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1   /*
2    * Copyright 2013 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.codec.spdy;
17  
18  import static io.netty.util.internal.ObjectUtil.checkNonEmpty;
19  import static io.netty.util.internal.ObjectUtil.checkNotNull;
20  
21  import io.netty.buffer.ByteBuf;
22  
23  final class SpdyCodecUtil {
24  
25      static final int SPDY_SESSION_STREAM_ID = 0;
26  
27      static final int SPDY_HEADER_TYPE_OFFSET   = 2;
28      static final int SPDY_HEADER_FLAGS_OFFSET  = 4;
29      static final int SPDY_HEADER_LENGTH_OFFSET = 5;
30      static final int SPDY_HEADER_SIZE          = 8;
31  
32      static final int SPDY_MAX_LENGTH = 0xFFFFFF; // Length is a 24-bit field
33  
34      static final byte SPDY_DATA_FLAG_FIN = 0x01;
35  
36      static final int SPDY_DATA_FRAME          = 0;
37      static final int SPDY_SYN_STREAM_FRAME    = 1;
38      static final int SPDY_SYN_REPLY_FRAME     = 2;
39      static final int SPDY_RST_STREAM_FRAME    = 3;
40      static final int SPDY_SETTINGS_FRAME      = 4;
41      static final int SPDY_PUSH_PROMISE_FRAME  = 5;
42      static final int SPDY_PING_FRAME          = 6;
43      static final int SPDY_GOAWAY_FRAME        = 7;
44      static final int SPDY_HEADERS_FRAME       = 8;
45      static final int SPDY_WINDOW_UPDATE_FRAME = 9;
46  
47      static final byte SPDY_FLAG_FIN            = 0x01;
48      static final byte SPDY_FLAG_UNIDIRECTIONAL = 0x02;
49  
50      static final byte SPDY_SETTINGS_CLEAR         = 0x01;
51      static final byte SPDY_SETTINGS_PERSIST_VALUE = 0x01;
52      static final byte SPDY_SETTINGS_PERSISTED     = 0x02;
53  
54      static final int SPDY_SETTINGS_MAX_ID = 0xFFFFFF; // ID is a 24-bit field
55  
56      static final int SPDY_MAX_NV_LENGTH = 0xFFFF; // Length is a 16-bit field
57  
58      // Zlib Dictionary
59      static final byte[] SPDY_DICT = {
60          0x00, 0x00, 0x00, 0x07, 0x6f, 0x70, 0x74, 0x69,   // - - - - o p t i
61          0x6f, 0x6e, 0x73, 0x00, 0x00, 0x00, 0x04, 0x68,   // o n s - - - - h
62          0x65, 0x61, 0x64, 0x00, 0x00, 0x00, 0x04, 0x70,   // e a d - - - - p
63          0x6f, 0x73, 0x74, 0x00, 0x00, 0x00, 0x03, 0x70,   // o s t - - - - p
64          0x75, 0x74, 0x00, 0x00, 0x00, 0x06, 0x64, 0x65,   // u t - - - - d e
65          0x6c, 0x65, 0x74, 0x65, 0x00, 0x00, 0x00, 0x05,   // l e t e - - - -
66          0x74, 0x72, 0x61, 0x63, 0x65, 0x00, 0x00, 0x00,   // t r a c e - - -
67          0x06, 0x61, 0x63, 0x63, 0x65, 0x70, 0x74, 0x00,   // - a c c e p t -
68          0x00, 0x00, 0x0e, 0x61, 0x63, 0x63, 0x65, 0x70,   // - - - a c c e p
69          0x74, 0x2d, 0x63, 0x68, 0x61, 0x72, 0x73, 0x65,   // t - c h a r s e
