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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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24 */
25package jdk.incubator.http.internal.hpack;
26
27import java.nio.ByteBuffer;
28
29/**
30 * Delivers results of the {@link Decoder#decode(ByteBuffer, boolean,
31 * DecodingCallback) decoding operation}.
32 *
33 * <p> Methods of the callback are never called by a decoder with any of the
34 * arguments being {@code null}.
35 *
36 * @apiNote
37 *
38 * <p> The callback provides methods for all possible <a
39 * href="https://tools.ietf.org/html/rfc7541#section-6">binary
40 * representations</a>. This could be useful for implementing an intermediary,
41 * logging, debugging, etc.
42 *
43 * <p> The callback is an interface in order to interoperate with lambdas (in
44 * the most common use case):
45 * <pre>{@code
46 *     DecodingCallback callback = (name, value) -> System.out.println(name + ", " + value);
47 * }</pre>
48 *
49 * <p> Names and values are {@link CharSequence}s rather than {@link String}s in
50 * order to allow users to decide whether or not they need to create objects. A
51 * {@code CharSequence} might be used in-place, for example, to be appended to
52 * an {@link Appendable} (e.g. {@link StringBuilder}) and then discarded.
53 *
54 * <p> That said, if a passed {@code CharSequence} needs to outlast the method
55 * call, it needs to be copied.
56 *
57 * @since 9
58 */
59@FunctionalInterface
60public interface DecodingCallback {
61
62    /**
63     * A method the more specific methods of the callback forward their calls
64     * to.
65     *
66     * @param name
67     *         header name
68     * @param value
69     *         header value
70     */
71    void onDecoded(CharSequence name, CharSequence value);
72
73    /**
74     * A more finer-grained version of {@link #onDecoded(CharSequence,
75     * CharSequence)} that also reports on value sensitivity.
76     *
77     * <p> Value sensitivity must be considered, for example, when implementing
78     * an intermediary. A {@code value} is sensitive if it was represented as <a
79     * href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal Header
80     * Field Never Indexed</a>.
81     *
82     * <p> It is required that intermediaries MUST use the {@linkplain
83     * Encoder#header(CharSequence, CharSequence, boolean) same representation}
84     * for encoding this header field in order to protect its value which is not
85     * to be put at risk by compressing it.
86     *
87     * @implSpec
88     *
89     * <p> The default implementation invokes {@code onDecoded(name, value)}.
90     *
91     * @param name
92     *         header name
93     * @param value
94     *         header value
95     * @param sensitive
96     *         whether or not the value is sensitive
97     *
98     * @see #onLiteralNeverIndexed(int, CharSequence, CharSequence, boolean)
99     * @see #onLiteralNeverIndexed(CharSequence, boolean, CharSequence, boolean)
100     */
101    default void onDecoded(CharSequence name, CharSequence value,
102                           boolean sensitive) {
103        onDecoded(name, value);
104    }
105
106    /**
107     * An <a href="https://tools.ietf.org/html/rfc7541#section-6.1">Indexed
108     * Header Field</a> decoded.
109     *
110     * @implSpec
111     *
112     * <p> The default implementation invokes
113     * {@code onDecoded(name, value, false)}.
114     *
115     * @param index
116     *         index of an entry in the table
117     * @param name
118     *         header name
119     * @param value
120     *         header value
121     */
122    default void onIndexed(int index, CharSequence name, CharSequence value) {
123        onDecoded(name, value, false);
124    }
125
126    /**
127     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.2">Literal
128     * Header Field without Indexing</a> decoded, where a {@code name} was
129     * referred by an {@code index}.
130     *
131     * @implSpec
132     *
133     * <p> The default implementation invokes
134     * {@code onDecoded(name, value, false)}.
135     *
136     * @param index
137     *         index of an entry in the table
138     * @param name
139     *         header name
140     * @param value
141     *         header value
142     * @param valueHuffman
143     *         if the {@code value} was Huffman encoded
144     */
145    default void onLiteral(int index, CharSequence name,
146                           CharSequence value, boolean valueHuffman) {
147        onDecoded(name, value, false);
148    }
149
150    /**
151     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.2">Literal
152     * Header Field without Indexing</a> decoded, where both a {@code name} and
153     * a {@code value} were literal.
