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NFS Client for Java - provides read/write access to data on NFS servers. The current implementation supports only NFS version 3.
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/**
 * Copyright 2016 EMC Corporation. All Rights Reserved.
 *
 * 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
 *
 * http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 * 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 java.io.FileNotFoundException;

import com.emc.ecs.nfsclient.rpc.Credential;
import com.emc.ecs.nfsclient.rpc.Xdr;

/**
 * The request, as specified by RFC 1813 (https://tools.ietf.org/html/rfc1813).
 * 
 * 
 * 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
     * offset of 0 means to read data starting at the beginning of
     * the file. If offset is greater than or equal to the size of
     * the file, the status, NFS3_OK, is returned with size set to
     * 0 and eof set to true, subject to access
     * permissions checking.
     */
    private final long _offset;

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

    /**
     * Creates the request, as specified by RFC 1813
     * (https://tools.ietf.org/html/rfc1813).
     * 
     * 
     * 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
     *            offset of 0 means to read data starting at the
     *            beginning of the file. If offset is greater than
     *            or equal to the size of the file, the status, NFS3_OK, is
     *            returned with size set to 0 and eof
     *            set to true, subject to access permissions
     *            checking.
     * @param size
     *            The number of bytes of data that are to be read. If
     *            size is 0, the READ will succeed and return 0
     *            bytes of data, subject to access permissions checking.
     *            size must be less than or equal to the value of
     *            the rtmax field in the FSINFO reply structure for
     *            the file system that contains file. If greater, the server may
     *            return only rtmax bytes, resulting in a short
     *            read.
     * @param credential
     *            The credential used for RPC authentication.
     * @param nfsVersion
     *            The NFS version number
     * @throws FileNotFoundException
     */
    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;
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.emc.ecs.nfsclient.nfs.NfsRequestBase#marshalling(com.emc.ecs.
     * nfsclient.rpc.Xdr)
     */
    public void marshalling(Xdr xdr) {
        super.marshalling(xdr);
        xdr.putLong(_offset);
        xdr.putUnsignedInt(_size);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#toString()
     */
    public String toString() {
        return startToString("NfsReadRequest").append(" offset:").append(String.valueOf(_offset)).append(" size:")
                .append(String.valueOf(_size)).toString();
    }

}