base64: Convert R vectors to/from the Base64 format

In caTools: Tools: Moving Window Statistics, GIF, Base64, ROC AUC, etc

Convert R vectors to/from the Base64 format

Description

Convert R vectors of any type to and from the Base64 format for encrypting any binary data as string using alphanumeric subset of ASCII character set.

Usage

  base64encode(x, size=NA, endian=.Platform$endian)
  base64decode(z, what, size=NA, signed = TRUE, endian=.Platform$endian)

Arguments

x	vector or any structure that can be converted to a vector by as.vector function. Strings are also allowed.
z	String with Base64 code, using [A-Z,a-z,0-9,+,/,=] subset of characters
what	Either an object whose mode will give the mode of the vector to be created, or a character vector of length one describing the mode: one of '"numeric", "double", "integer", "int", "logical", "complex", "character", "raw". Same as variable what in readBin functions.
size	integer. The number of bytes per element in the byte stream stored in r. The default, 'NA', uses the natural size. Same as variable size in readBin functions.
signed	logical. Only used for integers of sizes 1 and 2, when it determines if the quantity stored as raw should be regarded as a signed or unsigned integer. Same as variable signed in readBin functions.
endian	If provided, can be used to swap endian-ness. Using '"swap"' will force swapping of byte order. Use '"big"' (big-endian, aka IEEE, aka "network") or '"little"' (little-endian, format used on PC/Intel machines) to indicate type of data encoded in "raw" format. Same as variable endian in readBin functions.

Details

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.

Default sizes for different types of what: logical - 4, integer - 4, double - 8 , complex - 16, character - 2, raw - 1.

Value

Function base64encode returns a string with Base64 code. Function base64decode returns vector of appropriate mode and length (see x above).

Author(s)

Jarek Tuszynski (SAIC) [e-mail]

References

• Base64 description in Connected: An Internet Encyclopedia https://www.freesoft.org/CIE/RFC/1521/7.htm

• MIME RFC 1341 http://www.faqs.org/rfcs/rfc1341.html

• MIME RFC 1421 http://www.faqs.org/rfcs/rfc1421.html

• MIME RFC 2045 http://www.faqs.org/rfcs/rfc2045.html

• Portions of the code are based on Matlab code by Peter Acklam

See Also

xmlValue from XML package reads XML code which sometimes is encoded in Base64 format.

readBin, writeBin

Examples

   x = (10*runif(10)>5) # logical
   for (i in c(NA, 1, 2, 4)) {
     y = base64encode(x, size=i)
     z = base64decode(y, typeof(x), size=i)
     stopifnot(x==z)
   }
   print("Checked base64 for encode/decode logical type")

   x = as.integer(1:10) # integer
   for (i in c(NA, 1, 2, 4)) {
     y = base64encode(x, size=i)
     z = base64decode(y, typeof(x), size=i)
     stopifnot(x==z)
   }
   print("Checked base64 encode/decode for integer type")
   
   x = (1:10)*pi        # double
   for (i in c(NA, 4, 8)) {
     y = base64encode(x, size=i)
     z = base64decode(y, typeof(x), size=i)
     stopifnot(mean(abs(x-z))<1e-5)
   }
   print("Checked base64 for encode/decode double type")
   
   x = log(as.complex(-(1:10)*pi))        # complex
   y = base64encode(x)
   z = base64decode(y, typeof(x))
   stopifnot(x==z)
   print("Checked base64 for encode/decode complex type")
  
   x = "Chance favors the prepared mind" # character
   y = base64encode(x)
   z = base64decode(y, typeof(x))
   stopifnot(x==z)
   print("Checked base64 for encode/decode character type")

caTools documentation built on Sept. 11, 2024, 6:06 p.m.