{       SMIX is Copyright 1995 by Ethan Brodsky.  All rights reserved.       }

unit SMix; {Version 1.27}
 {$X+} {$G+} {$R-}
  interface
    const
      BlockLength   = 512;      {Size of digitized sound block               }
      LoadChunkSize = 2048;     {Chunk size used for loading sounds from disk}
      Voices        = 8;        {Number of available voices                  }
      SamplingRate  = 22025;    {Sampling rate for output                    }
    var
      test8086:byte;
    type
      PSound = ^TSound;
      TSound =
        record
          XMSHandle: word;
          StartOfs:  LongInt;
          SoundSize: LongInt;
        end;
    function InitSB(BaseIO: word; IRQ: byte; DMA, DMA16: byte): boolean;
      {Initializes control parameters, resets DSP, and installs int. handler }
      { Parameters: (Can be found using GetSettings procedure in Detect)     }
      {  BaseIO:   Sound card base IO address                                }
      {  IRQ:      Sound card IRQ setting                                    }
      {  DMA:      Sound card 8-bit DMA channel                              }
      {  DMA16:    Sound card 16-bit DMA channel (0 if not supported)        }
      { Returns:                                                             }
      {  TRUE:     Sound card successfully initialized (Maybe)               }
      {  FALSE:    Sound card could not be initialized                       }
    procedure ShutdownSB5;
      {Removes interrupt handler and resets DSP                              }

    procedure InitMixing;
      {Allocates internal buffers and starts digitized sound output          }
    procedure ShutdownMixing;
      {Deallocates internal buffers and stops digitized sound output         }

    function  InitXMS: boolean;
      {Attempts to intialize extended memory                                 }
      { Returns:                                                             }
      {  TRUE:     Extended memory successfully initialized                  }
      {  FALSE:    Extended memory could not be initialized                  }
    function  GetFreeXMS: word;
      {Returns amount of free XMS memory (In kilobytes)                      }

    procedure InitSharing;
      {Allocates an EMB that all sounds are stored in.  This preserves EMB   }
      {handles, which are a scarce resource.  Call this on initialization and}
      {all sounds will automatically be stored in one EMB.  Call LoadSound as}
      {usual to allocate a sound, but FreeSound only deallocates the sound   }
      {data structure.  Call ShutdownSharing before program termination to   }
      {free allocated extended memory.                                       }
    procedure ShutdownSharing;
      {Shuts down EMB sharing and frees all allocated extended memory        }

    procedure OpenSoundResourceFile(FileName: string);
      {Call this to open a resource file for loading sounds.  After this has }
      {been called, the Key parameter in the LoadSound function is used as a }
      {resource key to locate the sound data in this file.                   }
      { Parameters:                                                          }
      {  FileName: File name of resource file                                }
    procedure CloseSoundResourceFile;
      {Close sound resource file.  If you have called this, the Key parameter}
      {will act as a filename instead of a resource key.                     }

    procedure LoadSound(var Sound: PSound; Key: string);
      {Allocates an extended memory block and loads a sound from a file      }
      { Parameters:                                                          }
      {  Sound:    Unallocated pointer to sound data structure               }
      {  Key:      If a resource file has been opened then key is a resource }
      {            identifier.  Use the same ID as you used for SNDLIB.      }
      {            If a resource file has not been opened, then key is the   }
      {            filename to load the sound data from.                     }
    procedure FreeSound(var Sound: PSound);
      {Deallocates extended memory and destroys sound data structure         }
      { Parameters:                                                          }
      {  Sound:    Unallocated pointer to sound data structure               }

    procedure StartSound(Sound: PSound; Index: byte; Loop: boolean);
      {Starts playing a sound                                                }
      { Parameters:                                                          }
      {  Sound:    Pointer to sound data structure                           }
      {  Index:    A number to keep track of the sound with (Used to stop it)}
      {  Loop:     Indicates whether the sound should be continuously looped }
    procedure StopSound(Index: byte);
      {Stops playing sound                                                   }
      { Parameters:                                                          }
      {  Index:    Index of sound to stop (All with given index are stopped) }
    function SoundPlaying(Index: byte): boolean;
      {Checks if a sound is still playing                                    }
      { Parameters:                                                          }
      {  Index:    Index used when the sound was started                     }
      { Returns:                                                             }
      {  TRUE      At least oen sound with the specified index is playing    }
      {  FALSE     No sounds with the specified index are playing            }

