# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1387840504 -3600
# Node ID 0b05bc13aaddf42ac36364b347909e0fb1edb3a6
# Parent  ce33736066b1ee1c14f2962b56284a033892d3f8
function escapeRegEx()

diff -r ce33736066b1 -r 0b05bc13aadd java/sql-dk/src/info/globalcode/sql/dk/Functions.java
--- a/java/sql-dk/src/info/globalcode/sql/dk/Functions.java	Tue Dec 24 00:12:53 2013 +0100
+++ b/java/sql-dk/src/info/globalcode/sql/dk/Functions.java	Tue Dec 24 00:15:04 2013 +0100
@@ -133,4 +133,29 @@
 		Arrays.fill(array, ch);
 		return new String(array);
 	}
+
+	/**
+	 * @param original any text
+	 * @return escaped text that can be used as part of an regular expression, matches the original
+	 * text
+	 */
+	public static String escapeRegEx(String original) {
+		StringBuilder escaped = new StringBuilder(original.length() * 3);
+
+		escaped.append("\\Q"); // start quotation
+		for (int i = 0; i < original.length(); i++) {
+			char ch = original.charAt(i);
+			if (ch == 'E' && i > 0 && original.charAt(i - 1) == '\\') {
+				escaped.append(ch); // this unintentionally ends quotation
+				escaped.append("\\\\E"); // insert escaped \E (eaten before)
+				escaped.append("\\Q"); // re-start quotation
+			} else {
+				escaped.append(ch);
+			}
+
+		}
+		escaped.append("\\E"); // end quotation
+
+		return escaped.toString();
+	}
 }
diff -r ce33736066b1 -r 0b05bc13aadd java/sql-dk/test/info/globalcode/sql/dk/FunctionsTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/java/sql-dk/test/info/globalcode/sql/dk/FunctionsTest.java	Tue Dec 24 00:15:04 2013 +0100
@@ -0,0 +1,59 @@
+/**
+ * SQL-DK
+ * Copyright © 2013 František Kučera (frantovo.cz)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package info.globalcode.sql.dk;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.testng.annotations.Test;
+import static org.testng.Assert.*;
+
+/**
+ *
+ * @author Ing. František Kučera (frantovo.cz)
+ */
+public class FunctionsTest {
+
+	@Test
+	public void testEscapeRegEx() {
+		for (String original : new String[]{"abcd", "1234", "xxx", "\\Eescape\\Q", "\\Qescape\\E", "abc\\Eescape\\Qdef.", ".", ""}) {
+			String patternString = Functions.escapeRegEx(original);
+			System.out.println(original + " → " + patternString);
+
+			Pattern pattern = Pattern.compile(patternString);
+
+			String testString;
+			Matcher m;
+
+			testString = original;
+			m = pattern.matcher(testString);
+			assertTrue(m.matches(), "Pattern does not match original string: " + testString);
+
+			testString = original + "x";
+			m = pattern.matcher(testString);
+			assertFalse(m.matches(), "Pattern matches wrong string: " + testString);
+
+			testString = "x" + original;
+			m = pattern.matcher(testString);
+			assertFalse(m.matches(), "Pattern matches wrong string: " + testString);
+
+			testString = (original + "ab").substring(1);
+			m = pattern.matcher(testString);
+			assertFalse(m.matches(), "Pattern matches wrong string: " + testString);
+		}
+	}
+}