New method IntegerList.toCharArray()

runtime-testsuite/test/org/antlr/v4/test/runtime/java/TestIntegerList.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+package org.antlr.v4.test.runtime.java;
+
+import static org.junit.Assert.assertArrayEquals;
+
+import org.antlr.v4.runtime.misc.IntegerList;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+public class TestIntegerList {
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	@Test
+	public void emptyListToEmptyCharArray() {
+		IntegerList l = new IntegerList();
+		assertArrayEquals(new char[0], l.toCharArray());
+	}
+
+	@Test
+	public void negativeIntegerToCharArrayThrows() {
+		IntegerList l = new IntegerList();
+		l.add(-42);
+		thrown.expect(IllegalArgumentException.class);
+		l.toCharArray();
+	}
+
+	@Test
+	public void surrogateRangeIntegerToCharArray() {
+		IntegerList l = new IntegerList();
+		// Java allows dangling surrogates, so (currently) we do
+		// as well. We could change this if desired.
+		l.add(0xDC00);
+		char expected[] = new char[] { 0xDC00 };
+		assertArrayEquals(expected, l.toCharArray());
+	}
+
+	@Test
+	public void tooLargeIntegerToCharArrayThrows() {
+		IntegerList l = new IntegerList();
+		l.add(0x110000);
+		thrown.expect(IllegalArgumentException.class);
+		l.toCharArray();
+	}
+
+	@Test
+	public void unicodeBMPIntegerListToCharArray() {
+		IntegerList l = new IntegerList();
+		l.add(0x35);
+		l.add(0x4E94);
+		l.add(0xFF15);
+		char expected[] = new char[] { 0x35, 0x4E94, 0xFF15 };
+		assertArrayEquals(expected, l.toCharArray());
+	}
+
+	@Test
+	public void unicodeSMPIntegerListToCharArray() {
+		IntegerList l = new IntegerList();
+		l.add(0x104A5);
+		l.add(0x116C5);
+		l.add(0x1D7FB);
+		char expected[] = new char[] { 0xD801, 0xDCA5, 0xD805, 0xDEC5, 0xD835, 0xDFFB };
+		assertArrayEquals(expected, l.toCharArray());
+	}
+}

runtime/Java/src/org/antlr/v4/runtime/misc/IntegerList.java

@@ -272,4 +272,34 @@ public class IntegerList {
 		_data = Arrays.copyOf(_data, newLength);
 	}
 
+	public final char[] toCharArray() {
+		// Optimize for the common case (all data values are
+		// < 0xFFFF) to avoid an extra scan
+		char[] resultArray = new char[_size];
+		int resultIdx = 0;
+		boolean calculatedPreciseResultSize = false;
+		for (int i = 0; i < _size; i++) {
+			int codePoint = _data[i];
+			// Calculate the precise result size if we encounter
+			// a code point > 0xFFFF
+			if (!calculatedPreciseResultSize &&
+			    Character.isSupplementaryCodePoint(codePoint)) {
+				resultArray = Arrays.copyOf(resultArray, charArraySize());
+				calculatedPreciseResultSize = true;
+			}
+			// This will throw IllegalArgumentException if
+			// the code point is not a valid Unicode code point
+			int charsWritten = Character.toChars(codePoint, resultArray, resultIdx);
+			resultIdx += charsWritten;
+		}
+		return resultArray;
+	}
+
+	private int charArraySize() {
+		int result = 0;
+		for (int i = 0; i < _size; i++) {
+			result += Character.charCount(_data[i]);
+		}
+		return result;
+	}
 }

runtime/Java/src/org/antlr/v4/runtime/misc/Utils.java

@@ -136,12 +136,7 @@ public class Utils {
 	}
 
 	public static char[] toCharArray(IntegerList data) {
-		if ( data==null ) return null;
-		char[] cdata = new char[data.size()];
-		for (int i=0; i<data.size(); i++) {
-			cdata[i] = (char)data.get(i);
-		}
-		return cdata;
+		return data.toCharArray();
 	}
 
 	public static IntervalSet toSet(BitSet bits) {