hexo/node_modules/base64-js/index.js

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JavaScript
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2024-05-09 16:35:20 +08:00
'use strict'
exports.byteLength = byteLength
exports.toByteArray = toByteArray
exports.fromByteArray = fromByteArray
var lookup = []
var revLookup = []
var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array
var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
for (var i = 0, len = code.length; i < len; ++i) {
lookup[i] = code[i]
revLookup[code.charCodeAt(i)] = i
}
// Support decoding URL-safe base64 strings, as Node.js does.
// See: https://en.wikipedia.org/wiki/Base64#URL_applications
revLookup['-'.charCodeAt(0)] = 62
revLookup['_'.charCodeAt(0)] = 63
function getLens (b64) {
var len = b64.length
if (len % 4 > 0) {
throw new Error('Invalid string. Length must be a multiple of 4')
}
// Trim off extra bytes after placeholder bytes are found
// See: https://github.com/beatgammit/base64-js/issues/42
var validLen = b64.indexOf('=')
if (validLen === -1) validLen = len
var placeHoldersLen = validLen === len
? 0
: 4 - (validLen % 4)
return [validLen, placeHoldersLen]
}
// base64 is 4/3 + up to two characters of the original data
function byteLength (b64) {
var lens = getLens(b64)
var validLen = lens[0]
var placeHoldersLen = lens[1]
return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
}
function _byteLength (b64, validLen, placeHoldersLen) {
return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
}
function toByteArray (b64) {
var tmp
var lens = getLens(b64)
var validLen = lens[0]
var placeHoldersLen = lens[1]
var arr = new Arr(_byteLength(b64, validLen, placeHoldersLen))
var curByte = 0
// if there are placeholders, only get up to the last complete 4 chars
var len = placeHoldersLen > 0
? validLen - 4
: validLen
var i
for (i = 0; i < len; i += 4) {
tmp =
(revLookup[b64.charCodeAt(i)] << 18) |
(revLookup[b64.charCodeAt(i + 1)] << 12) |
(revLookup[b64.charCodeAt(i + 2)] << 6) |
revLookup[b64.charCodeAt(i + 3)]
arr[curByte++] = (tmp >> 16) & 0xFF
arr[curByte++] = (tmp >> 8) & 0xFF
arr[curByte++] = tmp & 0xFF
}
if (placeHoldersLen === 2) {
tmp =
(revLookup[b64.charCodeAt(i)] << 2) |
(revLookup[b64.charCodeAt(i + 1)] >> 4)
arr[curByte++] = tmp & 0xFF
}
if (placeHoldersLen === 1) {
tmp =
(revLookup[b64.charCodeAt(i)] << 10) |
(revLookup[b64.charCodeAt(i + 1)] << 4) |
(revLookup[b64.charCodeAt(i + 2)] >> 2)
arr[curByte++] = (tmp >> 8) & 0xFF
arr[curByte++] = tmp & 0xFF
}
return arr
}
function tripletToBase64 (num) {
return lookup[num >> 18 & 0x3F] +
lookup[num >> 12 & 0x3F] +
lookup[num >> 6 & 0x3F] +
lookup[num & 0x3F]
}
function encodeChunk (uint8, start, end) {
var tmp
var output = []
for (var i = start; i < end; i += 3) {
tmp =
((uint8[i] << 16) & 0xFF0000) +
((uint8[i + 1] << 8) & 0xFF00) +
(uint8[i + 2] & 0xFF)
output.push(tripletToBase64(tmp))
}
return output.join('')
}
function fromByteArray (uint8) {
var tmp
var len = uint8.length
var extraBytes = len % 3 // if we have 1 byte left, pad 2 bytes
var parts = []
var maxChunkLength = 16383 // must be multiple of 3
// go through the array every three bytes, we'll deal with trailing stuff later
for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)))
}
// pad the end with zeros, but make sure to not forget the extra bytes
if (extraBytes === 1) {
tmp = uint8[len - 1]
parts.push(
lookup[tmp >> 2] +
lookup[(tmp << 4) & 0x3F] +
'=='
)
} else if (extraBytes === 2) {
tmp = (uint8[len - 2] << 8) + uint8[len - 1]
parts.push(
lookup[tmp >> 10] +
lookup[(tmp >> 4) & 0x3F] +
lookup[(tmp << 2) & 0x3F] +
'='
)
}
return parts.join('')
}