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Coffeescript efficient base64 decode to typed array.
decodingTable = new Uint8Array(256)
for c, i in 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
decodingTable[c.charCodeAt(0)] = i
base64decode = (string) ->
last = string[string.length-2...string.length]
if last == '=='
remainder = 2
else if last[1] == '='
remainder = 1
else
remainder = 0
filledLength = string.length - string.length % 4
byteLength = (filledLength/4)*3 + remainder
result = new Uint8Array(byteLength)
for i in [0...filledLength] by 4
c1 = decodingTable[string.charCodeAt(i)]
c2 = decodingTable[string.charCodeAt(i+1)]
c3 = decodingTable[string.charCodeAt(i+2)]
c4 = decodingTable[string.charCodeAt(i+3)]
idx = (i/4)*3
result[idx] = (c1<<2) + (c2>>4)
result[idx+1] = ((c2&15)<<4) + (c3>>2)
result[idx+2] = ((c3&3)<<6) + c4
idx = (i/4)*3
if remainder > 0
c1 = decodingTable[string.charCodeAt(i)]
c2 = decodingTable[string.charCodeAt(i+1)]
result[idx] = (c1<<2) + (c2>>4)
if remainder > 1
c3 = decodingTable[string.charCodeAt(i+2)]
result[idx+1] = ((c2&15)<<4) + (c3>>2)
return result
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