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/*******************************************************************************
 * Copyright (c) 2015-2018 Skymind, Inc.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Apache License, Version 2.0 which is available at
 * https://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.
 *
 * SPDX-License-Identifier: Apache-2.0
 ******************************************************************************/

package org.datavec.api.io;

import java.io.ByteArrayInputStream;
import java.io.DataInput;
import java.io.DataInputStream;

/** A reusable {@link DataInput} implementation that reads from an in-memory
 * buffer.
 *
 * This saves memory over creating a new DataInputStream and
 * ByteArrayInputStream each time data is read.
 *
 * 
Typical usage is something like the following:
 *
 * DataInputBuffer buffer = new DataInputBuffer();
 * while (... loop condition ...) {
 *   byte[] data = ... get data ...;
 *   int dataLength = ... get data length ...;
 *   buffer.reset(data, dataLength);
 *   ... read buffer using DataInput methods ...
 * }
 * 
 *
 */
public class DataInputBuffer extends DataInputStream {
    private static class Buffer extends ByteArrayInputStream {
        public Buffer() {
            super(new byte[] {});
        }

        public void reset(byte[] input, int start, int length) {
            this.buf = input;
            this.count = start + length;
            this.mark = start;
            this.pos = start;
        }

        public byte[] getData() {
            return buf;
        }

        public int getPosition() {
            return pos;
        }

        public int getLength() {
            return count;
        }
    }

    private Buffer buffer;

    /** Constructs a new empty buffer. */
    public DataInputBuffer() {
        this(new Buffer());
    }

    private DataInputBuffer(Buffer buffer) {
        super(buffer);
        this.buffer = buffer;
    }

    /** Resets the data that the buffer reads. */
    public void reset(byte[] input, int length) {
        buffer.reset(input, 0, length);
    }

    /** Resets the data that the buffer reads. */
    public void reset(byte[] input, int start, int length) {
        buffer.reset(input, start, length);
    }

    public byte[] getData() {
        return buffer.getData();
    }

    /** Returns the current position in the input. */
    public int getPosition() {
        return buffer.getPosition();
    }

    /** Returns the length of the input. */
    public int getLength() {
        return buffer.getLength();
    }

}