(* Copyright (C) 1987 Jensen & Partners International *)
(*Global equates *)

(*
   The "ROM" string denotes those sections requiring modification when
   creating ROMmable code.
*)

(*ROM
   A number of these routines make use of the Int 8 timer tick - they are
   marked with an "(*INT8*)" string.  If the target machine does not provide
   a user timer tick via Int 8, then 1) don't use any of the facilities that
   need it; or 2) implement an Int 8.
*)

True=1
False=0

Timer=40H  (* 8253-5 Programmable Interval Timer *)
PPIport=60H  (* 8255A-5 Programmable Peripheral Interface *)
KBCtrl=61H

module AsmLib

segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$HashString : ssize= 12; segm=10; offs=8; modulus=6;
  push bp; mov bp,sp
  push ds; push es; push si; push di;
  sub dx,dx
  sub ax,ax
  mov cx,[bp][ssize]
  jcxz $Exit
  mov ds,[bp][segm]
  mov si,[bp][offs]
  sub bx,bx
  mov di,[bp][ssize]
$loop:
  lodsb
  or al,al
  jz $EndLoop
  xor dl,al
  rol dx,1
  rol dx,1
  rol dx,1
  add dx,di
  sub dx,cx
  loop $loop
$EndLoop:
  mov ax,dx
  sub dx,dx
  div word [bp][modulus]
$Exit:
  mov ax,dx
  pop di; pop si; pop es; pop ds
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Move : s_seg=14; s_ofs=12; d_seg=10; d_ofs=8; len=6
  push bp; mov bp,sp
  push ds; push es; push si; push di
  mov si,[bp][s_ofs]
  mov di,[bp][d_ofs]
  mov ax,[bp][s_seg]
  mov bx,[bp][d_seg]
  mov cx,si
  mov dx,di
  shr cx,1
  shr cx,1
  shr cx,1
  shr cx,1
  shr dx,1
  shr dx,1
  shr dx,1
  shr dx,1
  add ax,cx
  add bx,dx
  mov cx,[bp][len]
  and si,000FH;
  and di,000FH;
  cld
  mov ds,ax
  mov es,bx
  cmp ax,bx
  ja $Forwards    (* (at least a paragraph apart) *)
  jb $Backwards
  cmp si,di
  ja $Forwards
  je $Exit
  cmp si,di
  jae $Forwards
$Backwards:
  add si,cx
  add di,cx
  dec si
  dec di
  std
$Forwards:
  rep
  movsb
  cld
$Exit:
  pop di; pop si; pop es; pop ds
  pop bp; ret far 10

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$WordMove : s_seg=14; s_ofs=12; d_seg=10; d_ofs=8; len=6;
  push bp; mov bp,sp
  push ds; push es; push si; push di
  mov si,[bp][s_ofs]
  mov di,[bp][d_ofs]
  mov ax,[bp][s_seg]
  mov bx,[bp][d_seg]
  mov cx,si
  mov dx,di
  shr cx,1
  shr cx,1
  shr cx,1
  shr cx,1
  shr dx,1
  shr dx,1
  shr dx,1
  shr dx,1
  add ax,cx
  add bx,dx
  mov cx,[bp][len]
  and si,000FH
  and di,000FH
  cld
  mov ds,ax
  mov es,bx
  cmp ax,bx
  ja $Forwards    (* (at least a paragraph apart) *)
  jb $Backwards
  cmp si,di
  ja $Forwards
  je $Exit
  cmp si,di
  jae $Forwards
$Backwards:
  mov ax,cx
  dec ax
  shl ax,1
  add si,ax
  add di,ax
  std
$Forwards:
  rep
  movsw
  cld
$Exit:
  pop di; pop si; pop es; pop ds;
  pop bp; ret far 10

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Fill : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di
  mov cx,[bp][len]
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  mov ah,al
  shr cx,1
  rep
  stosw
  jnc $Exit
  stosb
$Exit:
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$WordFill : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di
  mov cx,[bp][len]
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  rep
  stosw
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE


public @NormPtr :
  mov cx,ax
  and ax,000FH
  shr cx,1
  shr cx,1
  shr cx,1
  shr cx,1
  add dx,cx
  ret near 0

