function CompareFiles(const File1, File2:TFileName): boolean;
var
 ms1, ms2: pStream;
begin
 Result:=False;
 ms1:=TMemoryStream.Create;
 try
   ms1.LoadFromFile(File1);
   ms2:=TMemoryStream.Create;
   try
     ms2.LoadFromFile(File2);
     if ms1.Size=ms2.Size then Result:=CompareMem(ms1.Memory, ms2.Memory, ms1.Size);
   finally
     ms2.Free;
   end;
 finally
   ms1.Free;
 end
end;

function CompareFiles(const File1, File2: String): Boolean;
var
 fs1, fs2, ms1, ms2: PStream;
begin
 Result := False;
 fs1 := NewReadFileStream(File1);
 fs2 := NewReadFileStream(File2);
 ms1 := NewMemoryStream;
 ms2 := NewMemoryStream;
 Stream2Stream(ms1, fs1, fs1.Size);
 Stream2Stream(ms2, fs2, fs2.Size);
 if ms1.Size = ms2.Size then
   Result := CompareMem(ms1.Memory, ms2.Memory, ms1.Size);
 ms2.Free;
 ms1.Free;
 fs2.Free;
 fs1.Free
end;

Function CompareFiles(Const p_strFileName1,p_strFileName2:String):Boolean;
Const
BUF_SIZE=1024*1024;
Var
 f1,f2:File;
 buf1,buf2:Pointer;
 n1,n2:Integer;
Begin
 AssignFile(f1,p_strFileName1);Reset(f1,1);
 AssignFile(f2,p_strFileName2);Reset(f2,1);
 Result:=FileSize(f1)=FileSize(f2);
 If Result Then
  Begin
   GetMem(Buf1,BUF_SIZE); GetMem(Buf2,BUF_SIZE);
   Try
    Repeat
     BlockRead(f1,Buf1^,BUF_SIZE,n);
     BlockRead(f2,Buf2^,BUF_SIZE,n);
     Result:=CompareMem(Buf1,Buf2,n);
     If Not Result Then Break;
    Until n=0;
   Finally
    FreeMem(Buf1); FreeMem(Buf2);
   End;
 CloseFile(f1);CloseFile(f2);
End;

function CompareFiles(const File1, File2:TFileName): boolean;
var
 ms1, ms2: pStream;
begin
 Result:=False;
 try
   ms1:=NewReadFileStream(File1);
   try
     ms2:=NewReadFileStream(File2);
     if ms1.Size=ms2.Size then Result:=CompareMem(@ms1.Memory, @ms2.Memory, ms1.Size);
   finally
     ms2.Free;
   end;
 finally
   ms1.Free;
 end
end;

Function CompareFiles2(Const p_strFileName1,p_strFileName2:String):Boolean;
Const
BUF_SIZE=32*1024*1024;

Type
TFileMapRec=Record
 _File:HFILE;
 _Map:THandle;
 _Size:Int64;
End;

Function OpenFile(Const p_strFileName:String):TFileMapRec;
Var
 slo,shi:Cardinal;
Begin
 Result._File:=CreateFile(PChar(p_strFileName),GENERIC_READ,FILE_SHARE_READ,Nil,O PEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0);
 slo:=Windows.GetFileSize(Result._File,@shi);
 Int64Rec(Result._Size).Lo:=slo;
 Int64Rec(Result._Size).Hi:=shi;
 Result._Map:=CreateFileMapping(Result._File,Nil,PAGE_READONLY,0,0,Nil);
End;

Procedure CloseFile(Var rp_rFile:TFileMapRec);
Begin
 CloseHandle(rp_rFile._Map);
 CloseHandle(rp_rFile._File);
End;

Function MapBuff(p_rFile:TFileMapRec;p_nFrom:Int64;p_nCount:Cardinal):Pointer;
Begin
 Result:=MapViewOfFile(p_rFile._Map,FILE_MAP_READ,Int64Rec(p_nFrom).Hi,Int64Rec(p _nFrom).Lo,p_nCount);
End;

Procedure UnMapBuff(Var p:Pointer);
Begin
 UnmapViewOfFile(p);
End;

Var
File1,File2:TFileMapRec;
Buf1,Buf2:Pointer;
p:Int64;

Function Compare(p_nFrom:Int64;p_nCount:Cardinal):Boolean;
Begin
 Buf1:=MapBuff(File1,p_nFrom,p_nCount);
 Try
  Buf2:=MapBuff(File2,p_nFrom,p_nCount);
  Try
   Result:=CompareMem(Buf1,Buf2,p_nCount);
  Finally
   UnMapBuff(Buf2);
  End;
 Finally
  UnMapBuff(Buf1);
 End;
End;

Begin
File1:=OpenFile(p_strFileName1);
Try
 File2:=OpenFile(p_strFileName2);
 Try
  Result:=File1._Size<>File2._Size;
  If Result Then Exit;
  p:=0;
  While True Do
   Begin
    If (p+BUF_SIZE)>File1._Size Then
     Begin
      Result:=Compare(p,File1._Size-p);
      Break;
     End Else
     Begin
      Result:=Compare(p,BUF_SIZE);
      If Not Result Then Break;
      Inc(p,BUF_SIZE);
     End;
   End;
 Finally
  CloseFile(File2);
 End;
Finally
 CloseFile(File1);
End;
End;