1 /*

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

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Oracle designates this

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

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

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

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

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 package jdk.internal.net.http.hpack;

    26 

    27 import java.nio.ByteBuffer;

    28 import java.util.Arrays;

    29 

    30 final class IntegerWriter {

    31 

    32     private static final int NEW                = 0;

    33     private static final int CONFIGURED         = 1;

    34     private static final int FIRST_BYTE_WRITTEN = 2;

    35     private static final int DONE               = 4;

    36 

    37     private int state = NEW;

    38 

    39     private int payload;

    40     private int N;

    41     private int value;

    42 

    43     //

    44     //      0   1   2   3   4   5   6   7

    45     //    +---+---+---+---+---+---+---+---+

    46     //    |   |   |   |   |   |   |   |   |

    47     //    +---+---+---+-------------------+

    48     //    |<--------->|<----------------->|

    49     //       payload           N=5

    50     //

    51     // payload is the contents of the left-hand side part of the octet;

    52     //         it is truncated to fit into 8-N bits, where 1 <= N <= 8;

    53     //

    54     public IntegerWriter configure(int value, int N, int payload) {

    55         if (state != NEW) {

    56             throw new IllegalStateException("Already configured");

    57         }

    58         if (value < 0) {

    59             throw new IllegalArgumentException("value >= 0: value=" + value);

    60         }

    61         checkPrefix(N);

    62         this.value = value;

    63         this.N = N;

    64         this.payload = payload & 0xFF & (0xFFFFFFFF << N);

    65         state = CONFIGURED;

    66         return this;

    67     }

    68 

    69     public boolean write(ByteBuffer output) {

    70         if (state == NEW) {

    71             throw new IllegalStateException("Configure first");

    72         }

    73         if (state == DONE) {

    74             return true;

    75         }

    76 

    77         if (!output.hasRemaining()) {

    78             return false;

    79         }

    80         if (state == CONFIGURED) {

    81             int max = (2 << (N - 1)) - 1;

    82             if (value < max) {

    83                 output.put((byte) (payload | value));

    84                 state = DONE;

    85                 return true;

    86             }

    87             output.put((byte) (payload | max));

    88             value -= max;

    89             state = FIRST_BYTE_WRITTEN;

    90         }

    91         if (state == FIRST_BYTE_WRITTEN) {

    92             while (value >= 128 && output.hasRemaining()) {

    93                 output.put((byte) (value % 128 + 128));

    94                 value /= 128;

    95             }

    96             if (!output.hasRemaining()) {

    97                 return false;

    98             }

    99             output.put((byte) value);

   100             state = DONE;

   101             return true;

   102         }

   103         throw new InternalError(Arrays.toString(

   104                 new Object[]{state, payload, N, value}));

   105     }

   106 

   107     private static void checkPrefix(int N) {

   108         if (N < 1 || N > 8) {

   109             throw new IllegalArgumentException("1 <= N <= 8: N= " + N);

   110         }

   111     }

   112 

   113     public IntegerWriter reset() {

   114         state = NEW;

   115         return this;

   116     }

   117 }