Difficulty with substring substitution

[shodan]

Hi,

I have a particularly thorny problem for you guys.

I am making a function which can modify batch file function calls.

I have identified 3 types of function calls and I need to change any one type to another.

Here are the name I gave to batch function calls

Internal function call

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Call :myfunction

External function call

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Call myfunction.bat

and function macrocall

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Call %:myfunction%

Because I am copying and combining multiple function in and out of batch files for maximum reusability.


Anyway, here is the actual problem


I have in memory the entire batchfile, line by line. Here is an particularly vexing example.

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set "textline=Call :myfunctiona some args & Call %:myfunctionb% some args & Call myfunctionc.bat some args & Call :myfunctiond some args && echo yes || echo no

What I want to do is find a replace function calls of a particular type and turn it into another type.

Example

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Call :ChangeInternalFunctionToExternal textline
Call :ChangeInternalFunctionToMacroCall textline 
Call :ChangeExternalFunctionToInternal textline
Call :ChangeExternalFunctionToMacroCall textline
Call :ChangeMacroCallFunctionToInternal textline
Call :ChangeMacroCallFunctionToExternal textline 

After :ChangeInternalFunctionToExternal

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textline=Call myfunctiona.bat some args & Call %:myfunctionb% some args & Call myfunctionc.bat some args & Call myfunctiond.bat some args && echo yes || echo no

After :ChangeInternalFunctionToMacroCall

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textline=Call %:myfunctiona% some args & Call %:myfunctionb% some args & Call myfunctionc.bat some args & Call %:myfunctiond% some args && echo yes || echo no

After :ChangeExternalFunctionToInternal

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textline=Call :myfunctiona some args & Call %:myfunctionb% some args & Call :myfunctionc some args & Call :myfunctiond some args && echo yes || echo no

After :ChangeExternalFunctionToMacroCall

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textline=Call :myfunctiona some args & Call %:myfunctionb% some args & Call %:myfunctionc% some args & Call :myfunctiond some args && echo yes || echo no

After :ChangeMacroCallFunctionToInternal

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textline=Call :myfunctiona some args & Call :myfunctionb some args & Call myfunctionc.bat some args & Call :myfunctiond some args && echo yes || echo no

After :ChangeMacroCallFunctionToExternal

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textline=Call :myfunctiona some args & Call myfunctionb.bat some args & Call myfunctionc.bat some args & Call :myfunctiond some args && echo yes || echo no

Based on the following answer by Aacini

https://stackoverflow.com/questions/510 ... batch-file

I tried the substring substitution trick, however, I am unsure if that is even possible due to the number of poison characters in the string

I tried a basic test

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@echo off
set "string=Call :myfunctiona & Call %:myfunctionb% & Call myfunctionc.bat & Call :myfunctiond && echo yes || echo no
set string
set "x=%string:Call :=" & set "substring=%"
set substring
set "x=%string:Call %=" & set "substring=%"
set substring
set "x=%string:Call =" & set "substring=%"
set substring
goto :eof

Unfortunately, the results as follows

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string=Call :myfunctiona & Call :myfunctionbmyfunctiond && echo yes || echo no
substring=myfunctionbmyfunctiond && echo yes || echo no
substring=myfunctionbmyfunctiond && echo yes || echo no
substring=:myfunctionbmyfunctiond && echo yes || echo no

[shodan]

So I think I will need to break down the task further. But maybe there are shortcuts to be taken.

For now, here is what I imagine it might look like.

find internal call index and replace

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Loop through every character, look for following (case insensitive) 
Call :
return functionname = all characters after : until space or ampersand or pipe or greater than or less than characters
return index number of : and of terminating character minus one
replace string from index to terminator functionname.bat or %:functionname%
continue until end of string

find macrocall index and replace

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Loop through every character, look for following (case insensitive) 
Call %:
return functionname = all characters after %: until %
return index number of the first % and of terminating character of the last %
replace string from index to terminator functionname.bat or :functionname
continue until end of string

find external call index and replace

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Loop through every character, look for following (case insensitive) 
call 
there was a space at the end of call there
return functionname = all characters after the space, until .bat
if there was a space before .bat, it is a regular call, not a function call
return index number of the first character and of terminating .bat
replace string from index to .bat terminator :functionname or %:functionname%
continue until end of string