1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
// Copyright 2022 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
/** Decodes and detokenizes strings from binary or Base64 input. */
import {Buffer} from 'buffer';
import {Frame} from 'pigweedjs/pw_hdlc';
import {TokenDatabase} from './token_database';
import {PrintfDecoder} from './printf_decoder';
const MAX_RECURSIONS = 9;
const BASE64CHARS = '[A-Za-z0-9+/-_]';
const PATTERN = new RegExp(
// Base64 tokenized strings start with the prefix character ($)
'\\$' +
// Tokenized strings contain 0 or more blocks of four Base64 chars.
`(?:${BASE64CHARS}{4})*` +
// The last block of 4 chars may have one or two padding chars (=).
`(?:${BASE64CHARS}{3}=|${BASE64CHARS}{2}==)?`,
'g'
);
interface TokenAndArgs {
token: number;
args: Uint8Array;
}
export class Detokenizer {
private database: TokenDatabase;
constructor(csvDatabase: string) {
this.database = new TokenDatabase(csvDatabase);
}
/**
* Detokenize frame data into actual string messages using the provided
* token database.
*
* If the frame doesn't match any token from database, the frame will be
* returned as string as-is.
*/
detokenize(tokenizedFrame: Frame): string {
return this.detokenizeUint8Array(tokenizedFrame.data);
}
/**
* Detokenize uint8 into actual string messages using the provided
* token database.
*
* If the data doesn't match any token from database, the data will be
* returned as string as-is.
*/
detokenizeUint8Array(data: Uint8Array): string {
const {token, args} = this.decodeUint8Array(data);
// Parse arguments if this is printf-style text.
const format = this.database.get(token);
if (format) {
return new PrintfDecoder().decode(String(format), args);
}
return new TextDecoder().decode(data);
}
/**
* Detokenize Base64-encoded frame data into actual string messages using the
* provided token database.
*
* If the frame doesn't match any token from database, the frame will be
* returned as string as-is.
*/
detokenizeBase64(
tokenizedFrame: Frame,
maxRecursion: number = MAX_RECURSIONS
): string {
const base64String = new TextDecoder().decode(tokenizedFrame.data);
return this.detokenizeBase64String(base64String, maxRecursion);
}
private detokenizeBase64String(
base64String: string,
recursions: number
): string {
return base64String.replace(PATTERN, base64Substring => {
const {token, args} = this.decodeBase64TokenFrame(base64Substring);
const format = this.database.get(token);
// Parse arguments if this is printf-style text.
if (format) {
const decodedOriginal = new PrintfDecoder().decode(
String(format),
args
);
// Detokenize nested Base64 tokens and their arguments.
if (recursions > 0) {
return this.detokenizeBase64String(decodedOriginal, recursions - 1);
}
return decodedOriginal;
}
return base64Substring;
});
}
private decodeUint8Array(data: Uint8Array): TokenAndArgs {
const token = new DataView(
data.buffer,
data.byteOffset,
4
).getUint32(0, true);
const args = new Uint8Array(data.buffer.slice(data.byteOffset + 4));
return {token, args};
}
private decodeBase64TokenFrame(base64Data: string): TokenAndArgs {
// Remove the prefix '$' and convert from Base64.
const prefixRemoved = base64Data.slice(1);
const noBase64 = Buffer.from(prefixRemoved, 'base64').toString('binary');
// Convert back to bytes and return token and arguments.
const bytes = noBase64.split('').map(ch => ch.charCodeAt(0));
const uIntArray = new Uint8Array(bytes);
const token = new DataView(
uIntArray.buffer,
uIntArray.byteOffset,
4
).getUint32(0, true);
const args = new Uint8Array(bytes.slice(4));
return {token, args};
}
}
|
