**
    326     * The characters used for quoting values.
    327     */
    328    private static final String QUOTE_CHARACTERS = "\"'";
    329
    330    /**
    331     * The line continuation character.
    332     */
    333    private static final String LINE_CONT = "\\";
    334
    335    /**
    336     * Creates a new builder.
    337     *
    338     * @return a new builder.
    339     * @since 2.9.0
    340     */
    341    public static Builder builder() {
    342        return new Builder();
    343    }
    344
    345    /**
    346     * Creates a new root node from the builders constructed while reading the configuration file.
    347     *
    348     * @param rootBuilder the builder for the top-level section
    349     * @param sectionBuilders a map storing the section builders
    350     * @return the root node of the newly created hierarchy
    351     */
    352    private static ImmutableNode createNewRootNode(final ImmutableNode.Builder rootBuilder, final Map<String, ImmutableNode.Builder> sectionBuilders) {
    353        sectionBuilders.forEach((k, v) -> rootBuilder.addChild(v.name(k).create()));
    354        return rootBuilder.create();
    355    }
    356
    357    /**
    358     * Checks for the occurrence of the specified separators in the given line. The index of the first separator is
    359     * returned.
    360     *
    361     * @param line the line to be investigated
    362     * @param separators a string with the separator characters to look for
    363     * @return the lowest index of a separator character or -1 if no separator is found
    364     */
    365    private static int findFirstOccurrence(final String line, final String separators) {
    366        int index = -1;
    367
    368        for (int i = 0; i < separators.length(); i++) {
    369            final char sep = separators.charAt(i);
    370            final int pos = line.indexOf(sep);
    371            if (pos >= 0 && (index < 0 || pos < index)) {
    372                index = pos;
    373            }
    374        }
    375
    376        return index;
    377    }
    378
    379    /**
    380     * Searches for a separator character directly before a quoting character. If the first non-whitespace character before
    381     * a quote character is a separator, it is considered the "real" separator in this line - even if there are other
    382     * separators before.
    383     *
    384     * @param line the line to be investigated
    385     * @param quoteIndex the index of the quote character
    386     * @return the index of the separator before the quote or &lt; 0 if there is none
    387     */
    388    private static int findSeparatorBeforeQuote(final String line, final int quoteIndex) {
    389        int index = quoteIndex - 1;
    390        while (index >= 0 && Character.isWhitespace(line.charAt(index))) {
    391            index--;
    392        }
    393
    394        if (index >= 0 && SEPARATOR_CHARS.indexOf(line.charAt(index)) < 0) {
    395            index = -1;
    396        }
    397
    398        return index;
    399    }
    400
    401    /**
    402     * Determine if the given line contains a section - inline comments are allowed.
    403     *
    404     * @param line The line to check.
    405     * @return true if the line contains a section
    406     */
    407    private static boolean isNonStrictSection(final String line) {
    408        return line.startsWith("[") && line.contains("]");
    409    }
    410
    411    /**
    412     * Checks whether the specified configuration node represents a section.
    413     *
    414     * @param node the node in question
    415     * @return a flag whether this node represents a section
    416     */
    417    private static boolean isSectionNode(final ImmutableNode node) {
    418        return node.getValue() == null;
    419    }
    420
    421    /**
    422     * Determine if the entire given line is a section - inline comments are not allowed.
    423     *
    424     * @param line The line to check.
    425     * @return true if the entire line is a section
    426     */
    427    private static boolean isStrictSection(final String line) {
    428        return line.startsWith("[") && line.endsWith("]");
    429    }
    430
    431    /**
    432     * Tests whether the specified string contains a line continuation marker.
    433     *
    434     * @param line the string to check
    435     * @return a flag whether this line continues
    436     */
    437    private static boolean lineContinues(final String line) {
    438        final String s = line.trim();
    439        return s.equals(LINE_CONT) || s.length() > 2 && s.endsWith(LINE_CONT) && Character.isWhitespace(s.charAt(s.length() - 2));
    440    }
    441
    442    /**
    443     * The separator used when writing an INI file.
    444     */
    445    private String separatorUsedInOutput = " = ";
    446
    447    /**
    448     * The separator used when reading an INI file.
    449     */
    450    private String separatorUsedInInput = SEPARATOR_CHARS;
    451
    452    /**
    453     * The characters used to separate keys from values when reading an INI file.
    454     */
    455    private String commentCharsUsedInInput = COMMENT_CHARS;
    456
    457    /**
    458     * The flag for decision, whether inline comments on the section line are allowed.
    459     */
    460    private boolean sectionInLineCommentsAllowed;
    461
    462    /**
    463     * Create a new empty INI Configuration.
