Regex... Repeating Block of Regex

[gruntydatsun 12]

I have an XML file and every time there are three lines in a row with only <null/> in them, i want to insert a fourth line with <null/>.   Each line starts with 3 white spaces, followed by <null/> and ends with a white space followed by CR LF.   The presence of the three lines as described is unique to the points where I want to insert a line in this document.

 I'm trying to figure out how to apply the repeating part of a regex  {1,4} but apply it to this whole segment. 

So far I have the below which picks up an individual line ok:

^\s{3}<null/>\s\r\n

I tried wrapping it all in braces () then adding {3} but I'm obviously getting something wrong. 

Attached is a section from the xml file with a block of nulls that should be matched if anyone would like to have a look.

Help_From_Forum.xml

[TheXman 161]

@gruntydatsun

Here's one of several ways you could do it.

example()

Func example()
    Local $sBefore = _
        '<row name="subTotal" mergeCellEnd="7" mergeCellStart="1"> ' & @CRLF & _
        '   <cell type="text" name="subTotal">Subtotal: Hotpants Sales To Senior Execs</cell> ' & @CRLF & _
        '   <null/> ' & @CRLF & _
        '   <null/> ' & @CRLF & _
        '   <null/> ' & @CRLF & _
        '   <cell type="number" name="Year 1">0</cell> ' & @CRLF & _
        '   <cell type="number" name="Year 2">0</cell> ' & @CRLF & _
        '   <cell type="number" name="Year 3 and 4">1,000</cell> ' & @CRLF & _
        '   <null/> ' & @CRLF & _
        '   <null/> ' & @CRLF & _
        '</row> ' & @CRLF

    Local $sAfter = StringRegExpReplace($sBefore, "(?sm)((?:^\s{3}<null/>\s\r\n){3})", "\1   <null/> " & @CRLF)

    ConsoleWrite("Before:" & @CRLF)
    ConsoleWrite($sBefore & @CRLF)
    ConsoleWrite("After:" & @CRLF)
    ConsoleWrite($sAfter & @CRLF)

EndFunc

 

[mikell 915]

6 hours ago, gruntydatsun said:

I tried wrapping it all in braces () then adding {3}

... and there is nothing more to do but add the \K  ("keep out") verb  

$sAfter = StringRegExpReplace($sBefore, "(?m)(^\s{3}<null/>\s\r\n){3}\K", "$1")

Edit
Please note that as \K is used here as a lookbehind alternative, obviously this works too

$sAfter = StringRegExpReplace($sBefore, "(?m)(?<=(^\s{3}<null/>\s\r\n){3})", "$1")

 

Edited November 12, 2018 by mikell

[gruntydatsun 12]

Thanks for the tips guys