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @NormPtr

public AsmLib$AddAddr : a_H=10; a_L=8; c_val=6
  push bp; mov bp,sp
  mov ax,[bp][a_L]
  mov dx,[bp][a_H]
  add ax,[bp][c_val]
  jnc $NoOverflow
  add dx,1000H
$NoOverflow:
  call near @NormPtr
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @NormPtr

public AsmLib$SubAddr : a_H=10; a_L=8; c_val=6
  push bp; mov bp,sp
  mov ax,[bp][a_L]
  mov dx,[bp][a_H]
  sub ax,[bp][c_val]
  jnc $NoOverflow
  sub dx,1000H
$NoOverflow:
  call near @NormPtr
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @NormPtr

public AsmLib$IncAddr : a_ptrH=10; a_ptrL=8; incr=6
  push bp; mov bp,sp
  push ds
  lds bx,[bp][a_ptrL]
  mov ax,[bx]
  mov dx,[bx][2]
  add ax,[bp][incr]
  jnc $NoOverflow
  add dx,1000H
$NoOverflow:
  call near @NormPtr
  mov [bx],ax
  mov [bx][2],dx
  pop ds
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @NormPtr

public AsmLib$DecAddr : a_ptrH=10; a_ptrL=8; decr=6
  push bp; mov bp,sp
  push ds
  lds bx,[bp][a_ptrL]
  mov ax,[bx]
  mov dx,[bx][2]
  sub ax,[bp][decr]
  jnc $NoOverflow
  sub dx,1000H
$NoOverflow:
  call near @NormPtr
  mov [bx],ax
  mov [bx][2],dx
  pop ds
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @UserBreak

public AsmLib$UserBreak :
  mov bp,sp
  jmp @UserBreak

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @Abort

public AsmLib$FatalError:
(* three parameters len,a_ptrH,a_ptrL *)
  pop ax
(*public AsmLib@FatalError:*)
  pop ax
  pop si
  pop ds
  pop cx
  sub sp,cx
  sub sp,2
  mov di,sp
  push ss
  pop es
  jcxz $abort
$Loop:
  lodsb
  or al,al
  jz $EndLoop
  stosb
  loop $Loop
$EndLoop:
  mov al,36 (* '$' *)
  stosb
  push es
  pop ds
  mov dx,sp
  mov ah,9
  int 21H
$abort:
  jmp @Abort

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @D_DATA
extrn @ErrorCode

public AsmLib$SetReturnCode : retcode=6
  push bp ; mov bp, sp; push ds
  mov ax,[bp][retcode]
  mov ds, cs:[@D_DATA]
  mov [@ErrorCode],al
  pop ds; pop bp; ret far 2

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @SetBreakInterrupt

public AsmLib$EnableBreakCheck :
  call @SetBreakInterrupt
  ret far 0

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @ResetBreakInterrupt

public AsmLib$DisableBreakCheck :
  push ds
  call @ResetBreakInterrupt
  sub ax,ax
  mov ds,ax
  pushf
  cli
  mov word ds:[23H*4], DummyBreak
  mov word ds:[23H*4][2],cs
  popf
  pop ds
  ret far 0

DummyBreak :
  iret

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$SetJmp :
  push bp
  mov bp,sp
  les di,[bp][6]  (* buffer *)
  push ss
  pop ds
  mov si,sp
  movsw
  movsw
  movsw
  mov ax,sp
  stosw
  sub ax,ax
JmpReturn:
  pop bp
  ret far 4

public AsmLib$LongJmp :
  add sp,4  (* remove return *)
  pop ax    (* return value *)
  pop si    (* buffer *)
  pop ds
  mov sp,[si][6]
  push ss
  pop es
  mov di,sp
  movsw
  movsw
  movsw
  jmp JmpReturn

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$ScanR : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di
  mov cx,[bp][len]
  jcxz ExitScan
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  repne
  scasb
  jne ExitScan
  inc cx
ExitScan:
  mov ax,[bp][len]
  sub ax,cx
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$ScanL : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di;
  mov cx,[bp][len]
  jcxz ExitScan
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  std
  repne
  scasb
  cld
  jne ExitScan
  inc cx
ExitScan:
  mov ax,[bp][len]
  sub ax,cx
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$ScanNeR : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di
  mov cx,[bp][len]
  jcxz ExitScan
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  repe
  scasb
  je ExitScan
  inc cx
ExitScan:
  mov ax,[bp][len]
  sub ax,cx
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$ScanNeL : d_seg=12; d_ofs=10; len=8; val=6
  push bp; mov bp,sp
  push es; push di
  mov cx,[bp][len]
  jcxz ExitScan
  les di,[bp][d_ofs]
  mov ax,[bp][val]
  std
  repe
  scasb
  cld
  je ExitScan
  inc cx
ExitScan:
  mov ax,[bp][len]
  sub ax,cx
  pop di; pop es
  pop bp; ret far 8

