Add support for different regex parsers

hsregex/build.gradle

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+// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+plugins {
+    id 'java-library'
+}
+
+group 'org.pgpainless'
+
+repositories {
+    mavenCentral()
+    mavenLocal()
+}
+
+dependencies {
+    testImplementation "org.junit.jupiter:junit-jupiter-api:$junitVersion"
+    testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junitVersion"
+
+    implementation(project(":pgpainless-core"))
+
+    // Henry Spencers Regular Expression (RegEx packets)
+    implementation 'com.basistech.tclre:tcl-regex:0.14.5'
+}
+
+test {
+    useJUnitPlatform()
+}

hsregex/src/main/java/org/pgpainless/algorithm/HSRegexInterpreterFactory.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.algorithm;
+
+import com.basistech.tclre.HsrePattern;
+import com.basistech.tclre.PatternFlags;
+import com.basistech.tclre.RePattern;
+import com.basistech.tclre.RegexException;
+
+public class HSRegexInterpreterFactory extends RegexInterpreterFactory {
+
+    public Regex instantiate(String regex) {
+        return new Regex() {
+
+            private final RePattern pattern;
+
+            {
+                try {
+                    pattern = HsrePattern.compile(regex, PatternFlags.ADVANCED);
+                } catch (RegexException e) {
+                    throw new IllegalArgumentException(e);
+                }
+            }
+
+            @Override
+            public boolean matches(String string) {
+                return pattern.matcher(string).find();
+            }
+        };
+    }
+}

hsregex/src/main/java/org/pgpainless/algorithm/package-info.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Regex interpreter implementation based on Henry Spencers Regular Expression library.
+ *
+ * @see <a href="https://www.rfc-editor.org/rfc/rfc4880#section-8">RFC4880 - §8. Regular Expressions</a>
+ */
+package org.pgpainless.algorithm;