cjacobi,

FASMDLL, perhaps?

// (C) 2013 White Hawk Software, Chris Jacobi
// Very rudimentary call of fasm from C#; needs to be embellished before real use.
// ...The native FASM dll goes into this applications bin/Debug directory.
// Permission to use or modify given to the FASM community.
   
using sys  = System;
using iops = System.Runtime.InteropServices;

namespace FasmTest
{
    class Program
    {
        
        //fasm_GetVersion()
        //...

        //fasm_Assemble(lpSource,lpMemory,cbMemorySize,nPassesLimit,hDisplayPipe)
        //Single threaded
        [iops.DllImport("FASM.dll")]
        public static extern int fasm_Assemble(
            string lpSource,
            byte[] lpMemory,
            uint   cbMemorySize,
            uint   nPassesLimit = 100,
            uint   hDisplayPipe = 0); //0 is only value which is supported here
            
        
        // Return values from fasm_Assemble
        public const int fasm_ok        = 0;
        public const int fasm_working   = 1;
        public const int fasm_error     = 2;
        public const int fasm_invalidParameter          = -1;
        public const int fasm_outOfMemory               = -2;
        public const int fasm_stackOverflow             = -3;
        public const int fasm_sourceNotFound            = -4;
        public const int fasm_unexpectedEndOfSource     = -5;
        public const int fasm_cannotGenerateCode            = -6;
        public const int fasm_formatLimitationsExceeded = -7;
        public const int fasm_writeFailed                       = -8;
  
        
        // errorcodes from fasm_Assemble
        // ...
        
        
        
        
        static byte[]  gMemory      = null;
        static uint    gStartAddr   = 0;
        
        const  int     memorySize   = 2000;
        static string  gInputString = "use32\n    push eax\n      retn\n";
        
        
        public static uint read4Bytes(ref byte[] buff, uint idx) {
            return ((uint)buff[idx]                +
                    (uint)buff[idx + 1] * 256      +
                    (uint)buff[idx + 2] * 0x10000  +
                    (uint)buff[idx + 3] * 0x1000000);   
        } //read4Bytes

        
        static void fasmTest() {
            if (gMemory == null ) {
                //Allocate memory
                gMemory = new byte[memorySize];
                //Pin memory
                iops.GCHandle handle = iops.GCHandle.Alloc(gMemory, iops.GCHandleType.Pinned);  //Won't be unpinned.
                //Compute real pointer
                int iAddr  = handle.AddrOfPinnedObject().ToInt32();
                gStartAddr = unchecked((uint) iAddr);
                sys.Console.WriteLine("Buffer start: 0x{0:x}", gStartAddr);
            }
            
            int returnVal = fasm_Assemble(
                lpSource: gInputString,
                lpMemory: gMemory,
                cbMemorySize: memorySize,
                nPassesLimit: 100,
                hDisplayPipe: 0);           
            uint cond   = read4Bytes(ref gMemory, 0);
            uint length = read4Bytes(ref gMemory, 4);
            uint ptr    = read4Bytes(ref gMemory, 8);
            uint index  = unchecked(ptr - gStartAddr);
            
            if (returnVal != 0) {
                sys.Console.WriteLine("Error from fasm_Assemble");
                return;
            }
            sys.Console.WriteLine("Returns:");
            sys.Console.WriteLine("   condition: {0}", cond);
            sys.Console.WriteLine("   ptr: 0x{0:x},   length: {1}", ptr, length);
            sys.Console.WriteLine("   index: {0}", index);
            if (index >= memorySize || index + length >= memorySize) {
                sys.Console.WriteLine("Result from fasm_Assemble looks wrong");
                return;
            }
            for (uint i = 0; i < length; i++) {
                sys.Console.Write("0x{0:x} ", gMemory[index + i]);
                if (i % 8 == 7 && i + 1 != length) {
                    sys.Console.WriteLine();
                }
            }
            sys.Console.WriteLine();
        } //fasmTest
        
        
        public static void Main(string[] args) {
            sys.Console.WriteLine("Calling fasm_Assemble as a DLL");            
            for (int i = 0; i < 100; i++) {
                fasmTest();
            }
            sys.Console.Write("Press any key to continue . . . ");
            sys.Console.ReadKey(true);
        } //Main
        
        
    } //class Program
} //namespace