org.filesys.locking.FileLockList Maven / Gradle / Ivy
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/*
* Copyright (C) 2006-2010 Alfresco Software Limited.
*
* This file is part of Alfresco
*
* Alfresco is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Alfresco 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Alfresco. If not, see Contains a list of the current locks on a file.
*
* @author gkspencer
*/
public class FileLockList implements Serializable {
// Serialization id
private static final long serialVersionUID = 1L;
// List of file locks
private ArrayList m_lockList;
/**
* Construct an empty file lock list.
*/
public FileLockList() {
m_lockList = new ArrayList();
}
/**
* Add a lock to the list
*
* @param lock Lock to be added to the list.
*/
public final void addLock(FileLock lock) {
m_lockList.add(lock);
}
/**
* Find the matching lock
*
* @param lock FileLock
* @return FileLock
*/
public final FileLock findLock(FileLock lock) {
return findLock(lock.getOffset(), lock.getLength(), lock.getProcessId());
}
/**
* Find the matching lock
*
* @param offset long
* @param len long
* @param pid int
* @return FileLock
*/
public final FileLock findLock(long offset, long len, int pid) {
// Check if there are any locks in the list
if (numberOfLocks() == 0)
return null;
// Search for the required lock
FileLock fLock = null;
for (int i = 0; i < numberOfLocks(); i++) {
// Get the current lock details
fLock = getLockAt(i);
if (fLock.getOffset() == offset && fLock.getLength() == len) {
// Return the matching lock
return fLock;
}
}
// Lock not found
return null;
}
/**
* Remove a lock from the list
*
* @param lock FileLock
* @return FileLock
*/
public final FileLock removeLock(FileLock lock) {
return removeLock(lock.getOffset(), lock.getLength(), lock.getProcessId());
}
/**
* Remove a lock from the list
*
* @param offset Starting offset of the lock
* @param len Locked section length
* @param pid Owner process id
* @return FileLock
*/
public final FileLock removeLock(long offset, long len, int pid) {
// Check if there are any locks in the list
if (numberOfLocks() == 0)
return null;
// Search for the required lock
for (int i = 0; i < numberOfLocks(); i++) {
// Get the current lock details
FileLock curLock = getLockAt(i);
if (curLock.getOffset() == offset && curLock.getLength() == len) {
// Remove the lock from the list
m_lockList.remove(i);
return curLock;
}
}
// Lock not found
return null;
}
/**
* Remove all locks from the list
*/
public final void removeAllLocks() {
m_lockList.clear();
}
/**
* Return the specified lock details
*
* @param idx Lock index
* @return FileLock
*/
public final FileLock getLockAt(int idx) {
if (idx < m_lockList.size())
return m_lockList.get(idx);
return null;
}
/**
* Remove the lock at the specified index in the list
*
* @param idx Lock index
* @return FileLock
*/
public final FileLock removeLockAt(int idx) {
if (idx < m_lockList.size())
return m_lockList.remove(idx);
return null;
}
/**
* Check if the new lock should be allowed by comparing with the locks in the list.
*
* @param lock FileLock
* @return boolean true if the lock can be granted, else false.
*/
public final boolean allowsLock(FileLock lock) {
// If the list is empty we can allow the lock request
if (numberOfLocks() == 0)
return true;
// Search for any overlapping locks
for (int i = 0; i < numberOfLocks(); i++) {
// Get the current lock details
FileLock curLock = getLockAt(i);
if (curLock.hasOverlap(lock))
return false;
}
// The lock does not overlap with any existing locks
return true;
}
/**
* Check if the file is readable for the specified section of the file and process id
*
* @param lock FileLock
* @return boolean
*/
public final boolean canReadFile(FileLock lock) {
return canReadFile(lock.getOffset(), lock.getLength(), lock.getProcessId());
}
/**
* Check if the file is readable for the specified section of the file and process id
*
* @param offset long
* @param len long
* @param pid int
* @return boolean
*/
public final boolean canReadFile(long offset, long len, int pid) {
// If the list is empty we can allow the read request
if (numberOfLocks() == 0)
return true;
// Search for a lock that prevents the read
for (int i = 0; i < numberOfLocks(); i++) {
// Get the current lock details
FileLock curLock = getLockAt(i);
// Check if the process owns the lock, if not then check if there is an overlap
if (curLock.getProcessId() != pid) {
// Check if the read overlaps with the locked area
if (curLock.hasOverlap(offset, len) == true)
return false;
}
}
// The lock does not overlap with any existing locks
return true;
}
/**
* Check if the file is writeable for the specified section of the file and process id
*
* @param lock FileLock
* @return boolean
*/
public final boolean canWriteFile(FileLock lock) {
return canWriteFile(lock.getOffset(), lock.getLength(), lock.getProcessId());
}
/**
* Check if the file is writeable for the specified section of the file and process id
*
* @param offset long
* @param len long
* @param pid int
* @return boolean
*/
public final boolean canWriteFile(long offset, long len, int pid) {
// If the list is empty we can allow the read request
if (numberOfLocks() == 0)
return true;
// Search for a lock that prevents the read
for (int i = 0; i < numberOfLocks(); i++) {
// Get the current lock details
FileLock curLock = getLockAt(i);
// Check if the process owns the lock, if not then check if there is an overlap
if (curLock.getProcessId() != pid) {
// Check if the read overlaps with the locked area
if (curLock.hasOverlap(offset, len) == true)
return false;
}
}
// The lock does not overlap with any existing locks
return true;
}
/**
* Return the count of locks in the list.
*
* @return int Number of locks in the list.
*/
public final int numberOfLocks() {
return m_lockList.size();
}
/**
* Return the lock list as a string
*
* @return String
*/
public String toString() {
StringBuilder str = new StringBuilder();
str.append("[Locklist:");
str.append(numberOfLocks());
if (numberOfLocks() > 0) {
for (int i = 0; i < numberOfLocks(); i++) {
str.append(getLockAt(i));
str.append(",");
}
}
str.append("]");
return str.toString();
}
}