digest (version 0.6.29)

getVDigest: 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"))

Value

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

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")))

See Also

digest, serialize, md5sum

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))