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Compare : s_seg=14; s_ofs=12; d_seg=10; d_ofs=8; len=6
  push bp; mov bp,sp
  push ds; push es; push si; push di
  mov cx,[bp][len]
  jcxz ExitScan
  lds si,[bp][s_ofs]
  les di,[bp][d_ofs]
  repe
  cmpsb
  je ExitScan
  inc cx
ExitScan:
  mov ax,[bp][len]
  sub ax,cx
  pop di; pop si; pop es; pop ds;
  pop bp; ret far 10

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE


section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Sound : FreqHz=6
(*ROM
   Generate sounds via the speaker.  The machine may not have a speaker, or it
   may be accessed in a different way.
*)
  push bp; mov bp,sp
  mov bx,[bp][FreqHz]
  mov ax,34DDH  (* 1.193181 MHz *)
  mov dx,0012H
  cmp dx,bx
  jnb SOU9
  div bx
  mov bx,ax
  in al,PPIport+1
  test al,03H
  jnz SOU1
  or al,03H
  out PPIport+1,al
                (* 10              11       011     0   *)
  mov al,0B6H  (* Select timer 2, LSB,MSB, mode 3, bin *)
  out Timer+3,al
SOU1:
  mov al,bl
  out Timer+2,al
  mov al,bh
  out Timer+2,al
SOU9:
  pop bp; ret far 2

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$NoSound :
(*ROM
   Stop producing sound via the speaker.  See the above comments.
*)
  in al,PPIport+1
  and al,0FCH
  out PPIport+1,al
  ret far 0

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Speaker : TotalTime=10; OnTime=8; OffTime=6
(*ROM
   Generate sounds via the speaker.  See the above comments.
*)
  push bp; mov bp,sp
  in al,KBCtrl
  push ax
  mov bx,TotalTime
$MainLoop:
  and al,0FCH
  jmp $Next
$Next:
  out KBCtrl,al
  mov cx,OffTime
$OffLoop:
  loop $OffLoop
  or al,2
  out KBCtrl,al
  mov cx,OnTime
$OnLoop:
  loop $OnLoop
  dec bx
  jnz $MainLoop
  pop ax
  out KBCtrl,al
  ret far 6

section;

segment D_DATA(M_DATA,28H)
segment INITCODE(CODE,28H)
segment C_CODE(CODE,28H)
group G_CODE(INITCODE,C_CODE)

select D_DATA

@DelayFactor : org 2
Iter         : org 2
Count        : org 2
Semaphor     : org 2

select C_CODE

extrn @D_DATA

public AsmLib$Delay : p_time=6
  push bp; mov bp,sp; push ds
  mov  ax, [bp][p_time]
  mov ds, cs:[@D_DATA]
  mov  ds:[Iter], ax
MoreDelay:
  cmp word ds:[Iter],0
  jz   DelayEnd
  mov  ax,ds:[@DelayFactor]
  mov  ds:[Count],ax
Here:
  mov  ax, ds:[Count]
  or   ax,ax
  jz   Here2
  dec word ds:[Count]
  jmp  Here
Here2:
  dec word ds:[Iter]
  jmp  MoreDelay
DelayEnd:
  pop ds; pop bp; ret far 2


(* the Int 1C ISR, installed below *)

TimeTrap:
  push ds
  mov ds, cs:[@D_DATA]
  inc word ds:[Semaphor]        (* used when establishing delay factor *)
  pop ds
  iret


select INITCODE

(* calibrate timer *)

(*ROM
(*INT8*)
  This routine uses the INT 1C hardware tick, instead of the INT 8 user timer
  tick.  It relies on the hardware tick happening at the rate defined for
  PC's.
*)

  xor ax,ax
  mov es,ax
  push es:[70H]
  push es:[72H]
  mov ds, cs:[@D_DATA]
  mov word ds:[Semaphor],0
  mov word ds:[@DelayFactor],55
  mov word ds:[Iter],0
  mov word ds:[Count],0
  cli
  mov word es:[70H],TimeTrap
  mov es:[72H],cs
  sti
Estab1:
  cmp word ds:[Semaphor],2
  jne  Estab1
Estab2:
  cmp word ds:[Semaphor],3
  jz   Estab5
  mov  ax,ds:[@DelayFactor]
  mov  ds:[Count],ax
Estab3:
  mov  ax,ds:[Count]
  or   ax,ax
  jz   Estab4
  dec word ds:[Count]
  jmp  Estab3
Estab4:
  inc word ds:[Iter]
  jmp  Estab2
Estab5:
  cli
  pop es:[72H]
  pop es:[70H]
  sti
  mov ax,ds:[Iter]
  mov ds:[@DelayFactor],ax

