HDFS-14564: Add libhdfs APIs for readFully; add readFully to ByteBufferPositionedReadable (apache#963) Contributed by Sahil Takiar.

Reviewed-by: Siyao Meng <[email protected]>

Author: sahilTakiar

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/CryptoInputStream.java

@@ -33,6 +33,7 @@
 import com.google.common.base.Preconditions;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.ByteBufferPositionedReadable;
 import org.apache.hadoop.fs.ByteBufferReadable;
 import org.apache.hadoop.fs.CanSetDropBehind;
 import org.apache.hadoop.fs.CanSetReadahead;
@@ -53,18 +54,19 @@
  * required in order to ensure that the plain text and cipher text have a 1:1
  * mapping. The decryption is buffer based. The key points of the decryption
  * are (1) calculating the counter and (2) padding through stream position:
- * <p/>
+ * <p>
  * counter = base + pos/(algorithm blocksize); 
  * padding = pos%(algorithm blocksize); 
- * <p/>
+ * <p>
  * The underlying stream offset is maintained as state.
  */
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
 public class CryptoInputStream extends FilterInputStream implements 
     Seekable, PositionedReadable, ByteBufferReadable, HasFileDescriptor, 
     CanSetDropBehind, CanSetReadahead, HasEnhancedByteBufferAccess, 
-    ReadableByteChannel, CanUnbuffer, StreamCapabilities {
+    ReadableByteChannel, CanUnbuffer, StreamCapabilities,
+    ByteBufferPositionedReadable {
   private final byte[] oneByteBuf = new byte[1];
   private final CryptoCodec codec;
   private final Decryptor decryptor;
@@ -328,20 +330,40 @@ public int read(long position, byte[] buffer, int offset, int length)
       throws IOException {
     checkStream();
     try {
-      final int n = ((PositionedReadable) in).read(position, buffer, offset, 
+      final int n = ((PositionedReadable) in).read(position, buffer, offset,
           length);
       if (n > 0) {
         // This operation does not change the current offset of the file
         decrypt(position, buffer, offset, n);
       }
-      
+
       return n;
     } catch (ClassCastException e) {
       throw new UnsupportedOperationException("This stream does not support " +
           "positioned read.");
     }
   }
-  
+
+  /**
+   * Positioned readFully using {@link ByteBuffer}s. This method is thread-safe.
+   */
+  @Override
+  public void readFully(long position, final ByteBuffer buf)
+      throws IOException {
+    checkStream();
+    if (!(in instanceof ByteBufferPositionedReadable)) {
+      throw new UnsupportedOperationException(in.getClass().getCanonicalName()
+          + " does not support positioned reads with byte buffers.");
+    }
+    int bufPos = buf.position();
+    ((ByteBufferPositionedReadable) in).readFully(position, buf);
+    final int n = buf.position() - bufPos;
+    if (n > 0) {
+      // This operation does not change the current offset of the file
+      decrypt(position, buf, n, bufPos);
+    }
+  }
+
   /**
    * Decrypt length bytes in buffer starting at offset. Output is also put 
    * into buffer starting at offset. It is thread-safe.
@@ -375,7 +397,7 @@ private void decrypt(long position, byte[] buffer, int offset, int length)
       returnDecryptor(decryptor);
     }
   }
-  
+
   /** Positioned read fully. It is thread-safe */
   @Override
   public void readFully(long position, byte[] buffer, int offset, int length)
@@ -407,7 +429,7 @@ public void seek(long pos) throws IOException {
     checkStream();
     try {
       /*
-       * If data of target pos in the underlying stream has already been read 
+       * If data of target pos in the underlying stream has already been read
        * and decrypted in outBuffer, we just need to re-position outBuffer.
        */
       if (pos <= streamOffset && pos >= (streamOffset - outBuffer.remaining())) {
@@ -523,7 +545,7 @@ public int read(ByteBuffer buf) throws IOException {
    * Output is also buf and same start position.
    * buf.position() and buf.limit() should be unchanged after decryption.
    */
-  private void decrypt(ByteBuffer buf, int n, int start) 
+  private void decrypt(ByteBuffer buf, int n, int start)
       throws IOException {
     final int pos = buf.position();
     final int limit = buf.limit();
@@ -605,7 +627,7 @@ public ByteBuffer read(ByteBufferPool bufferPool, int maxLength,
       }
       return buffer;
     } catch (ClassCastException e) {
-      throw new UnsupportedOperationException("This stream does not support " + 
+      throw new UnsupportedOperationException("This stream does not support " +
           "enhanced byte buffer access.");
     }
   }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/ByteBufferPositionedReadable.java

