tbXLLerator - A twinBASIC XLL Framework

A framework for building Excel XLL add-ins using twinBASIC, a modern replacement for VBA/VB6 that supports native DLL exports. This framework provides a complete foundation for developing high-performance, thread-safe Excel-User-Defined-Functions (UDFs) without requiring C/C++.

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Overview

Excel XLL add-ins are native DLLs that integrate directly with Excel's calculation engine. They offer significant advantages over VBA and COM add-ins, including support for high-performance multithreaded calculation, and Excel's Function Wizard support. Traditionally, XLL development requires C or C++. This framework enables XLL development entirely in twinBASIC.

This framework wraps the very excellent ExcelSDK written by Jon Johnson. It handles argument binding, type coercion, memory management, and Excel callback mechanics, allowing UDF authors to focus on modeling logic.

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Why?

My goal in writing this wrapper was to be able to easily design and use high-performance UDF's for large and complex spreadsheet models in a language that I am familiar with - twinBASIC. More specifically, I'm using UDFs in spreadsheet models along with the SolverWrapper for model parameter optimization, which requires very fast worksheet execution.

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Key Features

• Native twinBASIC — no C/C++ required, no external build tools
• Thread-safe UDF support — dynamic allocation pattern with xlbitDLLFree and xlAutoFree12 enables concurrent recalculation across CPU cores
• Unified argument binding — BindU() and BindQ() dispatchers handle btNumber, btString, btBool, btDate, btArray, btSingleCellRef, btValue
• Array input and output — CoerceToArray and GetXLMulti12 handle full round-trip array processing
• Excel built-in delegation — pass arguments directly to xlfSum, xlfTranspose, xlfRound, etc.
• Structured memory management — a well-defined pattern with AllocXLOPER12Result and xlAutoFree12
• UDF registration class — High-level mechanism including ThreadSafe and Volatile properties and automatic type-text construction
• Comprehensive demo module — 30+ UDFs demonstrating every major pattern
• Complete Wiki Documentation — See the tBXLLerator Wiki for help on writing your first XLL UDF.

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Requirements

• Wayne Phillip's twinBASIC
• Microsoft Excel 2010 or greater (both 32-bit and 64-bit) in MS Windows
• Jon Johnson's ExcelSDK.twin

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Quick Example

This shows a typical UDF callback:

' Converts a number to its Roman Numeral representation - thread-safe
' In Excel: =TBXLL_RomanNumeral(9) --> "IX"
[DllExport]
Public Function TBXLL_RomanNumeral(pIn As XLOPER12) As LongPtr
    Dim num As Long
    Dim xTemp As XLOPER12
    ' Convert the input XLOPER12 to a number
    If BindU(pIn, btNumber, num, xTemp) Then
        ' Do the calculations and convert string to XLOPER12 for return to worksheet
        ' num_getroman does all the work (written by Jon Johnson)
        xTemp = GetXLString12(num_getroman(num))
    End If
    Return AllocResultToCaller(xTemp)
End Function

Here is the corresponding registration pattern:

Private udfs As New Collection

[DllExport]
Public Function xlAutoOpen() As Long
    ' Required, handles registration
    Dim udf As UDF
    Set udf = New UDF
    With udf
        .ProcName = "TBXLL_RomanNumeral"
        .Category = "tB XLL UDF Add-In"
        .FuncHelp = "Converts a number to its Roman Numeral representation"
        .Volatile = False
        .ThreadSafe = True '<-- supports fast multi-threaded calculation
        .AddArgument Name:="number", Help:="Number to convert"
        .Register
    End With
    udfs.Add udf
    ' ... repeat pattern above for each UDF
    xlAutoOpen = 1
End Function

[DllExport]
Public Function xlAutoClose() As Long
    Dim udf As UDF
    For Each udf In udfs
        udf.UnRegister
    Next udf
    xlAutoClose = 1
End Function

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Architecture

Modules

Module	Purpose
ExcelSDK	XLOPER12 struct, constants, enums, Excel12v declaration (written by Jon Johnson)
Helpers	Bind framework, coercion helpers, higher-level memory management
AutoCallbacks	xlAutoOpen, xlAutoClose, xlAutoAdd, xlAutoRemove, xlAutoFree12, xlAddInManagerInfo12
UDFReg	Convenience wrapper classes for UDF registration
Demos	Demo UDFs illustrating every supported pattern

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More Information?

See the comprehensive tbXLLerator Wiki for the details.

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License

This project is licensed under the MIT License.