B4J Code Snippet [B4x] File records with fixed positions & lenghts

I had some projects where I needed fixed locations & lengths inside a record e.g. a field has a fixed length of 30 "chars". It's a pain to write such a file. Here's a snippet to make it easier:

FileRecord defines the varname, the length and the alignment (left or right). "Michael" is 7 chars long. So 23 spaces are added (30-7=23).

VarMap could be an array, too (just change it) and contains the var name (to be matched with FileRecord) and the data.

Nice side effect: You can sort the output/sequence of the data by just changing the order in FileRecord or adding new fields.

'Varname, fixed length, alignement
    Dim FileRecord() As String = Array As String("var1","4","L","var2","9","L","var3","1","L","var4","30","R","var5","30","L")
    
    'Input as a map (can be anything else, too)
    Dim VarMap As Map=CreateMap("var1":"123","var2":"abcdef","var3":"h","var4":"Michael","var5":"Miller")
    
    Dim RecordLength,VarLength,StartVarPos,EndVarPos As Int
    Dim Alignment,VarName,VarContent As String
    Dim Record As String
    For i=0 To FileRecord.Length-3 Step 3
        VarName=FileRecord(i)
        VarLength=FileRecord(i+1)
        Alignment=FileRecord(i+2)
        EndVarPos=StartVarPos+VarLength-1
        RecordLength=RecordLength+VarLength
        Log("Var: " & FileRecord(i) &", Length: " & VarLength &", Start: " & StartVarPos & ", End: " & EndVarPos &", Alignement: " & Alignment)
        VarContent=VarMap.Get(VarName)
        For l= 0 To VarLength-VarContent.length-1
            If Alignment="L" Then
               VarContent=VarContent & " " 'add spaces behind (align left)
            Else
                VarContent=" " & VarContent 'add spaces before (align right)
            End If
        Next
        Record=Record&VarContent
        StartVarPos=EndVarPos+1
    Next
    Log("Total recordlength: " & RecordLength)
    Log("Record: " & Record)

 

[udg]

Hi,
I may be wrong but this kind of assignment in a loop sounds inefficient:

VarContent=VarContent & " "

I prefer to define a costant string whose length is the max length I have to "align", then using a substring of the proper length on it in order to have a single assignment.
Something like:

VarContent=VarContent & MyCostant.Substring2(0,VarLength-VarContent.length-1)

where MyConstant is a string of up to 30 (or so) spaces (or any other filling char, an asterisk for example).