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• IonStreamUtils.java

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com.amazon.ion.util.IonStreamUtils Maven / Gradle / Ivy

/*
 * Copyright 2007-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * or in the "license" file accompanying this file. This file 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.amazon.ion.util;

import static com.amazon.ion.impl._Private_IonConstants.BINARY_VERSION_MARKER_1_0;
import static com.amazon.ion.util.GzipOrRawInputStream.GZIP_HEADER;

import com.amazon.ion.IonReader;
import com.amazon.ion.IonType;
import com.amazon.ion.IonWriter;
import com.amazon.ion.impl._Private_ListWriter;
import java.io.IOException;
import java.io.InputStream;

/**
 * Utility methods for working with the Ion streaming interfaces,
 * {@link IonReader} and {@link IonWriter}.
 */
public class IonStreamUtils
{
    /**
     * Determines whether a buffer contains Ion binary data by looking for the
     * presence of the Ion Version Marker at its start.
     * A {@code false} result does not imply that the buffer has Ion text,
     * just that it's not Ion binary.
     *
     * @param buffer the data to check.
     *
     * @return {@code true} if the buffer contains Ion binary (starting from
     *  offset zero); {@code false} if the buffer is null or too short.
     *
     * @see #isIonBinary(byte[], int, int)
     */
    public static boolean isIonBinary(byte[] buffer)
    {
        return buffer != null && isIonBinary(buffer, 0, buffer.length);
    }


    /**
     * Determines whether a buffer contains Ion binary data by looking for the
     * presence of the Ion Version Marker at a given offset.
     * A {@code false} result does not imply that the buffer has Ion text,
     * just that it's not Ion binary.
     *
     * @param buffer the data to check.
     * @param offset the position in the buffer at which to start reading.
     * @param length the number of bytes in the buffer that are valid,
     *  starting from {@code offset}.
     *
     * @return {@code true} if the buffer contains Ion binary (starting from
     *  {@code offset}); {@code false} if the buffer is null or if the
     *  {@code length} is too short.
     *
     * @see #isIonBinary(byte[])
     */
    public static boolean isIonBinary(byte[] buffer, int offset, int length)
    {
        return cookieMatches(BINARY_VERSION_MARKER_1_0, buffer, offset, length);
    }


    /**
     * Determines whether a buffer contains GZIPped data.
     *
     * @param buffer the data to check.
     * @param offset the position in the buffer at which to start reading.
     * @param length the number of bytes in the buffer that are valid,
     *  starting from {@code offset}.
     *
     * @return {@code true} if the buffer contains GZIPped data; {@code false}
     * if the buffer is null or if the {@code length} is too short.
     *
     */
    public static boolean isGzip(byte[] buffer, int offset, int length)
    {
        return cookieMatches(GZIP_HEADER, buffer, offset, length);
    }


    private static boolean cookieMatches(byte[] cookie,
                                         byte[] buffer,
                                         int offset,
                                         int length)
    {
        if (buffer == null || length < cookie.length)
        {
            return false;
        }

        for (int i = 0; i < cookie.length; i++)
        {
            if (cookie[i] != buffer[offset + i])
            {
                return false;
            }
        }
        return true;
    }


    /**
     * Returns a stream that decompresses a stream if it contains GZIPped data,
     * otherwise has no effect on the stream (but may wrap it).
     *
     */
    public static InputStream unGzip(InputStream in)
        throws IOException
    {
        return new GzipOrRawInputStream(in);
    }


    //=========================================================================


    /**
     * writes an IonList with a series of IonBool values. This
     * starts a List, writes the values (without any annoations)
     * and closes the list. For text and tree writers this is
     * just a convienience, but for the binary writer it can be
     * optimized internally.
     * @param values boolean values to populate the list with
     */
    public static void writeBoolList(IonWriter writer, boolean[] values)
        throws IOException
    {
        if (writer instanceof _Private_ListWriter) {
            ((_Private_ListWriter)writer).writeBoolList(values);
            return;
        }

        writer.stepIn(IonType.LIST);
        for (int ii=0; ii