Add ByteBufferInputStream (#2329)

Author: schmidt-sebastian

firebase-firestore/src/main/java/com/google/firebase/firestore/util/ByteBufferInputStream.java

@@ -0,0 +1,46 @@
+// Copyright 2021 Google LLC
+//
+// 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.firebase.firestore.util;
+
+import androidx.annotation.NonNull;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteBuffer;
+
+/** Wraps a ByteBuffer in an InputStream. */
+public class ByteBufferInputStream extends InputStream {
+  ByteBuffer buffer;
+
+  public ByteBufferInputStream(ByteBuffer buf) {
+    this.buffer = buf;
+  }
+
+  public int read() {
+    if (!buffer.hasRemaining()) {
+      return -1;
+    }
+    return buffer.get() & 0xFF;
+  }
+
+  public int read(@NonNull byte[] b, int off, int len) throws IOException {
+    if (!buffer.hasRemaining()) {
+      return -1;
+    }
+
+    len = Math.min(len, buffer.remaining());
+    buffer.get(b, off, len);
+    return len;
+  }
+}

firebase-firestore/src/test/java/com/google/firebase/firestore/util/ByteBufferInputStreamTest.java

@@ -0,0 +1,75 @@
+// Copyright 2021 Google LLC
+//
+// 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.firebase.firestore.util;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import org.junit.Test;
+import org.robolectric.annotation.Config;
+
+@org.junit.runner.RunWith(org.robolectric.RobolectricTestRunner.class)
+@Config(manifest = Config.NONE)
+public class ByteBufferInputStreamTest {
+
+  @Test
+  public void canReadSingleByte() {
+    ByteBuffer source = ByteBuffer.wrap(new byte[] {1, 2, 3});
+    ByteBufferInputStream inputStream = new ByteBufferInputStream(source);
+
+    assertEquals(1, inputStream.read());
+    assertEquals(2, inputStream.read());
+    assertEquals(3, inputStream.read());
+  }
+
+  @Test
+  public void canReadMultipleBytes() throws IOException {
+    ByteBuffer source = ByteBuffer.wrap(new byte[] {1, 2, 3});
+    ByteBufferInputStream inputStream = new ByteBufferInputStream(source);
+
+    byte[] destination = new byte[3];
+    int bytesRead = inputStream.read(destination);
+
+    assertEquals(3, bytesRead);
+    assertArrayEquals(new byte[] {1, 2, 3}, destination);
+  }
+
+  @Test
+  public void testHandlesEndOfStream() throws IOException {
+    ByteBuffer source = ByteBuffer.wrap(new byte[] {1});
+    ByteBufferInputStream inputStream = new ByteBufferInputStream(source);
+
+    byte[] destination = new byte[2];
+    int bytesRead = inputStream.read(destination);
+
+    assertEquals(1, bytesRead);
+    assertArrayEquals(new byte[] {1, 0}, destination);
+
+    assertEquals(-1, inputStream.read());
+  }
+
+  @Test
+  public void testHandlesNegativeBytes() throws IOException {
+    ByteBuffer source = ByteBuffer.wrap(new byte[] {-1});
+    ByteBufferInputStream inputStream = new ByteBufferInputStream(source);
+
+    int read = inputStream.read();
+    // The integer value for byte -1 is 255, as the last three bits are set for -1.
+    assertEquals(0xFF, read);
+    assertEquals(-1, (byte) read);
+  }
+}