(*********************************************************)
(*                                                       *)
(*           TURBO-ACCESS for MS-DOS, PC-DOS             *)
(*                                                       *)
(*               Toolbox version:   1.21                 *)
(*                                                       *)
(*                   ACCESS module                       *)
(*                                                       *)
(*          Use with TURBO PASCAL 3.0 or later           *)
(*                                                       *)
(*              Copyright (C) 1984,85,86 by              *)
(*               Borland International                   *)
(*                                                       *)
(*********************************************************)
(*
    IMPORTANT:

      Use this file, ACCESS.BOX, when compiling with TURBO 3.0.
      Use ACCESS2.BOX when compiling with TURBO 2.0.
*)
(*$A+,I-,R-*)
type
  TaStr64   =  string[64];
  DataFile  =  record
                 case Integer of
                   0 : (F          : file;
                        FirstFree,
                        NumberFree,
                        Int1,
                        Int2,
                        NumRec     : Integer);
                   1 : (Fil2       : array[0..12] of Byte;
                        TaName     : array[1..64] of Char);
               end;
  TaKeyStr  =  string[MaxKeyLen];
  TaItem    =  record
                 DataRef,PageRef : Integer;
                 Key : TaKeyStr;
               end;
  TaPage    =  record
                 ItemsOnPage : 0..PageSize;
                 BckwPageRef : Integer;
                 ItemArray   : array[1..PageSize] of TaItem;
               end;
  TaPagePtr =  ^TaPage;
  TaSearchStep =
               record
                 PageRef,ItemArrIndex : Integer;
               end;
  TaPath    =  array[1..MaxHeight] of TaSearchStep;
  IndexFile =  record
                 DataF         : DataFile;
                 AllowDuplKeys : Boolean;
                 KeyL,RR,PP    : Integer;
                 Path          : TaPath;
               end;
  IndexFilePtr = ^IndexFile;
  TaStackRec = record
                 Page      : TaPage;
                 IndexFPtr : IndexFilePtr;
                 PageRef   : Integer;
                 Updated   : Boolean;
               end;
  TaStackRecPtr = ^TaStackRec;
  TaPageStack = array[1..PageStackSize] of TaStackRec;
  TaPageMap  =  array[1..PageStackSize] of Integer;
  TaRecordBuffer  =
               record
                 case Integer of
                   0 : (Page : TaStackRec);
                   1 : (R : array[1..MaxDataRecSize] of Byte);
                   2 : (I : Integer);
               end;

var
  IOstatus  : Integer;
  OK        : Boolean;
  TaRecBuf  : TaRecordBuffer;
  TaPageStk : TaPageStack;
  TaPgMap   : TaPageMap;


procedure TaIOcheck(var DatF : DataFile; R : Integer);
var
  I : Integer;
begin
  if IOstatus <> 0 then with DatF do
  begin
    Writeln;
    Writeln('TURBO-access I/O error ',IOstatus);
    Write('File ');
    I := 1;
    while Ord(TaName[I]) <> 0 do
    begin
      Write(TaName[I]);  I := Succ(I);
    end;
    Writeln(' Record ',R);
    Writeln('Program aborted');
    Halt;
  end;
end;

procedure GetRec(var DatF   : DataFile;
                     R      : Integer;
                 var Buffer           );
begin
  Seek(DatF.F,R);
  IOstatus := IOresult;
  TaIOcheck(DatF,R);
  BlockRead(DatF.F,Buffer,1);
  IOstatus := IOresult;
  TaIOcheck(DatF,R);
end;

procedure PutRec(var DatF   : DataFile;
                     R      : Integer;
                 var Buffer           );
begin
  Seek(DatF.F,R);
  IOstatus := IOresult;
  TaIOcheck(DatF,R);
  BlockWrite(DatF.F,Buffer,1);
  IOstatus := IOresult;
  TaIOcheck(DatF,R);
end;

