    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><strong>Sections:</strong> 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><strong>Parameters:</strong> Items in a section are known as parameters. Parameters have a typical {@code key = value}
    074 * format.</li>
    075 * <li><strong>Comments:</strong> 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><strong>Comments:</strong> The '#' character is also accepted as a comment signifier.</li>
    086 * <li><strong>Key value separator:</strong> The ':' character is also accepted in place of '=' to separate keys and values in
    087 * parameters, for example {@code var1 : foo}.</li>
    088 * <li><strong>Duplicate sections:</strong> 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><strong>Duplicate parameters:</strong> 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 (for example 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         * Whether in-line comments on the section line are allowed.
    215         */
    216        private boolean sectionInLineCommentsAllowed;
    217
    218        /**
    219         * Builds a new INIConfiguration.
    220         *
    221         * @return a new INIConfiguration.
    222         */
    223        public INIConfiguration build() {
    224            return new INIConfiguration(sectionInLineCommentsAllowed);
    225        }
    226
    227        /**
    228         * Sets whether in-line comments on the section line are allowed.
    229         *
    230         * @param sectionInLineCommentsAllowed Whether in-line comments on the section line are allowed.
    231         * @return this instance.
    232         */
    233        public Builder setSectionInLineCommentsAllowed(final boolean sectionInLineCommentsAllowed) {
    234            this.sectionInLineCommentsAllowed = sectionInLineCommentsAllowed;
    235            return this;
    236        }
    237
    238    }
    239
    240    /**
    241     * A specialized node model implementation for the sub configuration representing the global section of the INI file.
    242     * This is a regular {@code TrackedNodeModel} with one exception: The {@code NodeHandler} used by this model applies a
    243     * filter on the children of the root node so that only nodes are visible that are no sub sections.
    244     */
    245    private static final class GlobalSectionNodeModel extends TrackedNodeModel {
    246        /**
    247         * Creates a new instance of {@code GlobalSectionNodeModel} and initializes it with the given underlying model.
    248         *
    249         * @param modelSupport the underlying {@code InMemoryNodeModel}
    250         * @param selector the {@code NodeSelector}
    251         */
    252        public GlobalSectionNodeModel(final InMemoryNodeModelSupport modelSupport, final NodeSelector selector) {
    253            super(modelSupport, selector, true);
    254        }
    255
    256        @Override
    257        public NodeHandler<ImmutableNode> getNodeHandler() {
    258            return new NodeHandlerDecorator<ImmutableNode>() {
    259                /**
    260                 * Filters the child nodes of the global section. This method checks whether the passed in node is the root node of the
    261                 * configuration. If so, from the list of children all nodes are filtered which are section nodes.
    262                 *
    263                 * @param node the node in question
    264                 * @param children the children of this node
    265                 * @return a list with the filtered children
    266                 */
    267                private List<ImmutableNode> filterChildrenOfGlobalSection(final ImmutableNode node, final List<ImmutableNode> children) {
    268                    final List<ImmutableNode> filteredList;
    269                    if (node == getRootNode()) {
    270                        filteredList = children.stream().filter(child -> !isSectionNode(child)).collect(Collectors.toList());
    271                    } else {
    272                        filteredList = children;
    273                    }
    274
    275                    return filteredList;
    276                }
    277
    278                @Override
    279                public ImmutableNode getChild(final ImmutableNode node, final int index) {
    280                    final List<ImmutableNode> children = super.getChildren(node);
    281                    return filterChildrenOfGlobalSection(node, children).get(index);
    282                }
    283
    284                @Override
    285                public List<ImmutableNode> getChildren(final ImmutableNode node) {
    286                    final List<ImmutableNode> children = super.getChildren(node);
    287                    return filterChildrenOfGlobalSection(node, children);
    288                }
    289
    290                @Override
    291                public List<ImmutableNode> getChildren(final ImmutableNode node, final String name) {
    292                    final List<ImmutableNode> children = super.getChildren(node, name);
    293                    return filterChildrenOfGlobalSection(node, children);
    294                }
    295
    296                @Override
    297                public int getChildrenCount(final ImmutableNode node, final String name) {
    298                    final List<ImmutableNode> children = name != null ? super.getChildren(node, name) : super.getChildren(node);
    299                    return filterChildrenOfGlobalSection(node, children).size();
    300                }
    301
    302                @Override
    303                protected NodeHandler<ImmutableNode> getDecoratedNodeHandler() {
    304                    return GlobalSectionNodeModel.super.getNodeHandler();
    305                }
    306
    307                @Override
    308                public int indexOfChild(final ImmutableNode parent, final ImmutableNode child) {
    309                    final List<ImmutableNode> children = super.getChildren(parent);
    310                    return filterChildrenOfGlobalSection(parent, children).indexOf(child);
    311                }
    312            };
    313        }
    314    }
    315
    316    /**
    317     * The empty key.