70          0x74, 0x00, 0x00, 0x00, 0x0f, 0x61, 0x63, 0x63,   // t - - - - a c c
71          0x65, 0x70, 0x74, 0x2d, 0x65, 0x6e, 0x63, 0x6f,   // e p t - e n c o
72          0x64, 0x69, 0x6e, 0x67, 0x00, 0x00, 0x00, 0x0f,   // d i n g - - - -
73          0x61, 0x63, 0x63, 0x65, 0x70, 0x74, 0x2d, 0x6c,   // a c c e p t - l
74          0x61, 0x6e, 0x67, 0x75, 0x61, 0x67, 0x65, 0x00,   // a n g u a g e -
75          0x00, 0x00, 0x0d, 0x61, 0x63, 0x63, 0x65, 0x70,   // - - - a c c e p
76          0x74, 0x2d, 0x72, 0x61, 0x6e, 0x67, 0x65, 0x73,   // t - r a n g e s
77          0x00, 0x00, 0x00, 0x03, 0x61, 0x67, 0x65, 0x00,   // - - - - a g e -
78          0x00, 0x00, 0x05, 0x61, 0x6c, 0x6c, 0x6f, 0x77,   // - - - a l l o w
79          0x00, 0x00, 0x00, 0x0d, 0x61, 0x75, 0x74, 0x68,   // - - - - a u t h
80          0x6f, 0x72, 0x69, 0x7a, 0x61, 0x74, 0x69, 0x6f,   // o r i z a t i o
81          0x6e, 0x00, 0x00, 0x00, 0x0d, 0x63, 0x61, 0x63,   // n - - - - c a c
82          0x68, 0x65, 0x2d, 0x63, 0x6f, 0x6e, 0x74, 0x72,   // h e - c o n t r
83          0x6f, 0x6c, 0x00, 0x00, 0x00, 0x0a, 0x63, 0x6f,   // o l - - - - c o
84          0x6e, 0x6e, 0x65, 0x63, 0x74, 0x69, 0x6f, 0x6e,   // n n e c t i o n
85          0x00, 0x00, 0x00, 0x0c, 0x63, 0x6f, 0x6e, 0x74,   // - - - - c o n t
86          0x65, 0x6e, 0x74, 0x2d, 0x62, 0x61, 0x73, 0x65,   // e n t - b a s e
87          0x00, 0x00, 0x00, 0x10, 0x63, 0x6f, 0x6e, 0x74,   // - - - - c o n t
88          0x65, 0x6e, 0x74, 0x2d, 0x65, 0x6e, 0x63, 0x6f,   // e n t - e n c o
89          0x64, 0x69, 0x6e, 0x67, 0x00, 0x00, 0x00, 0x10,   // d i n g - - - -
90          0x63, 0x6f, 0x6e, 0x74, 0x65, 0x6e, 0x74, 0x2d,   // c o n t e n t -
91          0x6c, 0x61, 0x6e, 0x67, 0x75, 0x61, 0x67, 0x65,   // l a n g u a g e
92          0x00, 0x00, 0x00, 0x0e, 0x63, 0x6f, 0x6e, 0x74,   // - - - - c o n t
93          0x65, 0x6e, 0x74, 0x2d, 0x6c, 0x65, 0x6e, 0x67,   // e n t - l e n g
94          0x74, 0x68, 0x00, 0x00, 0x00, 0x10, 0x63, 0x6f,   // t h - - - - c o
95          0x6e, 0x74, 0x65, 0x6e, 0x74, 0x2d, 0x6c, 0x6f,   // n t e n t - l o
96          0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x00, 0x00,   // c a t i o n - -
97          0x00, 0x0b, 0x63, 0x6f, 0x6e, 0x74, 0x65, 0x6e,   // - - c o n t e n
98          0x74, 0x2d, 0x6d, 0x64, 0x35, 0x00, 0x00, 0x00,   // t - m d 5 - - -
99          0x0d, 0x63, 0x6f, 0x6e, 0x74, 0x65, 0x6e, 0x74,   // - c o n t e n t
100         0x2d, 0x72, 0x61, 0x6e, 0x67, 0x65, 0x00, 0x00,   // - r a n g e - -
101         0x00, 0x0c, 0x63, 0x6f, 0x6e, 0x74, 0x65, 0x6e,   // - - c o n t e n
102         0x74, 0x2d, 0x74, 0x79, 0x70, 0x65, 0x00, 0x00,   // t - t y p e - -
103         0x00, 0x04, 0x64, 0x61, 0x74, 0x65, 0x00, 0x00,   // - - d a t e - -
