1 files changed, 99 insertions, 0 deletions
diff --git a/src/test/java/org/apache/commons/io/input/buffer/CircularBufferInputStreamTest.java b/src/test/java/org/apache/commons/io/input/buffer/CircularBufferInputStreamTest.java
new file mode 100644
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+++ b/src/test/java/org/apache/commons/io/input/buffer/CircularBufferInputStreamTest.java
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.commons.io.input.buffer;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.util.Random;
+
+import org.junit.jupiter.api.Test;
+
+public class CircularBufferInputStreamTest {
+    private final Random rnd = new Random(1530960934483L); // System.currentTimeMillis(), when this test was written.
+                                                           // Always using the same seed should ensure a reproducible test.
+
+    /**
+     * Create a large, but random input buffer.
+     */
+    private byte[] newInputBuffer() {
+        final byte[] buffer = new byte[16 * 512 + rnd.nextInt(512)];
+        rnd.nextBytes(buffer);
+        return buffer;
+    }
+
+    @Test
+    public void testIO683() throws IOException {
+        final byte[] buffer = {0, 1, -2, -2, -1, 4};
+        try (ByteArrayInputStream bais = new ByteArrayInputStream(buffer); final CircularBufferInputStream cbis = new CircularBufferInputStream(bais)) {
+            int b;
+            int i = 0;
+            while ((b = cbis.read()) != -1) {
+                assertEquals(buffer[i] & 0xFF, b, "byte at index " + i + " should be equal");
+                i++;
+            }
+            assertEquals(buffer.length, i, "Should have read all the bytes");
+        }
+    }
+
+    @Test
+    public void testRandomRead() throws Exception {
+        final byte[] inputBuffer = newInputBuffer();
+        final byte[] bufferCopy = new byte[inputBuffer.length];
+        final ByteArrayInputStream bais = new ByteArrayInputStream(inputBuffer);
+        @SuppressWarnings("resource")
+        final CircularBufferInputStream cbis = new CircularBufferInputStream(bais, 253);
+        int offset = 0;
+        final byte[] readBuffer = new byte[256];
+        while (offset < bufferCopy.length) {
+            switch (rnd.nextInt(2)) {
+            case 0: {
+                final int res = cbis.read();
+                if (res == -1) {
+                    throw new IllegalStateException("Unexpected EOF at offset " + offset);
+                }
+                if (inputBuffer[offset] != (byte) res) { // compare as bytes
+                    throw new IllegalStateException("Expected " + inputBuffer[offset] + " at offset " + offset + ", got " + res);
+                }
+                ++offset;
+                break;
+            }
+            case 1: {
+                final int res = cbis.read(readBuffer, 0, rnd.nextInt(readBuffer.length + 1));
+                if (res == -1) {
+                    throw new IllegalStateException("Unexpected EOF at offset " + offset);
+                }
+                if (res == 0) {
+                    throw new IllegalStateException("Unexpected zero-byte-result at offset " + offset);
+                }
+                for (int i = 0; i < res; i++) {
+                    if (inputBuffer[offset] != readBuffer[i]) {
+                        throw new IllegalStateException("Expected " + inputBuffer[offset] + " at offset " + offset + ", got " + readBuffer[i]);
+                    }
+                    ++offset;
+                }
+                break;
+            }
+            default:
+                throw new IllegalStateException("Unexpected random choice value");
+            }
+        }
+        assertTrue(true, "Test finished OK");
+    }
+}