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					151 lines
				
				3.8 KiB
			
		
		
			
		
	
	
					151 lines
				
				3.8 KiB
			| 
											3 years ago
										 | '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('') | ||
|  | } |