  in al,PPIport+1
  and al,0FCH
  out PPIport+1,al


section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE


axr=0;  bxr=2;  cxr=4;  dxr=6;  bpr=8;
sir=10; dir=12; dsr=14; esr=16; flags=18

public @LoadRegisters :
(* loads register in register pack pointed to by DS:SI *)
  push  [si][dsr]
  push  [si][sir]
  mov  ax,[si][axr]
  mov  bx,[si][bxr]
  mov cx,[si][cxr]
  mov  dx,[si][dxr]
  mov  di,[si][dir]
  mov  bp,[si][bpr]
  mov  es,[si][esr]
  pop  si
  pop  ds
  ret near 0

public @SaveRegisters :
(* saves register in register pack pointed to by pointer on stack *)
  push ds
  push si
  mov si,sp
  lds si,ss:[si][6]
  pushf
  pop  [si][flags]
  pop  [si][sir]
  pop  [si][dsr]
  mov  [si][axr],ax
  mov  [si][bxr],bx
  mov  [si][cxr],cx
  mov  [si][dxr],dx
  mov  [si][dir],di
  mov  [si][bpr],bp
  mov  [si][esr],es
  ret near 4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @D_DATA
extrn @LoadRegisters
extrn @SaveRegisters
extrn @InProgramFlag
extrn @StopProgramFlag
extrn AsmLib$FatalError

msg1 : db 'Fatal error: Dos reentered',0

public AsmLib$Dos : p_seg=8; p_off=6
(*ROM
   Perform a DOS call.  Since you're in ROM, DOS probably doesn't exist.  All
   references to this procedure should be removed.
*)
  push bp; mov bp,sp
  push ds; push es; push si; push di
  pushf
  mov ds, cs:[@D_DATA]
  cmp byte [@InProgramFlag], 1
  je ok
  cld
  mov ax,100
  push ax
  push cs
  mov ax, msg1
  push ax
  push cs
  call near AsmLib$FatalError
ok:
  cmp byte [@StopProgramFlag], 1
  je Stop                     (* wait for timer to stop us *)
  mov byte [@InProgramFlag], 0
  lds  si,[bp][p_off]
  push ds                     (* save register pointer *)
  push si
  call @LoadRegisters

  int  21H

  call @SaveRegisters

  mov ds, cs:[@D_DATA]
  mov byte [@InProgramFlag], 1
  popf
  pop di; pop si; pop es; pop ds
  pop bp; ret far 4
Stop:
  sti
  jmp Stop

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @LoadRegisters
extrn @SaveRegisters

public AsmLib$Intr : p_seg=10; p_off=8; p_num=6
(*ROM
   Perform a software interrupt.  This procedure uses self-modifying code to
   generate an arbitrary interrupt.
*)
  push bp; mov bp,sp
  push ds; push es; push si; push di
  pushf
  lds  si,[bp][p_off]
  push ds                     (* save register pointer *)
  push si

  mov al,[bp][p_num]
  cli
  mov cs:[InterruptNo],al

  call @LoadRegisters

  db   0CDH                   (* INT *)
InterruptNo :
  db   0

  call @SaveRegisters
  popf
  pop di; pop si; pop es; pop ds
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @D_DATA
extrn @PSP

public AsmLib$Environment : p_n=6
(*ROM
   Get an environment string.  The environment is set up by DOS, which
   probably doesn't exist.
*)
  push bp; mov bp,sp
  push ds; push es; push si; push di

  mov  ds, cs:[@D_DATA]
  mov  ds, [@PSP]
  mov  es, ds:[2CH]
  mov  di,0
  mov  cx,[bp][p_n]
  xor  ax,ax
  jcxz  EnFound
  cmp  byte es:[di],0
  je  EnFound
  mov  bx,cx
EnSeMo:
  mov  cx,8000H
  repne
  scasb
  cmp  es:[di],al
  je  EnFound
  dec  bx
  jnz  EnSeMo
EnFound:
  mov dx,es
  mov ax,di
  pop di; pop si; pop es; pop ds
  pop bp; ret far 2