    464     */
    465    public INIConfiguration() {
    466    }
    467
    468    /**
    469     * Create a new empty INI Configuration with option to allow inline comments on the section line.
    470     *
    471     * @param sectionInLineCommentsAllowed when true inline comments on the section line are allowed
    472     */
    473    private INIConfiguration(final boolean sectionInLineCommentsAllowed) {
    474        this.sectionInLineCommentsAllowed = sectionInLineCommentsAllowed;
    475    }
    476
    477    /**
    478     * Creates a new instance of {@code INIConfiguration} with the content of the specified
    479     * {@code HierarchicalConfiguration}.
    480     *
    481     * @param c the configuration to be copied
    482     * @since 2.0
    483     */
    484    public INIConfiguration(final HierarchicalConfiguration<ImmutableNode> c) {
    485        super(c);
    486    }
    487
    488    /**
    489     * Reads the content of an INI file from the passed in reader and creates a structure of builders for constructing the
    490     * {@code ImmutableNode} objects representing the data.
    491     *
    492     * @param in the reader
    493     * @param rootBuilder the builder for the top-level section
    494     * @param sectionBuilders a map storing the section builders
    495     * @throws IOException if an I/O error occurs.
    496     */
    497    private void createNodeBuilders(final BufferedReader in, final ImmutableNode.Builder rootBuilder, final Map<String, ImmutableNode.Builder> sectionBuilders)
    498        throws IOException {
    499        ImmutableNode.Builder sectionBuilder = rootBuilder;
    500        String line = in.readLine();
    501        while (line != null) {
    502            line = line.trim();
    503            if (!isCommentLine(line)) {
    504                if (isSectionLine(line)) {
    505                    final int length = sectionInLineCommentsAllowed ? line.indexOf("]") : line.length() - 1;
    506                    String section = line.substring(1, length);
    507                    if (section.isEmpty()) {
    508                        // use space for sections with no key
    509                        section = EMPTY_KEY;
    510                    }
    511                    sectionBuilder = sectionBuilders.computeIfAbsent(section, k -> new ImmutableNode.Builder());
    512                } else {
    513                    String key;
    514                    String value = "";
    515                    final int index = findSeparator(line);
    516                    if (index >= 0) {
    517                        key = line.substring(0, index);
    518                        value = parseValue(line.substring(index + 1), in);
    519                    } else {
    520                        key = line;
    521                    }
    522                    key = key.trim();
    523                    if (key.isEmpty()) {
    524                        // use space for properties with no key
    525                        key = EMPTY_KEY;
    526                    }
    527                    createValueNodes(sectionBuilder, key, value);
    528                }
    529            }
    530
    531            line = in.readLine();
    532        }
    533    }
    534
    535    /**
    536     * Creates the node(s) for the given key value-pair. If delimiter parsing is enabled, the value string is split if
    537     * possible, and for each single value a node is created. Otherwise only a single node is added to the section.
    538     *
    539     * @param sectionBuilder the section builder for adding new nodes
    540     * @param key the key
    541     * @param value the value string
    542     */
    543    private void createValueNodes(final ImmutableNode.Builder sectionBuilder, final String key, final String value) {
    544        getListDelimiterHandler().split(value, false).forEach(v -> sectionBuilder.addChild(new ImmutableNode.Builder().name(key).value(v).create()));
    545    }
    546
    547    /**
    548     * Escapes comment characters in the given value.
    549     *
    550     * @param value the value to be escaped
    551     * @return the value with comment characters escaped
    552     */
    553    private String escapeComments(final String value) {
    554        final String commentChars = getCommentLeadingCharsUsedInInput();
    555        boolean quoted = false;
    556
    557        for (int i = 0; i < commentChars.length(); i++) {
    558            final char c = commentChars.charAt(i);
    559            if (value.indexOf(c) != -1) {
    560                quoted = true;
    561                break;
    562            }
    563        }
    564
    565        if (quoted) {
    566            return '"' + value.replace("\"", "\\\"") + '"';
    567        }
    568        return value;
    569    }
    570
    571    /**
    572     * Escapes the given property value before it is written. This method add quotes around the specified value if it
    573     * contains a comment character and handles list delimiter characters.
    574     *
    575     * @param value the string to be escaped
    576     */
    577    private String escapeValue(final String value) {
    578        return String.valueOf(getListDelimiterHandler().escape(escapeComments(value), ListDelimiterHandler.NOOP_TRANSFORMER));
    579    }
    580
    581    /**
    582     * Tries to find the index of the separator character in the given string. This method checks for the presence of
    583     * separator characters in the given string. If multiple characters are found, the first one is assumed to be the
    584     * correct separator. If there are quoting characters, they are taken into account, too.