    var
      IntCount   : LongInt;  {Number of sound interrupts that have occured   }
      DSPVersion : real;     {Contains the version of the installed DSP chip }
      AutoInit   : boolean;  {Tells Auto-initialized DMA transfers are in use}
      SixteenBit : boolean;  {Tells whether 16-bit sound output is occuring  }
      VoiceCount : byte;     {Number of voices currently in use              }

  implementation
    uses
      CRT,
      DOS,
      XMS;
    const
      BufferLength = BlockLength * 2;
    var
      ResetPort        : word;
      ReadPort         : word;
      WritePort        : word;
      PollPort         : word;
      AckPort          : word;

      PICRotatePort    : word;
      PICMaskPort      : word;

      DMAMaskPort      : word;
      DMAClrPtrPort    : word;
      DMAModePort      : word;
      DMABaseAddrPort  : word;
      DMACountPort     : word;
      DMAPagePort      : word;

      IRQStartMask     : byte;
      IRQStopMask      : byte;
      IRQIntVector     : byte;

      DMAStartMask     : byte;
      DMAStopMask      : byte;
      DMAMode          : byte;
      DMALength        : word;

      OldIntVector     : pointer;
      OldExitProc      : pointer;

      HandlerInstalled : boolean;

    procedure WriteDSP(Value: byte);
      begin
        repeat until (Port[WritePort] and $80) = 0;
        Port[WritePort] := Value;
      end;

    function ReadDSP: byte;
      begin
        repeat until (Port[PollPort] and $80) <> 0;
        ReadDSP := Port[ReadPort];
      end;

    function ResetDSP: boolean;
      var
        i: byte;
      begin
        Port[ResetPort] := 1;
        Delay(1);                              {One millisecond}
        Port[ResetPort] := 0;
        i := 100;
        while (ReadDSP <> $AA) and (i > 0) do Dec(i);
        if i > 0
          then ResetDSP := true
          else ResetDSP := false;
      end;

    procedure InstallHandler; forward;
    procedure UninstallHandler; forward;

    procedure MixExitProc; far; forward;

    function InitSB(BaseIO: word; IRQ: byte; DMA, DMA16: byte): boolean;
      begin
       {Sound card IO ports}
        ResetPort  := BaseIO + $6;
        ReadPort   := BaseIO + $A;
        WritePort  := BaseIO + $C;
        PollPort   := BaseIO + $E;

       {Reset DSP, get version, and pick output mode}
        if not(ResetDSP)
          then
            begin
              InitSB := false;
              Exit;
            end;
        WriteDSP($E1);  {Get DSP version number}
        DSPVersion := ReadDSP;  DSPVersion := DSPVersion + ReadDSP/100;
        AutoInit := DSPVersion > 2.0;
        SixteenBit := (DSPVersion > 4.0) and (DMA16 <> $FF) and (DMA16 > 3);

       {Compute interrupt ports and parameters}
        if IRQ <= 7
          then
            begin
              IRQIntVector  := $08+IRQ;
              PICMaskPort   := $21;
            end
          else
            begin
              IRQIntVector  := $70+IRQ-8;
              PICMaskPort   := $A1;
            end;
        IRQStopMask  := 1 shl (IRQ mod 8);
        IRQStartMask := not(IRQStopMask);

