115 lines
3.4 KiB
JavaScript
115 lines
3.4 KiB
JavaScript
'use strict'
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exports.byteLength = byteLength
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exports.toByteArray = toByteArray
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exports.fromByteArray = fromByteArray
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var lookup = []
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var revLookup = []
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var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array
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var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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for (var i = 0, len = code.length; i < len; ++i) {
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lookup[i] = code[i]
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revLookup[code.charCodeAt(i)] = i
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}
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revLookup['-'.charCodeAt(0)] = 62
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revLookup['_'.charCodeAt(0)] = 63
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function placeHoldersCount (b64) {
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var len = b64.length
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if (len % 4 > 0) {
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throw new Error('Invalid string. Length must be a multiple of 4')
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}
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// the number of equal signs (place holders)
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// if there are two placeholders, than the two characters before it
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// represent one byte
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// if there is only one, then the three characters before it represent 2 bytes
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// this is just a cheap hack to not do indexOf twice
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return b64[len - 2] === '=' ? 2 : b64[len - 1] === '=' ? 1 : 0
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}
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function byteLength (b64) {
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// base64 is 4/3 + up to two characters of the original data
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return b64.length * 3 / 4 - placeHoldersCount(b64)
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}
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function toByteArray (b64) {
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var i, j, l, tmp, placeHolders, arr
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var len = b64.length
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placeHolders = placeHoldersCount(b64)
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arr = new Arr(len * 3 / 4 - placeHolders)
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// if there are placeholders, only get up to the last complete 4 chars
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l = placeHolders > 0 ? len - 4 : len
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var L = 0
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for (i = 0, j = 0; i < l; i += 4, j += 3) {
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tmp = (revLookup[b64.charCodeAt(i)] << 18) | (revLookup[b64.charCodeAt(i + 1)] << 12) | (revLookup[b64.charCodeAt(i + 2)] << 6) | revLookup[b64.charCodeAt(i + 3)]
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arr[L++] = (tmp >> 16) & 0xFF
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arr[L++] = (tmp >> 8) & 0xFF
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arr[L++] = tmp & 0xFF
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}
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if (placeHolders === 2) {
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tmp = (revLookup[b64.charCodeAt(i)] << 2) | (revLookup[b64.charCodeAt(i + 1)] >> 4)
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arr[L++] = tmp & 0xFF
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} else if (placeHolders === 1) {
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tmp = (revLookup[b64.charCodeAt(i)] << 10) | (revLookup[b64.charCodeAt(i + 1)] << 4) | (revLookup[b64.charCodeAt(i + 2)] >> 2)
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arr[L++] = (tmp >> 8) & 0xFF
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arr[L++] = tmp & 0xFF
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}
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return arr
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}
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function tripletToBase64 (num) {
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return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F]
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}
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function encodeChunk (uint8, start, end) {
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var tmp
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var output = []
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for (var i = start; i < end; i += 3) {
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tmp = (uint8[i] << 16) + (uint8[i + 1] << 8) + (uint8[i + 2])
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output.push(tripletToBase64(tmp))
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}
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return output.join('')
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}
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function fromByteArray (uint8) {
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var tmp
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var len = uint8.length
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var extraBytes = len % 3 // if we have 1 byte left, pad 2 bytes
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var output = ''
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var parts = []
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var maxChunkLength = 16383 // must be multiple of 3
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// go through the array every three bytes, we'll deal with trailing stuff later
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for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
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parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)))
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}
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// pad the end with zeros, but make sure to not forget the extra bytes
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if (extraBytes === 1) {
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tmp = uint8[len - 1]
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output += lookup[tmp >> 2]
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output += lookup[(tmp << 4) & 0x3F]
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output += '=='
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} else if (extraBytes === 2) {
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tmp = (uint8[len - 2] << 8) + (uint8[len - 1])
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output += lookup[tmp >> 10]
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output += lookup[(tmp >> 4) & 0x3F]
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output += lookup[(tmp << 2) & 0x3F]
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output += '='
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}
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parts.push(output)
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return parts.join('')
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}
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