CODEWITHSUNDEEP
stringtype-conversionjulia
tparker
tparker

Reputation: 724

Representing a non-numeric string as in integer in Julia

I'm looking for a simple and invertible way to represent a Julia string by an integer (e.g. for cryptography). To be clear, I'm not considering string representations of integers like "123", but arbitrary strings like "Hello". The representation doesn't need to be human-readable, but it needs to be easily invertible back to a unique string (so not a hash). It doesn't need to be efficient; I'm just looking for something as simple as possible. (Also, it's fine if it only works on a small character set, e.g. lowercase Roman letters.)

One naive way would be to collect the string into a vector of chars, parse(Int, _) each char to an integer, and concatenate the integers. But this seems cumbersome, and I suspect that there's in built-in Julia function (or small composition of functions) that will get the job done more easily.

Upvotes: 3

Views: 757

Answers (2)

mbauman
mbauman

Reputation: 31372

If your strings only use the numbers 0-9 and letters a-z and A-Z, then you can parse the string directly as base 62 BigInteger:

julia> s = randstring(123)
"RFXkzD6VpWcwvbsxOtdTxS4DGcgciKgDXECa9fEK0Djcdkcj5N75vIHEMVyuH9mcYgvFbLhbPdrKyPIO4JsK1DKgZIacov6WKDZdIpGJ5iJ15dpjmcCBCybMmxB"

julia> i = parse(BigInt, s, base=62)
12798646956721889529517502411501433963894611324020956397632780092623456213685688389093681112679380669903728068303911743800989012987014660454736389459814982802097607808640628339365945710572579898457023165244164689548286133

julia> string(i, base=62)
"RFXkzD6VpWcwvbsxOtdTxS4DGcgciKgDXECa9fEK0Djcdkcj5N75vIHEMVyuH9mcYgvFbLhbPdrKyPIO4JsK1DKgZIacov6WKDZdIpGJ5iJ15dpjmcCBCybMmxB"

Upvotes: 4

tparker
tparker

Reputation: 724

I created a (somewhat complicated) implementation that works for ASCII strings:

stringToInt(str::String) = sum(i -> Int(str[end-i]) * 128^i, 0:length(str)-1)

function intToString(m::Int)
  chars = Char[]
  for n in div(ceil(Int, log2(x)), 7)-1:-1:0
    d, m = divrem(m, 128^n)
    push!(chars, d)
  end
  String(chars)
end

Let me know if you can think of a better one.

Upvotes: 0

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