104         0x00, 0x04, 0x65, 0x74, 0x61, 0x67, 0x00, 0x00,   // - - e t a g - -
105         0x00, 0x06, 0x65, 0x78, 0x70, 0x65, 0x63, 0x74,   // - - e x p e c t
106         0x00, 0x00, 0x00, 0x07, 0x65, 0x78, 0x70, 0x69,   // - - - - e x p i
107         0x72, 0x65, 0x73, 0x00, 0x00, 0x00, 0x04, 0x66,   // r e s - - - - f
108         0x72, 0x6f, 0x6d, 0x00, 0x00, 0x00, 0x04, 0x68,   // r o m - - - - h
109         0x6f, 0x73, 0x74, 0x00, 0x00, 0x00, 0x08, 0x69,   // o s t - - - - i
110         0x66, 0x2d, 0x6d, 0x61, 0x74, 0x63, 0x68, 0x00,   // f - m a t c h -
111         0x00, 0x00, 0x11, 0x69, 0x66, 0x2d, 0x6d, 0x6f,   // - - - i f - m o
112         0x64, 0x69, 0x66, 0x69, 0x65, 0x64, 0x2d, 0x73,   // d i f i e d - s
113         0x69, 0x6e, 0x63, 0x65, 0x00, 0x00, 0x00, 0x0d,   // i n c e - - - -
114         0x69, 0x66, 0x2d, 0x6e, 0x6f, 0x6e, 0x65, 0x2d,   // i f - n o n e -
115         0x6d, 0x61, 0x74, 0x63, 0x68, 0x00, 0x00, 0x00,   // m a t c h - - -
116         0x08, 0x69, 0x66, 0x2d, 0x72, 0x61, 0x6e, 0x67,   // - i f - r a n g
117         0x65, 0x00, 0x00, 0x00, 0x13, 0x69, 0x66, 0x2d,   // e - - - - i f -
118         0x75, 0x6e, 0x6d, 0x6f, 0x64, 0x69, 0x66, 0x69,   // u n m o d i f i
119         0x65, 0x64, 0x2d, 0x73, 0x69, 0x6e, 0x63, 0x65,   // e d - s i n c e
120         0x00, 0x00, 0x00, 0x0d, 0x6c, 0x61, 0x73, 0x74,   // - - - - l a s t
121         0x2d, 0x6d, 0x6f, 0x64, 0x69, 0x66, 0x69, 0x65,   // - m o d i f i e
122         0x64, 0x00, 0x00, 0x00, 0x08, 0x6c, 0x6f, 0x63,   // d - - - - l o c
123         0x61, 0x74, 0x69, 0x6f, 0x6e, 0x00, 0x00, 0x00,   // a t i o n - - -
124         0x0c, 0x6d, 0x61, 0x78, 0x2d, 0x66, 0x6f, 0x72,   // - m a x - f o r
125         0x77, 0x61, 0x72, 0x64, 0x73, 0x00, 0x00, 0x00,   // w a r d s - - -
126         0x06, 0x70, 0x72, 0x61, 0x67, 0x6d, 0x61, 0x00,   // - p r a g m a -
127         0x00, 0x00, 0x12, 0x70, 0x72, 0x6f, 0x78, 0x79,   // - - - p r o x y
128         0x2d, 0x61, 0x75, 0x74, 0x68, 0x65, 0x6e, 0x74,   // - a u t h e n t
129         0x69, 0x63, 0x61, 0x74, 0x65, 0x00, 0x00, 0x00,   // i c a t e - - -
130         0x13, 0x70, 0x72, 0x6f, 0x78, 0x79, 0x2d, 0x61,   // - p r o x y - a
131         0x75, 0x74, 0x68, 0x6f, 0x72, 0x69, 0x7a, 0x61,   // u t h o r i z a
132         0x74, 0x69, 0x6f, 0x6e, 0x00, 0x00, 0x00, 0x05,   // t i o n - - - -
133         0x72, 0x61, 0x6e, 0x67, 0x65, 0x00, 0x00, 0x00,   // r a n g e - - -
134         0x07, 0x72, 0x65, 0x66, 0x65, 0x72, 0x65, 0x72,   // - r e f e r e r
135         0x00, 0x00, 0x00, 0x0b, 0x72, 0x65, 0x74, 0x72,   // - - - - r e t r
136         0x79, 0x2d, 0x61, 0x66, 0x74, 0x65, 0x72, 0x00,   // y - a f t e r -
137         0x00, 0x00, 0x06, 0x73, 0x65, 0x72, 0x76, 0x65,   // - - - s e r v e