    585     *
    586     * @param line the line to be checked
    587     * @return the index of the separator character or -1 if none is found
    588     */
    589    private int findSeparator(final String line) {
    590        int index = findSeparatorBeforeQuote(line, findFirstOccurrence(line, QUOTE_CHARACTERS));
    591        if (index < 0) {
    592            index = findFirstOccurrence(line, getSeparatorUsedInInput());
    593        }
    594        return index;
    595    }
    596
    597    /**
    598     * Gets comment leading separator used in INI reading. see {@code setCommentLeadingCharsUsedInInput} for further
    599     * explanation
    600     *
    601     * @return the current separator for reading the INI input
    602     * @since 2.5
    603     */
    604    public String getCommentLeadingCharsUsedInInput() {
    605        beginRead(false);
    606        try {
    607            return commentCharsUsedInInput;
    608        } finally {
    609            endRead();
    610        }
    611    }
    612
    613    /**
    614     * Creates a sub configuration for the global section of the represented INI configuration.
    615     *
    616     * @return the sub configuration for the global section
    617     */
    618    private SubnodeConfiguration getGlobalSection() {
    619        final InMemoryNodeModel parentModel = getSubConfigurationParentModel();
    620        final NodeSelector selector = new NodeSelector(null); // selects parent
    621        parentModel.trackNode(selector, this);
    622        final GlobalSectionNodeModel model = new GlobalSectionNodeModel(this, selector);
    623        final SubnodeConfiguration sub = new SubnodeConfiguration(this, model);
    624        initSubConfigurationForThisParent(sub);
    625        return sub;
    626    }
    627
    628    /**
    629     * Gets a configuration with the content of the specified section. This provides an easy way of working with a single
    630     * section only. The way this configuration is structured internally, this method is very similar to calling
    631     * {@link HierarchicalConfiguration#configurationAt(String)} with the name of the section in question. There are the
    632     * following differences however:
    633     * <ul>
    634     * <li>This method never throws an exception. If the section does not exist, it is created now. The configuration
    635     * returned in this case is empty.</li>
    636     * <li>If section is contained multiple times in the configuration, the configuration returned by this method is
    637     * initialized with the first occurrence of the section. (This can only happen if {@code addProperty()} has been used in
    638     * a way that does not conform to the storage scheme used by {@code INIConfiguration}. If used correctly, there will not
    639     * be duplicate sections.)</li>
    640     * <li>There is special support for the global section: Passing in <b>null</b> as section name returns a configuration
    641     * with the content of the global section (which may also be empty).</li>
    642     * </ul>
    643     *
    644     * @param name the name of the section in question; <b>null</b> represents the global section
    645     * @return a configuration containing only the properties of the specified section
    646     */
    647    public SubnodeConfiguration getSection(final String name) {
    648        if (name == null) {
    649            return getGlobalSection();
    650        }
    651        try {
    652            return (SubnodeConfiguration) configurationAt(name, true);
    653        } catch (final ConfigurationRuntimeException iex) {
    654            // the passed in key does not map to exactly one node
    655            // obtain the node for the section, create it on demand
    656            final InMemoryNodeModel parentModel = getSubConfigurationParentModel();
    657            final NodeSelector selector = parentModel.trackChildNodeWithCreation(null, name, this);
    658            return createSubConfigurationForTrackedNode(selector, this);
    659        }
    660    }
    661
    662    /**
    663     * Gets a set containing the sections in this ini configuration. Note that changes to this set do not affect the
    664     * configuration.
    665     *
    666     * @return a set containing the sections.
    667     */
    668    public Set<String> getSections() {
    669        final Set<String> sections = new LinkedHashSet<>();
    670        boolean globalSection = false;
    671        boolean inSection = false;
    672
    673        beginRead(false);
    674        try {
    675            for (final ImmutableNode node : getModel().getNodeHandler().getRootNode().getChildren()) {
    676                if (isSectionNode(node)) {
    677                    inSection = true;
    678                    sections.add(node.getNodeName());
    679                } else if (!inSection && !globalSection) {
    680                    globalSection = true;
    681                    sections.add(null);
    682                }
    683            }
    684        } finally {
    685            endRead();
    686        }
    687
    688        return sections;
    689    }
    690
    691    /**
    692     * Gets separator used in INI reading. see {@code setSeparatorUsedInInput} for further explanation
    693     *
    694     * @return the current separator for reading the INI input
    695     * @since 2.5
    696     */
    697    public String getSeparatorUsedInInput() {
    698        beginRead(false);
    699        try {
    700            return separatorUsedInInput;
    701        } finally {
    702            endRead();
    703        }
    704    }
    705
    706    /**
    707     * Gets separator used in INI output. see {@code setSeparatorUsedInOutput} for further explanation
    708     *
    709     * @return the current separator for writing the INI output
    710     * @since 2.2
    711     */
    712    public String getSeparatorUsedInOutput() {
    713        beginRead(false);
    714        try {
    715            return separatorUsedInOutput;
    716        } finally {
    717            endRead();
    718        }
    719    }
    720
    721    /**
    722     * Tests whether the specified character is a comment character.