    318     */
    319    private static final String EMPTY_KEY = " ";
    320
    321    /**
    322     * The default characters that signal the start of a comment line.
    323     */
    324    protected static final String COMMENT_CHARS = "#;";
    325
    326    /**
    327     * The default characters used to separate keys from values.
    328     */
    329    protected static final String SEPARATOR_CHARS = "=:";
    330
    331    /**
    332     * Constant for the line separator.
    333     */
    334    private static final String LINE_SEPARATOR = System.lineSeparator();
    335
    336    /**
    337     * The characters used for quoting values.
    338     */
    339    private static final String QUOTE_CHARACTERS = "\"'";
    340
    341    /**
    342     * The line continuation character.
    343     */
    344    private static final String LINE_CONT = "\\";
    345
    346    /**
    347     * Creates a new builder.
    348     *
    349     * @return a new builder.
    350     * @since 2.9.0
    351     */
    352    public static Builder builder() {
    353        return new Builder();
    354    }
    355
    356    /**
    357     * Creates a new root node from the builders constructed while reading the configuration file.
    358     *
    359     * @param rootBuilder the builder for the top-level section
    360     * @param sectionBuilders a map storing the section builders
    361     * @return the root node of the newly created hierarchy
    362     */
    363    private static ImmutableNode createNewRootNode(final ImmutableNode.Builder rootBuilder, final Map<String, ImmutableNode.Builder> sectionBuilders) {
    364        sectionBuilders.forEach((k, v) -> rootBuilder.addChild(v.name(k).create()));
    365        return rootBuilder.create();
    366    }
    367
    368    /**
    369     * Checks for the occurrence of the specified separators in the given line. The index of the first separator is
    370     * returned.
    371     *
    372     * @param line the line to be investigated
    373     * @param separators a string with the separator characters to look for
    374     * @return the lowest index of a separator character or -1 if no separator is found
    375     */
    376    private static int findFirstOccurrence(final String line, final String separators) {
    377        int index = -1;
    378
    379        for (int i = 0; i < separators.length(); i++) {
    380            final char sep = separators.charAt(i);
    381            final int pos = line.indexOf(sep);
    382            if (pos >= 0 && (index < 0 || pos < index)) {
    383                index = pos;
    384            }
    385        }
    386
    387        return index;
    388    }
    389
    390    /**
    391     * Searches for a separator character directly before a quoting character. If the first non-whitespace character before
    392     * a quote character is a separator, it is considered the "real" separator in this line - even if there are other
    393     * separators before.
    394     *
    395     * @param line the line to be investigated
    396     * @param quoteIndex the index of the quote character
    397     * @return the index of the separator before the quote or &lt; 0 if there is none
    398     */
    399    private static int findSeparatorBeforeQuote(final String line, final int quoteIndex) {
    400        int index = quoteIndex - 1;
    401        while (index >= 0 && Character.isWhitespace(line.charAt(index))) {
    402            index--;
    403        }
    404
    405        if (index >= 0 && SEPARATOR_CHARS.indexOf(line.charAt(index)) < 0) {
    406            index = -1;
    407        }
    408
    409        return index;
    410    }
    411
    412    /**
    413     * Determine if the given line contains a section - inline comments are allowed.