       {Compute DMA ports and parameters}
        if SixteenBit
          then {Sixteen bit}
            begin
              DMAMaskPort     := $D4;
              DMAClrPtrPort   := $D8;
              DMAModePort     := $D6;
              DMABaseAddrPort := $C0 + 4*(DMA16-4);
              DMACountPort    := $C2 + 4*(DMA16-4);
              case DMA16
                of
                  5:  DMAPagePort := $8B;
                  6:  DMAPagePort := $89;
                  7:  DMAPagePort := $8A;
                end;
              DMAStopMask  := DMA16-4 + $04;   {000001xx}
              DMAStartMask := DMA16-4 + $00;   {000000xx}
              DMAMode      := DMA16-4 + $58;   {010110xx}
              AckPort := BaseIO + $F;
            end
          else {Eight bit}
            begin
              DMAMaskPort     := $0A;
              DMAClrPtrPort   := $0C;
              DMAModePort     := $0B;
              DMABaseAddrPort := $00 + 2*DMA;
              DMACountPort    := $01 + 2*DMA;
              case DMA
                of
                  0:  DMAPagePort := $87;
                  1:  DMAPagePort := $83;
                  2:  DMAPagePort := $81;
                  3:  DMAPagePort := $82;
                end;
              DMAStopMask  := DMA + $04;       {000001xx}
              DMAStartMask := DMA + $00;       {000000xx}
              if AutoInit
                then DMAMode := DMA + $58      {010110xx}
                else DMAMode := DMA + $48;     {010010xx}
              AckPort := BaseIO + $E;
            end;
          if AutoInit
            then DMALength := BufferLength
            else DMALength := BlockLength;
          InstallHandler;

          OldExitProc := ExitProc;
          ExitProc    := @MixExitProc;
          InitSB := true;
      end;

    procedure ShutdownSB5;
      begin
        if HandlerInstalled
          then UninstallHandler;
        ResetDSP;
      end;

    function InitXMS: boolean;
      begin
        InitXMS := true;
        if not(XMSInstalled)
          then InitXMS := false
          else XMSInit;
      end;
    function GetFreeXMS: word;
      begin
        GetFreeXMS := XMSGetFreeMem;
      end;

   {Voice control}
    type
      PVoice = ^TVoice;
      TVoice =
        record
          Sound:     PSound;
          Index:     byte;
          CurPos:    LongInt;
          Loop:      boolean;
        end;
    var
      VoiceInUse: array[0..Voices-1] of boolean;
      Voice:      array[0..Voices-1] of TVoice;
      CurBlock:   byte;
   {Sound buffer}
    var
      SoundBlock: array[1..BlockLength+1] of ShortInt;
        {The length of XMS copies under HIMEM.SYS must be a mutiple  }
        {of two.  If the sound data ends in mid-block, it may not be }
        {possible to round up without corrupting memory.  Therefore, }
        {the copy buffer has been extended by one byte to eliminate  }
        {this problem.                                               }

   {Mixing buffers}
    type
      PMixingBlock = ^TMixingBlock;
      TMixingBlock = array[1..BlockLength] of integer;
    var
      MixingBlock  : TMixingBlock;

   {Output buffers}
    type {8-bit}
      POut8Block   = ^TOut8Block;
      TOut8Block   = array[1..BlockLength] of byte;
      POut8Buffer  = ^TOut8Buffer;
      TOut8Buffer  = array[1..2] of TOut8Block;
    type {16-bit}
      POut16Block  = ^TOut16Block;
      TOut16Block  = array[1..BlockLength] of integer;
      POut16Buffer = ^TOut16Buffer;
      TOut16Buffer = array[1..2] of TOut16Block;
    var
      OutMemArea  : pointer;
      Out8Buffer  : POut8Buffer;
      Out16Buffer : POut16Buffer;
    var
      BlockPtr    : array[1..2] of pointer;
      CurBlockPtr : pointer;
    var
     {For auto-initialized transfers (Whole buffer)}
      BufferAddr : LongInt;
      BufferPage : byte;
      BufferOfs  : word;
     {For single-cycle transfers (One block at a time)}
      BlockAddr  : array[1..2] of LongInt;
      BlockPage  : array[1..2] of byte;
      BlockOfs   : array[1..2] of word;