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn AsmLib@CommandLine

comma=44
space=32

public AsmLib$ParamStr : p_sl=12; p_sh=10; p_s=8; p_n=6
(*ROM
   Get an argument from the command line.  Since DOS probably doesn't exist,
   there won't be a command line.
*)
  push bp; mov bp,sp
  push ds; push es; push si; push di

  les di,[bp][p_s]
  mov  ax, seg AsmLib@CommandLine
  mov ds,ax
  lds si,ds:[AsmLib@CommandLine]
  mov cx,[bp][p_n]
  jcxz $Finished
  jmp $Loop1
$Loop:
  lodsb
  cmp al,0
  je $Finished
  cmp al,comma
  je $Loop1
  cmp al,space
  ja $Loop
  (* remove leading separators *)
$Loop1:
  lodsb
  cmp al,0
  je $Finished
  cmp al,comma
  je $Loop1
  cmp al,space
  jbe $Loop1
  loop $Loop

  mov cx,[bp][p_sl]
  add cx,di

$Loop2:
  stosb
  cmp di,cx
  je $Exit
  lodsb
  cmp al,0
  je $Finished
  cmp al,comma
  je $Finished
  cmp al,space
  ja $Loop2
$Finished:
  sub al,al
  stosb
$Exit:
  pop di; pop si; pop es; pop ds
  pop bp; ret far 8

public AsmLib$ParamCount :
(*ROM
   Return the number of arguments on the command line.  See the above comment.
*)
  push di; push si
  push bx
  mov si,sp
  sub di,di
$Loop3:
  inc di
  mov ax,1
  push ax
  push ss
  push si
  push di
  call far AsmLib$ParamStr
  cmp byte ss:[si],0
  jne $Loop3
  dec di
  mov ax,di
  pop bx
  pop si; pop di
  ret far 0

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Caps : Slen=10; Sseg=8; Sofs=6
  push bp; mov bp,sp
  push ds; push si

  lds si,[bp][Sofs]
  mov cx,[bp][Slen]
$loop:
  lodsb
  cmp al,97 (* 'a' *)
  jb $notSmall
  cmp al,122 (* 'z' *)
  ja $notSmall
  sub al,32
  mov [si][-1],al
$notSmall:
  or al,al
  loopnz $loop

  pop si; pop ds
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Length : Slen=10; Sseg=8; Sofs=6
  push bp; mov bp,sp
  push es; push di

  les di,[bp][Sofs]
  mov cx,[bp][Slen]
  sub al,al
  repne
  scasb
  jne ExitLength
  inc cx
ExitLength:
  mov ax,[bp][Slen]
  sub ax,cx
  pop di; pop es
  pop bp; ret far 6

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$CompareStr : S1len=16; S1seg=14; S1ofs=12; S2len=10; S2seg=8; S2ofs=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  lds si,[bp][S1ofs]
  les di,[bp][S2ofs]
  mov bx,[bp][S1len]
  mov dx,[bp][S2len]
  mov cx,bx
  cmp cx,dx
  jb CompareLoop
  mov cx,dx
CompareLoop:
  lodsb
  scasb
  jne NotEqual
  or al,al
  loopne CompareLoop
  je Equal
  cmp bx,dx
  je Equal
  ja CheckSi
  cmp byte es:[di],0
  je Equal
Less:
  mov ax,-1
  jmp Return
CheckSi:
  cmp byte [si],0
  je Equal
Greater:
  mov ax,1
  jmp Return
NotEqual:
  cmp al,es:[di][-1]
  jb Less
  jmp Greater
Equal:
  sub ax,ax
Return:
  pop di; pop es; pop si; pop ds
  pop bp; ret far 12

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE


public AsmLib$Concat : NSlen=22; NSseg=20; NSofs=18; S1len=16; S1seg=14; S1ofs=12; S2len=10; S2seg=8; S2ofs=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  mov cx,[bp][S2len]
  sub sp,cx
  lds si,[bp][S2ofs]
  push ss
  pop es
  mov di,sp
  rep
  movsb

  mov bx,[bp][NSlen]
  lds si,[bp][S1ofs]
  les di,[bp][NSofs]

