| Version: | 1.0-9 |
| Date: | 2024-10-03 |
| Title: | Bitwise Operations |
| Description: | Functions for bitwise operations on integer vectors. |
| License: | GPL-2 | GPL-3 [expanded from: GPL (≥ 2)] |
| URL: | https://github.com/mmaechler/R-bitops |
| BugReports: | https://github.com/mmaechler/R-bitops/issues |
| NeedsCompilation: | yes |
| Packaged: | 2024-10-03 09:17:35 UTC; maechler |
| Author: | Steve Dutky [aut] (S original; then (after MM's port) revised and
modified),
Martin Maechler 
[cre, aut] (Initial R port; tweaks) |
| Maintainer: | Martin Maechler <maechler@stat.math.ethz.ch> |
| Repository: | CRAN |
| Date/Publication: | 2024-10-03 23:00:54 UTC |
Bitwise And, Or and Xor Operations
Description
Bitwise operations, ‘and’ (&),
‘or’ (|), and ‘Xor’ (xor).
Usage
bitAnd(a, b)
a %&% b
bitOr (a, b)
a %|% b
bitXor(a, b)
a %^% b
Arguments
a, b |
numeric vectors of compatible length, each treated as 32 bit “strings”. |
Details
The bitwise operations are applied to the arguments cast as 32 bit
(unsigned long) integers. NA is returned wherever the magnitude of the
arguments is not less than 2^31, or, where either of the arguments is
not finite.
For bitwise ‘not’ (! in R), use bitFlip().
Value
non-negative integer valued numeric vector of maximum length of a or b.
Author(s)
Steve Dutky; idea for operators: Dan L Robertson
See Also
bitFlip, bitShiftL; further,
cksum.
Examples
bitAnd(15,7) == 7 ; identical(15 %&% 7, bitAnd(15, 7))
bitOr(15,7) == 15 ; identical(15 %|% 7, bitOr (15, 7))
bitXor(15,7) == 8 ; identical(15 %^% 7, bitXor(15,7))
bitOr(-1,0) == 4294967295 ; identical(-1 %|% 0, bitOr(-1,0))
Binary Flip (Not) Operator
Description
The binary flip (‘not’, R's !) operator, bitFlip(a, w), “flips every
bit” of a up to the w-th bit.
Usage
bitFlip(a, bitWidth = 32)
Arguments
a |
numeric vector. |
bitWidth |
scalar integer between 0 and 32. |
Value
(“binary”) numeric vector of the same length as a masked with
(2^bitWidth)-1. NA is returned for any value of
a that is not finite or whose magnitude is greater or equal to
2^{32}.
Note
bitFlip(a, w) is an “involution”, i.e. it is its own
inverse – when a is in \{0, 1, .., 2^{32}-1\}.
Notably, negative values a are equivalent to their values in the
above range, see also bitUnique() in the ‘Examples’.
Author(s)
Steve Dutky
See Also
Examples
bitFlip(0:5)
##
bitUnique <- function(x) bitFlip(bitFlip(x)) # "identity" when x in 0:(2^32-1)
bitUnique( 0:16 ) # identical (well, double precision)
bitUnique(-(1:16)) # 4294967295 ...
stopifnot(
identical(bitUnique(-(1:16)), 2^32 -(1:16)),
bitFlip(-1) == 0,
bitFlip(0 ) == 2^32 - 1,
bitFlip(0, bitWidth=8) == 255
)
Bitwise Shift Operator (to the Left or Right)
Description
These functions shift integers bitwise to the left or to the right,
returning unsigned integers, i.e., values in
{0, 1, \ldots, 2^{32}-1}.
Usage
bitShiftL(a, b)
a %<<% b
bitShiftR(a, b)
a %>>% b
Arguments
a |
numeric vector (integer valued), to be shifted. |
b |
integer (valued) vector. Internally, only |
Value
non-negative integer valued numeric vector of maximum length of
a or b containing
the value of a shifted to the left or right by b bits.
NA is returned wherever the value of a or b is not finite,
or, wherever the magnitude of a is greater than or equal to
2^{32}.
See Also
Examples
bitShiftL(0:4, 1) # 0 2 4 6 8
bitShiftL(0:3, 2) # 0 4 8 12
stopifnot(exprs = {
identical(bitShiftL(0:4, 1), 0:4 %<<% 1)
identical(bitShiftR(0:3, 2), 0:3 %>>% 2)
})
bitShiftR(0:7, 1) # 0 0 1 1 2 2 3 3 <==> N %/% 2
bitShiftR(0:7, 2) # 0 0 0 0 1 1 1 1 <==> N %/% 4
## all outputs are "unsigned integer" :
stopifnot( bitShiftL(-1, 0) == 2^32 - 1 ,
bitShiftL(-7, 0) == 4294967289 ,
bitShiftL(-7, 0) == bitShiftR(-7, 0))
bitShiftR(-1,1) == 2147483647
bitShiftL(2147483647,1) == 4294967294 # <==> * 2
bitShiftL( -1, 1) == 4294967294
bitShiftL(47, 32) # is 47
## 5 Christmas trees ( bitShiftL *rotates* to the left)
t(outer(1:5, 0:40, bitShiftL))
N <- as.numeric( rpois(1000, 100) )
stopifnot(identical(bitShiftL(N,0), N),
identical(bitShiftL(N,1), 2*N),
identical(bitShiftL(N,2), 4*N),
## right shift:
identical(bitShiftR(N,2), N %/% 4),
identical(bitShiftR(N,4), N %/% 16))
Compute Check Sum
Description
Return a cyclic redundancy checksum for each element in the argument.
Usage
cksum(a)
Arguments
a |
coerced to character vector |
Details
NA's appearing in the argument are returned as NA's.
The default calculation is identical to that given in pseudo-code in the ACM article (in the References).
Value
numeric vector of the same length as a.
Author(s)
Steve Dutky sdutky@terpalum.umd.edu
References
Fashioned from cksum(1) UNIX command line utility, i.e.,
man cksum.
Dilip V. Sarwate (1988) Computation of Cyclic Redundancy Checks Via Table Lookup, Communications of the ACM 31, 8, 1008–1013.
See Also
Examples
b <- "I would rather have a bottle in front of me than frontal lobotomy\n"
stopifnot(cksum(b) == 1342168430)
(bv <- strsplit(b, " ")[[1]])
cksum(bv) # now a vector of length 13