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@ -7,7 +7,7 @@
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// $LastChangedBy$
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//
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// LICENSE
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//
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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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@ -37,7 +37,7 @@ public class Stack {
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private final 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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@ -45,7 +45,7 @@ public class Stack {
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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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* 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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@ -53,7 +53,15 @@ public class Stack {
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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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* clear the stack content
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* @throws IOException
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*/
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public void clear() throws IOException {
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this.stack.clear();
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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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@ -63,11 +71,11 @@ public class 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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if (h <= this.lastHandle) h = this.lastHandle + 1;
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this.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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@ -76,7 +84,7 @@ public class Stack {
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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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@ -84,20 +92,20 @@ public class Stack {
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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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* @throws RowSpaceExceededException
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* @throws RowSpaceExceededException
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*/
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public synchronized long push(final byte[] b) throws IOException, RowSpaceExceededException {
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long handle = nextHandle();
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this.stack.insert(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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@ -105,19 +113,19 @@ public class 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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* @throws RowSpaceExceededException
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* @throws RowSpaceExceededException
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*/
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protected synchronized void push(final Entry e) throws IOException, RowSpaceExceededException {
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this.stack.insert(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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* @throws RowSpaceExceededException
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* @throws RowSpaceExceededException
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*/
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public synchronized byte[] get(final long handle) throws IOException, RowSpaceExceededException {
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byte[] k = NaturalOrder.encodeLong(handle, 8);
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@ -125,13 +133,13 @@ public class Stack {
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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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* @throws RowSpaceExceededException
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* @throws RowSpaceExceededException
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*/
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public synchronized byte[] remove(final long handle) throws IOException, RowSpaceExceededException {
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byte[] k = NaturalOrder.encodeLong(handle, 8);
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@ -140,7 +148,7 @@ public class Stack {
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this.stack.delete(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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@ -149,7 +157,7 @@ public class Stack {
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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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@ -160,7 +168,7 @@ public class Stack {
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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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@ -169,7 +177,7 @@ public class Stack {
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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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@ -180,7 +188,7 @@ public class Stack {
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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(final byte[] k, final 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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@ -196,12 +204,12 @@ public class Stack {
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if (remove) this.stack.delete(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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long h;
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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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@ -211,7 +219,7 @@ public class Stack {
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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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@ -221,31 +229,31 @@ public class Stack {
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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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return this.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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return this.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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@Override
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public void finalize() {
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this.close();
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Michael Peter Christen
13 years ago