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4127 :: How to read string slices as integers performantly?

• tim_st (orginal) [2018-08-12T23:47:49+02:00] view original

  Assuming I have a string

  var x = "aaaabbbbbbbbcccc"
  Run

  of length 16. I want to read the chars "aaaa" as int32, the chars "bbbbbbbb" as int64 and the chars "cccc" as int32.

  What would be the most performant way to read these 3 slices into the int types if I know the start index (here 0)?

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• lucian (orginal) [2018-08-13T14:06:12+02:00] view original

  see: https://forum.nim-lang.org/t/2626 for a similar question.

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• tim_st (orginal) [2018-08-13T14:31:41+02:00] view original

  Thanks, that's exactly what I needed!

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• tim_st (orginal) [2018-08-14T10:59:16+02:00] view original

  The link was indeed very helpful, so I used the following:

  From T to string:

  result = ""
    var t: T
    var fromTtoString = cast[ptr array[sizeof(T), char]](unsafeAddr(t))[]
    for c in fromTtoString: result.add(c)
  Run

  From string to T:

  var t: T = cast[ptr T](unsafeAddr(serializedStringData[stringIndex]))[]
  Run

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• cdome (orginal) [2018-08-14T11:28:27+02:00] view original

  These days it is possible that toOpenArray will also be handy to avoid copies. It is untested idea.

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