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1'use strict'
2
3exports.byteLength = byteLength
4exports.toByteArray = toByteArray
5exports.fromByteArray = fromByteArray
6
7var lookup = []
8var revLookup = []
9var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array
10
11var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
12for (var i = 0, len = code.length; i < len; ++i) {
13  lookup[i] = code[i]
14  revLookup[code.charCodeAt(i)] = i
15}
16
17// Support decoding URL-safe base64 strings, as Node.js does.
18// See: https://en.wikipedia.org/wiki/Base64#URL_applications
19revLookup['-'.charCodeAt(0)] = 62
20revLookup['_'.charCodeAt(0)] = 63
21
22function getLens (b64) {
23  var len = b64.length
24
25  if (len % 4 > 0) {
26    throw new Error('Invalid string. Length must be a multiple of 4')
27  }
28
29  // Trim off extra bytes after placeholder bytes are found
30  // See: https://github.com/beatgammit/base64-js/issues/42
31  var validLen = b64.indexOf('=')
32  if (validLen === -1) validLen = len
33
34  var placeHoldersLen = validLen === len
35    ? 0
36    : 4 - (validLen % 4)
37
38  return [validLen, placeHoldersLen]
39}
40
41// base64 is 4/3 + up to two characters of the original data
42function byteLength (b64) {
43  var lens = getLens(b64)
44  var validLen = lens[0]
45  var placeHoldersLen = lens[1]
46  return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
47}
48
49function _byteLength (b64, validLen, placeHoldersLen) {
50  return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
51}
52
53function toByteArray (b64) {
54  var tmp
55  var lens = getLens(b64)
56  var validLen = lens[0]
57  var placeHoldersLen = lens[1]
58
59  var arr = new Arr(_byteLength(b64, validLen, placeHoldersLen))
60
61  var curByte = 0
62
63  // if there are placeholders, only get up to the last complete 4 chars
64  var len = placeHoldersLen > 0
65    ? validLen - 4
66    : validLen
67
68  var i
69  for (i = 0; i < len; i += 4) {
70    tmp =
71      (revLookup[b64.charCodeAt(i)] << 18) |
72      (revLookup[b64.charCodeAt(i + 1)] << 12) |
73      (revLookup[b64.charCodeAt(i + 2)] << 6) |
74      revLookup[b64.charCodeAt(i + 3)]
75    arr[curByte++] = (tmp >> 16) & 0xFF
76    arr[curByte++] = (tmp >> 8) & 0xFF
77    arr[curByte++] = tmp & 0xFF
78  }
79
80  if (placeHoldersLen === 2) {
81    tmp =
82      (revLookup[b64.charCodeAt(i)] << 2) |
83      (revLookup[b64.charCodeAt(i + 1)] >> 4)
84    arr[curByte++] = tmp & 0xFF
85  }
86
87  if (placeHoldersLen === 1) {
88    tmp =
89      (revLookup[b64.charCodeAt(i)] << 10) |
90      (revLookup[b64.charCodeAt(i + 1)] << 4) |
91      (revLookup[b64.charCodeAt(i + 2)] >> 2)
92    arr[curByte++] = (tmp >> 8) & 0xFF
93    arr[curByte++] = tmp & 0xFF
94  }
95
96  return arr
97}
98
99function tripletToBase64 (num) {
100  return lookup[num >> 18 & 0x3F] +
101    lookup[num >> 12 & 0x3F] +
102    lookup[num >> 6 & 0x3F] +
103    lookup[num & 0x3F]
104}
105
106function encodeChunk (uint8, start, end) {
107  var tmp
108  var output = []
109  for (var i = start; i < end; i += 3) {
110    tmp =
111      ((uint8[i] << 16) & 0xFF0000) +
112      ((uint8[i + 1] << 8) & 0xFF00) +
113      (uint8[i + 2] & 0xFF)
114    output.push(tripletToBase64(tmp))
115  }
116  return output.join('')
117}
118
119function fromByteArray (uint8) {
120  var tmp
121  var len = uint8.length
122  var extraBytes = len % 3 // if we have 1 byte left, pad 2 bytes
123  var parts = []
124  var maxChunkLength = 16383 // must be multiple of 3
125
126  // go through the array every three bytes, we'll deal with trailing stuff later
127  for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
128    parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)))
129  }
130
131  // pad the end with zeros, but make sure to not forget the extra bytes
132  if (extraBytes === 1) {
133    tmp = uint8[len - 1]
134    parts.push(
135      lookup[tmp >> 2] +
136      lookup[(tmp << 4) & 0x3F] +
137      '=='
138    )
139  } else if (extraBytes === 2) {
140    tmp = (uint8[len - 2] << 8) + uint8[len - 1]
141    parts.push(
142      lookup[tmp >> 10] +
143      lookup[(tmp >> 4) & 0x3F] +
144      lookup[(tmp << 2) & 0x3F] +
145      '='
146    )
147  }
148
149  return parts.join('')
150}
151