RegEx Split String at every 'n' characters into Array

Decipher · June 8, 2012

The string only contains word characters and should only be 40 characters long.

String Example: ce1fc50bffb09962be8f3c49478cbeb65e2afe0f

I need to split the string into chunks of two.

Array[0] = ce

Array[1] = 1f

And so on.

My attempt:

Dim $aArray = StringRegExp($sString, '(w{2})+', 1, 1)

I would also like to know how to specify exclude characters or (if not) if there is similiar functionality with regex please.

This will be used to check torrent tracker status. I need to put % before every two characters. The above ex. string is SHA-1 Torrent Info Hash.

Edited June 8, 2012 by Decipher

czardas · June 8, 2012

I don't know if this is any help to you. Look at the second example in that post.

Edit

I'm not sure what you mean by exclude characters. You could remove unwanted characters before or after the split - leading to different results.

Edited June 8, 2012 by czardas

Decipher · June 8, 2012

I don't know if this is any help to you. Look at the second example in that post.

Edit
I'm not sure what you mean by exclude characters. You could remove unwanted characters before or after the split - leading to different results.

Thats what I asked for thank you. Lets say I wanted to write a regular expression where I wanted the statement to be true if it dosen't contain a given character. How would I do that?

#include <Array.au3>
Dim $aArray = _StringEqualSplit(StringUpper('962fb077e814c55a9a01b8f07e2fd2945cef6998'), 2)
ConsoleWrite('%' & _ArrayToString($aArray, '%') & @CRLF)
Func _StringEqualSplit($sString, $iNumChars)
    If (Not IsString($sString)) Or $sString = "" Then Return SetError(1, 0, 0)
    If (Not IsInt($iNumChars)) Or $iNumChars < 1 Then Return SetError(2, 0, 0)
    Return StringRegExp($sString, "(?s).{1," & $iNumChars & "}", 3)
EndFunc

The above code outputs: %96%2F%B0%77%E8%14%C5%5A%9A%01%B8%F0%7E%2F%D2%94%5C%EF%69%98

It is not valid. I am confused as how to encode the info hash to request information from a torrent tracker. This page shows what I'm trying to do, if someone dosen't mind helping me out.

http://nakkaya.com/2009/12/03/bittorrent-tracker-protocol/

Edited June 8, 2012 by Decipher

czardas · June 8, 2012

If your condition is based on there being only one character then I would use StringInStr() to check if the string contains the character you want to avoid. I'm not sure about the other technical details of your request. It sounds like it might take some study.

Edited June 8, 2012 by czardas

Decipher · June 8, 2012

Perhaps this is what you are after, but I'm not sure:
ConsoleWrite('%' & _ArrayToString($aArray, '') & @CRLF)
If your condition is based on there being only one character then I would use StringInStr() to check if the string contains the character you want to avoid. I'm not sure about the other technical details of your request. It sounds like it might take some study.

Thanks for your help, This my attempt to encode the hash.

ConsoleWrite(_HashEncode(_StringEqualSplit('123456789abcdef123456789abcdef123456789a', 2)) & @CRLF)
Func _HashEncode($aArray)
Local $url = "", $acode
For $i = 0 To UBound($aArray, 1) - 1
  $acode = $aArray[$i]
  Select
   Case ($acode >= 48 And $acode <= 57) Or _
     ($acode >= 65 And $acode <= 90) Or _
     ($acode >= 97 And $acode <= 122)
    $url = $url & Chr($acode)
   Case $acode = 45 Or $acode = 95 Or $acode = 46 Or $acode = 126
    $url = $url & Chr($acode)
   Case Else
    $url = $url & '%' & $aArray[$i]
  EndSelect
Next
Return $url
EndFunc   ;==>_URLEncode
Func _StringEqualSplit($sString, $iNumChars)
    If (Not IsString($sString)) Or $sString = "" Then Return SetError(1, 0, 0)
    If (Not IsInt($iNumChars)) Or $iNumChars < 1 Then Return SetError(2, 0, 0)
    Return StringRegExp($sString, "(?s).{1," & $iNumChars & "}", 3)
EndFunc

Output: %12%348N%9a%bc%de%f1%23-CY%ab%cd%ef%12%348N%9a

Needed Output: %124Vx%9a%bc%de%f1%23Eg%89%ab%cd%ef%124Vx%9a

Based on the above link.

