0) { 26 | throw new Error('Invalid string. Length must be a multiple of 4') 27 | } 28 | 29 | // Trim off extra bytes after placeholder bytes are found 30 | // See: https://github.com/beatgammit/base64-js/issues/42 31 | var validLen = b64.indexOf('=') 32 | if (validLen === -1) validLen = len 33 | 34 | var placeHoldersLen = validLen === len 35 | ? 0 36 | : 4 - (validLen % 4) 37 | 38 | return [validLen, placeHoldersLen] 39 | } 40 | 41 | // base64 is 4/3 + up to two characters of the original data 42 | function byteLength (b64) { 43 | var lens = getLens(b64) 44 | var validLen = lens[0] 45 | var placeHoldersLen = lens[1] 46 | return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen 47 | } 48 | 49 | function _byteLength (b64, validLen, placeHoldersLen) { 50 | return ((validLen + placeHoldersLen) * 3 / 4) - placeHoldersLen 51 | } 52 | 53 | function toByteArray (b64) { 54 | var tmp 55 | var lens = getLens(b64) 56 | var validLen = lens[0] 57 | var placeHoldersLen = lens[1] 58 | 59 | var arr = new Arr(_byteLength(b64, validLen, placeHoldersLen)) 60 | 61 | var curByte = 0 62 | 63 | // if there are placeholders, only get up to the last complete 4 chars 64 | var len = placeHoldersLen > 0 65 | ? validLen - 4 66 | : validLen 67 | 68 | var i 69 | for (i = 0; i < len; i += 4) { 70 | tmp = 71 | (revLookup[b64.charCodeAt(i)] << 18) | 72 | (revLookup[b64.charCodeAt(i + 1)] << 12) | 73 | (revLookup[b64.charCodeAt(i + 2)] << 6) | 74 | revLookup[b64.charCodeAt(i + 3)] 75 | arr[curByte++] = (tmp >> 16) & 0xFF 76 | arr[curByte++] = (tmp >> 8) & 0xFF 77 | arr[curByte++] = tmp & 0xFF 78 | } 79 | 80 | if (placeHoldersLen === 2) { 81 | tmp = 82 | (revLookup[b64.charCodeAt(i)] << 2) | 83 | (revLookup[b64.charCodeAt(i + 1)] >> 4) 84 | arr[curByte++] = tmp & 0xFF 85 | } 86 | 87 | if (placeHoldersLen === 1) { 88 | tmp = 89 | (revLookup[b64.charCodeAt(i)] << 10) | 90 | (revLookup[b64.charCodeAt(i + 1)] << 4) | 91 | (revLookup[b64.charCodeAt(i + 2)] >> 2) 92 | arr[curByte++] = (tmp >> 8) & 0xFF 93 | arr[curByte++] = tmp & 0xFF 94 | } 95 | 96 | return arr 97 | } 98 | 99 | function tripletToBase64 (num) { 100 | return lookup[num >> 18 & 0x3F] + 101 | lookup[num >> 12 & 0x3F] + 102 | lookup[num >> 6 & 0x3F] + 103 | lookup[num & 0x3F] 104 | } 105 | 106 | function encodeChunk (uint8, start, end) { 107 | var tmp 108 | var output = [] 109 | for (var i = start; i < end; i += 3) { 110 | tmp = 111 | ((uint8[i] << 16) & 0xFF0000) + 112 | ((uint8[i + 1] << 8) & 0xFF00) + 113 | (uint8[i + 2] & 0xFF) 114 | output.push(tripletToBase64(tmp)) 115 | } 116 | return output.join('') 117 | } 118 | 119 | function fromByteArray (uint8) { 120 | var tmp 121 | var len = uint8.length 122 | var extraBytes = len % 3 // if we have 1 byte left, pad 2 bytes 123 | var parts = [] 124 | var maxChunkLength = 16383 // must be multiple of 3 125 | 126 | // go through the array every three bytes, we'll deal with trailing stuff later 127 | for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) { 128 | parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength))) 129 | } 130 | 131 | // pad the end with zeros, but make sure to not forget the extra bytes 132 | if (extraBytes === 1) { 133 | tmp = uint8[len - 1] 134 | parts.push( 135 | lookup[tmp >> 2] + 136 | lookup[(tmp << 4) & 0x3F] + 137 | '==' 138 | ) 139 | } else if (extraBytes === 2) { 140 | tmp = (uint8[len - 2] << 8) + uint8[len - 1] 141 | parts.push( 142 | lookup[tmp >> 10] + 143 | lookup[(tmp >> 4) & 0x3F] + 144 | lookup[(tmp << 2) & 0x3F] + 145 | '=' 146 | ) 147 | } 148 | 149 | return parts.join('') 150 | } 151 | --------------------------------------------------------------------------------