How to determine newline while reading a file - autoit

Question

I have an AutoIt script that works, mostly. Reads a file, writes out what I want, but it does not preserve the original newline character. If I read a UNIX format file (LF only), it will write out a Windows format file (CR and LF).
Short of switching to something more robust, like Python, how do I solve this in AutoIt?
Opt("MustDeclareVars", 1) ;0 = no, 1 = require pre-declare
#include <File.au3>
#include <Array.au3>
Local $gInPath = $CmdLine[1]
Local $NumberOfLines = $CmdLine[2]
Local $gInDrive, $gInDir, $gInFName, $gInExt, $gOutPath
Local $gMsgBoxTitle = "Error in " & #ScriptName
Local $InLine
Local $LineCount
Local $oFileIn
Local $oFileOut
Local $FileStringAppend
If FileExists($gInPath) Then
Else
MsgBox(4096, $gMsgBoxTitle, "This file does not exist" & #CRLF & $gInPath)
Exit
EndIf
_PathSplit($gInPath, $gInDrive, $gInDir, $gInFName, $gInExt)
If $NumberOfLines >= 1000000 Then
$FileStringAppend = $NumberOfLines / 1000000 & "M"
ElseIf $NumberOfLines >= 1000 Then
$FileStringAppend = $NumberOfLines / 1000 & "K"
Else
$FileStringAppend = $NumberOfLines
EndIf
$gOutPath = _PathMake($gInDrive, $gInDir, $gInFName & "_" & $FileStringAppend, $gInExt)
If FileExists($gOutPath) Then
MsgBox(4096, $gMsgBoxTitle, "File already exists" & #CRLF & $gOutPath)
Exit
EndIf
$oFileIn = FileOpen($gInPath, 0)
$oFileOut = FileOpen($gOutPath, 1)
; Check if file opened for reading OK
If $oFileIn = -1 Then
MsgBox(4096, $gMsgBoxTitle, "Unable to open file for read" & #CRLF & $gInPath)
Exit
EndIf
; Check if file opened for writing OK
If $oFileOut = -1 Then
MsgBox(4096, $gMsgBoxTitle, "Unable to open file for write." & #CRLF & $gOutPath)
Exit
EndIf
; Read in lines of text until the EOF is reached
$LineCount = 0
While 1
$InLine = FileReadLine($oFileIn)
$LineCount += 1
If #error = -1 Then ExitLoop
If $LineCount > $NumberOfLines Then ExitLoop
FileWriteLine($oFileOut, $InLine & #CRLF)
WEnd
FileClose($oFileIn)
FileClose($oFileOut)

Answer 1

Looking at the function documentation at this link - https://www.autoitscript.com/autoit3/docs/functions/FileWriteLine.htm . It appears you can leave off the & #CRLF in your FileWriteLine command.
AutoIt should use the same line terminator that is read in, or
"If the line does NOT end in #CR or #LF then a DOS linefeed (#CRLF)
will be automatically added."

Answer 2

Here's the solution I came up. It works, but I'm not sure it's the cleanest.
Opt("MustDeclareVars", 1) ;0 = no, 1 = require pre-declare
#include <File.au3>
#include <Array.au3>
Local $gInPath = $CmdLine[1]
Local $NumberOfLines = $CmdLine[2]
Local $gInDrive, $gInDir, $gInFName, $gInExt, $gOutPath
Local $gMsgBoxTitle = "Error in " & #ScriptName
Local $InLine
Local $LineCount
Local $oFileIn
Local $oFileOut
Local $FileStringAppend
Local Const $CHAR_READ_BLOCK = 100
Local $CharsRead = 0
Local $CrFound = 0
Local $LfFound = 0
Local $Newline
Local $InBlock
If FileExists($gInPath) Then
Else
MsgBox(4096, $gMsgBoxTitle, "This file does not exist" & #CRLF & $gInPath)
Exit
EndIf
_PathSplit($gInPath, $gInDrive, $gInDir, $gInFName, $gInExt)
If $NumberOfLines >= 1000000 Then
$FileStringAppend = $NumberOfLines / 1000000 & "M"
ElseIf $NumberOfLines >= 1000 Then
$FileStringAppend = $NumberOfLines / 1000 & "K"
Else
$FileStringAppend = $NumberOfLines
EndIf
$gOutPath = _PathMake($gInDrive, $gInDir, $gInFName & "_" & $FileStringAppend, $gInExt)
If FileExists($gOutPath) Then
MsgBox(4096, $gMsgBoxTitle, "File already exists" & #CRLF & $gOutPath)
Exit
EndIf
$oFileIn = FileOpen($gInPath, 0)
$oFileOut = FileOpen($gOutPath, 1)
; Check if file opened for reading OK
If $oFileIn = -1 Then
MsgBox(4096, $gMsgBoxTitle, "Unable to open file for read" & #CRLF & $gInPath)
Exit
EndIf
; Check if file opened for writing OK
If $oFileOut = -1 Then
MsgBox(4096, $gMsgBoxTitle, "Unable to open file for write." & #CRLF & $gOutPath)
Exit
EndIf
While $CrFound = 0 And $LfFound = 0
$CharsRead += $CHAR_READ_BLOCK
$InBlock = FileRead($oFileIn, $CharsRead)
If StringRight($InBlock, 1) = #CR Then
$InBlock = $InBlock & FileRead($oFileIn, $CharsRead)
EndIf
$CrFound = StringInStr($InBlock, #CR)
$LfFound = StringInStr($InBlock, #LF)
If $CrFound > 0 And $LfFound > 0 Then
$Newline = #CRLF
ElseIf $CrFound > 0 Then
$Newline = #CR
Else
$Newline = #LF
EndIf
WEnd
; Read first line of text
$InLine = FileReadLine($oFileIn, 1)
$LineCount = 1
FileWriteLine($oFileOut, $InLine & $Newline)
; Read in lines of text until the EOF is reached
While 1
$InLine = FileReadLine($oFileIn)
$LineCount += 1
If #error = -1 Then ExitLoop
If $LineCount > $NumberOfLines Then ExitLoop
FileWriteLine($oFileOut, $InLine & $Newline)
WEnd
FileClose($oFileIn)
FileClose($oFileOut)