| UUID {uuid} | R Documentation |
S3 class "UUID" represents vector of UUIDs in native form
(128-bit). They are typically obtained by calling
UUIDgenerate, UUIDparse or as.UUID.
Methods exist for common operations such as as.character,
print, c, subsetting and comparison
operators. Note that arithmetic and other operations are not allowed.
UUIDs have three possible representations: as character vectors (in
the hyphenated 8-4-4-4-12 hexadecimal form), the UUID class
described here and raw vectors. In the latter case the raw vector must
be of length 16 or it must be a matrix with 16 rows. Since matrices in
R are stored in colum-major format, UUID must be contiguous and thus
form the columns of the raw matrix, which may be slightly
counter-intuitive, but is far moreefficient.
as.character method exist for UUID objects and converts it to a
character vector of lower-case UUID string representation.
as.raw method converts UUIDs to raw vectors or matrices as
describe above. Similarly, a as.UUID method for raw vectors
performs the inverse transformation.
as.UUID(x, ...)
is.UUID(x)
x |
object to coerce / check |
... |
unused |
Internally, the underlying object uses complex numbers to store 128-bit values with each UUID represented as one complex number. There may be cases where some operations strip the class attribute which will lead to complex values being visible, but their behavior should be regarded as undefined.
NA values in the UUID class are internally stored as a special
value a2070000-0000-f07f-a207-00000000f07f which is not a valid UUID
(since the version of that UUID is 15 which does not exist). This is
an R extension and will be automatically converted to NA where
possible, but the raw format does not support NAs so it will be
visible there. Coercions to/from string and UUIDs handle NAs
correctly and thus this internal representation should not be relied
upon by any code and may change in the future.
as.UUID returns an object of the class "UUID"
representing a vector of UUIDs. Any elements that are not
valid UUIDs will yield NA values.
is.UUID returns TRUE if the object is of the class
"UUID" and FALSE otherwise.
Comparisons are much faster between UUID vectors than between UUID vectors and other types, because in the latter case all values are coerced to strings before comparison which is very expensive.
However, x == y does not necessarily yield the same result as
as.UUID(x) == as.UUID(y). For example, for x a valid
UUID object of length one and y = "foo" the former will be
FALSE while the latter will be NA due to coercion not
yielding a valid UUID value represented by NA.
Simon Urbanek
(u <- as.UUID("837bc850-07d9-42f9-9afb-716409bf87b7"))
(uv <- c(u, NA, UUIDgenerate(n=3, output="uuid")))
as.character(u)
uv == u
is.na(uv)
identical(as.UUID(as.character(uv)), uv)
as.raw(u)
## all forms are can be coerced losslessly
identical(as.UUID(as.raw(uv)), uv)
identical(as.UUID(as.character(as.UUID(as.raw(uv)))), uv)