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							3.8 KiB
						
					
					
				
			
		
		
	
	
							151 lines
						
					
					
						
							3.8 KiB
						
					
					
				| 'use strict'
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| 
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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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| 
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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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| 
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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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| 
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| // Support decoding URL-safe base64 strings, as Node.js does.
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| // See: https://en.wikipedia.org/wiki/Base64#URL_applications
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| revLookup['-'.charCodeAt(0)] = 62
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| revLookup['_'.charCodeAt(0)] = 63
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| 
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| function getLens (b64) {
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|   var len = b64.length
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| 
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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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| 
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|   // Trim off extra bytes after placeholder bytes are found
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|   // See: https://github.com/beatgammit/base64-js/issues/42
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|   var validLen = b64.indexOf('=')
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|   if (validLen === -1) validLen = len
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| 
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|   var placeHoldersLen = validLen === len
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|     ? 0
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|     : 4 - (validLen % 4)
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| 
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|   return [validLen, placeHoldersLen]
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| }
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| 
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| // base64 is 4/3 + up to two characters of the original data
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| function byteLength (b64) {
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|   var lens = getLens(b64)
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|   var validLen = lens[0]
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|   var placeHoldersLen = lens[1]
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|   return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
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| }
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| 
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| function _byteLength (b64, validLen, placeHoldersLen) {
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|   return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
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| }
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| 
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| function toByteArray (b64) {
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|   var tmp
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|   var lens = getLens(b64)
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|   var validLen = lens[0]
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|   var placeHoldersLen = lens[1]
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| 
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|   var arr = new Arr(_byteLength(b64, validLen, placeHoldersLen))
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| 
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|   var curByte = 0
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| 
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|   // if there are placeholders, only get up to the last complete 4 chars
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|   var len = placeHoldersLen > 0
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|     ? validLen - 4
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|     : validLen
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| 
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|   var i
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|   for (i = 0; i < len; i += 4) {
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|     tmp =
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|       (revLookup[b64.charCodeAt(i)] << 18) |
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|       (revLookup[b64.charCodeAt(i + 1)] << 12) |
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|       (revLookup[b64.charCodeAt(i + 2)] << 6) |
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|       revLookup[b64.charCodeAt(i + 3)]
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|     arr[curByte++] = (tmp >> 16) & 0xFF
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|     arr[curByte++] = (tmp >> 8) & 0xFF
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|     arr[curByte++] = tmp & 0xFF
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|   }
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| 
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|   if (placeHoldersLen === 2) {
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|     tmp =
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|       (revLookup[b64.charCodeAt(i)] << 2) |
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|       (revLookup[b64.charCodeAt(i + 1)] >> 4)
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|     arr[curByte++] = tmp & 0xFF
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|   }
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| 
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|   if (placeHoldersLen === 1) {
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|     tmp =
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|       (revLookup[b64.charCodeAt(i)] << 10) |
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|       (revLookup[b64.charCodeAt(i + 1)] << 4) |
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|       (revLookup[b64.charCodeAt(i + 2)] >> 2)
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|     arr[curByte++] = (tmp >> 8) & 0xFF
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|     arr[curByte++] = tmp & 0xFF
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|   }
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| 
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|   return arr
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| }
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| 
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| function tripletToBase64 (num) {
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|   return lookup[num >> 18 & 0x3F] +
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|     lookup[num >> 12 & 0x3F] +
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|     lookup[num >> 6 & 0x3F] +
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|     lookup[num & 0x3F]
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| }
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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 =
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|       ((uint8[i] << 16) & 0xFF0000) +
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|       ((uint8[i + 1] << 8) & 0xFF00) +
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|       (uint8[i + 2] & 0xFF)
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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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| 
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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 parts = []
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|   var maxChunkLength = 16383 // must be multiple of 3
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| 
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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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| 
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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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|     parts.push(
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|       lookup[tmp >> 2] +
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|       lookup[(tmp << 4) & 0x3F] +
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|       '=='
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|     )
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|   } else if (extraBytes === 2) {
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|     tmp = (uint8[len - 2] << 8) + uint8[len - 1]
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|     parts.push(
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|       lookup[tmp >> 10] +
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|       lookup[(tmp >> 4) & 0x3F] +
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|       lookup[(tmp << 2) & 0x3F] +
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|       '='
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|     )
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|   }
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| 
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|   return parts.join('')
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| }
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