If you don't pay attention to the spec and send this directly to tracker you will get an error this should be in URL Encoded form. Padding every two chars with % sign also doesn't work, been there done that don't waste your time. Any hex in the hash that corresponds to a unreserved character should be replaced,

a-z A-Z 0-9 -_.~

Partition the hex in to chunks of two and check if the hex corresponds to any of these values, if they do replace them with the unreserved char,

(defn url-encode [hash]

(apply str

(map (fn [[a b]]

(let [byte (BigInteger. (str a 16) ]

(if (or (and (>= byte 65) (<= byte 90)) ; A-Z

(and (>= byte 97) (<= byte 122)) ; a-z

(and (>= byte 48) (<= byte 57)) ; 0-9

(= byte 45) (= byte 95) (= byte 46) (= byte 126))

(char byte) (str "%" a ) )) (partition 2 hash))))

So that a hash such as,

123456789abcdef123456789abcdef123456789a

becomes,

%124Vx%9a%bc%de%f1%23Eg%89%ab%cd%ef%124Vx%9a

notice that hex 34 became 4 which is what it is in ASCII. You can test the correctness of your hashes using the tracker url but don't request from announce request from file,

http://some.tracker.com/file?info_hash=hash

If you get a torrent back that means you have the correct hash.

Here are some tracker you can test it with:

Tr_1=udp://fr33domtracker.h33t.com:3310/announce

Tr_2=http://announce.torrentsmd.com:8080/announce

Tr_4=udp://9.rarbg.com:2710/announce

Tr_6=udp://tracker.openbittorrent.com:80/announce

Here are some info hashes for different torrents each on its on line:

89fc7b8e7aa220368213bc555e0f24b72295c35d1

1326dcb7fb42312d7d47d8347281a89b8c3804f3

a9e22c72041e3d336766a3ed5769070ebe9c548a

86e1b0fac439d34d34d96af168d8dfe7cbc42000

646ca38de9ec32ae6d1971fcc46665ab88c888fa

25942cb889387c509c165c923cf34c907b6e83aa

Before where I was asking how to exclude characters I was just asking out of curiosity not for my current project.

$sString = 'thisisatest'

Normally to check if it contains the word 'test' you could do StringRegExp($sString, 'test')

How could I tell it to return False if it also contains the word 'this'?

Edited June 8, 2012 by Decipher

czardas · June 8, 2012

Hmm, did you solve it? Here's what I wrote just now.

#include <Array.au3>
Dim $aArray = _StringEqualSplit('123456789abcdef123456789abcdef123456789a', 2)

$testStr = "0123456789abcdefghijklmnopqrstuvwxyz-_.~"
For $i = 0 To UBound($aArray) -1
    If StringInStr($testStr, Chr(Dec($aArray[$i]))) Then
        $aArray[$i] = Chr(Dec($aArray[$i]))
    Else
        $aArray[$i] = "%" & $aArray[$i]
    EndIf
Next
ConsoleWrite(_ArrayToString($aArray, "") & @CRLF)

Func _StringEqualSplit($sString, $iNumChars)
    If (Not IsString($sString)) Or $sString = "" Then Return SetError(1, 0, 0)
    If (Not IsInt($iNumChars)) Or $iNumChars < 1 Then Return SetError(2, 0, 0)
    Return StringRegExp($sString, "(?s).{1," & $iNumChars & "}", 3)
EndFunc

Decipher · June 8, 2012

Hmm, did you solve it? Here's what I wrote just now.