138         0x72, 0x00, 0x00, 0x00, 0x02, 0x74, 0x65, 0x00,   // r - - - - t e -
139         0x00, 0x00, 0x07, 0x74, 0x72, 0x61, 0x69, 0x6c,   // - - - t r a i l
140         0x65, 0x72, 0x00, 0x00, 0x00, 0x11, 0x74, 0x72,   // e r - - - - t r
141         0x61, 0x6e, 0x73, 0x66, 0x65, 0x72, 0x2d, 0x65,   // a n s f e r - e
142         0x6e, 0x63, 0x6f, 0x64, 0x69, 0x6e, 0x67, 0x00,   // n c o d i n g -
143         0x00, 0x00, 0x07, 0x75, 0x70, 0x67, 0x72, 0x61,   // - - - u p g r a
144         0x64, 0x65, 0x00, 0x00, 0x00, 0x0a, 0x75, 0x73,   // d e - - - - u s
145         0x65, 0x72, 0x2d, 0x61, 0x67, 0x65, 0x6e, 0x74,   // e r - a g e n t
146         0x00, 0x00, 0x00, 0x04, 0x76, 0x61, 0x72, 0x79,   // - - - - v a r y
147         0x00, 0x00, 0x00, 0x03, 0x76, 0x69, 0x61, 0x00,   // - - - - v i a -
148         0x00, 0x00, 0x07, 0x77, 0x61, 0x72, 0x6e, 0x69,   // - - - w a r n i
149         0x6e, 0x67, 0x00, 0x00, 0x00, 0x10, 0x77, 0x77,   // n g - - - - w w
150         0x77, 0x2d, 0x61, 0x75, 0x74, 0x68, 0x65, 0x6e,   // w - a u t h e n
151         0x74, 0x69, 0x63, 0x61, 0x74, 0x65, 0x00, 0x00,   // t i c a t e - -
152         0x00, 0x06, 0x6d, 0x65, 0x74, 0x68, 0x6f, 0x64,   // - - m e t h o d
153         0x00, 0x00, 0x00, 0x03, 0x67, 0x65, 0x74, 0x00,   // - - - - g e t -
154         0x00, 0x00, 0x06, 0x73, 0x74, 0x61, 0x74, 0x75,   // - - - s t a t u
155         0x73, 0x00, 0x00, 0x00, 0x06, 0x32, 0x30, 0x30,   // s - - - - 2 0 0
156         0x20, 0x4f, 0x4b, 0x00, 0x00, 0x00, 0x07, 0x76,   // - O K - - - - v
157         0x65, 0x72, 0x73, 0x69, 0x6f, 0x6e, 0x00, 0x00,   // e r s i o n - -
158         0x00, 0x08, 0x48, 0x54, 0x54, 0x50, 0x2f, 0x31,   // - - H T T P - 1
159         0x2e, 0x31, 0x00, 0x00, 0x00, 0x03, 0x75, 0x72,   // - 1 - - - - u r
160         0x6c, 0x00, 0x00, 0x00, 0x06, 0x70, 0x75, 0x62,   // l - - - - p u b
161         0x6c, 0x69, 0x63, 0x00, 0x00, 0x00, 0x0a, 0x73,   // l i c - - - - s
162         0x65, 0x74, 0x2d, 0x63, 0x6f, 0x6f, 0x6b, 0x69,   // e t - c o o k i
163         0x65, 0x00, 0x00, 0x00, 0x0a, 0x6b, 0x65, 0x65,   // e - - - - k e e
164         0x70, 0x2d, 0x61, 0x6c, 0x69, 0x76, 0x65, 0x00,   // p - a l i v e -
165         0x00, 0x00, 0x06, 0x6f, 0x72, 0x69, 0x67, 0x69,   // - - - o r i g i
166         0x6e, 0x31, 0x30, 0x30, 0x31, 0x30, 0x31, 0x32,   // n 1 0 0 1 0 1 2
167         0x30, 0x31, 0x32, 0x30, 0x32, 0x32, 0x30, 0x35,   // 0 1 2 0 2 2 0 5
168         0x32, 0x30, 0x36, 0x33, 0x30, 0x30, 0x33, 0x30,   // 2 0 6 3 0 0 3 0
169         0x32, 0x33, 0x30, 0x33, 0x33, 0x30, 0x34, 0x33,   // 2 3 0 3 3 0 4 3
170         0x30, 0x35, 0x33, 0x30, 0x36, 0x33, 0x30, 0x37,   // 0 5 3 0 6 3 0 7
171         0x34, 0x30, 0x32, 0x34, 0x30, 0x35, 0x34, 0x30,   // 4 0 2 4 0 5 4 0