  mov cx,[bp][S1len]
CopyLoop1:
  lodsb
  or al,al
  jz Finished1
  stosb
  dec bx
  loopnz CopyLoop1
  jz Exit
Finished1:
  push ss
  pop ds
  mov si,sp
  mov cx,[bp][S2len]
CopyLoop2:
  lodsb
  stosb
  or al,al
  jz Exit
  dec bx
  loopnz CopyLoop2
  jz Exit
  sub al,al
  stosb
Exit:
  add sp,[bp][S2len]
  pop di; pop es; pop si; pop ds
  pop bp; ret far NSlen-4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Append : NSlen=16; NSseg=14; NSofs=12; Slen=10; Sseg=8; Sofs=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  les di,[bp][NSofs]

  mov cx,[bp][NSlen]
  sub al,al
  repne
  scasb
  jne Exit
  dec di
  mov bx,cx
  inc bx
  lds si,[bp][Sofs]
  mov cx,[bp][Slen]
CopyLoop:
  lodsb
  stosb
  or al,al
  jz Exit
  dec bx
  loopnz CopyLoop
  jz Exit
  sub al,al
  stosb
Exit:
  pop di; pop es; pop si; pop ds
  pop bp; ret far NSlen-4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Copy : NSlen=16; NSseg=14; NSofs=12; Slen=10; Sseg=8; Sofs=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  les di,[bp][Sofs]
  mov cx,[bp][Slen]
  sub al,al
  repne
  scasb
  jne LengthCalc
  inc cx
LengthCalc:
  mov ax,[bp][Slen]
  sub ax,cx
  mov cx,[bp][NSlen]
  cmp ax,cx
  ja SourceBigger
  mov cx,ax
SourceBigger:
  lds si,[bp][ Sofs]
  les di,[bp][NSofs]
  rep
  movsb
  jae Exit
  sub al,al
  stosb
Exit:
  pop di; pop es; pop si; pop ds
  pop bp; ret far NSlen-4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Slice : NSlen=20; NSseg=18; NSofs=16; Slen=14; Sseg=12; Sofs=10; P=8; L=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  les di,[bp][Sofs]
  mov cx,[bp][Slen]
  sub al,al
  repne
  scasb
  jne LengthCalc
  inc cx
LengthCalc:
  mov ax,[bp][Slen]
  sub ax,cx

  mov bx,[bp][P]
  sub ax,bx
  ja NotBeyondEnd
  sub ax,ax
NotBeyondEnd:
  cmp ax,[bp][L]
  jb OffEnd
  mov ax,[bp][L]
OffEnd:
  lds si,[bp][Sofs]
  add si,[bp][P]
  mov cx,[bp][NSlen]
  cmp ax,cx
  ja SourceBigger
  mov cx,ax
SourceBigger:
  les di,[bp][NSofs]
  rep
  movsb
  jae Exit
  sub al,al
  stosb
Exit:
  pop di; pop es; pop si; pop ds
  pop bp; ret far NSlen-4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

public AsmLib$Pos : Slen=16; Sseg=14; Sofs=12; Plen=10; Pseg=8; Pofs=6
  push bp; mov bp,sp
  push ds; push si; push es; push di

  les di,[bp][Sofs]
  mov cx,[bp][Slen]
  mov bx,cx
  sub al,al
  repne
  scasb
  jne LengthCalc1
  inc cx
LengthCalc1:
  sub bx,cx
  les di,[bp][Pofs]
  mov cx,[bp][Plen]
  mov dx,cx
  sub al,al
  repne
  scasb
  jne LengthCalc2
  inc cx
LengthCalc2:
  sub dx,cx
  sub bx,dx
  jb NotFound

  mov ds,[bp][Sseg]
  sub ax,ax
SearchLoop:
  mov si,[bp][Sofs]
  add si,ax
  mov di,[bp][Pofs]
  mov cx,dx
  repe
  cmpsb
  je Found
  inc ax
  cmp ax,bx
  jbe SearchLoop
NotFound:
  mov ax,0FFFFH
Found:
Exit:
  pop di; pop es; pop si; pop ds
  pop bp; ret far Slen-4

section ;
segment D_DATA(M_DATA,28H); segment C_CODE(CODE,28H); group G_CODE(C_CODE);

(*ROM
   These values are for direct-memory access to the screen memory.
*)

