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321 lines
11 KiB
321 lines
11 KiB
// kelondroMHashMap.java
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// -----------------------
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// part of YaCy
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// (C) by Michael Peter Christen; mc@yacy.net
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// first published on http://www.anomic.de
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// Frankfurt, Germany, 2005
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// Created 08.12.2005
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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.util;
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import java.util.Iterator;
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public class CompressedHashMap {
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int keylen;
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int valuelen;
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int reclen, count;
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byte[] mem;
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private final byte[] emptykey;
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public CompressedHashMap(final int valuelen) {
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// initializes a hash map with integer access key
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this(4, valuelen);
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}
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public CompressedHashMap(final int keylen, final int valuelen) {
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this.keylen = keylen;
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this.valuelen = valuelen;
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this.reclen = keylen + valuelen;
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this.mem = new byte[1 * reclen];
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this.count = 0;
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this.emptykey = new byte[keylen];
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for (int i = 0; i < keylen; i++) emptykey[i] = 0;
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for (int i = 0; i < (mem.length / reclen); i++) System.arraycopy(emptykey, 0, mem, i * reclen, keylen);
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}
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private boolean equals(final int posKeyInMem, final byte[] otherkey) {
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assert (otherkey.length == keylen);
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int pos = posKeyInMem * reclen;
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int i = 0;
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while (i < keylen) if (mem[pos++] != otherkey[i++]) return false;
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return true;
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}
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private int rehashtry() {
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return 1 + mem.length / 2;
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}
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private int capacity() {
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return mem.length / reclen;
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}
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private static int hashkey(final byte[] key, final int capacity) {
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int h = 0;
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for (int i = 0; i < key.length; i++) h = h * 15 + (0xff & key[i]);
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//System.out.println("hash code of key " + new String(key) + " is " + h);
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return h % capacity;
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}
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private static int rehash(int previousKey, final int capacity) {
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if (previousKey == 0) previousKey = capacity;
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return previousKey - 1;
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}
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public int size() {
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return count;
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}
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private int findExisting(final byte[] key) {
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// returns an index position if found; -1 otherwise
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int hash = hashkey(key, capacity());
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//System.out.println("first guess for key " + new String(key) + ": " + hash + "( capacity is " + capacity() + " )");
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int testcount = 0;
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while (testcount++ < rehashtry()) {
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if (mem[hash * reclen] == 0) return -1;
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if (equals(hash, key)) return hash;
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hash = rehash(hash, capacity());
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}
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return -1;
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}
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private int findSpace(final byte[] key) {
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// returns an new index position which is empty
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// if there is no space left -1 is returned
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int hash = hashkey(key, capacity());
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int testcount = 0;
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while (testcount++ < rehashtry()) {
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if (mem[hash * reclen] == 0) return hash;
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hash = rehash(hash, capacity());
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}
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return -1;
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}
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private static int findSpace(final byte[] m, final byte[] key, final int rl, final int trycount, final int capacity) {
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// returns an new index position which is empty
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// if there is no space left -1 is returned
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int hash = hashkey(key, capacity);
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int testcount = 0;
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while (testcount++ < trycount) {
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if (m[hash * rl] == 0) return hash;
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hash = rehash(hash, capacity);
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}
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return -1;
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}
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private static byte[] toByteKey(int v) {
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assert (v >= 0);
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v = v | 0x80000000; // set bit in first byte
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return new byte[]{(byte) ((v >>> 24) & 0xFF), (byte) ((v >>> 16) & 0xFF),
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(byte) ((v >>> 8) & 0xFF), (byte) ((v >>> 0) & 0xFF)};
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}
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public void put(final int key, final byte[] value) {
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put(toByteKey(key), value);
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}
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public void put(final byte[] key, final byte[] value) {
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// inserts a new value or overwrites existing
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// if the hash is full, a RuntimeException is thrown
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// this method does not return the old value to avoid generation of objects
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assert (key.length == keylen);
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assert (value.length == valuelen);
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int hash = findExisting(key);
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if (hash < 0) {
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// insert new entry
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hash = findSpace(key);
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if (hash < 0) {
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// increase space of hashtable
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// create temporary bigger hashtable and insert all
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synchronized (mem) {
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System.out.println("increasing space to " + mem.length * 2);
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final int newspace = mem.length * 2;
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final int newcapacity = capacity() * 2;
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byte[] newmem = new byte[newspace];
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final Iterator<entry> i = entries();
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CompressedHashMap.entry e;
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int mempos;
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while (i.hasNext()) {
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e = i.next();
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hash = findSpace(newmem, e.key, reclen, newspace, newcapacity);
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mempos = hash * reclen;
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System.arraycopy(e.key, 0, newmem, mempos, keylen);
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System.arraycopy(e.value, 0, newmem, mempos + keylen, valuelen);
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}
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// finally insert new value