   {Clipping for 8-bit output}
    var
       Clip8 : array[-128*Voices..128*Voices] of byte;

    function TimeConstant(Rate: word): byte;
      begin
        TimeConstant := 256 - (1000000 div Rate);
      end;

    procedure StartDAC;
      begin
        Port[DMAMaskPort]     := DMAStopMask;
        Port[DMAClrPtrPort]   := $00;
        Port[DMAModePort]     := DMAMode;
        Port[DMABaseAddrPort] := Lo(BufferOfs);
        Port[DMABaseAddrPort] := Hi(BufferOfs);
        Port[DMACountPort]    := Lo(DMALength-1);
        Port[DMACountPort]    := Hi(DMALength-1);
        Port[DMAPagePort]     := BufferPage;
        Port[DMAMaskPort]     := DMAStartMask;

        if SixteenBit
          then {Sixteen bit: SB16 and up (DSP 4.xx)}
            begin
              WriteDSP($41);        {Set digitized sound output sampling rate}
              WriteDSP(Hi(SamplingRate));
              WriteDSP(Lo(SamplingRate));
              WriteDSP($B6);        {16-bit DMA command: D/A, Auto-Init, FIFO}
              WriteDSP($10);        {16-bit DMA mode:    Signed Mono         }
              WriteDSP(Lo(BlockLength - 1));
              WriteDSP(Hi(BlockLength - 1));
            end
          else {Eight bit}
            begin
              WriteDSP($D1);        {Turn on speaker                         }
              WriteDSP($40);        {Set digitized sound time constant       }
              WriteDSP(TimeConstant(SamplingRate));
              if AutoInit
                then {Eight bit auto-initialized: SBPro and up (DSP 2.00+)}
                  begin
                    WriteDSP($48);  {Set DSP block transfer size             }
                    WriteDSP(Lo(BlockLength - 1));
                    WriteDSP(Hi(BlockLength - 1));
                    WriteDSP($1C);  {8-bit auto-init DMA mono sound output   }
                  end
                else {Eight bit single-cycle: Sound Blaster (DSP 1.xx+)}
                  begin
                    WriteDSP($14);  {8-bit single-cycle DMA sound output     }
                    WriteDSP(Lo(BlockLength - 1));
                    WriteDSP(Hi(BlockLength - 1));
                  end;
            end;
      end;

    procedure StopDAC;
      begin
        if SixteenBit
          then {Sixteen bit}
            begin
              WriteDSP($D5);        {Pause 16-bit DMA sound I/O              }
            end
          else {Eight bit}
            begin
              WriteDSP($D0);        {Pause 8-bit DMA mode sound I/O          }
              WriteDSP($D3);        {Turn off speaker                        }
            end;
        Port[DMAMaskPort] := DMAStopMask;
      end;

   {Setup for storing all sounds in one extended memory block (Saves handles)}
    var
      SharedEMB    : boolean;
      SharedHandle : word;
      SharedSize   : LongInt;
    procedure InitSharing;
      begin
        SharedEMB  := true;
        SharedSize := 0;
        XMSAllocate(SharedHandle, SharedSize);
      end;
    procedure ShutdownSharing;
      begin
        if SharedEMB then XMSFree(SharedHandle);
        SharedEMB := false;
      end;

   {Setup for sound resource files}
    var
      ResourceFile     : boolean;
      ResourceFilename : string;

    procedure OpenSoundResourceFile(FileName: string);
      begin
        ResourceFile     := true;
        ResourceFilename := FileName;
      end;

    procedure CloseSoundResourceFile;
      begin
        ResourceFile     := false;
        ResourceFilename := '';
      end;

    type
      TKey = array[1..8] of char;

    var
      SoundFile : file;
      SoundSize : LongInt;

    function MatchingKeys(a, b: TKey): boolean;
      var
        i: integer;
      begin
        MatchingKeys := true;

        for i := 1 to 8 do
          if a <> b
            then
              MatchingKeys := false;
      end;

    procedure GetSoundFile(Key: string);
      type
        Resource =
          record
            Key:   TKey;
            Start: LongInt;
            Size:  LongInt;
          end;
      var
        NumSounds: integer;
        ResKey:    TKey;
        ResHeader: Resource;
        Index:     integer;
        i:         integer;
        Found:     boolean;
      begin
        if ResourceFile
          then
            begin
              for i := 1 to 8 do
                if i <= Length(Key)
                  then ResKey[i] := Key[i]
                  else ResKey[i] := #0;

              Assign(SoundFile, ResourceFilename);  Reset(SoundFile, 1);
              BlockRead(SoundFile, NumSounds, SizeOf(NumSounds));

