digest: vdigest – R documentation

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vdigest

Set a vectorised function for creating hash function digests

Description

The getVDigest function extends digest by allowing one to set a function that returns hash summaries as a character vector of the same length as the input. It also provides a performance advantage when repeated calls are necessary (e.g. applying a hash function repeatedly to an object). The returned function contains the same arguments as digest with the exception of the raw argument (see digest for more details).

Usage

getVDigest(algo=c("md5", "sha1", "crc32", "sha256", "sha512", "xxhash32",
            "xxhash64", "murmur32", "spookyhash"),
             errormode=c("stop","warn","silent"))

Arguments

`algo`	The algorithms to be used; currently available choices are `md5`, which is also the default, `sha1`, `crc32`, `sha256`, `sha512`, `xxhash32`, `xxhash64`, `murmur32` and `spookyhash`.
`errormode`	A character value denoting a choice for the behaviour in the case of error: ‘stop’ aborts (and is the default value), ‘warn’ emits a warning and returns `NULL` and ‘silent’ suppresses the error and returns an empty string.

Details

Note that since one hash summary will be returned for each element passed as input, care must be taken when determining whether or not to include the data structure as part of the object. For instance, to return the equivalent output of digest(list("a")) it would be necessary to wrap the list object itself getVDigest()(list(list("a")))

Value

The getVDigest function returns a function for a given algorithm and error-mode.

Examples

stretch_key <- function(d, n) {
    md5 <- getVDigest()
    for (i in seq_len(n))
        d <- md5(d, serialize = FALSE)
    d
}
stretch_key('abc123', 65e3)
sha1 <- getVDigest(algo = 'sha1')
sha1(letters)

md5Input <-
    c("",
      "a",
      "abc",
      "message digest",
      "abcdefghijklmnopqrstuvwxyz",
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
      paste("12345678901234567890123456789012345678901234567890123456789012",
            "345678901234567890", sep=""))
md5Output <-
    c("d41d8cd98f00b204e9800998ecf8427e",
      "0cc175b9c0f1b6a831c399e269772661",
      "900150983cd24fb0d6963f7d28e17f72",
      "f96b697d7cb7938d525a2f31aaf161d0",
      "c3fcd3d76192e4007dfb496cca67e13b",
      "d174ab98d277d9f5a5611c2c9f419d9f",
      "57edf4a22be3c955ac49da2e2107b67a")

md5 <- getVDigest()
stopifnot(identical(md5(md5Input, serialize = FALSE), md5Output))
stopifnot(identical(digest(list("abc")),
                 md5(list(list("abc")))))

sha512Input <-c(
    "",
    "The quick brown fox jumps over the lazy dog."
    )
sha512Output <- c(
    paste0("cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce",
           "47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e"),
    paste0("91ea1245f20d46ae9a037a989f54f1f790f0a47607eeb8a14d12890cea77a1bb",
           "c6c7ed9cf205e67b7f2b8fd4c7dfd3a7a8617e45f3c463d481c7e586c39ac1ed")
    )

sha512 <- getVDigest(algo = 'sha512')
stopifnot(identical(sha512(sha512Input, serialize = FALSE), sha512Output))

digest

Create Compact Hash Digests of R Objects

v0.6.27

GPL (>= 2)

Authors

Dirk Eddelbuettel <edd@debian.org> with contributions by Antoine Lucas, Jarek Tuszynski, Henrik Bengtsson, Simon Urbanek, Mario Frasca, Bryan Lewis, Murray Stokely, Hannes Muehleisen, Duncan Murdoch, Jim Hester, Wush Wu, Qiang Kou, Thierry Onkelinx, Michel Lang, Viliam Simko, Kurt Hornik, Radford Neal, Kendon Bell, Matthew de Queljoe, Ion Suruceanu, Bill Denney, Dirk Schumacher, and Winston Chang.

Initial release

2020-10-20