    414     *
    415     * @param line The line to check.
    416     * @return true if the line contains a section
    417     */
    418    private static boolean isNonStrictSection(final String line) {
    419        return line.startsWith("[") && line.contains("]");
    420    }
    421
    422    /**
    423     * Checks whether the specified configuration node represents a section.
    424     *
    425     * @param node the node in question
    426     * @return a flag whether this node represents a section
    427     */
    428    private static boolean isSectionNode(final ImmutableNode node) {
    429        return node.getValue() == null;
    430    }
    431
    432    /**
    433     * Determine if the entire given line is a section - inline comments are not allowed.
    434     *
    435     * @param line The line to check.
    436     * @return true if the entire line is a section
    437     */
    438    private static boolean isStrictSection(final String line) {
    439        return line.startsWith("[") && line.endsWith("]");
    440    }
    441
    442    /**
    443     * Tests whether the specified string contains a line continuation marker.
    444     *
    445     * @param line the string to check
    446     * @return a flag whether this line continues
    447     */
    448    private static boolean lineContinues(final String line) {
    449        final String s = line.trim();
    450        return s.equals(LINE_CONT) || s.length() > 2 && s.endsWith(LINE_CONT) && Character.isWhitespace(s.charAt(s.length() - 2));
    451    }
    452
    453    /**
    454     * The separator used when writing an INI file.
    455     */
    456    private String separatorUsedInOutput = " = ";
    457
    458    /**
    459     * The separator used when reading an INI file.
    460     */
    461    private String separatorUsedInInput = SEPARATOR_CHARS;
    462
    463    /**
    464     * The characters used to separate keys from values when reading an INI file.
    465     */
    466    private String commentCharsUsedInInput = COMMENT_CHARS;
    467
    468    /**
    469     * The flag for decision, whether inline comments on the section line are allowed.
    470     */
    471    private boolean sectionInLineCommentsAllowed;
    472
    473    /**
    474     * Create a new empty INI Configuration.
    475     */
    476    public INIConfiguration() {
    477    }
    478
    479    /**
    480     * Create a new empty INI Configuration with option to allow inline comments on the section line.
    481     *
    482     * @param sectionInLineCommentsAllowed when true inline comments on the section line are allowed
    483     */
    484    private INIConfiguration(final boolean sectionInLineCommentsAllowed) {
    485        this.sectionInLineCommentsAllowed = sectionInLineCommentsAllowed;
    486    }
    487
    488    /**
    489     * Creates a new instance of {@code INIConfiguration} with the content of the specified
    490     * {@code HierarchicalConfiguration}.
    491     *
    492     * @param c the configuration to be copied
    493     * @since 2.0
    494     */
    495    public INIConfiguration(final HierarchicalConfiguration<ImmutableNode> c) {
    496        super(c);
    497    }
    498
    499    /**
    500     * Reads the content of an INI file from the passed in reader and creates a structure of builders for constructing the
    501     * {@code ImmutableNode} objects representing the data.
    502     *
    503     * @param in the reader
    504     * @param rootBuilder the builder for the top-level section
    505     * @param sectionBuilders a map storing the section builders
    506     * @throws IOException if an I/O error occurs.
