A:

{

 This is an InMemoryTable example. Free for anyone to use, modify and do
 whatever else you wish.

 Just like all things free it comes with no guarantees. I cannot be responsible
 for any damage this code may cause. Let me repeat this:

 WARNING! THIS CODE IS PROVIDED AS IS WITH NO GUARANTEES OF ANY KIND!
 USE THIS AT YOUR OWN RISK - YOU ARE THE ONLY PERSON RESPONSIBLE FOR
 ANY DAMAGE THIS CODE MAY CAUSE - YOU HAVE BEEN WARNED!

 THANKS to Steve Garland <72700.2407@compuserve.com> for his help. He
 created his own variation of an in-memory table component and I used it
 to get started.

 InMemory tables are a feature of the Borland Database Engine (BDE).
 InMemory tables are created in RAM and deleted when you close them. They
 are much faster and are very useful when you need fast operations on small
 tables. This example uses the DbiCreateInMemoryTable DBE function call.

 This object should work just like a regular table, except InMemory tables
 do not support certain features (like referntial integrity, secondary
 indexes and BLOBs) and currently this code doesn't do anything to
 prevent you from trying to use them. You will probably get some error if
 you try to create a memo field.

 If you have comments - please contact me at INTERNET:grisha@mira.com

 Happy hacking!

 Gregory Trubetskoy
 http://www.mira.com/home/grisha

}

unit Inmem;

interface

uses DBTables, WinTypes, WinProcs, DBITypes, DBIProcs, DB, SysUtils;
 

type TInMemoryTable = class(TTable)
  private
    hCursor: hDBICur;
    procedure EncodeFieldDesc(var FieldDesc: FLDDesc;
      const Name: string; DataType: TFieldType; Size: Word);
    function CreateHandle: HDBICur; override;
  public
    procedure CreateTable;
  end;

implementation

{ luckely this function is virtual - so I could override it. In the original
  VCL code for TTable this function actually opens the table - but since
  we already have the handle to the table - we just return it }

function TInMemoryTable.CreateHandle;
begin
  Result := hCursor;
end;

{ This function is cut-and-pasted from the VCL source code. I had to do this
  because it is declared private in the TTable component so I had no access
  to it from here. }

procedure TInMemoryTable.EncodeFieldDesc(var FieldDesc: FLDDesc;
  const Name: string; DataType: TFieldType; Size: Word);
const
  TypeMap: array[TFieldType] of Byte = (
    fldUNKNOWN, fldZSTRING, fldINT16, fldINT32, fldUINT16, fldBOOL,
    fldFLOAT, fldFLOAT, fldBCD, fldDATE, fldTIME, fldTIMESTAMP, fldBYTES,
    fldVARBYTES, fldBLOB, fldBLOB, fldBLOB);
begin
  with FieldDesc do
  begin
    AnsiToNative(Locale, Name, szName, SizeOf(szName) - 1);
    iFldType := TypeMap[DataType];
    case DataType of
      ftString, ftBytes, ftVarBytes, ftBlob, ftMemo, ftGraphic:
        iUnits1 := Size;
      ftBCD:
        begin
          iUnits1 := 32;
          iUnits2 := Size;
        end;
    end;
    case DataType of
      ftCurrency:
        iSubType := fldstMONEY;
      ftBlob:
        iSubType := fldstBINARY;
      ftMemo:
        iSubType := fldstMEMO;
      ftGraphic:
        iSubType := fldstGRAPHIC;
    end;
  end;
end;

{ This is where all the fun happens. I copied this function from the VCL source
  and then changed it to use DbiCreateInMemoryTable instead of DbiCreateTable.
  Since InMemory tables do not support Indexes - I took all of the index-related
  things out }

procedure TInMemoryTable.CreateTable;
var
  I: Integer;
  pFieldDesc: pFLDDesc;
  szTblName: DBITBLNAME;
  iFields: Word;
  Dogs: pfldDesc;
begin
  CheckInactive;
  if FieldDefs.Count = 0 then
    for I := 0 to FieldCount - 1 do
      with Fields[I] do
        if not Calculated then
          FieldDefs.Add(FieldName, DataType, Size, Required);
  pFieldDesc := nil;
  SetDBFlag(dbfTable, True);
  try
    AnsiToNative(Locale, TableName, szTblName, SizeOf(szTblName) - 1);
    iFields := FieldDefs.Count;
    pFieldDesc := AllocMem(iFields * SizeOf(FLDDesc));
    for I := 0 to FieldDefs.Count - 1 do
      with FieldDefs[I] do
      begin
        EncodeFieldDesc(PFieldDescList(pFieldDesc)^[I], Name,
          DataType, Size);
      end;
      { the driver type is nil = logical fields }
      Check(DbiTranslateRecordStructure(nil, iFields, pFieldDesc,
        nil, nil, pFieldDesc));
      { here we go - this is where hCursor gets its value }
    Check(DbiCreateInMemTable(DBHandle, szTblName, iFields, pFieldDesc, hCursor));
  finally
    if pFieldDesc <> nil then FreeMem(pFieldDesc, iFields * SizeOf(FLDDesc));
    SetDBFlag(dbfTable, False);
  end;
end;

end.