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/* CWrapper -- wrapping C structures
* Copyright (C) 2014 Galois, Inc.
*
* This library is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this library. If not, see <http://www.gnu.org/licenses/>.
*
* To contact Galois, complete the Web form at
* <http://corp.galois.com/contact/> or write to Galois, Inc., 421 Southwest
* 6th Avenue, Suite 300, Portland, Oregon, 97204-1622. */
package com.galois.ppaml.tracer;
/**
* A class which wraps a C structure and associated functions.
*
* <p> This class is intended to work hand-in-hand with Java Native Interface
* code that follows a four-stage lifecycle:
*
* <dl>
* <dt>Allocation</dt><dd>The system reserves memory and resources needed by
* the structure.</dd>
* <dt>Initialization</dt><dd>The system installs data into the structure to
* make it ready for use.</dd>
* <dt>Finalization</dt><dd>The system cleans up the data structure under the
* assumption that it will not be used anymore.</dd>
* <dt>Freeing</dt><dd>The system releases memory and resources needed by the
* structure.</dd>
* </dl>
*
* This class defines abstract methods associated with each of these phases; by
* defining contracts on them, it can then consolidate the phases into two
* concretely-implemented operations:
*
* <dl>
* <dt>Open</dt><dd>The system allocates and initializes the underlying
* structure.</dd>
* <dt>Close</dt><dd>The system finalizes and frees the underlying
* structure.</dd>
* </dl>
*
* <p> <b>This class is not intended to be instantiated directly. Only
* instantiate its concrete subclasses.
*/
abstract class CWrapper {
/**
* C pointer to the underlying data structure.
*/
protected long cPointer;
/////////////////////////// Low-level life cycle ///////////////////////////
/**
* Reserves memory and resources needed by the structure.
*
* <p> <b>Precondition:</b> <code>cPointer</code> is <code>0</code>.
*
* <p> <b>Postcondition:</b> If allocation was successful,
* <code>cPointer</code> is not <code>0</code>.
*/
abstract protected void allocateCPointer();
/**
* Installs data into the structure to make it ready for use.
*
* <p> <b>Precondition:</b> Allocation succeeded.
*/
abstract protected void initializeCPointer();
/**
* Cleans up the structure under the assumption that it will not be used
* anymore.
*
* <p> <b>Precondition:</b> Initialization succeeded.
*/
abstract protected void finalizeCPointer();
/**
* Releases memory and resources needed by the structure.
*
* <p> <b>Precondition:</b> <code>cPointer</code> is not <code>0</code>. <br>
* <b>Precondition:</b> Finalization succeeded.
*
* <p> <b>Postcondition:</b> <code>cPointer</code> is <code>0</code>.
*/
abstract protected void freeCPointer();
////////////////////////// High-level life cycle //////////////////////////
/**
* Allocates and initializes the underlying structure.
*
* @throws OpenedException the underlying structure has already been opened.
*
* @throws NativeOutOfMemoryError allocation failed.
*/
protected synchronized void open() {
if (cPointer != 0) {
throw new OpenedException();
}
allocateCPointer();
if (cPointer == 0) {
throw new NativeOutOfMemoryError();
}
initializeCPointer();
}
/**
* Finalizes and frees the underlying structure.
*
* @throws ClosedException the underlying structure has already been closed.
*/
public synchronized void close() {
if (cPointer == 0) {
throw new ClosedException();
}
finalizeCPointer();
freeCPointer();
cPointer = 0;
}
////////////////////////// Associated exceptions //////////////////////////
/**
* Signals that the underlying structure is already open.
*/
public class OpenedException extends java.lang.IllegalStateException {
static final long serialVersionUID = -7226578680647930527L;
/**
* Constructs a <code>CWrapper.OpenedException</code> with no detail
* message.
*/
protected OpenedException() {
super();
}
}
/**
* Signals that the underlying structure is already closed.
*/
public class ClosedException extends java.lang.IllegalStateException {
static final long serialVersionUID = -2471059099211958977L;
/**
* Constructs a <code>CWrapper.ClosedException</code> with no detail
* message.
*/
protected ClosedException() {
super();
}
}
////////////////////////////// Miscellaneous //////////////////////////////
@Override
protected void finalize() {
close();
}
@Override
protected Object clone() throws java.lang.CloneNotSupportedException {
throw new java.lang.CloneNotSupportedException();
}
}
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