test: add test example of fillFrom properly handling 0 byte reads (#2545)

Author: BenWhitehead

google-cloud-storage/src/test/java/com/google/cloud/storage/BuffersTest.java

@@ -16,10 +16,15 @@
 
 package com.google.cloud.storage;
 
+import static com.google.cloud.storage.TestUtils.assertAll;
+import static com.google.cloud.storage.TestUtils.xxd;
 import static com.google.common.truth.Truth.assertThat;
 
+import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.nio.channels.ReadableByteChannel;
 import java.security.SecureRandom;
+import java.util.concurrent.atomic.AtomicInteger;
 import org.junit.Test;
 
 public final class BuffersTest {
@@ -72,4 +77,87 @@ public void allocateAligned_evenlyDivisible_capacityGtAlignment() {
  ByteBuffer b1 = Buffers.allocateAligned(8, 4);
  assertThat(b1.capacity()).isEqualTo(8);
  }
+
+ @Test
+ public void fillFrom_handles_0SizeRead_someBytesRead() throws Exception {
+ byte[] bytes = new byte[14];
+ ByteBuffer buf = ByteBuffer.wrap(bytes);
+
+ byte[] expected =
+ new byte[] {
+ (byte) 'A',
+ (byte) 'B',
+ (byte) 'C',
+ (byte) 'A',
+ (byte) 'B',
+ (byte) 'A',
+ (byte) 'A',
+ (byte) 'A',
+ (byte) 'B',
+ (byte) 'A',
+ (byte) 'B',
+ (byte) 'C',
+ (byte) 0,
+ (byte) 0
+ };
+
+ int[] acceptSequence = new int[] {3, 2, 1, 0, 0, 1, 2, 3};
+ AtomicInteger readCount = new AtomicInteger(0);
+
+ ReadableByteChannel c =
+ new ReadableByteChannel() {
+ @Override
+ public int read(ByteBuffer dst) throws IOException {
+ int i = readCount.getAndIncrement();
+ if (i == acceptSequence.length) {
+ return -1;
+ }
+ int bytesToRead = acceptSequence[i];
+ if (bytesToRead > 0) {
+ long copy =
+ Buffers.copy(DataGenerator.base64Characters().genByteBuffer(bytesToRead), dst);
+ assertThat(copy).isEqualTo(bytesToRead);
+ }
+
+ return bytesToRead;
+ }
+
+ @Override
+ public boolean isOpen() {
+ return true;
+ }
+
+ @Override
+ public void close() throws IOException {}
+ };
+ int filled = Buffers.fillFrom(buf, c);
+
+ assertAll(
+ () -> assertThat(filled).isEqualTo(12),
+ () -> assertThat(xxd(bytes)).isEqualTo(xxd(expected)));
+ }
+
+ @Test
+ public void fillFrom_handles_0SizeRead_noBytesRead() throws Exception {
+ ByteBuffer buf = ByteBuffer.allocate(3);
+
+ ReadableByteChannel c =
+ new ReadableByteChannel() {
+ @Override
+ public int read(ByteBuffer dst) throws IOException {
+ return -1;
+ }
+
+ @Override
+ public boolean isOpen() {
+ return true;
+ }
+
+ @Override
+ public void close() throws IOException {}
+ };
+ int filled = Buffers.fillFrom(buf, c);
+
+ assertThat(filled).isEqualTo(-1);
+ }
 }