ColorStatusReg    =03DAH  (* port value for color status register *)
ColorRetrace      =1      (* mask in color status for horiz. retrace *)
ColorVertRetrace  =8      (* mask in color status for vert. retrace *)

extrn @D_DATA

select D_DATA

public AsmLib@ActivePage : org 1
public AsmLib@IsColor    : org 1
public AsmLib@IsSnow     : org 1

select C_CODE

public AsmLib@BWSeg      : dw 0B000H
public AsmLib@ColorSeg   : dw 0B800H

public AsmLib$BufferWrite : BuffH=16; BuffL=14; StrH=12; StrL=10; Len=8; Attr=6
  push bp; mov bp,sp
  push ds; push es; push si; push di
  mov cx,[bp][Len]
  jcxz $Exit
  mov bx,[bp][Attr]
  lds si,[bp][StrL]
  les di,[bp][BuffL]
LDoWrite:
  cld
  mov ah,bl
LWriteLoop:
  lodsb
  stosw
  loop LWriteLoop
$Exit:
  pop di; pop si; pop es; pop ds
  pop bp; ret far BuffH-4

public AsmLib$PalXlat : ToH=18; ToL=16; FromH=14; FromL=12; Len=10; PalH=8; PalL=6
  push bp; mov bp,sp

  push ds; push es; push si; push di
  mov cx,[bp][Len]
  jcxz PXExit
  sub sp,10
  mov di,sp
(* copy pallette onto stack *)
  lds si,[bp][PalL]
  push ss
  pop es
  mov cx,5
  rep
  movsw
  mov bx,sp
  lds si,[bp][FromL]
  les di,[bp][ToL]
  mov cx,[bp][Len]
PXloop:
  lodsw
  xchg al,ah
  db 36H        (* ss override for xlat *)
  xlat
  xchg al,ah
  stosw
  loop PXloop
  add sp,10

PXExit:
  pop di; pop si; pop es; pop ds
  pop bp; ret far ToH-4

public AsmLib$BufferToScreen : X=14; Y=12; SourceH=10; SourceL=8; Len=6
  push bp; mov bp,sp
  push ds; push es; push si; push di

  lds si,[bp][SourceL]
  mov ax,[bp][Y]
  mov di,[bp][X]

  mov cl,4
  shl ax,cl  (* 16Y *)
  add di,ax
  shl ax,1
  shl ax,1
  add di,ax  (* +64Y=80Y *)
  shl di,1
  mov cx,[bp][Len]
  mov es,cs:[AsmLib@BWSeg]
  push ds
  mov ds, cs:[@D_DATA]
  cmp byte [AsmLib@IsColor],True
  jne BtsIsBW
  cmp byte [AsmLib@IsSnow],True
  mov es,cs:[AsmLib@ColorSeg]
  jne BtsNoSnowMove
  pop ds
  pushf
  mov dx,ColorStatusReg
  mov bl,1
  cld
  sti
  push bp
BtsLoop:
  lodsw
  mov bp,ax
BtsWaitNotHoriz:
  in al,dx
  rcr al,1
  jc BtsWaitNotHoriz
  cli
BtsWait:
  in al,dx
  rcr al,1
  jnc BtsWait
  xchg ax,bp
  stosw
  sti
  loop BtsLoop
  pop bp
  popf
  jmp BtsRet
BtsNoSnowMove:
BtsIsBW:
  pop ds
  cld
  rep
  movsw
BtsRet:
  pop di; pop si; pop es; pop ds
  pop bp; ret far X-4

public AsmLib$ScreenToBuffer : X=14; Y=12; DestH=10; DestL=8; Len=6
  push bp; mov bp,sp
  push ds; push es; push si; push di

  les di,[bp][DestL]
  mov ax,[bp][Y]
  mov si,[bp][X]

  mov cl,4
  shl ax,cl  (* 16Y *)
  add si,ax
  shl ax,1
  shl ax,1
  add si,ax  (* +64Y=80Y *)
  shl si,1
  mov cx,[bp][Len]
  mov ds, cs:[@D_DATA]
  cmp byte [AsmLib@IsColor],True
  mov ds, cs:[AsmLib@BWSeg]
  jne StbIsBW
  mov ds, cs:[@D_DATA]
  cmp byte [AsmLib@IsSnow],True
  mov ds, cs:[AsmLib@ColorSeg]
  jne StbNoSnowMove
  pushf
  mov dx,ColorStatusReg
  add cx,cx              (* bytes *)
  mov bl,1
  cld
StbLoop:
StbWaitNotHoriz:
  in al,dx
  rcr al,1
  jc StbWaitNotHoriz
  cli
StbWait:
  in al,dx
  rcr al,1
  jnc StbWait
  movsb
  sti
  loop StbLoop
  popf
  jmp StbRet
StbNoSnowMove:
StbIsBW:
  cld
  rep
  movsw
StbRet:
  pop di; pop si; pop es; pop ds
  pop bp; ret far X-4

