org.nustaq.offheap.FSTAsciiStringOffheapMap Maven / Gradle / Ivy

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A fast java serialization drop in-replacement and some serialization based utils such as Structs and OffHeap Memory.
There is a newer version: 3.0.4-jdk17
/*
 * Copyright 2014 Ruediger Moeller.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.nustaq.offheap;

import org.nustaq.offheap.bytez.ByteSource;
import org.nustaq.offheap.bytez.bytesource.LeftCutStringByteSource;
import org.nustaq.serialization.FSTConfiguration;
import org.nustaq.serialization.simpleapi.DefaultCoder;
import org.nustaq.serialization.simpleapi.FSTCoder;

/**
 * Created by ruedi on 27.06.14.
 *
 * An offheap hashmap. Keys are strings with a given max length. The longer the strings, the slower
 * lookup will be. Values < 50 are ok'ish.
 *
 * The Map can reside on disk (using mmapped files) or just in offheap.
 *
 * Note that changing stored classes will lead to decoding errors in case of persisted files.
 * You need to make use of FST versioning annotation in order to avoid this.
 */
public class FSTAsciiStringOffheapMap extends FSTSerializedOffheapMap {

    LeftCutStringByteSource tmpKey;

    /**
     * see other mem constructor, additional allows to insert a coder.
     * Useful to preregister classes (speed+size gain, no classnames written!).
     * E.g. new DefaultCoder(MyValue.class, MyOtherValue.class, .. )
     */
    public FSTAsciiStringOffheapMap(int keyLen, long sizeMemBytes, int numberOfEleems, FSTCoder coder) {
        super(keyLen, sizeMemBytes, numberOfEleems, coder);
        tmpKey = new LeftCutStringByteSource(null,0,keyLen);
    }

    /**
     *
     * @param keyLen - maximum len of a key
     * @param sizeMemBytes - size of memory (not bigger than OS heap
     * @param numberOfEleems - estimation on number of key-value pairs (autogrow, just educated guess)
     */
    public FSTAsciiStringOffheapMap(int keyLen, long sizeMemBytes, int numberOfEleems) {
        super(keyLen, sizeMemBytes, numberOfEleems, new DefaultCoder());
        tmpKey = new LeftCutStringByteSource(null,0,keyLen);
    }

    /**
     * see other mem mapped file constructor + additional allows to insert a coder.
     * Useful to preregister classes (speed+size gain, no classnames written!).
     * E.g. new DefaultCoder(MyValue.class, MyOtherValue.class, .. )
     */
    public FSTAsciiStringOffheapMap(String mappedFile, int keyLen, long sizeMemBytes, int numberOfElems,FSTCoder coder) throws Exception {
        super(mappedFile, keyLen, sizeMemBytes, numberOfElems, coder);
        tmpKey = new LeftCutStringByteSource(null,0,keyLen);
    }

    /**
     * create a memory mapped offheap hashmap
     * @param file - the file location. If file exists, it will be loaded
     *             Attention: in case classes changed you need to delete files as
     *             objects won't be compatible (except you made use of fst versioning features)
     * @param keylen - the maximum len of a key
     * @param size   - max size of file (can be GB, check OS settings to avoid eager write-to-disk)
     * @param numelem - estimated number of key-value pairs (will auto-grow, just educated guess)
     * @throws Exception
     */
    public FSTAsciiStringOffheapMap(String file, int keylen, long size, int numelem) throws Exception {
        this(file,keylen,size,numelem,new DefaultCoder());
    }

    public ByteSource encodeKey(String key) {
        if ( key.length() > tmpKey.length() ) {
            int length = (int) tmpKey.length();
            StringBuilder buf = new StringBuilder(length);
            for ( int i = 0; i < length; i++ ) {
                char c = key.charAt(i);
                if ( i+length < key.length() ) {
                    c = (char) ((c + key.charAt(i+length))/2);
                }
                buf.append(c);
            }
            key = buf.toString();
        }
        tmpKey.setString(key);
        return tmpKey;
    }

}