              Found := false;
              Index := 0;

              while not(Found) and (Index < NumSounds) do
                begin
                  Index := Index + 1;
                  BlockRead(SoundFile, ResHeader, SizeOf(ResHeader));

                  if MatchingKeys(ResHeader.Key, ResKey)
                    then
                      Found := true;
                end;

              if Found
                then
                  begin
                    Seek(SoundFile, ResHeader.Start);
                    SoundSize := ResHeader.Size;
                  end
                else
                  Halt(255);
            end
          else
            begin
              Assign(SoundFile, Key);  Reset(SoundFile, 1);
              SoundSize := FileSize(SoundFile);
            end;
      end;

    function Min(a, b: LongInt): LongInt;
      begin
        if a < b
          then Min := a
          else Min := b;
      end;

   {Loading and freeing sounds}
    var
      MoveParams: TMoveParams; {The XMS driver doesn't like this on the stack}
    procedure LoadSound(var Sound: PSound; Key: string);
      var
        Size: LongInt;
        InBuffer: array[1..LoadChunkSize] of byte;
        Remaining: LongInt;
      begin
        GetSoundFile(Key);

        New(Sound);
        Sound^.SoundSize := SoundSize;

        if not(SharedEMB)
          then
            begin
              Sound^.StartOfs := 0;
              XMSAllocate(Sound^.XMSHandle, (SoundSize + 1023) div 1024);
            end
          else
            begin
              Sound^.StartOfs := SharedSize;
              Sound^.XMSHandle := SharedHandle;
              SharedSize := SharedSize + SoundSize;
              XMSReallocate(SharedHandle, (SharedSize + 1023) div 1024);
            end;
        MoveParams.SourceHandle := 0;
        MoveParams.SourceOffset := LongInt(Addr(InBuffer));
        MoveParams.DestHandle   := Sound^.XMSHandle;
        MoveParams.DestOffset   := Sound^.StartOfs;

        Remaining := Sound^.SoundSize;

        repeat
          MoveParams.Length := Min(Remaining, LoadChunkSize);
          BlockRead(SoundFile, InBuffer, MoveParams.Length);
          MoveParams.Length := ((MoveParams.Length+1) div 2) * 2;
            {XMS copy lengths must be a multiple of two}
          XMSMove(@MoveParams);
          Inc(MoveParams.DestOffset, MoveParams.Length);
          Dec(Remaining, MoveParams.Length);
        until not(Remaining > 0);

        Close(SoundFile);
      end;

    procedure FreeSound(var Sound: PSound);
      begin
        if not(SharedEMB) then XMSFree(Sound^.XMSHandle);
        Dispose(Sound); Sound := nil;
      end;

   {Voice maintainance}
    procedure DeallocateVoice(VoiceNum: byte);
      begin
        VoiceInUse[VoiceNum] := false;
        with Voice[VoiceNum] do
          begin
            Sound    := nil;
            Index    := 0;
            CurPos   := 0;
            Loop     := false;
          end;
      end;

    procedure StartSound(Sound: PSound; Index: byte; Loop: boolean);
      var
        i, Slot: byte;
      begin
        Slot := $FF; i := 0;
        repeat
          if not(VoiceInUse[i])
            then Slot := i;
          Inc(i);
        until ((Slot <> $FF) or (i=Voices));
        if Slot <> $FF
          then
            begin
              Inc(VoiceCount);
              Voice[Slot].Sound    := Sound;
              Voice[Slot].Index    := Index;
              Voice[Slot].CurPos   := 0;
              Voice[Slot].Loop     := Loop;

              VoiceInUse[Slot] := true;
            end;
      end;

    procedure StopSound(Index: byte);
      var
        i: byte;
      begin
        for i := 0 to Voices-1 do
          if Voice[i].Index = Index
            then
              begin
                DeallocateVoice(i);
                Dec(VoiceCount);
              end;
      end;

    function SoundPlaying(Index: byte): boolean;
      var
        i: byte;
      begin
        SoundPlaying := False;

        for i := 0 to Voices-1 do
          if Voice[i].Index = Index
            then SoundPlaying := True;
      end;

    procedure UpdateVoices;
      var
        VoiceNum: byte;
      begin
        for VoiceNum := 0 to Voices-1 do
          begin
            if VoiceInUse[VoiceNum]
              then
                if Voice[VoiceNum].CurPos >= Voice[VoiceNum].Sound^.SoundSize
                  then
                    begin
                      DeallocateVoice(VoiceNum);
                      Dec(VoiceCount);
                    end;
          end;
      end;


