- added new Stack class that implements a stack on BLOB files - added new Stacks class that can be used for a set of Stacks (a 'Stack Database') - added methods to other classes to support the new stacks git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@6169 6c8d7289-2bf4-0310-a012-ef5d649a1542pull/1/head
parent
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commit
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// Stack.java
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// (C) 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 03.07.2009 on http://yacy.net
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//
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// $LastChangedDate: 2008-03-14 01:16:04 +0100 (Fr, 14 Mrz 2008) $
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// $LastChangedRevision: 4558 $
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// $LastChangedBy: orbiter $
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//
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// LICENSE
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package de.anomic.kelondro.blob;
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import java.io.File;
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import java.io.IOException;
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import java.util.Iterator;
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import de.anomic.kelondro.order.NaturalOrder;
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public class Stack {
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private Heap stack;
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private long lastHandle;
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/**
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* create a new stack object.
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* a stack object is backed by a blob file that contains the stack entries.
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* all stack entries can be accessed with a long handle; the handle is
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* represented as b256-encoded byte[] as key in the blob.
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* The handle is created using the current time. That means that the top
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* element on the stack has the maximum time as key handle and the element
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* at the bottom of the stack has the minimum time as key handle
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* @param stackFile
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* @throws IOException
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*/
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public Stack(final File stackFile) throws IOException {
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this.stack = new Heap(stackFile, 8, NaturalOrder.naturalOrder, 0);
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this.lastHandle = 0;
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}
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/**
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* create a new time handle. In case that the method is called
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* within a single millisecond twice, a new handle is created using
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* an increment of the previous handle to avoid handle collisions.
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* This method must be called in an synchronized environment
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* @return a unique handle for this stack
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*/
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private long nextHandle() {
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long h = System.currentTimeMillis();
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if (h <= this.lastHandle) h = lastHandle + 1;
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lastHandle = h;
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return h;
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}
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/**
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* Iterate all handles from the stack as Long numbers
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* @return an iterator of all handles of the stack
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* @throws IOException
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*/
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public synchronized Iterator<Long> handles() throws IOException {
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return NaturalOrder.LongIterator(this.stack.keys(true, false));
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}
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/**
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* get the size of a stack
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* @return the number of entries on the stack
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*/
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public synchronized int size() {
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return this.stack.size();
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}
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/**
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* push a new element on the top of the stack
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* @param b the new stack element
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* @return the handle used to store the new element
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* @throws IOException
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*/
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public synchronized long push(byte[] b) throws IOException {
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long handle = nextHandle();
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this.stack.put(NaturalOrder.encodeLong(handle, 8), b);
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return handle;
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}
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/**
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* push a new element on the top of the stack using a entry object
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* this is only useful for internal processes where a special handle
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* is created
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* @param b the new stack element
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* @return the handle used to store the new element
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* @throws IOException
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*/
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protected synchronized void push(Entry e) throws IOException {
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this.stack.put(NaturalOrder.encodeLong(e.h, 8), e.b);
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}
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/**
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* get an element from the stack using the handle
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* @param handle
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* @return the object that belongs to the handle
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* or null if no such element exists
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* @throws IOException
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*/
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public synchronized byte[] get(long handle) throws IOException {
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byte[] k = NaturalOrder.encodeLong(handle, 8);
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byte[] b = this.stack.get(k);
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if (b == null) return null;
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return b;
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}
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/**
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* remove an element from the stack using the entry handle
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* @param handle
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* @return the removed element
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* @throws IOException
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*/
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public synchronized byte[] remove(long handle) throws IOException {
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byte[] k = NaturalOrder.encodeLong(handle, 8);
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byte[] b = this.stack.get(k);
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if (b == null) return null;
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this.stack.remove(k);
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return b;
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}
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/**
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* remove the top element from the stack
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* @return the top element or null if the stack is empty
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* @throws IOException
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*/
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public synchronized Entry pop() throws IOException {
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return po(this.stack.lastKey(), true);
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}
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/**
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* return the top element of the stack.
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* The element is not removed from the stack.
