[Question] What methods are cross-platform

dipterix commented 2 years ago

Sorry if I asked a dumb question. From all methods supported, is there a list of methods that are cross-platform reproducible?

The conditions include:

On different CPU arch (x86, x64, ARM)
On different OS (windows, osx, ubuntu, Solaris, ...)
Little / big endianess
Using digest(serialize=FALSE, seed=0)

For example, can expect digest("aaa", serialize=FALSE, algo="xxhash64") to produces the EXACT same results on all OS, endianess, and all CPUs?

eddelbuettel commented 2 years ago

In general, there are two aspect there:

Is the object serialization the same? R deals with this, and you have to check serialize() for the string it creates
Is the hash digest the same? In general it should be.

Look for example at the package unit tests which check against invariant test output. Here is one for md5:

## Standard RFC 1321 test vectors
md5Input <-
    c("",
      "a",
      "abc",
      "message digest",
      "abcdefghijklmnopqrstuvwxyz",
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
      paste("12345678901234567890123456789012345678901234567890123456789012",
            "345678901234567890", sep=""))
md5Output <-
    c("d41d8cd98f00b204e9800998ecf8427e",
      "0cc175b9c0f1b6a831c399e269772661",
      "900150983cd24fb0d6963f7d28e17f72",
      "f96b697d7cb7938d525a2f31aaf161d0",
      "c3fcd3d76192e4007dfb496cca67e13b",
      "d174ab98d277d9f5a5611c2c9f419d9f",
      "57edf4a22be3c955ac49da2e2107b67a")

for (i in seq(along.with=md5Input)) {
    md5 <- digest(md5Input[i], serialize=FALSE)
    expect_true(identical(md5, md5Output[i]))
    #cat(md5, "\n")
}

md5 <- getVDigest()
expect_identical(md5(md5Input, serialize = FALSE), md5Output)

We run this test on every platform the package is checked. And we have similar checks for the other methods.

As your question was very specifically about xxhash64 I would encourage you to see what its upstream repo has to say about the matter. We just use it here as one among a number of hashing functions.

dipterix commented 2 years ago

Thanks for answering my question.

Is the hash digest the same? In general it should be.

Is this the case for sha-256?

Thanks

eddelbuettel commented 2 years ago

Well everything I said in the previous applies here too so I do not understand what you are asking now.

Also, as you know, thhe package is open source and there are sha256 unit tests.

eddelbuettel / digest

[Question] What methods are cross-platform #176