Fix DataSourceInputStream + add unit test

Issue: #2162

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=141177715

library/src/androidTest/java/com/google/android/exoplayer2/upstream/DataSourceInputStreamTest.java

+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.android.exoplayer2.upstream;
+
+import android.test.MoreAsserts;
+import com.google.android.exoplayer2.testutil.FakeDataSource;
+import com.google.android.exoplayer2.testutil.TestUtil;
+import java.io.IOException;
+import java.util.Arrays;
+import junit.framework.TestCase;
+
+/**
+ * Unit tests for {@link DataSourceInputStream}.
+ */
+public class DataSourceInputStreamTest extends TestCase {
+
+  private static final byte[] TEST_DATA = TestUtil.buildTestData(16);
+
+  public void testReadSingleBytes() throws IOException {
+    DataSourceInputStream inputStream = buildTestInputStream();
+    // No bytes read yet.
+    assertEquals(0, inputStream.bytesRead());
+    // Read bytes.
+    for (int i = 0; i < TEST_DATA.length; i++) {
+      int readByte = inputStream.read();
+      assertTrue(0 <= readByte && readByte < 256);
+      assertEquals(TEST_DATA[i] & 0xFF, readByte);
+      assertEquals(i + 1, inputStream.bytesRead());
+    }
+    // Check end of stream.
+    assertEquals(-1, inputStream.read());
+    assertEquals(TEST_DATA.length, inputStream.bytesRead());
+    // Check close succeeds.
+    inputStream.close();
+  }
+
+  public void testRead() throws IOException {
+    DataSourceInputStream inputStream = buildTestInputStream();
+    // Read bytes.
+    byte[] readBytes = new byte[TEST_DATA.length];
+    int totalBytesRead = 0;
+    while (totalBytesRead < TEST_DATA.length) {
+      long bytesRead = inputStream.read(readBytes, totalBytesRead,
+          TEST_DATA.length - totalBytesRead);
+      assertTrue(bytesRead > 0);
+      totalBytesRead += bytesRead;
+      assertEquals(totalBytesRead, inputStream.bytesRead());
+    }
+    // Check the read data.
+    MoreAsserts.assertEquals(TEST_DATA, readBytes);
+    // Check end of stream.
+    assertEquals(TEST_DATA.length, inputStream.bytesRead());
+    assertEquals(TEST_DATA.length, totalBytesRead);
+    assertEquals(-1, inputStream.read());
+    // Check close succeeds.
+    inputStream.close();
+  }
+
+  public void testSkip() throws IOException {
+    DataSourceInputStream inputStream = buildTestInputStream();
+    // Skip bytes.
+    long totalBytesSkipped = 0;
+    while (totalBytesSkipped < TEST_DATA.length) {
+      long bytesSkipped = inputStream.skip(Long.MAX_VALUE);
+      assertTrue(bytesSkipped > 0);
+      totalBytesSkipped += bytesSkipped;
+      assertEquals(totalBytesSkipped, inputStream.bytesRead());
+    }
+    // Check end of stream.
+    assertEquals(TEST_DATA.length, inputStream.bytesRead());
+    assertEquals(TEST_DATA.length, totalBytesSkipped);
+    assertEquals(-1, inputStream.read());
+    // Check close succeeds.
+    inputStream.close();
+  }
+
+  private static DataSourceInputStream buildTestInputStream() {
+    FakeDataSource.Builder fakeDataSourceBuilder = new FakeDataSource.Builder()
+        .appendReadData(Arrays.copyOfRange(TEST_DATA, 0, 5))
+        .appendReadData(Arrays.copyOfRange(TEST_DATA, 5, 10))
+        .appendReadData(Arrays.copyOfRange(TEST_DATA, 10, 15))
+        .appendReadData(Arrays.copyOfRange(TEST_DATA, 15, TEST_DATA.length));
+    return new DataSourceInputStream(fakeDataSourceBuilder.build(), new DataSpec(null));
+  }
+
+}

library/src/main/java/com/google/android/exoplayer2/upstream/DataSourceInputStream.java

@@ -67,20 +67,12 @@ public final class DataSourceInputStream extends InputStream {
   @Override
   public int read() throws IOException {
     int length = read(singleByteArray);
-    if (length == -1) {
-      return -1;
-    }
-    totalBytesRead++;
-    return singleByteArray[0] & 0xFF;
+    return length == -1 ? -1 : (singleByteArray[0] & 0xFF);
   }
 
   @Override
   public int read(byte[] buffer) throws IOException {
-    int bytesRead = read(buffer, 0, buffer.length);
-    if (bytesRead != -1) {
-      totalBytesRead += bytesRead;
-    }
-    return bytesRead;
+    return read(buffer, 0, buffer.length);
   }
 
   @Override
@@ -97,15 +89,6 @@ public final class DataSourceInputStream extends InputStream {
   }
 
   @Override
-  public long skip(long byteCount) throws IOException {
-    Assertions.checkState(!closed);
-    checkOpened();
-    long bytesSkipped = super.skip(byteCount);
-    totalBytesRead += bytesSkipped;
-    return bytesSkipped;
-  }
-
-  @Override
   public void close() throws IOException {
     if (!closed) {
       dataSource.close();