   {Utility functions}
    procedure SetCurBlock(BlockNum: byte);
      begin
        CurBlock := BlockNum;
        CurBlockPtr := pointer(BlockPtr[BlockNum]);
      end;

    procedure ToggleBlock;
      begin
        if CurBlock = 1
          then SetCurBlock(2)
          else SetCurBlock(1);
      end;

    procedure SilenceBlock;
      begin
        FillChar(MixingBlock, BlockLength*2, 0);  {FillChar uses REP STOSW}
      end;

    function GetLinearAddr(Ptr: pointer): LongInt;
      begin
        GetLinearAddr := LongInt(Seg(Ptr^))*16 + LongInt(Ofs(Ptr^));
      end;

    function NormalizePtr(p: pointer): pointer;
      var
        LinearAddr: LongInt;
      begin
        LinearAddr := GetLinearAddr(p);
        NormalizePtr := Ptr(LinearAddr div 16, LinearAddr mod 16);
      end;


    procedure InitClip8;
      var
        i, Value: integer;
      begin
        for i := -128*Voices to 128*Voices do
          begin
            Value := i;
            if (Value < -128) then Value := -128;
            if (Value > +127) then Value := +127;

            Clip8[i] := Value + 128;
          end;
      end;

    procedure InitMixing;
      var
        i: integer;
      begin
        for i := 0 to Voices-1 do DeallocateVoice(i);
        VoiceCount := 0;

        if SixteenBit
          then
            begin
             {Find a block of memory that does not cross a page boundary}
              GetMem(OutMemArea, 4*BufferLength);
              if ((GetLinearAddr(OutMemArea) div 2) mod 65536)+BufferLength < 65536
                then Out16Buffer := OutMemArea
                else Out16Buffer := NormalizePtr(Ptr(Seg(OutMemArea^), Ofs(OutMemArea^)+2*BufferLength));
              for i := 1 to 2 do
                BlockPtr[i] := NormalizePtr(Addr(Out16Buffer^[i]));
             {DMA parameters}
              BufferAddr := GetLinearAddr(pointer(Out16Buffer));
              BufferPage := BufferAddr div 65536;
              BufferOfs  := (BufferAddr div 2) mod 65536;
              for i := 1 to 2 do
                BlockAddr[i] := GetLinearAddr(pointer(BlockPtr[i]));
              for i := 1 to 2 do
                BlockPage[i] := BlockAddr[i] div 65536;
              for i := 1 to 2 do
                BlockOfs[i]  := (BlockAddr[i] div 2) mod 65536;
              FillChar(Out16Buffer^, BufferLength*2, $00);   {Signed   16-bit}
            end
          else
            begin
             {Find a block of memory that does not cross a page boundary}
              GetMem(OutMemArea, 2*BufferLength);
              if (GetLinearAddr(OutMemArea) mod 65536)+BufferLength < 65536
                then Out8Buffer := OutMemArea
                else Out8Buffer := NormalizePtr(Ptr(Seg(OutMemArea^), Ofs(OutMemArea^)+BufferLength));
              for i := 1 to 2 do
                BlockPtr[i] := NormalizePtr(Addr(Out8Buffer^[i]));
             {DMA parameters}
              BufferAddr := GetLinearAddr(pointer(Out8Buffer));
              BufferPage := BufferAddr div 65536;
              BufferOfs  := BufferAddr mod 65536;
              for i := 1 to 2 do
                BlockAddr[i] := GetLinearAddr(pointer(BlockPtr[i]));
              for i := 1 to 2 do
                BlockPage[i] := BlockAddr[i] div 65536;
              for i := 1 to 2 do
                BlockOfs[i]  := BlockAddr[i] mod 65536;
              FillChar(Out8Buffer^, BufferLength, $80);      {Unsigned  8-bit}

              InitClip8;
            end;

        FillChar(MixingBlock, BlockLength*2, $00);

