source: trip-planner-front/node_modules/hpack.js/lib/hpack/encoder.js@ 76712b2

Last change on this file since 76712b2 was 6a3a178, checked in by Ema <ema_spirova@…>, 3 years ago

initial commit

  • Property mode set to 100644
File size: 2.7 KB
Line 
1var hpack = require('../hpack');
2var utils = hpack.utils;
3var huffman = hpack.huffman.encode;
4var assert = utils.assert;
5
6var WBuf = require('wbuf');
7
8function Encoder() {
9 this.buffer = new WBuf();
10 this.word = 0;
11 this.bitOffset = 0;
12}
13module.exports = Encoder;
14
15Encoder.create = function create() {
16 return new Encoder();
17};
18
19Encoder.prototype.render = function render() {
20 return this.buffer.render();
21};
22
23Encoder.prototype.encodeBit = function encodeBit(bit) {
24 var octet;
25
26 this.word <<= 1;
27 this.word |= bit;
28 this.bitOffset++;
29
30 if (this.bitOffset === 8) {
31 this.buffer.writeUInt8(this.word);
32 this.word = 0;
33 this.bitOffset = 0;
34 }
35};
36
37Encoder.prototype.encodeBits = function encodeBits(bits, len) {
38 var left = bits;
39 var leftLen = len;
40
41 while (leftLen > 0) {
42 var avail = Math.min(leftLen, 8 - this.bitOffset);
43 var toWrite = left >>> (leftLen - avail);
44
45 if (avail === 8) {
46 this.buffer.writeUInt8(toWrite);
47 } else {
48 this.word <<= avail;
49 this.word |= toWrite;
50 this.bitOffset += avail;
51 if (this.bitOffset === 8) {
52 this.buffer.writeUInt8(this.word);
53 this.word = 0;
54 this.bitOffset = 0;
55 }
56 }
57
58 leftLen -= avail;
59 left &= (1 << leftLen) - 1;
60 }
61};
62
63// Just for testing
64Encoder.prototype.skipBits = function skipBits(num) {
65 this.bitOffset += num;
66 this.buffer.skip(this.bitOffset >> 3);
67 this.bitOffset &= 0x7;
68};
69
70Encoder.prototype.encodeInt = function encodeInt(num) {
71 var prefix = 8 - this.bitOffset;
72
73 // We are going to end up octet-aligned
74 this.bitOffset = 0;
75
76 var max = (1 << prefix) - 1;
77
78 // Fast case - int fits into the prefix
79 if (num < max) {
80 this.buffer.writeUInt8((this.word << prefix) | num);
81 return octet;
82 }
83
84 var left = num - max;
85 this.buffer.writeUInt8((this.word << prefix) | max);
86 do {
87 var octet = left & 0x7f;
88 left >>= 7;
89 if (left !== 0)
90 octet |= 0x80;
91
92 this.buffer.writeUInt8(octet);
93 } while (left !== 0);
94};
95
96Encoder.prototype.encodeStr = function encodeStr(value, isHuffman) {
97 this.encodeBit(isHuffman ? 1 : 0);
98
99 if (!isHuffman) {
100 this.buffer.reserve(value.length + 1);
101 this.encodeInt(value.length);
102 for (var i = 0; i < value.length; i++)
103 this.buffer.writeUInt8(value[i]);
104 return;
105 }
106
107 var codes = [];
108 var len = 0;
109 var pad = 0;
110
111 for (var i = 0; i < value.length; i++) {
112 var code = huffman[value[i]];
113 codes.push(code);
114 len += code[0];
115 }
116 if (len % 8 !== 0)
117 pad = 8 - (len % 8);
118 len += pad;
119
120 this.buffer.reserve((len / 8) + 1);
121 this.encodeInt(len / 8);
122 for (var i = 0; i < codes.length; i++) {
123 var code = codes[i];
124 this.encodeBits(code[1], code[0]);
125 }
126
127 // Append padding
128 this.encodeBits(0xff >>> (8 - pad), pad);
129};
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