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ActiveMQ example source code file (HashBin.java)

This example ActiveMQ source code file (HashBin.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

hashbin, hashbin, hashentry, hashentry, hashindex, hashpage, hashpageinfo, hashpageinfo, io, ioexception, ioexception, string

The ActiveMQ HashBin.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.activemq.kaha.impl.index.hash;

import java.io.IOException;

/**
 * Bin in a HashIndex
 * 
 * 
 */
class HashBin {
    private HashIndex hashIndex;
    private int id;
    private int maximumEntries;
    private int size;
    private int numberOfPages =0;
    private HashPageInfo root = null;
    private HashPageInfo tail = null;

    /**
     * Constructor
     * 
     * @param hashIndex
     * @param id
     * @param maximumEntries
     */
    HashBin(HashIndex hashIndex, int id, int maximumEntries) {
        this.hashIndex = hashIndex;
        this.id = id;
        this.maximumEntries = maximumEntries;
    }

    public String toString() {
        return "HashBin[" + getId() + "]";
    }

    public boolean equals(Object o) {
        boolean result = false;
        if (o instanceof HashBin) {
            HashBin other = (HashBin)o;
            result = other.id == id;
        }
        return result;
    }

    public int hashCode() {
        return (int)getId();
    }

     int  getId() {
        return id;
    }

     void setId(int id) {
        this.id = id;
    }

     boolean isEmpty() {
        return true;
    }

     int getMaximumEntries() {
        return this.maximumEntries;
    }

     void setMaximumEntries(int maximumEntries) {
        this.maximumEntries = maximumEntries;
    }

     int size() {
        return size;
    }

     HashPageInfo addHashPageInfo(long id, int size) throws IOException {
        HashPageInfo info = new HashPageInfo(hashIndex);
        info.setId(id);
        info.setSize(size);
        if (root == null) {
            root=info;
        }else {
            tail.linkAfter(info);
        }
        tail=info;
        this.numberOfPages++;
        this.size += size;
        return info;
    }

     public HashEntry find(HashEntry key) throws IOException {
        HashEntry result = null;
        try {
            int low = 0;
            int high = size()-1;
            while (low <= high) {
                int mid = (low + high) >> 1;
                HashEntry te = getHashEntry(mid);
                int cmp = te.compareTo(key);
                if (cmp == 0) {
                    result = te;
                    break;
                } else if (cmp < 0) {
                    low = mid + 1;
                } else {
                    high = mid - 1;
                }
            }
        } finally {
            end();
        }
        return result;
    }

     boolean put(HashEntry newEntry) throws IOException {
        boolean replace = false;
        try {
            int low = 0;
            int high = size()-1;
            while (low <= high) {
                int mid = (low + high) >> 1;
                HashEntry midVal = getHashEntry(mid);
                int cmp = midVal.compareTo(newEntry);
                if (cmp < 0) {
                    low = mid + 1;
                } else if (cmp > 0) {
                    high = mid - 1;
                } else {
                    replace = true;
                    midVal.setIndexOffset(newEntry.getIndexOffset());
                    break;
                }
            }
            if (!replace) {
                addHashEntry(low, newEntry);
                size++;
            }
        } finally {
            end();
        }
        return replace;
    }

     HashEntry remove(HashEntry entry) throws IOException {
        HashEntry result = null;
        try {
            int low = 0;
            int high = size() - 1;
            while (low <= high) {
                int mid = (low + high) >> 1;
                HashEntry te = getHashEntry(mid);
                int cmp = te.compareTo(entry);
                if (cmp == 0) {
                    result = te;
                    removeHashEntry(mid);
                    size--;
                    break;
                } else if (cmp < 0) {
                    low = mid + 1;
                } else {
                    high = mid - 1;
                }
            }
        } finally {
            end();
        }
        return result;
    }

