com.alibaba.supersonic.base.infrastructure.View.java Source code

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Here is the source code for com.alibaba.supersonic.base.infrastructure.View.java

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/*
 * 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 com.alibaba.supersonic.base.infrastructure;

import com.google.common.base.Preconditions;

/**
 * Read-only view of a multi-column 'block' of data. The data is usually owned
 * by one or more {@link Block}s.
 * 
 * @author Min Zhou (coderplay@gmail.com)
 */
public class View {

    private final TupleSchema schema_;
    private Column[] columns_;
    private int row_count_;

    // Views are copyable.

    /**
     * Creates an empty view that can hold data of the specified schema.
     */
    public View(final TupleSchema schema) {
        this.schema_ = schema;
        this.columns_ = new Column[schema.attributeCount()];
        this.row_count_ = 0;
        init();
    }

    /**
     * A convenience copy constructor.
     * 
     * @param other
     */
    public View(final View other) {
        this.schema_ = other.schema();
        this.columns_ = new Column[other.schema().attributeCount()];
        this.row_count_ = 0;
        init();
        resetFrom(other);
    }

    /**
     * A convenience 'subrange' copy constructor.
     */
    public View(final View other, int offset, int row_count) {

        this.schema_ = other.schema();
        this.columns_ = new Column[other.schema().attributeCount()];
        this.row_count_ = 0;
        init();
        resetFromSubRange(other, offset, row_count);
    }

    /**
     * A convenience constructor, wrapping a single column into a view.
     */
    public View(final Column column, int row_count) {
        this.schema_ = TupleSchema.singleton(column.attribute().getName(), column.attribute().getType(),
                column.attribute().getNullability());
        this.columns_ = new Column[1];
        this.row_count_ = row_count;
        init();
        // mutable_column(0)->ResetFrom(column);
    }

    /**
     * Returns the view's schema.
     * @return
     */
    public final TupleSchema schema() {
        return schema_;
    }

    /**
     * Equivalent to schema().attributeCount().
     * @return
     */
    public int columnCount() {
        return schema().attributeCount();
    }

    /**
     * Returns the number of rows in the view.
     * @return the number of rows in the view.
     */
    public int rowCount() {
        return row_count_;
    }

    /**
     * Sets the row count. Unchecked.
     * @param row_count
     */
    public void setRowCount(final int row_count) {
        row_count_ = row_count;
    }

    /**
     * Returns an immutable reference to the specified column.
     * @param column_index
     * @return
     */
    public final Column column(int column_index) {
        Preconditions.checkPositionIndex(column_index, columnCount());
        return columns_[column_index];
    }

    /**
     * Returns a pointer to the mutable (resettable) column.
     * 
     * @param column_index
     * @return
     */
    Column mutableColumn(int column_index) {
        Preconditions.checkPositionIndex(column_index, columnCount());
        return columns_[column_index];
    }

    /**
     * Resets View's columns from another View. Sets the row_count as well.
     * @param other
     */
    void resetFrom(final View other) {
        for (int i = 0; i < schema_.attributeCount(); ++i) {
            mutableColumn(i).resetFrom(other.column(i));
        }
        setRowCount(other.rowCount());
    }

    /**
     * Resets View's columns from a sub-range in an another View. Sets the
     * row_count as well.
     * 
     * @param other
     * @param offset
     * @param row_count
     */
    void resetFromSubRange(final View other, int offset, int row_count) {
        Preconditions.checkPositionIndex(offset, other.rowCount());
        for (int i = 0; i < columnCount(); ++i) {
            mutableColumn(i).resetFromPlusOffset(other.column(i), offset);
        }
        setRowCount(row_count);
    }

    /**
     * Advances the view by the specified offset. Reduces view size accordingly.
     * In debug mode, guards against moving past the range.
     * Note: views can only more forward; the offset is unsigned.
     * 
     * @param offset
     */
    void advance(int offset) {
        Preconditions.checkPositionIndex(offset, rowCount());
        for (int i = 0; i < columnCount(); i++) {
            Column column = mutableColumn(i);
            column.resetFromPlusOffset(column, offset);
        }
        row_count_ -= (row_count_ < offset ? row_count_ : offset);
    }

    private void init() {
        for (int i = 0; i < schema_.attributeCount(); i++) {
            columns_[i].init(schema_.getAttributeAt(i));
        }
    }

};