Как создать таблицу в памяти?

{ 
  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. 
} 
 
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. 

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