    507     */
    508    private void createNodeBuilders(final BufferedReader in, final ImmutableNode.Builder rootBuilder, final Map<String, ImmutableNode.Builder> sectionBuilders)
    509        throws IOException {
    510        ImmutableNode.Builder sectionBuilder = rootBuilder;
    511        String line = in.readLine();
    512        while (line != null) {
    513            line = line.trim();
    514            if (!isCommentLine(line)) {
    515                if (isSectionLine(line)) {
    516                    final int length = sectionInLineCommentsAllowed ? line.indexOf("]") : line.length() - 1;
    517                    String section = line.substring(1, length);
    518                    if (section.isEmpty()) {
    519                        // use space for sections with no key
    520                        section = EMPTY_KEY;
    521                    }
    522                    sectionBuilder = sectionBuilders.computeIfAbsent(section, k -> new ImmutableNode.Builder());
    523                } else {
    524                    String key;
    525                    String value = "";
    526                    final int index = findSeparator(line);
    527                    if (index >= 0) {
    528                        key = line.substring(0, index);
    529                        value = parseValue(line.substring(index + 1), in);
    530                    } else {
    531                        key = line;
    532                    }
    533                    key = key.trim();
    534                    if (key.isEmpty()) {
    535                        // use space for properties with no key
    536                        key = EMPTY_KEY;
    537                    }
    538                    createValueNodes(sectionBuilder, key, value);
    539                }
    540            }
    541
    542            line = in.readLine();
    543        }
    544    }
    545
    546    /**
    547     * Creates the node(s) for the given key value-pair. If delimiter parsing is enabled, the value string is split if
    548     * possible, and for each single value a node is created. Otherwise only a single node is added to the section.
    549     *
    550     * @param sectionBuilder the section builder for adding new nodes
    551     * @param key the key
    552     * @param value the value string
    553     */
    554    private void createValueNodes(final ImmutableNode.Builder sectionBuilder, final String key, final String value) {
    555        getListDelimiterHandler().split(value, false).forEach(v -> sectionBuilder.addChild(new ImmutableNode.Builder().name(key).value(v).create()));
    556    }
    557
    558    /**
    559     * Escapes comment characters in the given value.
    560     *
    561     * @param value the value to be escaped
    562     * @return the value with comment characters escaped
    563     */
    564    private String escapeComments(final String value) {
    565        final String commentChars = getCommentLeadingCharsUsedInInput();
    566        boolean quoted = false;
    567
    568        for (int i = 0; i < commentChars.length(); i++) {
    569            final char c = commentChars.charAt(i);
    570            if (value.indexOf(c) != -1) {
    571                quoted = true;
    572                break;
    573            }
    574        }
    575
    576        if (quoted) {
    577            return '"' + value.replace("\"", "\\\"") + '"';
    578        }
    579        return value;
    580    }
    581
    582    /**
    583     * Escapes the given property value before it is written. This method add quotes around the specified value if it
    584     * contains a comment character and handles list delimiter characters.
    585     *
    586     * @param value the string to be escaped
    587     */
    588    private String escapeValue(final String value) {
    589        return String.valueOf(getListDelimiterHandler().escape(escapeComments(value), ListDelimiterHandler.NOOP_TRANSFORMER));
    590    }
    591
    592    /**
    593     * Tries to find the index of the separator character in the given string. This method checks for the presence of
    594     * separator characters in the given string. If multiple characters are found, the first one is assumed to be the
    595     * correct separator. If there are quoting characters, they are taken into account, too.
    596     *
    597     * @param line the line to be checked
    598     * @return the index of the separator character or -1 if none is found
    599     */
    600    private int findSeparator(final String line) {
    601        int index = findSeparatorBeforeQuote(line, findFirstOccurrence(line, QUOTE_CHARACTERS));
    602        if (index < 0) {
    603            index = findFirstOccurrence(line, getSeparatorUsedInInput());
    604        }
    605        return index;
    606    }
    607
    608    /**
    609     * Gets comment leading separator used in INI reading. see {@code setCommentLeadingCharsUsedInInput} for further
    610     * explanation
    611     *
    612     * @return the current separator for reading the INI input
    613     * @since 2.5
    614     */
    615    public String getCommentLeadingCharsUsedInInput() {
    616        return syncReadValue(commentCharsUsedInInput, false);
    617    }
    618
    619    /**
    620     * Creates a sub configuration for the global section of the represented INI configuration.
