buffer-base62/buffer-base62.js at master · dreamcreated/buffer-base62 · GitHub

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
let BufferBase62 = module.exports = {}
var BigNumber = require('big-number');
var reverseInplace = require("buffer-reverse/inplace")
var _ = require('underscore');


let m_base62Mapping = new Array(
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',
	'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K',
	'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U',
	'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e',
	'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
	'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
);

let m_base62MappingRev = new Map(
	[['0' , 0 ],
    ['1' , 1 ],
    ['2' , 2 ],
    ['3' , 3 ],
    ['4' , 4 ],
    ['5' , 5 ],
    ['6' , 6 ],
    ['7' , 7 ],
    ['8' , 8 ],
    ['9' , 9 ],
    ['A' , 10],
	['B' , 11],
    ['C' , 12],
    ['D' , 13],
    ['E' , 14],
    ['F' , 15],
    ['G' , 16],
    ['H' , 17],
    ['I' , 18],
    ['J' , 19],
    ['K' , 20],
	['L' , 21],
    ['M' , 22],
    ['N' , 23],
    ['O' , 24],
    ['P' , 25],
    ['Q' , 26],
    ['R' , 27],
    ['S' , 28],
    ['T' , 29],
    ['U' , 30],
	['V' , 31],
    ['W' , 32],
    ['X' , 33],
    ['Y' , 34],
    ['Z' , 35],
    ['a' , 36],
    ['b' , 37],
    ['c' , 38],
    ['d' , 39],
    ['e' , 40],
	['f' , 41],
    ['g' , 42],
    ['h' , 43],
    ['i' , 44],
    ['j' , 45],
    ['k' , 46],
    ['l' , 47],
    ['m' , 48],
    ['n' , 49],
    ['o' , 50],
	['p' , 51],
    ['q' , 52],
    ['r' , 53],
    ['s' , 54],
    ['t' , 55],
    ['u' , 56],
    ['v' , 57],
    ['w' , 58],
    ['x' , 59],
    ['y' , 60],
    ['z' , 61]]
);

function setBase62Mapping(arrayMapping) {
    m_base62Mapping = arrayMapping;
    m_base62MappingRev = new Map();
    for (let i = 0; i < m_base62Mapping.length; i++) {
        m_base62MappingRev.set(m_base62Mapping[i], i);
    }
}

BufferBase62.setBase62Mapping = setBase62Mapping;


function fromBase62(str) {
    let number = BigNumber(0);
    for (let i = 0; i < str.length; i++) {
        let curNum = m_base62MappingRev.get(str[i]);
        let pos = str.length-i-1;
        number = number.plus(BigNumber(62).pow(pos).multiply(curNum));
    }
    let retBuffer = Buffer.alloc(512);
    let offset = 0;
    while(number.gt(255)) {
        let cur = number.mod(256);
        retBuffer.writeUInt8(cur, offset++);
    }
    retBuffer.writeUInt8(parseInt(number.val()), offset++);
    retBuffer = retBuffer.slice(0, offset);
    reverseInplace(retBuffer);
    return retBuffer;
}
BufferBase62.fromBase62 = fromBase62;

function toBase62(buffer) {
    let number = toBigNumber(buffer);
    let outArray = new Array();
	while (number.gt(61)) {
		let cur = number.mod(62);
		outArray.push(m_base62Mapping[cur]);
	}
	outArray.push(m_base62Mapping[parseInt(number.val())]);
    outArray.reverse();
	return outArray.join('');
}
BufferBase62.toBase62 = toBase62;

function toBigNumber(buffer) {
    let number = BigNumber(0);
    for (let offset = 0; offset < buffer.length; offset++) {
        let curNum = buffer.readUInt8(offset);
        let pos = buffer.length-offset-1;
        number = number.plus(BigNumber(256).pow(pos).multiply(curNum));
    }
    return number;
}
BufferBase62.toBigNumber = toBigNumber;