        SetCurBlock(1);
        IntCount := 0;
        StartDAC;
      end;

    procedure ShutdownMixing;
      begin
        StopDAC;

        if SixteenBit
          then FreeMem(OutMemArea, 4*BufferLength)
          else FreeMem(OutMemArea, 2*BufferLength);
      end;



    var {The XMS driver doesn't like parameter blocks in the stack}
      IntMoveParams: TMoveParams;  {In case LoadSound is interrupted}
    procedure CopySound(Sound: PSound; var CurPos: LongInt; CopyLength: word; Loop: boolean);
      var
        SoundSize: LongInt;
        DestPtr: pointer;
      begin
        SoundSize := Sound^.SoundSize;
        DestPtr := pointer(@SoundBlock);
        IntMoveParams.SourceHandle := Sound^.XMSHandle;
        IntMoveParams.DestHandle   := 0;
        while CopyLength > 0 do
          begin
           {Compute max transfer size}
            if CopyLength < SoundSize-CurPos
              then IntMoveParams.Length := CopyLength
              else IntMoveParams.Length := SoundSize-CurPos;

           {Compute starting dest. offset and update offset for next block}
            IntMoveParams.SourceOffset := Sound^.StartOfs + CurPos;
            CurPos := CurPos + IntMoveParams.Length;
            if Loop then CurPos := CurPos mod SoundSize;

           {Compute starting source offset and update offset for next block}
            IntMoveParams.DestOffset := LongInt(DestPtr);
            DestPtr := NormalizePtr(Ptr(Seg(DestPtr^), Ofs(DestPtr^)+IntMoveParams.Length));

           {Update remaining count for next iteration}
            CopyLength := CopyLength - IntMoveParams.Length;

           {Move block}
            IntMoveParams.Length := ((IntMoveParams.Length+1) div 2) * 2;
              {XMS copy lengths must be a multiple of two}
            XMSMove(@IntMoveParams);  {Luckily, the XMS driver is re-entrant}
          end;
      end;

    procedure MixVoice(VoiceNum: byte);
      var
        MixLength: word;
      begin
        with Voice[VoiceNum] do
          if Loop
            then
              MixLength := BlockLength
            else
              if BlockLength < Sound^.SoundSize-CurPos
                then MixLength := BlockLength
                else MixLength := Sound^.SoundSize-CurPos;
        CopySound(Voice[VoiceNum].Sound, Voice[VoiceNum].CurPos, MixLength, Voice[VoiceNum].Loop);
        asm
          lea  si, SoundBlock         {DS:SI -> Sound data (Source)          }
          mov  ax, ds                 {ES:DI -> Mixing block (Destination)   }
          mov  es, ax
          lea  di, MixingBlock
          mov  cx, MixLength          {CX = Number of samples to copy        }

         @MixSample:
          mov  al, [si]               {Load a sample from the sound block    }
          inc  si                     { increment pointer                    }
          cbw                         {Convert it to a 16-bit signed sample  }
          add  es:[di], ax            {Add it into the mixing buffer         }
          add  di, 2                  {Next word in mixing buffer            }
          dec  cx                     {Loop for next sample                  }
          jnz  @MixSample
        end;
      end;

    procedure MixVoices;
      var
        i: word;
      begin
        SilenceBlock;
        for i := 0 to Voices-1 do
          if VoiceInUse[i]
            then
              MixVoice(i);
      end;

    procedure CopyData16; assembler;
      asm
        lea   si, MixingBlock         {DS:SI -> 16-bit input block           }
        les   di, [CurBlockPtr]       {ES:DI -> 16-bit output block          }
        mov   cx, BlockLength         {CX = Number of samples to copy        }

       @CopySample:
        mov   ax, [si]                {Load a sample from the mixing block   }
        add   di, 2                   {Increment destination pointer         }
        sal   ax, 5                   {Shift sample left to fill 16-bit range}
        add   si, 2                   {Increment source pointer              }
        mov   es:[di-2], ax           {Store sample in output block          }
        dec   cx                      {Process the next sample               }
        jnz   @CopySample
      end;

    procedure CopyData8; assembler;
      asm
        push  bp
        mov   dx, ss                  {Preserve SS in DX                     }
        pushf
        cli                           {Disable interrupts                    }
        mov   ax, ds                  {Using SS for data                     }
        mov   ss, ax

        lea   si, Clip8               {DS:SI -> 8-bit clipping buffer        }
        add   si, 128*Voices          {DS:SI -> Center of clipping buffer    }

        lea   bp, MixingBlock         {SS:BP -> 16-bit input block           }
        les   di, [CurBlockPtr]       {ES:DI -> 8-bit output block           }
        mov   cx, BlockLength         {CX = Number of samples to copy        }