154     *
155     * @implSpec
156     *
157     * <p> The default implementation invokes
158     * {@code onDecoded(name, value, false)}.
159     *
160     * @param name
161     *         header name
162     * @param nameHuffman
163     *         if the {@code name} was Huffman encoded
164     * @param value
165     *         header value
166     * @param valueHuffman
167     *         if the {@code value} was Huffman encoded
168     */
169    default void onLiteral(CharSequence name, boolean nameHuffman,
170                           CharSequence value, boolean valueHuffman) {
171        onDecoded(name, value, false);
172    }
173
174    /**
175     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal
176     * Header Field Never Indexed</a> decoded, where a {@code name}
177     * was referred by an {@code index}.
178     *
179     * @implSpec
180     *
181     * <p> The default implementation invokes
182     * {@code onDecoded(name, value, true)}.
183     *
184     * @param index
185     *         index of an entry in the table
186     * @param name
187     *         header name
188     * @param value
189     *         header value
190     * @param valueHuffman
191     *         if the {@code value} was Huffman encoded
192     */
193    default void onLiteralNeverIndexed(int index, CharSequence name,
194                                       CharSequence value,
195                                       boolean valueHuffman) {
196        onDecoded(name, value, true);
197    }
198
199    /**
200     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.3">Literal
201     * Header Field Never Indexed</a> decoded, where both a {@code
202     * name} and a {@code value} were literal.
203     *
204     * @implSpec
205     *
206     * <p> The default implementation invokes
207     * {@code onDecoded(name, value, true)}.
208     *
209     * @param name
210     *         header name
211     * @param nameHuffman
212     *         if the {@code name} was Huffman encoded
213     * @param value
214     *         header value
215     * @param valueHuffman
216     *         if the {@code value} was Huffman encoded
217     */
218    default void onLiteralNeverIndexed(CharSequence name, boolean nameHuffman,
219                                       CharSequence value, boolean valueHuffman) {
220        onDecoded(name, value, true);
221    }
222
223    /**
224     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.1">Literal
225     * Header Field with Incremental Indexing</a> decoded, where a {@code name}
226     * was referred by an {@code index}.
227     *
228     * @implSpec
229     *
230     * <p> The default implementation invokes
231     * {@code onDecoded(name, value, false)}.
232     *
233     * @param index
234     *         index of an entry in the table
235     * @param name
236     *         header name
237     * @param value
238     *         header value
239     * @param valueHuffman
240     *         if the {@code value} was Huffman encoded
241     */
242    default void onLiteralWithIndexing(int index,
243                                       CharSequence name,
244                                       CharSequence value, boolean valueHuffman) {
245        onDecoded(name, value, false);
246    }
247
248    /**
249     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.2.1">Literal
250     * Header Field with Incremental Indexing</a> decoded, where both a {@code
251     * name} and a {@code value} were literal.
252     *
253     * @implSpec
254     *
255     * <p> The default implementation invokes
256     * {@code onDecoded(name, value, false)}.
257     *
258     * @param name
259     *         header name
260     * @param nameHuffman
261     *         if the {@code name} was Huffman encoded
262     * @param value
263     *         header value
264     * @param valueHuffman
265     *         if the {@code value} was Huffman encoded
266     */
267    default void onLiteralWithIndexing(CharSequence name, boolean nameHuffman,
268                                       CharSequence value, boolean valueHuffman) {
269        onDecoded(name, value, false);
270    }
271
272    /**
273     * A <a href="https://tools.ietf.org/html/rfc7541#section-6.3">Dynamic Table
274     * Size Update</a> decoded.
275     *
276     * @implSpec
277     *
278     * <p> The default implementation does nothing.
279     *
280     * @param capacity
281     *         new capacity of the header table
282     */
283    default void onSizeUpdate(int capacity) { }
284}
285