    621     *
    622     * @return the sub configuration for the global section
    623     */
    624    private SubnodeConfiguration getGlobalSection() {
    625        final InMemoryNodeModel parentModel = getSubConfigurationParentModel();
    626        final NodeSelector selector = new NodeSelector(null); // selects parent
    627        parentModel.trackNode(selector, this);
    628        final GlobalSectionNodeModel model = new GlobalSectionNodeModel(this, selector);
    629        final SubnodeConfiguration sub = new SubnodeConfiguration(this, model);
    630        initSubConfigurationForThisParent(sub);
    631        return sub;
    632    }
    633
    634    /**
    635     * Gets a configuration with the content of the specified section. This provides an easy way of working with a single
    636     * section only. The way this configuration is structured internally, this method is very similar to calling
    637     * {@link HierarchicalConfiguration#configurationAt(String)} with the name of the section in question. There are the
    638     * following differences however:
    639     * <ul>
    640     * <li>This method never throws an exception. If the section does not exist, it is created now. The configuration
    641     * returned in this case is empty.</li>
    642     * <li>If section is contained multiple times in the configuration, the configuration returned by this method is
    643     * initialized with the first occurrence of the section. (This can only happen if {@code addProperty()} has been used in
    644     * a way that does not conform to the storage scheme used by {@code INIConfiguration}. If used correctly, there will not
    645     * be duplicate sections.)</li>
    646     * <li>There is special support for the global section: Passing in <strong>null</strong> as section name returns a configuration
    647     * with the content of the global section (which may also be empty).</li>
    648     * </ul>
    649     *
    650     * @param name the name of the section in question; <strong>null</strong> represents the global section
    651     * @return a configuration containing only the properties of the specified section
    652     */
    653    public SubnodeConfiguration getSection(final String name) {
    654        if (name == null) {
    655            return getGlobalSection();
    656        }
    657        try {
    658            return (SubnodeConfiguration) configurationAt(name, true);
    659        } catch (final ConfigurationRuntimeException iex) {
    660            // the passed in key does not map to exactly one node
    661            // obtain the node for the section, create it on demand
    662            final InMemoryNodeModel parentModel = getSubConfigurationParentModel();
    663            final NodeSelector selector = parentModel.trackChildNodeWithCreation(null, name, this);
    664            return createSubConfigurationForTrackedNode(selector, this);
    665        }
    666    }
    667
    668    /**
    669     * Gets a set containing the sections in this INI configuration. Note that changes to this set do not affect the
    670     * configuration.
    671     *
    672     * @return a set containing the sections.
    673     */
    674    public Set<String> getSections() {
    675        return syncRead(() -> {
    676            final Set<String> sections = new LinkedHashSet<>();
    677            boolean globalSection = false;
    678            boolean inSection = false;
    679            for (final ImmutableNode node : getModel().getNodeHandler().getRootNode().getChildren()) {
    680                if (isSectionNode(node)) {
    681                    inSection = true;
    682                    sections.add(node.getNodeName());
    683                } else if (!inSection && !globalSection) {
    684                    globalSection = true;
    685                    sections.add(null);
    686                }
    687            }
    688            return sections;
    689        }, false);
    690    }
    691
    692    /**
    693     * Gets separator used in INI reading. see {@code setSeparatorUsedInInput} for further explanation
    694     *
    695     * @return the current separator for reading the INI input
    696     * @since 2.5
    697     */
    698    public String getSeparatorUsedInInput() {
    699        return syncReadValue(separatorUsedInInput, false);
    700    }
    701
    702    /**
    703     * Gets separator used in INI output. see {@code setSeparatorUsedInOutput} for further explanation
    704     *
    705     * @return the current separator for writing the INI output
    706     * @since 2.2
    707     */
    708    public String getSeparatorUsedInOutput() {
    709        return syncReadValue(separatorUsedInOutput, false);
    710    }
    711
    712    /**
    713     * Tests whether the specified character is a comment character.
    714     *
    715     * @param c the character
    716     * @return a flag whether this character starts a comment
    717     */
    718    private boolean isCommentChar(final char c) {
    719        return getCommentLeadingCharsUsedInInput().indexOf(c) >= 0;
    720    }
    721
    722    /**
    723     * Determine if the given line is a comment line.
    724     *
    725     * @param line The line to check.
