com.netflix.zeno.fastblob.record.FastBlobSchema Maven / Gradle / Ivy

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netflix-zeno developed by Netflix
There is a newer version: 2.22.3
/*
 *
 *  Copyright 2013 Netflix, Inc.
 *
 *     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 com.netflix.zeno.fastblob.record;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Arrays;

/**
 * A schema for a record contained in a FastBlob.
 *
 * The fields each have a position, which is the order in which they will appear in a FastBlob serialized representation.

 *
 * The schema is a hash table of Strings (field name) to field position.

 *
 * Schemas are flat lists of fields, each specified by (fieldName, fieldType).
 *
 * @author dkoszewnik
 *
 */
public class FastBlobSchema {

    private final String schemaName;

    private final int hashedPositionArray[];
    private final String fieldNames[];
    private final FieldType fieldTypes[];

    private int size;

    public FastBlobSchema(String schemaName, int numFields) {
        this.schemaName = schemaName;

        this.hashedPositionArray = new int[1 << (32 - Integer.numberOfLeadingZeros(numFields * 10 / 7))];
        this.fieldNames = new String[numFields];
        this.fieldTypes = new FieldType[numFields];

        Arrays.fill(hashedPositionArray, -1);
    }

    public String getName() {
        return schemaName;
    }

    /**
     * Add a field into this FastBlobSchema.
     *
     * The position of the field is hashed into the hashedPositionArray by the hashCode of the fieldName.
     *
     * @return the position of the field.
     */
    public int addField(String fieldName, FieldType fieldType) {
        fieldNames[size] = fieldName;
        fieldTypes[size] = fieldType;
        hashPositionIntoArray(size);

        return size++;
    }

    /**
     * Returns the position of a field previously added to the map, or -1 if the field has not been added to the map.
     *
     * The positions of the fields are hashed into the hashedPositionArray by the hashCode of the fieldName.
     */
    public int getPosition(String fieldName) {
        int hash = hashInt(fieldName.hashCode());

        int bucket = hash % hashedPositionArray.length;
        int position = hashedPositionArray[bucket];

        while(position != -1) {
            if(fieldNames[position].equals(fieldName))
                return position;

            bucket = (bucket + 1) % hashedPositionArray.length;
            position = hashedPositionArray[bucket];
        }

        return -1;
    }

    /**
     * @return The name of the field at the specified position
     */
    public String getFieldName(int fieldPosition) {
        return fieldNames[fieldPosition];
    }

    /**
     * @return The type of the field with the given name
     */
    public FieldType getFieldType(String fieldName) {
        int position = getPosition(fieldName);

        if(position == -1)
            throw new IllegalArgumentException("Field name " + fieldName + " does not exist in schema " + schemaName);

        return fieldTypes[getPosition(fieldName)];
    }

    /**
     * @return The type of the field at the specified position
     */
    public FieldType getFieldType(int fieldPosition) {
        return fieldTypes[fieldPosition];
    }

    /**
     * @return The number of fields in this schema.
     */
    public int numFields() {
        return size;
    }

    private void hashPositionIntoArray(int ordinal) {
        int hash = hashInt(fieldNames[ordinal].hashCode());

        int bucket = hash % hashedPositionArray.length;

        while(hashedPositionArray[bucket] != -1) {
            bucket = (bucket + 1) % hashedPositionArray.length;
        }

        hashedPositionArray[bucket] = ordinal;
    }

    private int hashInt(int key) {
        key = ~key + (key << 15);
        key = key ^ (key >>> 12);
        key = key + (key << 2);
        key = key ^ (key >>> 4);
        key = key * 2057;
        key = key ^ (key >>> 16);
        return key & Integer.MAX_VALUE;
    }

    /**
     * Write this FastBlobSchema to a stream.
     */
    public void writeTo(DataOutputStream dos) throws IOException {
        dos.writeUTF(schemaName);
        dos.writeShort(size);
        for(int i=0;i