100 lines
1.9 KiB
Java
100 lines
1.9 KiB
Java
package btools.util;
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/**
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* Something like LinkedHashMap, but purpose build, less dynamic and memory efficient
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*
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* @author ab
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*/
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public final class LruMap {
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private int hashbins;
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private int maxsize;
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private int size;
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private LruMapNode lru;
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private LruMapNode mru;
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private LruMapNode[] binArray;
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public LruMap(int bins, int size) {
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hashbins = bins;
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maxsize = size;
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binArray = new LruMapNode[hashbins];
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}
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public LruMapNode get(LruMapNode key) {
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int bin = (key.hash & 0xfffffff) % hashbins;
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LruMapNode e = binArray[bin];
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while (e != null) {
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if (key.equals(e)) {
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return e;
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}
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e = e.nextInBin;
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}
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return null;
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}
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// put e to the mru end of the queue
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public void touch(LruMapNode e) {
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LruMapNode n = e.next;
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LruMapNode p = e.previous;
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if (n == null) {
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return; // already at mru
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}
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n.previous = p;
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if (p != null) {
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p.next = n;
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} else {
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lru = n;
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}
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mru.next = e;
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e.previous = mru;
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e.next = null;
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mru = e;
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}
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public LruMapNode removeLru() {
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if (size < maxsize) {
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return null;
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}
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size--;
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// unlink the lru from it's bin-queue
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int bin = (lru.hashCode() & 0xfffffff) % hashbins;
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LruMapNode e = binArray[bin];
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if (e == lru) {
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binArray[bin] = lru.nextInBin;
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} else {
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while (e != null) {
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LruMapNode prev = e;
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e = e.nextInBin;
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if (e == lru) {
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prev.nextInBin = lru.nextInBin;
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break;
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}
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}
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}
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LruMapNode res = lru;
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lru = lru.next;
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lru.previous = null;
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return res;
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}
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public void put(LruMapNode val) {
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int bin = (val.hashCode() & 0xfffffff) % hashbins;
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val.nextInBin = binArray[bin];
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binArray[bin] = val;
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val.previous = mru;
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val.next = null;
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if (mru == null) {
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lru = val;
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} else {
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mru.next = val;
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}
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mru = val;
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size++;
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}
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}
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