    726     * @return true if the line is empty or starts with one of the comment characters
    727     */
    728    protected boolean isCommentLine(final String line) {
    729        if (line == null) {
    730            return false;
    731        }
    732        // blank lines are also treated as comment lines
    733        return line.isEmpty() || getCommentLeadingCharsUsedInInput().indexOf(line.charAt(0)) >= 0;
    734    }
    735
    736    /**
    737     * Determine if the given line is a section.
    738     *
    739     * @param line The line to check.
    740     * @return true if the line contains a section
    741     */
    742    protected boolean isSectionLine(final String line) {
    743        if (line == null) {
    744            return false;
    745        }
    746        return sectionInLineCommentsAllowed ? isNonStrictSection(line) : isStrictSection(line);
    747    }
    748
    749    /**
    750     * Tests whether the specified string contains a line continuation marker after the specified position. This method
    751     * parses the string to remove a comment that might be present. Then it checks whether a line continuation marker can be
    752     * found at the end.
    753     *
    754     * @param line the line to check
    755     * @param pos the start position
    756     * @return a flag whether this line continues
    757     */
    758    private boolean lineContinues(final String line, final int pos) {
    759        final String s;
    760
    761        if (pos >= line.length()) {
    762            s = line;
    763        } else {
    764            int end = pos;
    765            while (end < line.length() && !isCommentChar(line.charAt(end))) {
    766                end++;
    767            }
    768            s = line.substring(pos, end);
    769        }
    770
    771        return lineContinues(s);
    772    }
    773
    774    /**
    775     * Parse the value to remove the quotes and ignoring the comment. Example:
    776     *
    777     * <pre>
    778     * &quot;value&quot; ; comment -&gt; value
    779     * </pre>
    780     *
    781     * <pre>
    782     * 'value' ; comment -&gt; value
    783     * </pre>
    784     *
    785     * Note that a comment character is only recognized if there is at least one whitespace character before it. So it can
    786     * appear in the property value, for example:
    787     *
    788     * <pre>
    789     * C:\\Windows;C:\\Windows\\system32
    790     * </pre>
    791     *
    792     * @param val the value to be parsed
    793     * @param reader the reader (needed if multiple lines have to be read)
    794     * @throws IOException if an IO error occurs
    795     */
    796    private String parseValue(final String val, final BufferedReader reader) throws IOException {
    797        final StringBuilder propertyValue = new StringBuilder();
    798        boolean lineContinues;
    799        String value = val.trim();
    800
    801        do {
    802            final boolean quoted = value.startsWith("\"") || value.startsWith("'");
    803            boolean stop = false;
    804            boolean escape = false;
    805
    806            final char quote = quoted ? value.charAt(0) : 0;
    807
    808            int i = quoted ? 1 : 0;
    809
    810            final StringBuilder result = new StringBuilder();
    811            char lastChar = 0;
    812            while (i < value.length() && !stop) {
    813                final char c = value.charAt(i);
    814
    815                if (quoted) {
    816                    if ('\\' == c && !escape) {
    817                        escape = true;
    818                    } else if (!escape && quote == c) {
    819                        stop = true;
    820                    } else {
    821                        if (escape && quote == c) {
    822                            escape = false;
    823                        } else if (escape) {
    824                            escape = false;
    825                            result.append('\\');
    826                        }
    827                        result.append(c);
    828                    }
    829                } else if (isCommentChar(c) && Character.isWhitespace(lastChar)) {
    830                    stop = true;
    831                } else {
    832                    result.append(c);
    833                }
    834
    835                i++;
    836                lastChar = c;
    837            }
    838
    839            String v = result.toString();
    840            if (!quoted) {
    841                v = v.trim();
    842                lineContinues = lineContinues(v);
    843                if (lineContinues) {
    844                    // remove trailing "\"
    845                    v = v.substring(0, v.length() - 1).trim();
    846                }
    847            } else {
    848                lineContinues = lineContinues(value, i);
    849            }
    850            propertyValue.append(v);
    851
    852            if (lineContinues) {
    853                propertyValue.append(LINE_SEPARATOR);
    854                value = reader.readLine();
    855            }
    856        } while (lineContinues && value != null);
    857
    858        return propertyValue.toString();
    859    }
    860
    861    /**
    862     * Load the configuration from the given reader. Note that the {@code clear()} method is not called so the configuration
    863     * read in will be merged with the current configuration.