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* Successive calls to this method will always return the same element
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* @return the element on the top of the stack or null, if stack is empty
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* @throws IOException
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*/
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public synchronized Entry top() throws IOException {
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return po(this.stack.lastKey(), false);
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}
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/**
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* remove the bottom element from the stack
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* @return the bottom element or null if the stack is empty
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* @throws IOException
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*/
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public synchronized Entry pot() throws IOException {
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return po(this.stack.firstKey(), true);
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}
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/**
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* return the bottom element of the stack.
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* The element is not removed from the stack.
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* Successive calls to this method will always return the same element
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* @return the element on the bottom of the stack or null, if stack is empty
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* @throws IOException
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*/
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public synchronized Entry bot() throws IOException {
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return po(this.stack.firstKey(), false);
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}
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private Entry po(byte[] k, boolean remove) throws IOException {
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if (k == null) return null;
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assert k.length == 8;
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byte[] b = this.stack.get(k);
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assert b != null;
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if (b == null) return null;
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if (remove) this.stack.remove(k);
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return new Entry(k, b);
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}
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public class Entry {
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private long h;
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private byte[] b;
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/**
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* create a new entry object using a long handle
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* @param h
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* @param b
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*/
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public Entry(long h, byte[] b) {
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this.h = h;
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this.b = b;
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}
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/**
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* create a new entry object using the byte[] encoded handle
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* @param k
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* @param b
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*/
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public Entry(byte[] k, byte[] b) {
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this.h = NaturalOrder.decodeLong(k);
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this.b = b;
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}
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/**
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* get the handle
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* @return the handle
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*/
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public long handle() {
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return h;
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}
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/**
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* get the blob entry
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* @return the blob
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*/
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public byte[] blob() {
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return b;
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}
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}
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/**
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* close the stack file and write a handle index
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*/
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public synchronized void close() {
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this.stack.close(true);
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}
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public void finalize() {
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this.close();
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}
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}
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@ -0,0 +1,274 @@
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// Stacks.java
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// (C) 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 03.07.2009 on http://yacy.net
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//
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// $LastChangedDate: 2008-03-14 01:16:04 +0100 (Fr, 14 Mrz 2008) $
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// $LastChangedRevision: 4558 $
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// $LastChangedBy: orbiter $
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//
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// LICENSE
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package de.anomic.kelondro.blob;
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import java.io.File;
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import java.io.IOException;
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import java.util.Iterator;
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import java.util.concurrent.ConcurrentHashMap;
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public class Stacks {
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private File stacksLocation;
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private String stacksPrefix;
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private ConcurrentHashMap<String, StackInstance> stacks;
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/**
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* create a stack organizing object.
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* Stacks can be created on-the-fly in the given stacksLocation directory
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* using simple push operations that create first entries in the stack
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* Stacks that do not contain any element upon the close() operation are removed
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* @param stackFile
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* @throws IOException
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*/
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public Stacks(final File stacksLocation, String stacksPrefix) {
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if (!stacksLocation.exists()) stacksLocation.mkdirs();
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assert stacksLocation.isDirectory();
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this.stacksLocation = stacksLocation;
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this.stacksPrefix = stacksPrefix;
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// initialize the stacks map
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this.stacks = new ConcurrentHashMap<String, StackInstance>();
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String[] sl = this.stacksLocation.list();
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for (String s: sl) {
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if (!s.startsWith(this.stacksPrefix + "_")) continue;
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StackInstance si;
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try {
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si = new StackInstance(new File(this.stacksLocation, s));
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this.stacks.put(si.name, si);
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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private class StackInstance {
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private String name;
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private File location;
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private Stack stack;
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public StackInstance(File location) throws IOException {
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String filename = location.getName();
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assert filename.startsWith(stacksPrefix + "_");
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assert filename.endsWith(".bstack");
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this.name = filename.substring(stacksPrefix.length() + 1, filename.length() - 7);
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this.location = location;
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this.stack = new Stack(location);
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}
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public StackInstance(String stack) throws IOException {
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this.location = new File(stacksLocation, stacksPrefix + "_" + stack + ".bstack");
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this.name = stack;
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this.stack = new Stack(location);
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}
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public String name() {
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return this.name;
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}
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public Stack stack() {
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return this.stack;
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}
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public File location() {
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return this.location;
