(*
    Copyright 2016 Anton Krotov

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*)

MODULE API;

IMPORT sys := SYSTEM;

CONST

  MAX_SIZE  = 16 * 400H;
  HEAP_SIZE =  1 * 100000H;

VAR

  heap, endheap: INTEGER;
  pockets: ARRAY MAX_SIZE DIV 32 + 1 OF INTEGER;

PROCEDURE [stdcall] zeromem*(size, adr: INTEGER);
BEGIN
  sys.CODE("578B7D0C8B4D0833C09CFCF3AB9D5F")
END zeromem;

PROCEDURE mem_commit*(adr, size: INTEGER);
VAR tmp: INTEGER;
BEGIN
  FOR tmp := adr TO adr + size - 1 BY 4096 DO
    sys.PUT(tmp, 0)
  END
END mem_commit;

PROCEDURE strncmp*(a, b, n: INTEGER): INTEGER;
VAR A, B: CHAR; Res: INTEGER;
BEGIN
  Res := 0;
  WHILE n > 0 DO
    sys.GET(a, A); INC(a);
    sys.GET(b, B); INC(b);
    DEC(n);
    IF A # B THEN
      Res := ORD(A) - ORD(B);
      n := 0
    ELSIF A = 0X THEN
      n := 0
    END
  END
  RETURN Res
END strncmp;

PROCEDURE [stdcall] sysfunc1(arg1: INTEGER): INTEGER;
BEGIN
  sys.CODE("8B4508");           (* mov     eax, [ebp + 08h] *)
  sys.CODE("CD40");             (* int     40h              *)
  sys.CODE("C9");               (* leave                    *)
  sys.CODE("C20400");           (* ret     04h              *)
  RETURN 0
END sysfunc1;

PROCEDURE [stdcall] sysfunc2(arg1, arg2: INTEGER): INTEGER;
BEGIN
  sys.CODE("53");               (* push    ebx              *)
  sys.CODE("8B4508");           (* mov     eax, [ebp + 08h] *)
  sys.CODE("8B5D0C");           (* mov     ebx, [ebp + 0Ch] *)
  sys.CODE("CD40");             (* int     40h              *)
  sys.CODE("5B");               (* pop     ebx              *)
  sys.CODE("C9");               (* leave                    *)
  sys.CODE("C20800");           (* ret     08h              *)
  RETURN 0
END sysfunc2;

PROCEDURE [stdcall] sysfunc3(arg1, arg2, arg3: INTEGER): INTEGER;
BEGIN
  sys.CODE("53");               (* push    ebx              *)
  sys.CODE("8B4508");           (* mov     eax, [ebp + 08h] *)
  sys.CODE("8B5D0C");           (* mov     ebx, [ebp + 0Ch] *)
  sys.CODE("8B4D10");           (* mov     ecx, [ebp + 10h] *)
  sys.CODE("CD40");             (* int     40h              *)
  sys.CODE("5B");               (* pop     ebx              *)
  sys.CODE("C9");               (* leave                    *)
  sys.CODE("C20C00");           (* ret     0Ch              *)
  RETURN 0
END sysfunc3;

PROCEDURE _NEW*(size: INTEGER): INTEGER;
VAR res, idx, temp: INTEGER;
BEGIN
  IF size <= MAX_SIZE THEN
    idx := ASR(size, 5);
    res := pockets[idx];
    IF res # 0 THEN
      sys.GET(res, pockets[idx]);
      sys.PUT(res, size);
      INC(res, 4)
    ELSE
      temp := 0;
      IF heap + size >= endheap THEN
	IF sysfunc2(18, 16) > ASR(HEAP_SIZE, 10) THEN
	  temp := sysfunc3(68, 12, HEAP_SIZE)
	ELSE
	  temp := 0
	END;
	IF temp # 0 THEN
	  mem_commit(temp, HEAP_SIZE);
	  heap := temp;
	  endheap := heap + HEAP_SIZE
	ELSE
	  temp := -1
	END
      END;
      IF (heap # 0) & (temp # -1) THEN
	sys.PUT(heap, size);
	res := heap + 4;
	heap := heap + size
      ELSE
	res := 0
      END
    END
  ELSE
    IF sysfunc2(18, 16) > ASR(size, 10) THEN
      res := sysfunc3(68, 12, size);
      IF res # 0 THEN
	mem_commit(res, size);
	sys.PUT(res, size);
	INC(res, 4)
      END
    ELSE
      res := 0
    END
  END;
  IF res # 0 THEN
    zeromem(ASR(size, 2) - 1, res)
  END
  RETURN res
END _NEW;

PROCEDURE _DISPOSE*(ptr: INTEGER): INTEGER;
VAR size, idx: INTEGER;
BEGIN
  DEC(ptr, 4);
  sys.GET(ptr, size);
  IF size <= MAX_SIZE THEN
    idx := ASR(size, 5);
    sys.PUT(ptr, pockets[idx]);
    pockets[idx] := ptr
  ELSE
    size := sysfunc3(68, 13, ptr)
  END
  RETURN 0
END _DISPOSE;

PROCEDURE ExitProcess*(p1: INTEGER);
BEGIN
  p1 := sysfunc1(-1)
END ExitProcess;

PROCEDURE OutChar(c: CHAR);
VAR res: INTEGER;
BEGIN
  res := sysfunc3(63, 1, ORD(c))
END OutChar;

PROCEDURE DebugMsg*(lpText, lpCaption: INTEGER);
VAR c: CHAR;
BEGIN
  IF lpCaption # 0 THEN
    OutChar(0DX);
    OutChar(0AX);
    REPEAT
      sys.GET(lpCaption, c);
      IF c # 0X THEN
	OutChar(c)
      END;
      INC(lpCaption)
    UNTIL c = 0X;
    OutChar(":");
    OutChar(0DX);
    OutChar(0AX)
  END;
  REPEAT
    sys.GET(lpText, c);
    IF c # 0X THEN
      OutChar(c)
    END;
    INC(lpText)
  UNTIL c = 0X;
  IF lpCaption # 0 THEN
    OutChar(0DX);
    OutChar(0AX)
  END
END DebugMsg;

PROCEDURE init* (p1: INTEGER);
BEGIN
  p1 := sysfunc2(68, 11)
END init;

END API.