    private void addHashEntry(int index, HashEntry entry) throws IOException {
        HashPageInfo pageToUse = null;
        int offset = 0;
        if (index >= getMaximumBinSize()) {
            while(index >= getMaximumBinSize()) {
                HashPage hp = hashIndex.createPage(id);
                pageToUse = addHashPageInfo(hp.getId(), 0);
                pageToUse.setPage(hp);
            }
            offset = 0;
        } else {
            int count = 0;
            int countSoFar=0;
            int pageNo = 0;
            HashPageInfo page = root;
            while (page != null) {
                count += page.size();
                pageToUse=page;
                if (index < count ) {
                    offset = index - countSoFar;
                    break;
                }
                if (index == count && page.size()+1 <= maximumEntries) {
                    offset = page.size();
                    break;
                }
                countSoFar += page.size();
                pageNo++;
                page = (HashPageInfo) page.getNext();
            }
            while(pageNo >= this.numberOfPages) {
                HashPage hp  = hashIndex.createPage(id);
                pageToUse = addHashPageInfo(hp.getId(), 0);               
            }            
        }
        pageToUse.begin();  
        pageToUse.addHashEntry(offset, entry);
        doOverFlow(index);
    }

    private HashEntry removeHashEntry(int index) throws IOException {
        HashPageInfo page = getRetrievePage(index);
        int offset = getRetrieveOffset(index);
        HashEntry result = page.removeHashEntry(offset);
        
        if (page.isEmpty()) {
            if (root.equals(page)) {
                root=(HashPageInfo) root.getNext();
            }
            if (tail.equals(page)) {
                tail=(HashPageInfo) page.getPrevious();
            }
            page.unlink();
            this.numberOfPages--;
            hashIndex.releasePage(page.getPage());
        }
        doUnderFlow(index);
        return result;
    }

    private HashEntry getHashEntry(int index) throws IOException {
        HashPageInfo page = getRetrievePage(index);
        page.begin();
        int offset = getRetrieveOffset(index);
        HashEntry result = page.getHashEntry(offset);
        return result;
    }
    

    private int getMaximumBinSize() {
        return maximumEntries * this.numberOfPages;
    }

    private HashPageInfo getRetrievePage(int index) throws IOException {
        HashPageInfo result = null;
        int count = 0;
        HashPageInfo page = root;
        while (page != null) {
            count += page.size();
            result = page;
            if (index < count) {
                break;
            }
            page = (HashPageInfo) page.getNext();
        }
        
        result.begin();
        return result;
    }

    private int getRetrieveOffset(int index) throws IOException {
        int result = 0;
        int count = 0;
        HashPageInfo page = root;
        while (page != null) {
            if ((index + 1) <= (count + page.size())) {
                result = index - count;
                break;
            }
            count += page.size();
            page = (HashPageInfo) page.getNext();
        }
        return result;
    }

    private void doOverFlow(int index) throws IOException {
        HashPageInfo info = getRetrievePage(index);
        if (info.size() > maximumEntries) {
            // overflowed
            info.begin();
            HashEntry entry = info.removeHashEntry(info.size() - 1);
            doOverFlow(getNextPage(info), entry);
        }
    }

    private void doOverFlow(HashPageInfo next, HashEntry entry) throws IOException {
        HashPageInfo info = null;
        if (next == null) {
            HashPage page = hashIndex.createPage(id);
            info = addHashPageInfo(page.getId(), 0);
            info.setPage(page);
        } else {
            info = next;
        }
        info.begin();
        info.addHashEntry(0, entry);
        if (info.size() > maximumEntries) {
            // overflowed
            HashEntry overflowed = info.removeHashEntry(info.size() - 1);
            doOverFlow(getNextPage(info), overflowed);
        }
    }
    
    private HashPageInfo getNextPage(HashPageInfo start) {
        return (HashPageInfo) start.getNext();
    }

    private void doUnderFlow(int index) {
    }

    String dump() throws IOException {
        String str = "[" + this.numberOfPages+"]";
        HashPageInfo page = root;
        while (page != null) {
            page.begin();
            str +=page.dump();
            page.end();
            page = (HashPageInfo) page.getNext();
        }
        return str;
    }
    private void end() throws IOException {
        HashPageInfo page = root;
        while (page != null) {
            page.end();
            page = (HashPageInfo) page.getNext();
        }
    }
}

Other ActiveMQ examples (source code examples)

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