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 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.internal.net.http.hpack;

import java.nio.ByteBuffer;

/**

 * Delivers results of the {@link Decoder#decode(ByteBuffer, boolean,

 * DecodingCallback) decoding operation}.

 *

 * <p> Methods of the callback are never called by a decoder with any of the

 * arguments being {@code null}.

 *

 * @apiNote

 *

 * <p> The callback provides methods for all possible

 * <a href="https://tools.ietf.org/html/rfc7541#section-6">binary representations</a>.

 * This could be useful for implementing an intermediary, logging, debugging,

 * etc.

 *

 * <p> The callback is an interface in order to interoperate with lambdas (in

 * the most common use case):

 * <pre>{@code

 *     DecodingCallback callback = (name, value) -> System.out.println(name + ", " + value);

 * }</pre>

 *

 * <p> Names and values are {@link CharSequence}s rather than {@link String}s in

 * order to allow users to decide whether or not they need to create objects. A

 * {@code CharSequence} might be used in-place, for example, to be appended to

 * an {@link Appendable} (e.g. {@link StringBuilder}) and then discarded.

 *

 * <p> That said, if a passed {@code CharSequence} needs to outlast the method

 * call, it needs to be copied.

 *

 * @since 9

 */

@FunctionalInterface

public interface DecodingCallback {

    /**

     * A method the more specific methods of the callback forward their calls

     * to.

     *

     * @param name

     *         header name

     * @param value

     *         header value

     */

    void onDecoded(CharSequence name, CharSequence value);

    /**

     * A more finer-grained version of {@link #onDecoded(CharSequence,

     * CharSequence)} that also reports on value sensitivity.

     *

     * <p> Value sensitivity must be considered, for example, when implementing

     * an intermediary. A {@code value} is sensitive if it was represented as <a

     * href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal Header

     * Field Never Indexed</a>.

     *

     * <p> It is required that intermediaries MUST use the {@linkplain

     * Encoder#header(CharSequence, CharSequence, boolean) same representation}

     * for encoding this header field in order to protect its value which is not

     * to be put at risk by compressing it.

     *

     * @implSpec

     *

     * <p> The default implementation invokes {@code onDecoded(name, value)}.

     *

     * @param name

     *         header name

     * @param value

     *         header value

     * @param sensitive

     *         whether or not the value is sensitive

     *

     * @see #onLiteralNeverIndexed(int, CharSequence, CharSequence, boolean)

     * @see #onLiteralNeverIndexed(CharSequence, boolean, CharSequence, boolean)

     */

    default void onDecoded(CharSequence name,

                           CharSequence value,

                           boolean sensitive) {

        onDecoded(name, value);

    }

    /**

     * An <a href="https://tools.ietf.org/html/rfc7541#section-6.1">Indexed

     * Header Field</a> decoded.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, false)}.

     *

     * @param index

     *         index of an entry in the table

     * @param name

     *         header name

     * @param value

     *         header value

     */

    default void onIndexed(int index, CharSequence name, CharSequence value) {

        onDecoded(name, value, false);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.2">Literal

     * Header Field without Indexing</a> decoded, where a {@code name} was

     * referred by an {@code index}.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, false)}.

     *

     * @param index

     *         index of an entry in the table

     * @param name

     *         header name

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteral(int index,

                           CharSequence name,

                           CharSequence value,

                           boolean valueHuffman) {

        onDecoded(name, value, false);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.2">Literal

     * Header Field without Indexing</a> decoded, where both a {@code name} and

     * a {@code value} were literal.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, false)}.

     *

     * @param name

     *         header name

     * @param nameHuffman

     *         if the {@code name} was Huffman encoded

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteral(CharSequence name,

                           boolean nameHuffman,

                           CharSequence value,

                           boolean valueHuffman) {

        onDecoded(name, value, false);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal

     * Header Field Never Indexed</a> decoded, where a {@code name}

     * was referred by an {@code index}.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, true)}.

     *

     * @param index

     *         index of an entry in the table

     * @param name

     *         header name

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteralNeverIndexed(int index,

                                       CharSequence name,

                                       CharSequence value,

                                       boolean valueHuffman) {

        onDecoded(name, value, true);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal

     * Header Field Never Indexed</a> decoded, where both a {@code

     * name} and a {@code value} were literal.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, true)}.

     *

     * @param name

     *         header name

     * @param nameHuffman

     *         if the {@code name} was Huffman encoded

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteralNeverIndexed(CharSequence name,

                                       boolean nameHuffman,

                                       CharSequence value,

                                       boolean valueHuffman) {

        onDecoded(name, value, true);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.1">Literal

     * Header Field with Incremental Indexing</a> decoded, where a {@code name}

     * was referred by an {@code index}.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, false)}.

     *

     * @param index

     *         index of an entry in the table

     * @param name

     *         header name

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteralWithIndexing(int index,

                                       CharSequence name,

                                       CharSequence value,

                                       boolean valueHuffman) {

        onDecoded(name, value, false);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.1">Literal

     * Header Field with Incremental Indexing</a> decoded, where both a {@code

     * name} and a {@code value} were literal.

     *

     * @implSpec

     *

     * <p> The default implementation invokes

     * {@code onDecoded(name, value, false)}.

     *

     * @param name

     *         header name

     * @param nameHuffman

     *         if the {@code name} was Huffman encoded

     * @param value

     *         header value

     * @param valueHuffman

     *         if the {@code value} was Huffman encoded

     */

    default void onLiteralWithIndexing(CharSequence name,

                                       boolean nameHuffman,

                                       CharSequence value,

                                       boolean valueHuffman) {

        onDecoded(name, value, false);

    }

    /**

     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.3">Dynamic Table

     * Size Update</a> decoded.

     *

     * @implSpec

     *

     * <p> The default implementation does nothing.

     *

     * @param capacity

     *         new capacity of the header table

     */

    default void onSizeUpdate(int capacity) { }

}