    864     *
    865     * @param in the reader to read the configuration from.
    866     * @throws ConfigurationException If an error occurs while reading the configuration
    867     * @throws IOException if an I/O error occurs.
    868     */
    869    @Override
    870    public void read(final Reader in) throws ConfigurationException, IOException {
    871        final BufferedReader bufferedReader = new BufferedReader(in);
    872        final Map<String, ImmutableNode.Builder> sectionBuilders = new LinkedHashMap<>();
    873        final ImmutableNode.Builder rootBuilder = new ImmutableNode.Builder();
    874
    875        createNodeBuilders(bufferedReader, rootBuilder, sectionBuilders);
    876        final ImmutableNode rootNode = createNewRootNode(rootBuilder, sectionBuilders);
    877        addNodes(null, rootNode.getChildren());
    878    }
    879
    880    /**
    881     * Allows setting the leading comment separator which is used in reading an INI file
    882     *
    883     * @param separator String of the new separator for INI reading
    884     * @since 2.5
    885     */
    886    public void setCommentLeadingCharsUsedInInput(final String separator) {
    887        beginRead(false);
    888        try {
    889            this.commentCharsUsedInInput = separator;
    890        } finally {
    891            endRead();
    892        }
    893    }
    894
    895    /**
    896     * Allows setting the key and value separator which is used in reading an INI file
    897     *
    898     * @param separator String of the new separator for INI reading
    899     * @since 2.5
    900     */
    901    public void setSeparatorUsedInInput(final String separator) {
    902        beginRead(false);
    903        try {
    904            this.separatorUsedInInput = separator;
    905        } finally {
    906            endRead();
    907        }
    908    }
    909
    910    /**
    911     * Allows setting the key and value separator which is used for the creation of the resulting INI output
    912     *
    913     * @param separator String of the new separator for INI output
    914     * @since 2.2
    915     */
    916    public void setSeparatorUsedInOutput(final String separator) {
    917        syncWrite(() -> this.separatorUsedInOutput = separator, false);
    918    }
    919
    920    /**
    921     * Save the configuration to the specified writer.
    922     *
    923     * @param writer   The writer to save the configuration to.
    924     * @throws ConfigurationException If an error occurs while writing the configuration
    925     * @throws IOException if an I/O error occurs.
    926     */
    927    @Override
    928    public void write(final Writer writer) throws ConfigurationException, IOException {
    929        syncRead(() -> {
    930            final PrintWriter out = new PrintWriter(writer);
    931            boolean first = true;
    932            final String separator = getSeparatorUsedInOutput();
    933            for (final ImmutableNode node : getModel().getNodeHandler().getRootNode().getChildren()) {
    934                if (isSectionNode(node)) {
    935                    if (!first) {
    936                        out.println();
    937                    }
    938                    out.print("[");
    939                    out.print(node.getNodeName());
    940                    out.print("]");
    941                    out.println();
    942
    943                    node.forEach(child -> writeProperty(out, child.getNodeName(), child.getValue(), separator));
    944                } else {
    945                    writeProperty(out, node.getNodeName(), node.getValue(), separator);
    946                }
    947                first = false;
    948            }
    949            out.println();
    950            out.flush();
    951
    952        }, false);
    953    }
    954
    955    /**
    956     * Writes data about a property into the given stream.
    957     *
    958     * @param out the output stream
    959     * @param key the key
    960     * @param value the value
    961     */
    962    private void writeProperty(final PrintWriter out, final String key, final Object value, final String separator) {
    963        out.print(key);
    964        out.print(separator);
    965        out.print(escapeValue(value.toString()));
    966        out.println();
    967    }
    968}