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#===========================================================================#
# caTools - R library #
# Copyright (C) 2005 Jarek Tuszynski #
# Distributed under GNU General Public License version 3 #
#===========================================================================#
#===============================================================================
# The Base64 encoding is designed to encode arbitrary binary information for
# transmission by electronic mail. It is defined by MIME (Multipurpose Internet
# Mail Extensions) specification RFC 1341, RFC 1421, RFC 2045 and others.
# Triplets of 8-bit octets are encoded as groups of four characters, each
# representing 6 bits of the source 24 bits. Only a 65-character subset
# ([A-Z,a-z,0-9,+,/,=]) present in all variants of ASCII and EBCDIC is used,
# enabling 6 bits to be represented per printable character
#===============================================================================
base64encode = function(x, size=NA, endian=.Platform$endian)
{
library(bitops) # needed for bitOr and bitAnd
if (typeof(x)!="raw") x = writeBin(x, raw(), size=size, endian=endian)
x = as.integer(x)
ndByte = length(x) # number of decoded bytes
nBlock = ceiling(ndByte / 3) # number of blocks/groups
neByte = 4 * nBlock # number of encoded bytes
# add padding if necessary, to make the length of x a multiple of 3
if (ndByte < 3*nBlock) x[(ndByte+1) : (3*nBlock)] = 0;
dim(x) = c(3, nBlock) # reshape the data
y = matrix(as.integer(0), 4, nBlock) # for the encoded data
#-------------------------------------------
# Split up every 3 bytes into 4 pieces
# x = aaaaaabb bbbbcccc ccdddddd
# to form
# y = 00aaaaaa 00bbbbbb 00cccccc 00dddddd
# than convert y to integers in 0-63 range
# This section is based on Matlab code by Peter Acklam
# http://home.online.no/~pjacklam/matlab/software/util/datautil/
#-------------------------------------------
y[1,] = bitShiftR(x[1,], 2) # 6 highest bits of x(1,:)
y[2,] = bitOr(bitShiftL(x[1,], 4), bitShiftR(x[2,], 4))
y[3,] = bitOr(bitShiftL(x[2,], 2), bitShiftR(x[3,], 6))
y[4,] = x[3,]
y = bitAnd(y, 63) # trim numbers to lower 6-bits
#----------------------------------
# Perform the following mapping
# 0 - 25 -> A-Z
# 26 - 51 -> a-z
# 52 - 61 -> 0-9
# 62 -> +
# 63 -> /
#----------------------------------
alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
alpha = strsplit(alpha, NULL)[[1]] # convert string to array of characters
z = alpha[y+1] # rearrange characters
#-------------------------
# Add padding if necessary.
#-------------------------
npbytes = 3 * nBlock - ndByte # number of padding bytes needed
if (npbytes>0) z[(neByte-npbytes+1) : neByte] = '=' # '=' is used for padding
z = paste(z, collapse = "") # combine characters into a string
return (z)
}
#====================================================================
base64decode = function(z, what, size=NA, signed = TRUE, endian=.Platform$endian)
{
library(bitops) # needed for bitOr and bitAnd
if (!is.character(z))
stop("base64decode: Input argument 'z' is suppose to be a string")
if (length(z)==1) z = strsplit(z, NULL)[[1]] # convert string to array of characters
if (length(z)%%4!=0)
warning("In base64decode: Length of base64 data (z) not a multiple of 4.")
#-----------------------------------
# Now perform the following mapping
# A-Z -> 0 - 25
# a-z -> 26 - 51
# 0-9 -> 52 - 61
# + -> 62
# / -> 63
# = -> 64 - special padding character
# otherwise -1
#-----------------------------------
alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
alpha = strsplit(alpha, NULL)[[1]] # convert string to array of characters
y = match(z, alpha, nomatch=-1)-1 # lookup number of each character
if (any(y == -1))
stop("base64decode: Input string is not in Base64 format")
if (any(y == 64)) y = y[y != 64] # remove padding
neByte = length(y); # number of encoded bytes
nBlock = ceiling(neByte/4); # number of blocks/groups
ndByte = 3 * nBlock # number of decoded bytes
# add padding if necessary
if (neByte < 4*nBlock) y[(neByte+1) : (4*nBlock)] = 0;
dim(y) = c(4, nBlock); # shape into a matrix
x = matrix(as.integer(0), 3, nBlock); # for the decoded data
#---------------------------------------------
# Rearrange every 4 bytes into 3 bytes
# y = 00aaaaaa 00bbbbbb 00cccccc 00dddddd
# to form
# x = aaaaaabb bbbbcccc ccdddddd
# This section is based on Matlab code by Peter Acklam
# http://home.online.no/~pjacklam/matlab/software/util/datautil/
#---------------------------------------------
x[1,] = bitOr(bitShiftL(y[1,], 2), bitShiftR(y[2,], 4))
x[2,] = bitOr(bitShiftL(y[2,], 4), bitShiftR(y[3,], 2))
x[3,] = bitOr(bitShiftL(y[3,], 6), y[4,])
x = bitAnd(x, 255) # trim numbers to lower 8-bits
# remove padding
if (neByte %% 4 == 2) x = x[1:(ndByte-2)]
if (neByte %% 4 == 3) x = x[1:(ndByte-1)]
# perform final conversion from 'raw' to type given by 'what'
r = as.raw(x)
TypeList = c("logical", "integer", "double", "complex", "character", "raw",
"numeric", "int")
if (!is.character(what) || length(what) != 1 || !(what %in% TypeList))
what <- typeof(what)
if (what=="raw") return(r)
if (is.na(size)) size = switch(match(what, TypeList), 4, 4, 8, 16, 2, 1, 8, 4)
n = length(r)
if (n%%size) stop("raw2bin: number of elements in 'r' is not multiple of 'size'")
x = readBin(r, what, n = n%/%size, size=size, signed=signed, endian=endian)
if (what=="character") x = paste(x, collapse = "") # convert arrays of characters to strings
return (x)
}
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