#include <Array.au3>
Dim $aArray = _StringEqualSplit('123456789abcdef123456789abcdef123456789a', 2)

$testStr = "0123456789abcdefghijklmnopqrstuvwxyz-_.~"
For $i = 0 To UBound($aArray) -1
    If StringInStr($testStr, Chr(Dec($aArray[$i]))) Then
        $aArray[$i] = Chr(Dec($aArray[$i]))
    Else
        $aArray[$i] = "%" & $aArray[$i]
    EndIf
Next
ConsoleWrite(_ArrayToString($aArray, "") & @CRLF)

Func _StringEqualSplit($sString, $iNumChars)
    If (Not IsString($sString)) Or $sString = "" Then Return SetError(1, 0, 0)
    If (Not IsInt($iNumChars)) Or $iNumChars < 1 Then Return SetError(2, 0, 0)
    Return StringRegExp($sString, "(?s).{1," & $iNumChars & "}", 3)
EndFunc

Yes you did.

Do you mind explaining how your using dec and char for future reference aka break it down?

czardas · June 8, 2012

The function Chr only accepts decimal input, and because the 2 digits in each element represent hex values, they first need to be converted to decimal using Dec before you pass them to the Chr function. This can be done easily by passing the functions as parameters in the correct sequence as I did (but it isn't necessary to do it this way). You should look up these functions in the help file and check out the ascii character codes page in there too.

I hope that makes sense. You might need to study it a bit.

One thing that isn't clear to me from the artucle is whether or not the string needs to begin with %. You may need to watch out for this if the first array element is replaced (my code will not always add a preceeding % at the start). I'm unfamiliar with bencode but it is easy to add % at the start of the string if it is needed.

Edited June 8, 2012 by czardas

Decipher · June 8, 2012

The function Chr only accepts decimal input, and because the 2 digits in each element represent hex values, they first need to be converted to decimal using Dec before you pass them to the Chr function. This can be done easily by passing the functions as parameters in the correct sequence as I did (but it isn't necessary to do it this way). You should look up these functions in the help file and check out the ascii character codes page in there too.
I hope that makes sense. You might need to study it a bit.
One thing that isn't clear to me from the artucle is whether or not the string needs to begin with %. You may need to watch out for this if the first array element is replaced (my code will not always add a preceeding % at the start). I'm unfamiliar with bencode but it is easy to add % at the start of the string if it is needed.

Awesome, I think I got everything I need now. I appreciate your help with this.

czardas · June 8, 2012

It was interesting to spend time on. I'm happy to help.

Edit

Actually looking at this again, it can be improved slightly. It's not a major change.

#include <Array.au3>
Dim $aArray = _StringEqualSplit('123456789abcdef123456789abcdef123456789a', 2)

$testStr = "0123456789abcdefghijklmnopqrstuvwxyz-_.~"
For $i = 0 To UBound($aArray) -1
    $sChar = Chr(Dec($aArray[$i])) ; This should make it slightly faster - less conversion involved.
    If StringInStr($testStr, $sChar) Then
        $aArray[$i] = $sChar
    Else
        $aArray[$i] = "%" & $aArray[$i]
    EndIf
Next
ConsoleWrite(_ArrayToString($aArray, "") & @CRLF)

Func _StringEqualSplit($sString, $iNumChars)
    If (Not IsString($sString)) Or $sString = "" Then Return SetError(1, 0, 0)
    If (Not IsInt($iNumChars)) Or $iNumChars < 1 Then Return SetError(2, 0, 0)
    Return StringRegExp($sString, "(?s).{1," & $iNumChars & "}", 3)
EndFunc

It may be possible to do all this with one complicated RegExpReplace, but that would take some thinking about (I have my doubts about it). Also whether it would be better or not is perhaps debatable (depending on the complexity).

Edited June 8, 2012 by czardas

Robjong · June 8, 2012

If you want to increase speed you should get rid of _ArrayToString.