172         0x36, 0x34, 0x30, 0x37, 0x34, 0x30, 0x38, 0x34,   // 6 4 0 7 4 0 8 4
173         0x30, 0x39, 0x34, 0x31, 0x30, 0x34, 0x31, 0x31,   // 0 9 4 1 0 4 1 1
174         0x34, 0x31, 0x32, 0x34, 0x31, 0x33, 0x34, 0x31,   // 4 1 2 4 1 3 4 1
175         0x34, 0x34, 0x31, 0x35, 0x34, 0x31, 0x36, 0x34,   // 4 4 1 5 4 1 6 4
176         0x31, 0x37, 0x35, 0x30, 0x32, 0x35, 0x30, 0x34,   // 1 7 5 0 2 5 0 4
177         0x35, 0x30, 0x35, 0x32, 0x30, 0x33, 0x20, 0x4e,   // 5 0 5 2 0 3 - N
178         0x6f, 0x6e, 0x2d, 0x41, 0x75, 0x74, 0x68, 0x6f,   // o n - A u t h o
179         0x72, 0x69, 0x74, 0x61, 0x74, 0x69, 0x76, 0x65,   // r i t a t i v e
180         0x20, 0x49, 0x6e, 0x66, 0x6f, 0x72, 0x6d, 0x61,   // - I n f o r m a
181         0x74, 0x69, 0x6f, 0x6e, 0x32, 0x30, 0x34, 0x20,   // t i o n 2 0 4 -
182         0x4e, 0x6f, 0x20, 0x43, 0x6f, 0x6e, 0x74, 0x65,   // N o - C o n t e
183         0x6e, 0x74, 0x33, 0x30, 0x31, 0x20, 0x4d, 0x6f,   // n t 3 0 1 - M o
184         0x76, 0x65, 0x64, 0x20, 0x50, 0x65, 0x72, 0x6d,   // v e d - P e r m
185         0x61, 0x6e, 0x65, 0x6e, 0x74, 0x6c, 0x79, 0x34,   // a n e n t l y 4
186         0x30, 0x30, 0x20, 0x42, 0x61, 0x64, 0x20, 0x52,   // 0 0 - B a d - R
187         0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x34, 0x30,   // e q u e s t 4 0
188         0x31, 0x20, 0x55, 0x6e, 0x61, 0x75, 0x74, 0x68,   // 1 - U n a u t h
189         0x6f, 0x72, 0x69, 0x7a, 0x65, 0x64, 0x34, 0x30,   // o r i z e d 4 0
190         0x33, 0x20, 0x46, 0x6f, 0x72, 0x62, 0x69, 0x64,   // 3 - F o r b i d
191         0x64, 0x65, 0x6e, 0x34, 0x30, 0x34, 0x20, 0x4e,   // d e n 4 0 4 - N
192         0x6f, 0x74, 0x20, 0x46, 0x6f, 0x75, 0x6e, 0x64,   // o t - F o u n d
193         0x35, 0x30, 0x30, 0x20, 0x49, 0x6e, 0x74, 0x65,   // 5 0 0 - I n t e
194         0x72, 0x6e, 0x61, 0x6c, 0x20, 0x53, 0x65, 0x72,   // r n a l - S e r
195         0x76, 0x65, 0x72, 0x20, 0x45, 0x72, 0x72, 0x6f,   // v e r - E r r o
196         0x72, 0x35, 0x30, 0x31, 0x20, 0x4e, 0x6f, 0x74,   // r 5 0 1 - N o t
197         0x20, 0x49, 0x6d, 0x70, 0x6c, 0x65, 0x6d, 0x65,   // - I m p l e m e
198         0x6e, 0x74, 0x65, 0x64, 0x35, 0x30, 0x33, 0x20,   // n t e d 5 0 3 -
199         0x53, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65, 0x20,   // S e r v i c e -
200         0x55, 0x6e, 0x61, 0x76, 0x61, 0x69, 0x6c, 0x61,   // U n a v a i l a
201         0x62, 0x6c, 0x65, 0x4a, 0x61, 0x6e, 0x20, 0x46,   // b l e J a n - F
202         0x65, 0x62, 0x20, 0x4d, 0x61, 0x72, 0x20, 0x41,   // e b - M a r - A
203         0x70, 0x72, 0x20, 0x4d, 0x61, 0x79, 0x20, 0x4a,   // p r - M a y - J
204         0x75, 0x6e, 0x20, 0x4a, 0x75, 0x6c, 0x20, 0x41,   // u n - J u l - A
205         0x75, 0x67, 0x20, 0x53, 0x65, 0x70, 0x74, 0x20,   // u g - S e p t -