procedure MakeFile(var DatF   : DataFile;
                       FName  : TaStr64;
                       RecLen : Integer);
begin
  Assign(DatF.F,FName);
  IOstatus := IOresult;
  TaIOcheck(DatF, 0);
  Rewrite(DatF.F,RecLen);
  IOstatus := IOresult;
  if IOstatus = $F1 then
    OK := false
  else
  begin
    TaIOcheck(DatF,0);
    DatF.FirstFree := -1;
    DatF.NumberFree := 0;
    DatF.Int1 := 0;
    DatF.Int2 := 0;
    Move(DatF.FirstFree,TaRecBuf,8);
    PutRec(DatF,0,TaRecBuf);
    DatF.NumRec := 1;
    OK := true;
  end;
end;

procedure OpenFile(var DatF   : DataFile;
                       FName  : TaStr64;
                       RecLen : Integer);
begin
  Assign(DatF.F,FName);
  IOstatus := IOresult;
  TaIOcheck(DatF,0);
  Reset(DatF.F,RecLen);
  IOstatus := IOresult;
  if IOstatus = 1 then OK := false
  else
  begin
    TaIOcheck(DatF,0);
    GetRec(DatF,0,TaRecBuf);
    Move(TaRecBuf,DatF.FirstFree,8);
    DatF.NumRec := FileSize(DatF.F);
    OK := true;
  end;
end;

procedure CloseFile(var DatF : DataFile);
begin
  DatF.Int2 := DatF.NumRec;
  Move(DatF.FirstFree,TaRecBuf,8);
  PutRec(DatF,0,TaRecBuf);
  Close(DatF.F);
  IOstatus := IOresult;
  TaIOcheck(DatF,0);
end;

procedure NewRec(var DatF  : DataFile;
                 var R     : Integer  );
begin
  if DatF.FirstFree = -1 then
  begin
    R := DatF.NumRec;
    DatF.NumRec := Succ(DatF.NumRec)
  end
  else
  begin
    R := DatF.FirstFree;
    GetRec(DatF,R,TaRecBuf);
    DatF.FirstFree := TaRecBuf.I;
    DatF.NumberFree := DatF.NumberFree - 1;
  end;
end;

procedure AddRec(var DatF  : DataFile;
                 var R     : Integer;
                 var Buffer           );
begin
  NewRec(DatF,R);
  PutRec(DatF,R,Buffer);
end;

procedure DeleteRec(var DatF : DataFile;
                        R    : Integer);
begin
  TaRecBuf.I := DatF.FirstFree;
  PutRec(DatF,R,TaRecBuf);
  DatF.FirstFree := R;
  DatF.NumberFree := DatF.NumberFree + 1;
end;

function FileLen(var DatF : DataFile) : Integer;
begin
  FileLen := DatF.NumRec;
end;

function UsedRecs(var DatF : DataFile) : Integer;
begin
  UsedRecs := DatF.NumRec - DatF.NumberFree - 1;
end;

procedure InitIndex;
var
  I : Integer;
begin
  for I := 1 to PageStackSize do
  begin
    TaPageStk[I].IndexFPtr := nil;
    TaPageStk[I].Updated := false;
    TaPgMap[I] := I;
  end;
end;

procedure TaPack(var Page : TaPage;
                     KeyL : Integer);
var
  I : Integer;
  P : array[0..MaxInt] of Byte absolute Page;
begin
  if KeyL <> MaxKeyLen then
    for I := 1 to PageSize do
      Move(Page.ItemArray[I],P[(I - 1) * (KeyL + 5) + 3],KeyL + 5);
end;

procedure TaUnpack(var Page : TaPage;
                       KeyL : Integer);
var
  I : Integer;
  P : array[0..MaxInt] of Byte absolute Page;
begin
  if KeyL <> MaxKeyLen then
    for I := PageSize downto 1 do
      Move(P[(I - 1) * (KeyL + 5) + 3],Page.ItemArray[I],KeyL + 5);
end;

procedure MakeIndex(var IdxF   : IndexFile;
                        FName  : TaStr64;
                        KeyLen,
                        S      : Integer);
var
  K : Integer;
begin
  K := (KeyLen + 5)*PageSize + 3;
  MakeFile(IdxF.DataF,FName,K);
  IdxF.AllowDuplKeys := S <> 0;
  IdxF.KeyL := KeyLen;
  IdxF.RR := 0;
  IdxF.PP := 0;
end;