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hash = findSpace(newmem, key, reclen, newspace, newcapacity);
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mempos = hash * reclen;
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System.arraycopy(key, 0, newmem, mempos, keylen);
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System.arraycopy(value, 0, newmem, mempos + keylen, valuelen);
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// move newmem to mem
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mem = newmem;
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}
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} else {
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// there is enough space
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//System.out.println("put " + new String(key) + " into cell " + hash);
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final int mempos = hash * reclen;
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System.arraycopy(key, 0, mem, mempos, keylen);
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System.arraycopy(value, 0, mem, mempos + keylen, valuelen);
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}
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count++;
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} else {
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// overwrite old entry
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final int mempos = hash * reclen;
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System.arraycopy(key, 0, mem, mempos, keylen);
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System.arraycopy(value, 0, mem, mempos + keylen, valuelen);
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}
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}
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public byte[] get(final int key) {
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return get(toByteKey(key));
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}
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public byte[] get(final byte[] key) {
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assert (key.length == keylen);
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final int hash = findExisting(key);
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//System.out.println("get " + new String(key) + " from cell " + hash);
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if (hash < 0) {
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return null;
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}
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// read old entry
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final byte[] value = new byte[valuelen];
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System.arraycopy(mem, hash * reclen + keylen, value, 0, valuelen);
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return value;
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}
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public void remove(final int key) {
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remove(toByteKey(key));
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}
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public void remove(final byte[] key) {
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assert (key.length == keylen);
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System.out.println("REMOVE!");
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final int hash = findExisting(key);
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if (hash >= 0) {
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// overwrite old key
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System.arraycopy(emptykey, 0, mem, hash * reclen, keylen);
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count--;
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}
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}
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Iterator<entry> entries() {
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return new entryIterator();
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}
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public class entryIterator implements Iterator<entry> {
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int hashkey;
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public entryIterator() {
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hashkey = anyhashpos(0);
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}
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public boolean hasNext() {
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return hashkey >= 0;
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}
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public entry next() {
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final int i = hashkey;
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hashkey = anyhashpos(hashkey + 1);
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return new entry(i);
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}
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public void remove() {
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mem[hashkey * reclen] = 0;
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}
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}
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public void removeany() {
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//System.out.println("CALLED REMOVEANY");
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int start = 0;
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while (start < capacity()) {
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if (mem[start * reclen] != 0) {
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System.arraycopy(emptykey,0, mem, start * reclen, keylen);
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count--;
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return;
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}
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start++;
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}
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return;
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}
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protected int anyhashpos(int start) {
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while (start < capacity()) {
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if (mem[start * reclen] != 0) return start;
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start++;
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}
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return -1;
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}
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public byte[] anykey() {
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int hash = 0;
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int mempos;
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while (hash < capacity()) {
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mempos = hash * reclen;
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if (mem[mempos] != 0) {
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final byte[] key = new byte[keylen];
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System.arraycopy(mem, mempos, key, 0, keylen);
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return key;
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}
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hash++;
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}
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return null;
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}
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public class entry {
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public byte[] key, value;
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public entry(final int index) {
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this.key = new byte[keylen];
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this.value = new byte[valuelen];
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final int mempos = index * (reclen);
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System.arraycopy(mem, mempos, key, 0, keylen);
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System.arraycopy(mem, mempos + keylen, value, 0, valuelen);
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}
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public entry(final byte[] key, final byte[] value) {
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this.key = key;
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this.value = value;
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}
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}
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public static void main(final String[] args) {
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final long start = System.currentTimeMillis();
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final CompressedHashMap map = new CompressedHashMap(4);
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for (int i = 0; i < 100; i++) map.put(3333 + i, ("" + (1000 + i)).getBytes());
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final Iterator<entry> i = map.entries();
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CompressedHashMap.entry e;
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System.out.println("Enumeration of elements: count=" + map.size());
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int c = 0;
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while (i.hasNext()) {
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e = i.next();
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System.out.println("key=" + new String(e.key) + ", value=" + new String(e.value) + ", retrieved=" + new String(map.get(e.key)));
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c++;
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}
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System.out.println("c = " + c + "; re-catch:");
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for (int j = 0; j < 100; j++) {
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System.out.println("key=" + j + ", retrieved=" + new String(map.get(3333 + j)));
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}
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System.out.println("runtime = " + (System.currentTimeMillis() - start));
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}
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}
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