206         0x4f, 0x63, 0x74, 0x20, 0x4e, 0x6f, 0x76, 0x20,   // O c t - N o v -
207         0x44, 0x65, 0x63, 0x20, 0x30, 0x30, 0x3a, 0x30,   // D e c - 0 0 - 0
208         0x30, 0x3a, 0x30, 0x30, 0x20, 0x4d, 0x6f, 0x6e,   // 0 - 0 0 - M o n
209         0x2c, 0x20, 0x54, 0x75, 0x65, 0x2c, 0x20, 0x57,   // - - T u e - - W
210         0x65, 0x64, 0x2c, 0x20, 0x54, 0x68, 0x75, 0x2c,   // e d - - T h u -
211         0x20, 0x46, 0x72, 0x69, 0x2c, 0x20, 0x53, 0x61,   // - F r i - - S a
212         0x74, 0x2c, 0x20, 0x53, 0x75, 0x6e, 0x2c, 0x20,   // t - - S u n - -
213         0x47, 0x4d, 0x54, 0x63, 0x68, 0x75, 0x6e, 0x6b,   // G M T c h u n k
214         0x65, 0x64, 0x2c, 0x74, 0x65, 0x78, 0x74, 0x2f,   // e d - t e x t -
215         0x68, 0x74, 0x6d, 0x6c, 0x2c, 0x69, 0x6d, 0x61,   // h t m l - i m a
216         0x67, 0x65, 0x2f, 0x70, 0x6e, 0x67, 0x2c, 0x69,   // g e - p n g - i
217         0x6d, 0x61, 0x67, 0x65, 0x2f, 0x6a, 0x70, 0x67,   // m a g e - j p g
218         0x2c, 0x69, 0x6d, 0x61, 0x67, 0x65, 0x2f, 0x67,   // - i m a g e - g
219         0x69, 0x66, 0x2c, 0x61, 0x70, 0x70, 0x6c, 0x69,   // i f - a p p l i
220         0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2f, 0x78,   // c a t i o n - x
221         0x6d, 0x6c, 0x2c, 0x61, 0x70, 0x70, 0x6c, 0x69,   // m l - a p p l i
222         0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2f, 0x78,   // c a t i o n - x
223         0x68, 0x74, 0x6d, 0x6c, 0x2b, 0x78, 0x6d, 0x6c,   // h t m l - x m l
224         0x2c, 0x74, 0x65, 0x78, 0x74, 0x2f, 0x70, 0x6c,   // - t e x t - p l
225         0x61, 0x69, 0x6e, 0x2c, 0x74, 0x65, 0x78, 0x74,   // a i n - t e x t
226         0x2f, 0x6a, 0x61, 0x76, 0x61, 0x73, 0x63, 0x72,   // - j a v a s c r
227         0x69, 0x70, 0x74, 0x2c, 0x70, 0x75, 0x62, 0x6c,   // i p t - p u b l
228         0x69, 0x63, 0x70, 0x72, 0x69, 0x76, 0x61, 0x74,   // i c p r i v a t
229         0x65, 0x6d, 0x61, 0x78, 0x2d, 0x61, 0x67, 0x65,   // e m a x - a g e
230         0x3d, 0x67, 0x7a, 0x69, 0x70, 0x2c, 0x64, 0x65,   // - g z i p - d e
231         0x66, 0x6c, 0x61, 0x74, 0x65, 0x2c, 0x73, 0x64,   // f l a t e - s d
232         0x63, 0x68, 0x63, 0x68, 0x61, 0x72, 0x73, 0x65,   // c h c h a r s e
233         0x74, 0x3d, 0x75, 0x74, 0x66, 0x2d, 0x38, 0x63,   // t - u t f - 8 c
234         0x68, 0x61, 0x72, 0x73, 0x65, 0x74, 0x3d, 0x69,   // h a r s e t - i
235         0x73, 0x6f, 0x2d, 0x38, 0x38, 0x35, 0x39, 0x2d,   // s o - 8 8 5 9 -
236         0x31, 0x2c, 0x75, 0x74, 0x66, 0x2d, 0x2c, 0x2a,   // 1 - u t f - - -
237         0x2c, 0x65, 0x6e, 0x71, 0x3d, 0x30, 0x2e          // - e n q - 0 -
238     };
239 
240     private SpdyCodecUtil() {
241     }
242 
243     /**
244      * Reads a big-endian unsigned short integer from the buffer.
