NfsReadRequest.java

/**
 * Copyright 2016-2018 Dell Inc. or its subsidiaries. All rights reserved.
 *
 * <p>Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file
 * except in compliance with the License. A copy of the License is located at
 *
 * <p>http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 * <p>or in the "license" file accompanying this file. This file 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.emc.ecs.nfsclient.nfs;

import com.emc.ecs.nfsclient.rpc.Credential;
import com.emc.ecs.nfsclient.rpc.Xdr;
import java.io.FileNotFoundException;

/**
 * The request, as specified by RFC 1813 (https://tools.ietf.org/html/rfc1813).
 *
 * <p>Procedure READ reads data from a file.
 *
 * @author seibed
 */
public class NfsReadRequest extends NfsRequestBase {

  /**
   * The position within the file at which the read is to begin. An <code>offset</code> of 0 means
   * to read data starting at the beginning of the file. If <code>offset</code> is greater than or
   * equal to the size of the file, the status, NFS3_OK, is returned with <code>size</code> set to 0
   * and <code>eof</code> set to <code>true</code>, subject to access permissions checking.
   */
  private final long _offset;

  /**
   * The number of bytes of data that are to be read. If <code>size</code> is 0, the READ will
   * succeed and return 0 bytes of data, subject to access permissions checking. <code>size</code>
   * must be less than or equal to the value of the <code>rtmax</code> field in the FSINFO reply
   * structure for the file system that contains file. If greater, the server may return only <code>
   * rtmax</code> bytes, resulting in a short read.
   */
  private final int _size;

  /**
   * Creates the request, as specified by RFC 1813 (https://tools.ietf.org/html/rfc1813).
   *
   * <p>Procedure READ reads data from a file.
   *
   * @param fileHandle The file handle of the file from which data is to be read. This must identify
   *     a file system object of type, NF3REG.
   * @param offset The position within the file at which the read is to begin. An <code>offset
   *     </code> of 0 means to read data starting at the beginning of the file. If <code>offset
   *     </code> is greater than or equal to the size of the file, the status, NFS3_OK, is returned
   *     with <code>size</code> set to 0 and <code>eof</code> set to <code>true</code>, subject to
   *     access permissions checking.
   * @param size The number of bytes of data that are to be read. If <code>size</code> is 0, the
   *     READ will succeed and return 0 bytes of data, subject to access permissions checking.
   *     <code>size</code> must be less than or equal to the value of the <code>rtmax</code> field
   *     in the FSINFO reply structure for the file system that contains file. If greater, the
   *     server may return only <code>rtmax</code> bytes, resulting in a short read.
   * @param credential The credential used for RPC authentication.
   * @param nfsVersion The NFS version number
   */
  public NfsReadRequest(
      byte[] fileHandle, long offset, int size, Credential credential, int nfsVersion)
      throws FileNotFoundException {
    super(Nfs.RPC_PROGRAM, nfsVersion, Nfs.NFSPROC3_READ, credential, fileHandle);
    _offset = offset;
    _size = size;
  }

  /** {@inheritDoc} */
  @Override
  public void marshalling(Xdr xdr) {
    super.marshalling(xdr);
    xdr.putLong(_offset);
    xdr.putUnsignedInt(_size);
  }

  /** {@inheritDoc} */
  @Override
  public String toString() {
    return startToString("NfsReadRequest")
        .append(" offset:")
        .append(String.valueOf(_offset))
        .append(" size:")
        .append(String.valueOf(_size))
        .toString();
  }
}