@@ -0,0 +1,90 @@
+/**
+ * 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.hadoop.fs;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/**
+ * Implementers of this interface provide a positioned read API that writes to a
+ * {@link ByteBuffer} rather than a {@code byte[]}.
+ *
+ * @see PositionedReadable
+ * @see ByteBufferReadable
+ */
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
+public interface ByteBufferPositionedReadable {
+  /**
+   * Reads up to {@code buf.remaining()} bytes into buf from a given position
+   * in the file and returns the number of bytes read. Callers should use
+   * {@code buf.limit(...)} to control the size of the desired read and
+   * {@code buf.position(...)} to control the offset into the buffer the data
+   * should be written to.
+   * <p>
+   * After a successful call, {@code buf.position()} will be advanced by the
+   * number of bytes read and {@code buf.limit()} will be unchanged.
+   * <p>
+   * In the case of an exception, the state of the buffer (the contents of the
+   * buffer, the {@code buf.position()}, the {@code buf.limit()}, etc.) is
+   * undefined, and callers should be prepared to recover from this
+   * eventuality.
+   * <p>
+   * Callers should use {@link StreamCapabilities#hasCapability(String)} with
+   * {@link StreamCapabilities#PREADBYTEBUFFER} to check if the underlying
+   * stream supports this interface, otherwise they might get a
+   * {@link UnsupportedOperationException}.
+   * <p>
+   * Implementations should treat 0-length requests as legitimate, and must not
+   * signal an error upon their receipt.
+   * <p>
+   * This does not change the current offset of a file, and is thread-safe.
+   *
+   * @param position position within file
+   * @param buf the ByteBuffer to receive the results of the read operation.
+   * @return the number of bytes read, possibly zero, or -1 if reached
+   *         end-of-stream
+   * @throws IOException if there is some error performing the read
+   */
+  int read(long position, ByteBuffer buf) throws IOException;
+
+  /**
+   * Reads {@code buf.remaining()} bytes into buf from a given position in
+   * the file or until the end of the data was reached before the read
+   * operation completed. Callers should use {@code buf.limit(...)} to
+   * control the size of the desired read and {@code buf.position(...)} to
+   * control the offset into the buffer the data should be written to.
+   * <p>
+   * This operation provides similar semantics to
+   * {@link #read(long, ByteBuffer)}, the difference is that this method is
+   * guaranteed to read data until the {@link ByteBuffer} is full, or until
+   * the end of the data stream is reached.
+   *
+   * @param position position within file
+   * @param buf the ByteBuffer to receive the results of the read operation.
+   * @throws IOException if there is some error performing the read
+   * @throws EOFException the end of the data was reached before
+   * the read operation completed
+   * @see #read(long, ByteBuffer)
+   */
+  void readFully(long position, ByteBuffer buf) throws IOException;
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataInputStream.java

@@ -38,7 +38,8 @@
 public class FSDataInputStream extends DataInputStream
     implements Seekable, PositionedReadable, 
       ByteBufferReadable, HasFileDescriptor, CanSetDropBehind, CanSetReadahead,
-      HasEnhancedByteBufferAccess, CanUnbuffer, StreamCapabilities {
+      HasEnhancedByteBufferAccess, CanUnbuffer, StreamCapabilities,
+      ByteBufferPositionedReadable {
   /**
    * Map ByteBuffers that we have handed out to readers to ByteBufferPool 
    * objects
@@ -50,8 +51,8 @@ public class FSDataInputStream extends DataInputStream
   public FSDataInputStream(InputStream in) {
     super(in);
     if( !(in instanceof Seekable) || !(in instanceof PositionedReadable) ) {
-      throw new IllegalArgumentException(
-          "In is not an instance of Seekable or PositionedReadable");
+      throw new IllegalArgumentException(in.getClass().getCanonicalName() +
+          " is not an instance of Seekable or PositionedReadable");
     }
   }
 
@@ -147,7 +148,8 @@ public int read(ByteBuffer buf) throws IOException {
       return ((ByteBufferReadable)in).read(buf);
     }
 
-    throw new UnsupportedOperationException("Byte-buffer read unsupported by input stream");
+    throw new UnsupportedOperationException("Byte-buffer read unsupported " +
+            "by " + in.getClass().getCanonicalName());
   }
 
   @Override
@@ -167,9 +169,8 @@ public void setReadahead(Long readahead)
     try {
       ((CanSetReadahead)in).setReadahead(readahead);
     } catch (ClassCastException e) {
-      throw new UnsupportedOperationException(
-          "this stream does not support setting the readahead " +
-          "caching strategy.");
+      throw new UnsupportedOperationException(in.getClass().getCanonicalName() +
+          " does not support setting the readahead caching strategy.");
     }
   }
 
@@ -246,4 +247,23 @@ public boolean hasCapability(String capability) {
   public String toString() {
     return super.toString() + ": " + in;
   }
+
+  @Override
+  public int read(long position, ByteBuffer buf) throws IOException {
+    if (in instanceof ByteBufferPositionedReadable) {
+      return ((ByteBufferPositionedReadable) in).read(position, buf);
+    }
+    throw new UnsupportedOperationException("Byte-buffer pread unsupported " +
+        "by " + in.getClass().getCanonicalName());
+  }
+
+  @Override
+  public void readFully(long position, ByteBuffer buf) throws IOException {
+    if (in instanceof ByteBufferPositionedReadable) {
+      ((ByteBufferPositionedReadable) in).readFully(position, buf);
+    } else {
+      throw new UnsupportedOperationException("Byte-buffer pread " +
+              "unsupported by " + in.getClass().getCanonicalName());
+    }
+  }
 }