Attribute VB_Name = "TextFileUtils"
Option Explicit
Public Enum FileEncoding
    FileEncodingASCII
    FileEncodingUnicode
End Enum
' reads all text from a file. sets original file encoding into the encoding parameter
Public Function ReadTextFile(ByVal fileName As String, ByRef encoding As FileEncoding) As String
    Dim FileNo As Integer
    FileNo = FreeFile
    Open fileName For Binary Access Read As FileNo
    Dim prefix As String
    prefix = StrConv(InputB(2, FileNo), vbUnicode)
    If prefix = Chr(&HFF) + Chr(&HFE) Then
        encoding = FileEncodingUnicode
        ReadTextFile = InputB(LOF(FileNo) - 2, FileNo)
    Else
        encoding = FileEncodingASCII
        ReadTextFile = prefix & StrConv(InputB(LOF(FileNo) - 2, FileNo), vbUnicode)
    End If
    Close FileNo
End Function
' creates a text file with text as content encoded using the encoding parameter
Public Sub WriteTextFile(ByVal fileName As String, ByVal encoding As FileEncoding, ByVal text As String)
    Dim FileNo As Integer
    FileNo = FreeFile
    Select Case encoding
    Case FileEncodingASCII
        Open fileName For Output As FileNo
        Print #FileNo, text;
    Case FileEncodingUnicode
        ' truncate file
        Open fileName For Output As FileNo
        Close FileNo
        
        Open fileName For Binary Access Write As FileNo
        Dim signature(1 To 2) As Byte
        signature(1) = &HFF
        signature(2) = &HFE
        Put FileNo, , signature
        Dim content() As Byte
        content = text
        Put FileNo, , content
    End Select
    Close FileNo
End Sub
Sub test()
    Call WriteTextFile("c:\test1.txt", FileEncodingASCII, "test 1" & vbCrLf & "test 2")
    
    Dim f As FileEncoding
    Dim s As String
    s = ReadTextFile("c:\test1.txt", f)
    
    Call WriteTextFile("c:\test2.txt", FileEncodingUnicode, s)
    
    Debug.Assert ReadTextFile("c:\test2.txt", f) = s
End Sub