Extract RegexUtils.getNotFollowingEscapePattern()

Author: idodeclare

src/org/opensolaris/opengrok/util/RegexUtils.java

@@ -0,0 +1,54 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * See LICENSE.txt included in this distribution for the specific
+ * language governing permissions and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at LICENSE.txt.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2017, Chris Fraire <[email protected]>.
+ */
+
+package org.opensolaris.opengrok.util;
+
+/**
+ * Represents a container for regex-related utility methods.
+ */
+public class RegexUtils {
+
+    /** Private to enforce singleton. */
+    private RegexUtils() {
+    }
+
+    /**
+     * Gets a zero-width expression intended to follow a character match that
+     * asserts that the character either does not follow a backslash escape or
+     * follows an even number¹ of backslash escapes.
+     * <p>
+     * ¹"even number" is limited to 2,4,6 because Java look-behind is not
+     * variable length but instead must have a definite upper bound in the
+     * regex definition.
+     * @return a defined expression:
+     * <pre>
+     * {@code
+     * ((?<=^.)|(?<=[^\\].)|(?<=^(\\\\){1,3}.)|(?<=[^\\](\\\\){1,3}.))
+     * }
+     * </pre>
+     * (Edit above and paste below [in NetBeans] for easy String escaping.)
+     */
+    public static String getNotFollowingEscapePattern() {
+        return "((?<=^.)|(?<=[^\\\\].)|(?<=^(\\\\\\\\){1,3}.)|(?<=[^\\\\](\\\\\\\\){1,3}.))";
+    }
+}

src/org/opensolaris/opengrok/util/StringUtils.java

@@ -36,20 +36,13 @@ public final class StringUtils {
 
     /**
      * Matches an apostrophe not following a backslash escape or following an
-     * even number¹ of backslash escapes:
-     * <pre>
-     * {@code
-     * \'((?<=^.)|(?<=[^\\].)|(?<=^(\\\\){1,3}.)|(?<=[^\\](\\\\){1,3}.))
-     * }
-     * </pre>
-     * (Edit above and paste below [in NetBeans] for easy String escaping.)
+     * even number¹ of backslash escapes.
      * <p>
-     * ¹"even number" is limited to 2,4,6 because Java look-behind is not
-     * variable length but instead must have a definite upper bound in the
-     * regex definition.
+     * ¹See {@link RegexUtils#getNotFollowingEscapePattern()} for a caveat
+     * about the backslash assertion.
      */
     public static final Pattern APOS_NO_BSESC =
-        Pattern.compile("\\'((?<=^.)|(?<=[^\\\\].)|(?<=^(\\\\\\\\){1,3}.)|(?<=[^\\\\](\\\\\\\\){1,3}.))");
+        Pattern.compile("\\'" + RegexUtils.getNotFollowingEscapePattern());
 
     /**
      * Matches the close of a C comment: