logread.nc

来自「tinyos-2.x.rar」· NC 代码 · 共 126 行

/**
 * Copyright (c) 2005-2006 Arch Rock Corporation
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the
 *   distribution.
 * - Neither the name of the Arch Rock Corporation nor the names of
 *   its contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * ARCHED ROCK OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE
 *
 * Copyright (c) 2002-2006 Intel Corporation
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE     
 * file. If you do not find these files, copies can be found by writing to
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300, Berkeley, CA, 
 * 94704.  Attention:  Intel License Inquiry.
 */

/**
 * Read interface for the log storage abstraction described in
 * TEP103.
 *
 * @author Jonathan Hui <[e-mail]>
 * @author David Gay
 * @version $Revision: 1.5 $ $Date: 2008/06/04 03:00:29 $
 */

#include "Storage.h"

interface LogRead {
  /**
   * Initiate a read operation from the current position within a given log
   * volume. On SUCCESS, the <code>readDone</code> event will signal
   * completion of the operation.
   * 
   * @param 'void* COUNT(len) buf' buffer to place read data.
   * @param len number of bytes to read.
   * @return 
   *   <li>SUCCESS if the request was accepted, 
   *   <li>EBUSY if a request is already being processed.
   */
  command error_t read(void* buf, storage_len_t len);

  /**
   * Signals the completion of a read operation. The current read position is
   * advanced by <code>len</code> bytes.
   *
   * @param addr starting address of read.
   * @param 'void* COUNT(len) buf' buffer where read data was placed.
   * @param len number of bytes read - this may be less than requested
   *    (even equal to 0) if the end of the log was reached
   * @param error SUCCESS if read was possible, FAIL otherwise
   */
  event void readDone(void* buf, storage_len_t len, error_t error);

  /**
   * Return a "cookie" representing the current read offset within the
   * log. This cookie can be used in a subsequent seek operation to
   * return to the same place in the log (if it hasn't been overwritten).
   *
   * @return Cookie representing current offset. 
   *   <code>SEEK_BEGINNING</code> will be returned if:<ul>
   *   <li> a write in a circular log overwrote the previous read position
   *   <li> seek was passed a cookie representing a position before the
   *        current beginning of a circular log
   *   </ul>
   *   Note that <code>SEEK_BEGINNING</code> can also be returned at
   *   other times (just after erasing a log, etc).
   */
  command storage_cookie_t currentOffset();

  /**
   * Set the read position in the log, using a cookie returned by the
   * <code>currentOffset</code> commands of <code>LogRead</code> or
   * <code>LogWrite</code>, or the special value <code>SEEK_BEGINNING</code>.
   *
   * If the specified position has been overwritten, the read position
   * will be set to the beginning of the log.
   *
   * @return 
   *   <li>SUCCESS if the request was accepted, 
   *   <li>EBUSY if a request is already being processed.
   */
  command error_t seek(storage_cookie_t offset);

  /**
   * Report success of seek operation. If <code>SUCCESS</code> is returned,
   * the read position has been changed as requested. If other values are
   * returned, the read position is undefined.
   *
   * @param error SUCCESS if the seek was succesful, EINVAL if the cookie
   *   was invalid and FAIL for other errors.
   */
  event void seekDone(error_t error);
  
  /**
   * Report approximate log capacity in bytes. Note that use of
   * <code>sync</code>, failures and general overhead may reduce the number
   * of bytes available to the log. 
   *
   * @return Volume size.
   */
  command storage_len_t getSize();
}