public AsmLib$SetVideoPage : NewPage=6
  push bp; mov bp,sp; push ds
  mov ax,[bp][NewPage]
  mov ds, cs:[@D_DATA]
  mov [AsmLib@ActivePage],al
  mov ah,5
  push bp
  int 10H
  pop bp
  mov ax,[bp][NewPage]
  mov bx,100H
  mul bx
  add ax,0B800H
  mov cs:[AsmLib@ColorSeg],ax
  pop ds; pop bp; ret far NewPage-4

public AsmLib$ActivePage :
  push ds
  mov ds, cs:[@D_DATA]
  mov al, [AsmLib@ActivePage]
  cbw
  pop ds; ret far 0

(* initialize screen type *)
public AsmLib$InitScreenType : IsSnow=6
  push bp; mov bp,sp
  push ds; push es; push si; push di
  mov ds, cs:[@D_DATA]
  mov byte [AsmLib@IsColor],True
  mov byte [AsmLib@ActivePage],0
  mov ah,15
  push bp
  int 10H
  pop bp
  cmp al,7
  jne LIsColor
  mov byte [AsmLib@IsColor],False
LIsColor:
  mov ax,[bp][IsSnow]
  mov [AsmLib@IsSnow],al
  pop di; pop si; pop es; pop ds
  pop bp; ret far 2

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

SaveSS : dw 0
SaveSP : dw 0

public AsmLib$DosExec : NameLen=14; NameSeg=12; NameOfs=10; ParamSeg=8; ParamOfs=6
(*ROM
   Execute a DOS program.  Even if, for some very strange reason, a ROMmed
   program could call this, it wouldn't work - this procedure needs to alter
   certain values in the code segment (which is presumably ROM).
*)
  push bp; mov bp,sp
  push ds; push es; push si; push di

  pushf
  mov ax,4B00H
  mov ds,[bp][NameSeg]
  mov dx,[bp][NameOfs]
  mov es,[bp][ParamSeg]
  mov bx,[bp][ParamOfs]
  push bp
  push ss:[2EH]            (* where DOS doth tread *)
  push ss:[30H]
  push cs:[SaveSS]                (* to restore code seg *)
  push cs:[SaveSP]
  mov cs:[SaveSS],ss
  mov cs:[SaveSP],sp
  int 21H
  mov ss,cs:[SaveSS]
  mov sp,cs:[SaveSP]
  pop cs:[SaveSP]
  pop cs:[SaveSS]
  pop ss:[30H]
  pop ss:[2EH]
  pop bp
  jc ExitExec
  sub ax,ax
ExitExec:
  popf
  pop di; pop si; pop es; pop ds
  pop bp; ret far NameLen-4

section ; segment C_CODE(CODE,28H); group G_CODE(C_CODE); select C_CODE

extrn @D_DATA
extrn @InProgramFlag

public AsmLib$SetInProgramFlag : on=6
  push bp; mov bp,sp; push ds
  mov al, [bp][on]
  mov ds, cs:[@D_DATA]
  mov [@InProgramFlag], al
  pop ds; pop bp; ret far 2

public AsmLib$GetInProgramFlag :
  push ds
  sub ah,ah
  mov ds, cs:[@D_DATA]
  mov al, [@InProgramFlag]
  pop ds
  ret far 0

section

extrn @D_DATA
extrn @PSP

segment INITCODE(CODE,28H); group G_CODE(INITCODE)

segment D_DATA(M_DATA,28H);

select D_DATA

public AsmLib@CommandLine : org 4
public AsmLib@PSP : org 2

select INITCODE

(*ROM
   All of this initialization deals with the PSP and command line.  It should
   be safe to just comment it out.
*)

(* set up PSP and command line *)

  mov ds, cs:[@D_DATA]
  mov ds, [@PSP]
  mov ax, D_DATA
  mov es, ax
  mov es:[AsmLib@PSP],ds
  mov es:[AsmLib@CommandLine][2],ds
  mov word es:[AsmLib@CommandLine],81H

(* make command line into asciiz string *)

  mov byte bl,ds:[80H]   (* make it a asciiz string *)
  xor bh,bh
  add bx,81H
  mov byte [bx],0
  mov bx,81H
again:
  cmp byte [bx],0
  je EndFound
  cmp byte [bx],32   (* skip blanks *)
  jne StartFound
  inc bx
  jmp again
EndFound:
StartFound:
  mov  es:[AsmLib@CommandLine],bx

end