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}
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}
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private Stack getStack(String stack) {
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StackInstance si = this.stacks.get(stack);
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if (si == null) {
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// create a new Stack on the fly
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try {
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si = new StackInstance(stack);
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this.stacks.put(stack, si);
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return si.stack();
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} catch (IOException e) {
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e.printStackTrace();
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return null;
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}
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}
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return si.stack();
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}
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/**
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* get the number of stacks organized by this object
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* @return the number of stack objects
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*/
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public int size() {
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return this.stacks.size();
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}
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/**
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* iterate all stack names
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* @return an iterator for the stack names
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*/
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public Iterator<String> stacks() {
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return this.stacks.keySet().iterator();
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}
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/**
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* get the size of a stack
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* @param stack the name of the stack
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* @return the number of entries on the stack
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*/
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public int size(String stack) {
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Stack s = getStack(stack);
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if (s == null) return -1;
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return s.size();
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}
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/**
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* Iterate all handles from a stack as Long numbers
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* @param stack the name of the stack
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* @return an iterator of all handles of the stack
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* @throws IOException
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*/
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public synchronized Iterator<Long> handles(String stack) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.handles();
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}
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/**
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* push a new element on the top of the stack
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* @param stack the name of the stack
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* @param b the new stack element
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* @return the handle used to store the new element
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* @throws IOException
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*/
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public long push(String stack, byte[] b) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return -1;
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return s.push(b);
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}
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/**
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* push a new element on the top of the stack using a entry object
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* this is only useful for internal processes where a special handle
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* is created
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* @param stack the name of the stack
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* @param b the new stack element
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* @return the handle used to store the new element
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* @throws IOException
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*/
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protected void push(String stack, Stack.Entry e) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return;
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s.push(e);
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}
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/**
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* get an element from the stack using the handle
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* @param stack the name of the stack
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* @param handle
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* @return the object that belongs to the handle
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* or null if no such element exists
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* @throws IOException
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*/
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public byte[] get(String stack, long handle) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.get(handle);
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}
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/**
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* remove an element from the stack using the entry handle
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* @param stack the name of the stack
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* @param handle
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* @return the removed element
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* @throws IOException
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*/
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public byte[] remove(String stack, long handle) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.remove(handle);
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}
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/**
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* remove the top element from the stack
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* @param stack the name of the stack
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* @return the top element or null if the stack is empty
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* @throws IOException
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*/
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public Stack.Entry pop(String stack) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.pop();
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}
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/**
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* return the top element of the stack.
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* The element is not removed from the stack.
|
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* Successive calls to this method will always return the same element
|
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* @param stack the name of the stack
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* @return the element on the top of the stack or null, if stack is empty
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* @throws IOException
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*/
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public Stack.Entry top(String stack) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.top();
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}
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/**
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* remove the bottom element from the stack
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* @param stack the name of the stack
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* @return the bottom element or null if the stack is empty
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* @throws IOException
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||||
*/
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||||
public Stack.Entry pot(String stack) throws IOException {
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Stack s = getStack(stack);
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if (s == null) return null;
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return s.pot();
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||||
}
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||||
|
||||
/**
|
||||
* return the bottom element of the stack.
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||||
* The element is not removed from the stack.
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||||
* Successive calls to this method will always return the same element
|
||||
* @param stack the name of the stack
|
||||
* @return the element on the bottom of the stack or null, if stack is empty
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||||
* @throws IOException
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||||
*/
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public Stack.Entry bot(String stack) throws IOException {
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Stack s = getStack(stack);
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||||
if (s == null) return null;
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return s.bot();
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}
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/**
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* close all stack files
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||||
*/
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public synchronized void close() {
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for (StackInstance se: this.stacks.values()) {
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se.stack.close();
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||||
}
|
||||
}
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||||
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||||
public void finalize() {
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||||
this.close();
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||||
}
|
||||
}
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