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TripleStore implementation for SemanticWebBuilder using LevelDB

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/**
 * Copyright (C) 2011 the original author or authors.
 * See the notice.md file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * 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.iq80.leveldb.table;

import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import org.iq80.leveldb.util.Slice;

import java.util.Arrays;
import java.util.Map.Entry;

import static com.google.common.base.Charsets.UTF_8;

/**
 * Binary Structure
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name offset length description
shared key length 0 vary variable length encoded int: size of shared key prefix with the key from the previous entry
non-shared key length vary vary variable length encoded int: size of non-shared key suffix in this entry
value length vary vary variable length encoded int: size of value in this entry
non-shared key vary non-shared key length non-shared key data
value vary value length value data
 */
public class BlockEntry implements Entry
{
    public static final Function GET_KEY = new Function()
    {
        @Override
        public Slice apply(BlockEntry blockEntry)
        {
            return blockEntry.getKey();
        }
    };

    private final Slice key;
    private final Slice value;

    public BlockEntry(Slice key, Slice value)
    {
        Preconditions.checkNotNull(key, "key is null");
        Preconditions.checkNotNull(value, "value is null");
        this.key = key;
        this.value = value;
    }

    public Slice getKey()
    {
        return key;
    }

    public Slice getValue()
    {
        return value;
    }


    /**
     * @throws UnsupportedOperationException always
     */
    @Override
    public final Slice setValue(Slice value)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean equals(Object o)
    {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        BlockEntry entry = (BlockEntry) o;

        if (!key.equals(entry.key)) {
            return false;
        }
        if (!value.equals(entry.value)) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode()
    {
        int result = key.hashCode();
        result = 31 * result + value.hashCode();
        return result;
    }

    @Override
    public String toString()
    {
        final StringBuilder sb = new StringBuilder();
        sb.append("BlockEntry");
        sb.append("{key=").append(key.toString(UTF_8));      // todo don't print the real value
        sb.append(", value=").append(value.toString(UTF_8));
        sb.append('}');
        return sb.toString();
    }
}

name	offset	length	description
shared key length	0	vary	variable length encoded int: size of shared key prefix with the key from the previous entry
non-shared key length	vary	vary	variable length encoded int: size of non-shared key suffix in this entry
value length	vary	vary	variable length encoded int: size of value in this entry
non-shared key	vary	non-shared key length	non-shared key data
value	vary	value length	value data