       @CopySample:
        mov   bx, [bp]                {BX = Sample from mixing block         }
        inc   di                      {Increment destination pointer (DI)    }
        add   bp, 2                   {Increment source pointer (BP)         }
        mov   al, [si+bx]             {AL = Clipped sample                   }
        mov   es:[di-1], al           {Store sample in output block          }
        dec   cx                      {Process the next sample               }
        jnz   @CopySample

        mov   ss, dx                  {Restore SS                            }
        popf                          {Restore flags                         }
        pop   bp
      end;

    procedure CopyData;
      begin
        if SixteenBit
          then CopyData16
          else CopyData8;
      end;

    procedure StartBlock_SC; {Starts a single-cycle DMA transfer}
      begin
        Port[DMAMaskPort]     := DMAStopMask;
        Port[DMAClrPtrPort]   := $00;
        Port[DMAModePort]     := DMAMode;
        Port[DMABaseAddrPort] := Lo(BlockOfs[CurBlock]);
        Port[DMABaseAddrPort] := Hi(BlockOfs[CurBlock]);
        Port[DMACountPort]    := Lo(DMALength-1);
        Port[DMACountPort]    := Hi(DMALength-1);
        Port[DMAPagePort]     := BlockPage[CurBlock];
        Port[DMAMaskPort]     := DMAStartMask;
        WriteDSP($14);                {8-bit single-cycle DMA sound output   }
        WriteDSP(Lo(BlockLength - 1));
        WriteDSP(Hi(BlockLength - 1));
      end;

    var Save_Test8086: byte; {CPU type flag}

    procedure IntHandler; interrupt;
      var
        Temp: byte;
      begin
       {On a 386 or higher, Turbo Pascal uses 32-bit registers for LongInt   }
       {math.  Unfortunately, it doesn't preserve these registers when       }
       {generating code to handle interrupts, so they are occasionally       }
       {corrupted.  This can cause a problem with LongInt math in your       }
       {program or in TSRs. The below code disables 32-bit instructions for  }
       {the interrupt to prevent 32-bit register corruption.                 }
        Save_Test8086 := Test8086;
        Test8086 := 0;

        Inc(IntCount);

        if not(AutoInit) {Start next block first if not using auto-init DMA}
          then
            begin
              StartBlock_SC;
              CopyData;
              ToggleBlock;
            end;

        UpdateVoices;
        MixVoices;

        if (AutoInit)
          then
            begin
              CopyData;
              ToggleBlock;
            end;

        Test8086 := Save_Test8086;

        Temp := Port[AckPort];
        Port[$A0] := $20;
        Port[$20] := $20;
      end;

    procedure EnableInterrupts;  InLine($FB); {STI}
    procedure DisableInterrupts; InLine($FA); {CLI}

    procedure InstallHandler;
      begin
        DisableInterrupts;
        Port[PICMaskPort] := Port[PICMaskPort] or IRQStopMask;
        GetIntVec(IRQIntVector, OldIntVector);
        SetIntVec(IRQIntVector, @IntHandler);
        Port[PICMaskPort] := Port[PICMaskPort] and IRQStartMask;
        EnableInterrupts;
        HandlerInstalled := true;
      end;

    procedure UninstallHandler;
      begin
        DisableInterrupts;
        Port[PICMaskPort] := Port[PICMaskPort] or IRQStopMask;
        SetIntVec(IRQIntVector, OldIntVector);
        EnableInterrupts;
        HandlerInstalled := false;
      end;

    procedure MixExitProc;       {Called automatically on program termination}
      begin
        ExitProc := OldExitProc;

        StopDAC;
        ShutdownSB5;
      end;

  begin
    HandlerInstalled := false;
    SharedEMB        := false;
    ResourceFile     := false;
  end.