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
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
* @format
*/
'use strict';
const encode = require('./encode');
const MAX_SEGMENT_LENGTH = 7;
const ONE_MEG = 1024 * 1024;
const COMMA = 0x2c;
const SEMICOLON = 0x3b;
/**
* Efficient builder for base64 VLQ mappings strings.
*
* This class uses a buffer that is preallocated with one megabyte and is
* reallocated dynamically as needed, doubling its size.
*
* Encoding never creates any complex value types (strings, objects), and only
* writes character values to the buffer.
*
* For details about source map terminology and specification, check
* https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit
*/
class B64Builder {
buffer: Buffer;
pos: number;
hasSegment: boolean;
constructor() {
this.buffer = Buffer.alloc(ONE_MEG);
this.pos = 0;
this.hasSegment = false;
}
/**
* Adds `n` markers for generated lines to the mappings.
*/
markLines(n: number): this {
if (n < 1) {
return this;
}
this.hasSegment = false;
if (this.pos + n >= this.buffer.length) {
this._realloc();
}
while (n--) {
this.buffer[this.pos++] = SEMICOLON;
}
return this;
}
/**
* Starts a segment at the specified column offset in the current line.
*/
startSegment(column: number): this {
if (this.hasSegment) {
this._writeByte(COMMA);
} else {
this.hasSegment = true;
}
this.append(column);
return this;
}
/**
* Appends a single number to the mappings.
*/
append(value: number): this {
if (this.pos + MAX_SEGMENT_LENGTH >= this.buffer.length) {
this._realloc();
}
this.pos = encode(value, this.buffer, this.pos);
return this;
}
/**
* Returns the string representation of the mappings.
*/
toString(): string {
return this.buffer.toString('ascii', 0, this.pos);
}
_writeByte(byte: number) {
if (this.pos === this.buffer.length) {
this._realloc();
}
this.buffer[this.pos++] = byte;
}
_realloc() {
const {buffer} = this;
this.buffer = Buffer.alloc(buffer.length * 2);
buffer.copy(this.buffer);
}
}
module.exports = B64Builder;