+/*
+ * Copyright 2008 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.common.reedsolomon;
+
+import junit.framework.TestCase;
+
+import java.util.BitSet;
+import java.util.Random;
+
+/**
+ * @author srowen@google.com (Sean Owen)
+ */
+public final class ReedSolomonDecoderQRCodeTestCase extends TestCase {
+
+ /** See ISO 18004, Appendix I, from which this example is taken. */
+ private static final int[] QR_CODE_TEST =
+ { 0x10, 0x20, 0x0C, 0x56, 0x61, 0x80, 0xEC, 0x11, 0xEC,
+ 0x11, 0xEC, 0x11, 0xEC, 0x11, 0xEC, 0x11, 0xA5 };
+ private static final int[] QR_CODE_TEST_WITH_EC =
+ { 0x10, 0x20, 0x0C, 0x56, 0x61, 0x80, 0xEC, 0x11, 0xEC,
+ 0x11, 0xEC, 0x11, 0xEC, 0x11, 0xEC, 0x11, 0xA5, 0x24,
+ 0xD4, 0xC1, 0xED, 0x36, 0xC7, 0x87, 0x2C, 0x55 };
+ private static final int QR_CODE_CORRECTABLE = (QR_CODE_TEST_WITH_EC.length - QR_CODE_TEST.length) / 2;
+
+ private final ReedSolomonDecoder qrRSDecoder = new ReedSolomonDecoder(GF256.QR_CODE_FIELD);
+
+ public void testNoError() throws ReedSolomonException {
+ int[] received = new int[QR_CODE_TEST_WITH_EC.length];
+ System.arraycopy(QR_CODE_TEST_WITH_EC, 0, received, 0, received.length);
+ // no errors
+ checkQRRSDecode(received);
+ }
+
+ public void testOneError() throws ReedSolomonException {
+ int[] received = new int[QR_CODE_TEST_WITH_EC.length];
+ Random random = new Random(0xDEADBEEFL);
+ for (int i = 0; i < received.length; i++) {
+ System.arraycopy(QR_CODE_TEST_WITH_EC, 0, received, 0, received.length);
+ received[i] = random.nextInt(256);
+ checkQRRSDecode(received);
+ }
+ }
+
+ public void testMaxErrors() throws ReedSolomonException {
+ int[] received = new int[QR_CODE_TEST_WITH_EC.length];
+ Random random = new Random(0xDEADBEEFL);
+ for (int i = 0; i < QR_CODE_TEST.length; i++) { // # iterations is kind of arbitrary
+ System.arraycopy(QR_CODE_TEST_WITH_EC, 0, received, 0, received.length);
+ corrupt(received, QR_CODE_CORRECTABLE, random);
+ checkQRRSDecode(received);
+ }
+ }
+
+ public void testTooManyErrors() {
+ int[] received = new int[QR_CODE_TEST_WITH_EC.length];
+ System.arraycopy(QR_CODE_TEST_WITH_EC, 0, received, 0, received.length);
+ Random random = new Random(0xDEADBEEFL);
+ corrupt(received, QR_CODE_CORRECTABLE + 1, random);
+ try {
+ checkQRRSDecode(received);
+ fail("Should not have decoded");
+ } catch (ReedSolomonException rse) {
+ // good
+ }
+ }
+
+ private void checkQRRSDecode(int[] received) throws ReedSolomonException {
+ qrRSDecoder.decode(received, 2*QR_CODE_CORRECTABLE, false);
+ for (int i = 0; i < QR_CODE_TEST.length; i++) {
+ assertEquals(received[i], QR_CODE_TEST[i]);
+ }
+ }
+
+ private static void corrupt(int[] received, int howMany, Random random) {
+ BitSet corrupted = new BitSet(received.length);
+ for (int j = 0; j < howMany; j++) {
+ int location = random.nextInt(received.length);
+ if (corrupted.get(location)) {
+ j--;
+ } else {
+ corrupted.set(location);
+ int newByte = random.nextInt(256);
+ received[location] = newByte;
+ }
+ }
+ }
+}
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