    723     *
    724     * @param c the character
    725     * @return a flag whether this character starts a comment
    726     */
    727    private boolean isCommentChar(final char c) {
    728        return getCommentLeadingCharsUsedInInput().indexOf(c) >= 0;
    729    }
    730
    731    /**
    732     * Determine if the given line is a comment line.
    733     *
    734     * @param line The line to check.
    735     * @return true if the line is empty or starts with one of the comment characters
    736     */
    737    protected boolean isCommentLine(final String line) {
    738        if (line == null) {
    739            return false;
    740        }
    741        // blank lines are also treated as comment lines
    742        return line.isEmpty() || getCommentLeadingCharsUsedInInput().indexOf(line.charAt(0)) >= 0;
    743    }
    744
    745    /**
    746     * Determine if the given line is a section.
    747     *
    748     * @param line The line to check.
    749     * @return true if the line contains a section
    750     */
    751    protected boolean isSectionLine(final String line) {
    752        if (line == null) {
    753            return false;
    754        }
    755        return sectionInLineCommentsAllowed ? isNonStrictSection(line) : isStrictSection(line);
    756    }
    757
    758    /**
    759     * Tests whether the specified string contains a line continuation marker after the specified position. This method
    760     * parses the string to remove a comment that might be present. Then it checks whether a line continuation marker can be
    761     * found at the end.
    762     *
    763     * @param line the line to check
    764     * @param pos the start position
    765     * @return a flag whether this line continues
    766     */
    767    private boolean lineContinues(final String line, final int pos) {
    768        final String s;
    769
    770        if (pos >= line.length()) {
    771            s = line;
    772        } else {
    773            int end = pos;
    774            while (end < line.length() && !isCommentChar(line.charAt(end))) {
    775                end++;
    776            }
    777            s = line.substring(pos, end);
    778        }
    779
    780        return lineContinues(s);
    781    }
    782
    783    /**
    784     * Parse the value to remove the quotes and ignoring the comment. Example:
    785     *
    786     * <pre>
    787     * &quot;value&quot; ; comment -&gt; value
    788     * </pre>
    789     *
    790     * <pre>
    791     * 'value' ; comment -&gt; value
    792     * </pre>
    793     *
    794     * Note that a comment character is only recognized if there is at least one whitespace character before it. So it can
    795     * appear in the property value, e.g.:
    796     *
    797     * <pre>
    798     * C:\\Windows;C:\\Windows\\system32
    799     * </pre>
    800     *
    801     * @param val the value to be parsed
    802     * @param reader the reader (needed if multiple lines have to be read)
    803     * @throws IOException if an IO error occurs
    804     */
    805    private String parseValue(final String val, final BufferedReader reader) throws IOException {
    806        final StringBuilder propertyValue = new StringBuilder();
    807        boolean lineContinues;
    808        String value = val.trim();
    809
    810        do {
    811            final boolean quoted = value.startsWith("\"") || value.startsWith("'");
    812            boolean stop = false;
    813            boolean escape = false;
    814
    815            final char quote = quoted ? value.charAt(0) : 0;
    816
    817            int i = quoted ? 1 : 0;
    818
    819            final StringBuilder result = new StringBuilder();
    820            char lastChar = 0;
    821            while (i < value.length() && !stop) {
    822                final char c = value.charAt(i);
    823
    824                if (quoted) {
    825                    if ('\\' == c && !escape) {
    826                        escape = true;
    827                    } else if (!escape && quote == c) {
    828                        stop = true;
    829                    } else {
    830                        if (escape && quote == c) {
    831                            escape = false;
    832                        } else if (escape) {
    833                            escape = false;
    834                            result.append('\\');
    835                        }
    836                        result.append(c);
    837                    }
    838                } else if (isCommentChar(c) && Character.isWhitespace(lastChar)) {
    839                    stop = true;
    840                } else {
    841                    result.append(c);
    842                }
    843
    844                i++;
    845                lastChar = c;
    846            }
    847
    848            String v = result.toString();
    849            if (!quoted) {
    850                v = v.trim();
    851                lineContinues = lineContinues(v);
    852                if (lineContinues) {
    853                    // remove trailing "\"
    854                    v = v.substring(0, v.length() - 1).trim();
    855                }
    856            } else {
    857                lineContinues = lineContinues(value, i);
    858            }
    859            propertyValue.append(v);
    860
    861            if (lineContinues) {
    862                propertyValue.append(LINE_SEPARATOR);
    863                value = reader.readLine();
    864            }
    865        } while (lineContinues && value != null);
    866
    867        return propertyValue.toString();
    868    }
    869
    870    /**
    871     * Load the configuration from the given reader. Note that the {@code clear()} method is not called so the configuration
    872     * read in will be merged with the current configuration.