procedure OpenIndex(var IdxF   : IndexFile;
                        FName  : TaStr64;
                        KeyLen,
                        S      : Integer);
var
  K : Integer;
begin
  K := (KeyLen + 5) * PageSize + 3;
  OpenFile(IdxF.DataF,FName,K);
  IdxF.AllowDuplKeys := S <> 0;
  IdxF.KeyL := KeyLen;
  IdxF.RR := IdxF.DataF.Int1;
  IdxF.PP := 0;
end;

procedure CloseIndex(var IdxF : IndexFile);
var
  I : Integer;
begin
  for I := 1 to PageStackSize do
    with TaPageStk[I] do
      if IndexFPtr = Addr(IdxF) then
      begin
        IndexFPtr := nil;
        if Updated then
        begin
          TaPack(Page,IdxF.KeyL);
          PutRec(IdxF.DataF,PageRef,Page);
          Updated := false;
        end;
      end;
  IdxF.DataF.Int1 := IdxF.RR;
  CloseFile(IdxF.DataF);
end;

procedure TaLast(I : Integer);
var
  J,K : Integer;
begin
  J := 1;
  while (TaPgMap[J] <> I) and (J < PageStackSize) do
    J := J + 1;
  for K := J to PageStackSize - 1 do
    TaPgMap[K] := TaPgMap[K + 1];
  TaPgMap[PageStackSize] := I;
end;

procedure TaGetPage(var IdxF  : IndexFile;
                        R     : Integer;
                    var PgPtr : TaPagePtr);
var
  I     : Integer;
  Found : Boolean;
begin
  I := 0;
  repeat
    I := I + 1;
    with TaPageStk[I] do
      Found := (IndexFPtr = Addr(IdxF)) and (PageRef = R);
  until Found or (I = PageStackSize);

  if not Found then
  begin
    I := TaPgMap[1];
    with TaPageStk[I] do
    begin
      if Updated then
      begin
        TaPack(Page,IndexFPtr^.KeyL);
        PutRec(IndexFPtr^.DataF,PageRef,Page);
      end;
      GetRec(IdxF.DataF,R,Page);
      TaUnpack(Page,IdxF.KeyL);
      IndexFPtr := Addr(IdxF);
      PageRef := R;
      Updated := false;
    end;
  end;
  TaLast(I);
  PgPtr := Addr(TaPageStk[I]);
end;

procedure TaNewPage(var IdxF  : IndexFile;
                    var R     : Integer;
                    var PgPtr : TaPagePtr);
var
  I : Integer;
begin
  I := TaPgMap[1];
  with TaPageStk[I] do
  begin
    if Updated then
    begin
      TaPack(Page,IndexFPtr^.KeyL);
      PutRec(IndexFPtr^.DataF,PageRef,Page);
    end;
    NewRec(IdxF.DataF,R);
    IndexFPtr := Addr(IdxF);
    PageRef := R;
    Updated := false;
  end;
  TaLast(I);
  PgPtr := Addr(TaPageStk[I]);
end;

procedure TaUpdatePage(PgPtr : TaPagePtr);
var
  P : TaStackRecPtr absolute PgPtr;
begin
  P^.Updated := true;
end;

procedure TaReturnPage(var PgPtr : TaPagePtr);
var
  P : TaStackRecPtr absolute PgPtr;
begin
  with P^ do
  begin
    DeleteRec(IndexFPtr^.DataF,PageRef);
    IndexFPtr := nil;
    Updated := false;
  end;
end;

procedure TaXKey(var K;
                     KeyL : Integer);
var
  Key : TaKeyStr absolute K;
begin
  if Ord(Key[0]) > KeyL then Key[0] := Chr(KeyL);
end;

function TaCompKeys(var K1,
                        K2;
                        DR1,
                        DR2 : Integer;
                        Dup : Boolean ) : Integer;
var
  Key1 : TaKeyStr absolute K1;
  Key2 : TaKeyStr absolute K2;
begin
  if Key1 = Key2 then
    if Dup then
      TaCompKeys := DR1 - DR2
    else TaCompKeys := 0
  else
    if Key1 > Key2 then
      TaCompKeys := 1
    else TaCompKeys :=  - 1;
end;

procedure ClearKey(var IdxF : IndexFile);
begin
  IdxF.PP := 0;
end;