Convert to or from Raw Vectors

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Description

Conversion and manipulation of objects of type "raw".

Usage

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charToRaw(x)
rawToChar(x, multiple = FALSE)

rawShift(x, n)

rawToBits(x)
intToBits(x)
packBits(x, type = c("raw", "integer"))

Arguments

x

object to be converted or shifted.

multiple

logical: should the conversion be to a single character string or multiple individual characters?

n

the number of bits to shift. Positive numbers shift right and negative numbers shift left: allowed values are -8 ... 8.

type

the result type, partially matched.

Details

packBits accepts raw, integer or logical inputs, the last two without any NAs.

Note that ‘bytes’ are not necessarily the same as characters, e.g. in UTF-8 locales.

Value

charToRaw converts a length-one character string to raw bytes. It does so without taking into account any declared encoding (see Encoding).

rawToChar converts raw bytes either to a single character string or a character vector of single bytes (with "" for 0). (Note that a single character string could contain embedded nuls; only trailing nulls are allowed and will be removed.) In either case it is possible to create a result which is invalid in a multibyte locale, e.g. one using UTF-8. Long vectors are allowed if multiple is true.

rawShift(x, n) shift the bits in x by n positions to the right, see the argument n, above.

rawToBits returns a raw vector of 8 times the length of a raw vector with entries 0 or 1. intToBits returns a raw vector of 32 times the length of an integer vector with entries 0 or 1. (Non-integral numeric values are truncated to integers.) In both cases the unpacking is least-significant bit first.

packBits packs its input (using only the lowest bit for raw or integer vectors) least-significant bit first to a raw or integer vector.

Examples

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x <- "A test string"
(y <- charToRaw(x))
is.vector(y) # TRUE

rawToChar(y)
rawToChar(y, multiple = TRUE)
(xx <- c(y,  charToRaw("&"), charToRaw("more")))
rawToChar(xx)

rawShift(y, 1)
rawShift(y, -2)

rawToBits(y)

showBits <- function(r) stats::symnum(as.logical(rawToBits(r)))

z <- as.raw(5)
z ; showBits(z)
showBits(rawShift(z, 1)) # shift to right
showBits(rawShift(z, 2))
showBits(z)
showBits(rawShift(z, -1)) # shift to left
showBits(rawShift(z, -2)) # ..
showBits(rawShift(z, -3)) # shifted off entirely

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