'Batch" Issue with file names having &'s in them - batch-file

Question

Not quite sure how to title my issue that I'm running into (tried as best I could), but what I'm having issues with is when I'm trying to read in file names and then use them in a backup script I've wrote. I had originally tested it on files without &'s in the name (didn't remember that I had any with them in it, and didn't realize that there would be an issue until now).
Here is part of the code that is being used upto the call in the below example:
:backup2
if %DEBUG%=="t" echo Begin backup part 2
for %%? in ("!FILEREADIN!") do (
SET "FILENAME=%%~n?%%~x?"
SET "BACKUPFQP=%%~f?"
SET "BACKUPLAST=%%~t?"
call :getlength FILELENGTH "!FILENAME!"
Anyway the part that I'm running into the issue with when I'm working with the file name in my code to get the length of the file name (used in a separate section of script).
:getlength
SETLOCAL enabledelayedexpansion
if %DEBUG%=="t" echo %2 parsed... %%2 delayed... !%2!
SET "LENGTH=!%1!"
SET "STRING=%2"
REM need to correct the string for the "" that get added from passing in %2
REM Issue arises with this part below when working on a file name with a &
SET "STRING=!STRING:~1,-1!"
:getlengthwhile
if %DEBUG%=="t" echo Length !LENGTH!
if %DEBUG%=="t" echo String left: !STRING!
SET /a "LENGTH+=1"
REM Issue here too when working with file names with &'s
SET "STRING=%STRING:~1%"
if %DEBUG%=="t" echo Length now !LENGTH!
if %DEBUG%=="t" echo String now left: !STRING!
if %DEBUG%=="t" pause
if not ["%STRING%"]==[""] (
if %DEBUG%=="t" echo Continuing source length calculation
Goto :getlengthwhile
) else (
if %DEBUG%=="t" echo Length calculated)
ENDLOCAL & SET TEMPNUM=%LENGTH%
SET "%~1=%TEMPNUM%"
if %DEBUG%=="t" echo !%1!
if %DEBUG%=="t" pause
goto :eof
I know that there is escaping &'s to normally not have the error of the batch script trying to use the stuff right of the & as a command, but when reading in a file with one (or more) in its name how do I get it to work properly?
Here's an example of a file name that I'm having issue with and what happens when I'm running my script:
File "E:\Projects\.\Abilities&Events.docx"
Press any key to continue . . .
Begin backup part 2
"Abilities&Events.docx" parsed... %2 delayed...
'Events.docx""' is not recognized as an internal or external command, operable program or batch file.

Answer 1

As said, you should use more quotes and more delayed expansion.
Btw. Your code add the length to the variable in %1, perhaps this was intended, else you should change SET "LENGTH=!%1!" to set LENGTH=0
:getlength
SETLOCAL Enabledelayedexpansion
SET "LENGTH=!%1!"
SET "STRING=%~2"
:getlengthwhile
if defined STRING (
set /a LENGTH+=1
set "string=!string:~0,-1!"
goto :getlengthwhile
)
echo !LENGTH!
(
ENDLOCAL
SET "%~1=%LENGTH%"
)
goto :eof
Another problem of your code is this line
call :getlength FILELENGTH "!FILENAME!"
It fails with filenames containing ^, as they are doubled by the CALL.
So it's better to use
call :getlength FILELENGTH FILENAME
...
:getlength
SETLOCAL Enabledelayedexpansion
SET "LENGTH=!%1!"
SET "STRING=!%2!"
For much faster strlen functions you could look at SO: How do you get the string length in a batch file?

Answer 2

I found an answer to my problem. Thanks all for the help.
My solution was after finding out that I can replace parts of a variable (which I can use to delete parts of them even) from this site: http://ss64.com/nt/syntax-replace.html
I didn't know that replacing could be done (I knew that getting a part of a variable was possible (site for reference: http://ss64.com/nt/syntax-substring.html"))
I ended up ditching my getlength function (since it was no longer needed). and ended up with something like this:
:backup2
if %DEBUG%=="t" echo Begin backup part 2
for %%? in ("!FILEREADIN!") do (
SET "FILENAME=%%~n?%%~x?"
SET "BACKUPFQP=%%~f?"
SET "BACKUPLAST=%%~t?"
if %DEBUG%=="t" echo Filename before "!FILENAME!"
SET FILETESTPART=!FILEREADIN!
if %DEBUG%=="t" echo !FILETESTPART!
SET "FILETESTPART=!FILETESTPART:%SOURCE%=!"
if %DEBUG%=="t" echo Filename after "!FILETESTPART!"
SET "FILETESTPART=!FILETESTPART:~3!"
if %DEBUG%=="t" echo Filename after "!FILETESTPART!"