$sHash = '123456789abcdef123456789abcdef123456789a'
ConsoleWrite(_BencodeHash($sHash) & @CRLF) ; '%124Vx%9a%bc%de%f1%23Eg%89%ab%cd%ef%124Vx%9a'

Func _BencodeHash($sStr)
    Local $aArray = StringRegExp($sStr, 'w{2}', 3)
    Local $sReturn = '', $sChar = ''
    For $i = 0 To UBound($aArray) -1
        $sChar = Chr(Dec($aArray[$i]))
        If StringInStr("0123456789abcdefghijklmnopqrstuvwxyz-_.~", $sChar) Then
            $sReturn &= $sChar
        Else
            $sReturn &= "%" & $aArray[$i]
        EndIf
    Next
    Return $sReturn
EndFunc

$sString = 'thisisatest'
Normally to check if it contains the word 'test' you could do StringRegExp($sString, 'test')
How could I tell it to return False if it also contains the word 'this'?

I think you want something like this:

#cs
    A(?!.*this).*test
    A                Anchor the match at the beginning of the string
    (?!             Start a negative lookahead subpattern
      .*            Match 0 or more of any characters, except newline
      this           The word we do NOT want in the string
    )               Close the negative lookahead
    .*               Match 0 or more of any characters, except newline
    test             The word we do want in the string

    The lookahead is a zero width assertion, so matching will continue at the
    same position after matching the subpattern, provided it did not terminate.
    Because it is a "negative" lookahead the subpattern will be satisfied if it
    can NOT match and continue with the rest of the pattern, it will terminate
    if it does match.
#ce

$sString = 'this is a test'
$sString = 'that was a test'
If StringRegExp($sString, 'A(?!.*this).*test') Then
    ConsoleWrite("Contains 'test' and NOT 'this'" & @CRLF)
ElseIf StringRegExp($sString, 'test') Then
    ConsoleWrite("Contains 'test' and 'this'" & @CRLF)
Else
    ConsoleWrite("Does not contain 'test'" & @CRLF)
EndIf

But for such simple needs, why not just use StringInStr?

$sString = 'this is a test'
$sString = 'that was a test'
If StringInStr($sString, 'test') And Not StringInStr($sString, 'this') Then
    ConsoleWrite("Contains 'test' and NOT 'this'" & @CRLF)
ElseIf StringInStr($sString, 'test') Then
    ConsoleWrite("Contains 'test' and 'this'" & @CRLF)
Else
    ConsoleWrite("Does not contain 'test'" & @CRLF)
EndIf

Edited June 8, 2012 by Robjong

czardas · June 8, 2012

If you want to increase speed you should get rid of _ArrayToString.

$sHash = '123456789abcdef123456789abcdef123456789a'
ConsoleWrite(_BencodeHash($sHash) & @CRLF) ; '%124Vx%9a%bc%de%f1%23Eg%89%ab%cd%ef%124Vx%9a'

Func _BencodeHash($sStr)
    Local $aArray = StringRegExp($sStr, 'w{2}', 3)
    Local $sReturn = '', $sChar = ''
    For $i = 0 To UBound($aArray) -1
        $sChar = Chr(Dec($aArray[$i]))
        If StringInStr("0123456789abcdefghijklmnopqrstuvwxyz-_.~", $sChar) Then
            $sReturn &= $sChar
        Else
            $sReturn &= "%" & $aArray[$i]
        EndIf
    Next
    Return $sReturn
EndFunc

Yeah that should run slightly faster. I wonder which regexp is quicker. I might test it later.

Of course there are no error checks.

Edited June 8, 2012 by czardas

Robjong · June 8, 2012

There should not be a noticeable difference.

czardas · June 8, 2012

Probably not but it's interesting nontheless. I never heard of Bencode before today.

Decipher · June 17, 2012

Thanks for your help and information.

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RegEx Split String at every 'n' characters into Array

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