    873     *
    874     * @param in the reader to read the configuration from.
    875     * @throws ConfigurationException If an error occurs while reading the configuration
    876     * @throws IOException if an I/O error occurs.
    877     */
    878    @Override
    879    public void read(final Reader in) throws ConfigurationException, IOException {
    880        final BufferedReader bufferedReader = new BufferedReader(in);
    881        final Map<String, ImmutableNode.Builder> sectionBuilders = new LinkedHashMap<>();
    882        final ImmutableNode.Builder rootBuilder = new ImmutableNode.Builder();
    883
    884        createNodeBuilders(bufferedReader, rootBuilder, sectionBuilders);
    885        final ImmutableNode rootNode = createNewRootNode(rootBuilder, sectionBuilders);
    886        addNodes(null, rootNode.getChildren());
    887    }
    888
    889    /**
    890     * Allows setting the leading comment separator which is used in reading an INI file
    891     *
    892     * @param separator String of the new separator for INI reading
    893     * @since 2.5
    894     */
    895    public void setCommentLeadingCharsUsedInInput(final String separator) {
    896        beginRead(false);
    897        try {
    898            this.commentCharsUsedInInput = separator;
    899        } finally {
    900            endRead();
    901        }
    902    }
    903
    904    /**
    905     * Allows setting the key and value separator which is used in reading an INI file
    906     *
    907     * @param separator String of the new separator for INI reading
    908     * @since 2.5
    909     */
    910    public void setSeparatorUsedInInput(final String separator) {
    911        beginRead(false);
    912        try {
    913            this.separatorUsedInInput = separator;
    914        } finally {
    915            endRead();
    916        }
    917    }
    918
    919    /**
    920     * Allows setting the key and value separator which is used for the creation of the resulting INI output
    921     *
    922     * @param separator String of the new separator for INI output
    923     * @since 2.2
    924     */
    925    public void setSeparatorUsedInOutput(final String separator) {
    926        beginWrite(false);
    927        try {
    928            this.separatorUsedInOutput = separator;
    929        } finally {
    930            endWrite();
    931        }
    932    }
    933
    934    /**
    935     * Save the configuration to the specified writer.
    936     *
    937     * @param writer - The writer to save the configuration to.
    938     * @throws ConfigurationException If an error occurs while writing the configuration
    939     * @throws IOException if an I/O error occurs.
    940     */
    941    @Override
    942    public void write(final Writer writer) throws ConfigurationException, IOException {
    943        final PrintWriter out = new PrintWriter(writer);
    944        boolean first = true;
    945        final String separator = getSeparatorUsedInOutput();
    946
    947        beginRead(false);
    948        try {
    949            for (final ImmutableNode node : getModel().getNodeHandler().getRootNode().getChildren()) {
    950                if (isSectionNode(node)) {
    951                    if (!first) {
    952                        out.println();
    953                    }
    954                    out.print("[");
    955                    out.print(node.getNodeName());
    956                    out.print("]");
    957                    out.println();
    958
    959                    node.forEach(child -> writeProperty(out, child.getNodeName(), child.getValue(), separator));
    960                } else {
    961                    writeProperty(out, node.getNodeName(), node.getValue(), separator);
    962                }
    963                first = false;
    964            }
    965            out.println();
    966            out.flush();
    967        } finally {
    968            endRead();
    969        }
    970    }
    971
    972    /**
    973     * Writes data about a property into the given stream.
    974     *
    975     * @param out the output stream
    976     * @param key the key
    977     * @param value the value
    978     */
    979    private void writeProperty(final PrintWriter out, final String key, final Object value, final String separator) {
    980        out.print(key);
    981        out.print(separator);
    982        out.print(escapeValue(value.toString()));
    983        out.println();
    984    }
    985}