245      */
246     static int getUnsignedShort(ByteBuf buf, int offset) {
247         return (buf.getByte(offset)     & 0xFF) << 8 |
248                 buf.getByte(offset + 1) & 0xFF;
249     }
250 
251     /**
252      * Reads a big-endian unsigned medium integer from the buffer.
253      */
254     static int getUnsignedMedium(ByteBuf buf, int offset) {
255         return (buf.getByte(offset)     & 0xFF) << 16 |
256                (buf.getByte(offset + 1) & 0xFF) <<  8 |
257                 buf.getByte(offset + 2) & 0xFF;
258     }
259 
260     /**
261      * Reads a big-endian (31-bit) integer from the buffer.
262      */
263     static int getUnsignedInt(ByteBuf buf, int offset) {
264         return (buf.getByte(offset)     & 0x7F) << 24 |
265                (buf.getByte(offset + 1) & 0xFF) << 16 |
266                (buf.getByte(offset + 2) & 0xFF) <<  8 |
267                 buf.getByte(offset + 3) & 0xFF;
268     }
269 
270     /**
271      * Reads a big-endian signed integer from the buffer.
272      */
273     static int getSignedInt(ByteBuf buf, int offset) {
274         return (buf.getByte(offset)     & 0xFF) << 24 |
275                (buf.getByte(offset + 1) & 0xFF) << 16 |
276                (buf.getByte(offset + 2) & 0xFF) <<  8 |
277                 buf.getByte(offset + 3) & 0xFF;
278     }
279 
280     /**
281      * Returns {@code true} if ID is for a server initiated stream or ping.
282      */
283     static boolean isServerId(int id) {
284         // Server initiated streams and pings have even IDs
285         return id % 2 == 0;
286     }
287 
288     /**
289      * Validate a SPDY header name.
290      */
291     static void validateHeaderName(CharSequence name) {
292         checkNonEmpty(name, "name");
293         // Since name may only contain ascii characters, for valid names
294         // name.length() returns the number of bytes when UTF-8 encoded.
295         if (name.length() > SPDY_MAX_NV_LENGTH) {
296             throw new IllegalArgumentException(
297                     "name exceeds allowable length: " + name);
298         }
299         for (int i = 0; i < name.length(); i ++) {
300             char c = name.charAt(i);
301             if (c == 0) {
302                 throw new IllegalArgumentException(
303                         "name contains null character: " + name);
304             }
305             if (c >= 'A' && c <= 'Z') {
306                 throw new IllegalArgumentException("name must be all lower case.");
307             }
308             if (c > 127) {
309                 throw new IllegalArgumentException(
310                         "name contains non-ascii character: " + name);
311             }
312         }
313     }
314 
315     /**
316      * Validate a SPDY header value. Does not validate max length.
317      */
318     static void validateHeaderValue(CharSequence value) {
319         checkNotNull(value, "value");
320         for (int i = 0; i < value.length(); i ++) {
321             char c = value.charAt(i);
322             if (c == 0) {
323                 throw new IllegalArgumentException(
324                         "value contains null character: " + value);
325             }
326         }
327     }
328 }