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					151 lines
				
				3.8 KiB
			
		
		
			
		
	
	
					151 lines
				
				3.8 KiB
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											3 years ago
										 
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								'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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								// 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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								function getLens (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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								  // 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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								  var placeHoldersLen = validLen === len
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								    ? 0
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								    : 4 - (validLen % 4)
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								  return [validLen, placeHoldersLen]
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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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								function _byteLength (b64, validLen, placeHoldersLen) {
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								  return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen
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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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								  var arr = new Arr(_byteLength(b64, validLen, placeHoldersLen))
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								  var curByte = 0
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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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								  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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								  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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								  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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								  return arr
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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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								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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								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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								  // 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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								    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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								  return parts.join('')
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								}
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