Github user ppadma commented on a diff in the pull request:
https://github.com/apache/drill/pull/611#discussion_r85153296
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/util/filereader/DirectBufInputStream.java
---
@@ -0,0 +1,183 @@
+/**
+ * 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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.drill.exec.util.filereader;
+
+import com.google.common.base.Preconditions;
+import io.netty.buffer.DrillBuf;
+import org.apache.drill.exec.memory.BufferAllocator;
+import org.apache.hadoop.fs.ByteBufferReadable;
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.parquet.hadoop.util.CompatibilityUtil;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.nio.ByteBuffer;
+
+public class DirectBufInputStream extends FilterInputStream {
+
+ private static final org.slf4j.Logger logger =
+ org.slf4j.LoggerFactory.getLogger(DirectBufInputStream.class);
+
+ protected boolean enableHints = true;
+ protected String streamId; // a name for logging purposes only
+ protected BufferAllocator allocator;
+ /**
+ * The length of the data we expect to read. The caller may, in fact,
+ * ask for more or less bytes. However this is useful for providing
hints where
+ * the underlying InputStream supports hints (e.g. fadvise)
+ */
+ protected final long totalByteSize;
+
+ /**
+ * The offset in the underlying stream to start reading from
+ */
+ protected final long startOffset;
+
+ public DirectBufInputStream(InputStream in, BufferAllocator allocator,
String id, long startOffset,
+ long totalByteSize, boolean enableHints) {
+ super(in);
+ Preconditions.checkArgument(startOffset >= 0);
+ Preconditions.checkArgument(totalByteSize >= 0);
+ this.streamId = id;
+ this.allocator = allocator;
+ this.startOffset = startOffset;
+ this.totalByteSize = totalByteSize;
+ this.enableHints = enableHints;
+ }
+
+ public void init() throws IOException, UnsupportedOperationException {
+ checkStreamSupportsByteBuffer();
+ if (enableHints) {
+ fadviseIfAvailable(getInputStream(), this.startOffset,
this.totalByteSize);
+ }
+ getInputStream().seek(this.startOffset);
+ return;
+ }
+
+ public int read() throws IOException {
+ return getInputStream().read();
+ }
+
+ public synchronized int read(DrillBuf buf, int off, int len) throws
IOException {
+ buf.clear();
+ ByteBuffer directBuffer = buf.nioBuffer(0, len);
+ int lengthLeftToRead = len;
+ while (lengthLeftToRead > 0) {
+ lengthLeftToRead -= CompatibilityUtil.getBuf(getInputStream(),
directBuffer, lengthLeftToRead);
+ }
+ buf.writerIndex(len);
+ return len;
+ }
+
+ public synchronized DrillBuf getNext(int bytes) throws IOException {
+ DrillBuf b = allocator.buffer(bytes);
+ int bytesRead = -1;
+ try {
+ bytesRead = read(b, 0, bytes);
+ } catch (IOException e){
+ b.release();
+ throw e;
+ }
+ if (bytesRead <= -1) {
--- End diff --
bytesRead = 0 ?
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