Bit-packed structure (record) in Free Pascal and Delphi

Submitted by st on Sat, 19/12/2015 - 11:58

Here is the code explaining some methods to pack bit accessing logic in your program.

program project1;
 
type
  TRec1 = packed record // Doesn't pack at all
    b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16: boolean;
  end;
 
  TRec2 = bitpacked record // Free Pascal specific
    b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16: boolean;
  end;
 
  TRecByte = (b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16);
  TRecBytes = set of TRecByte;
var
  r1: TRec1;
  r2: TRec2;
  s1: TRecBytes;

Programming

Delphi |
Free Pascal

Interface implementations and multiple inheritance in C++

Submitted by st on Sat, 30/05/2015 - 12:02

Multiple inheritance of interfaces which are pure abstract classes indeed is not a problem until you need to use the interface implementation in other classes.

Suppose there are two interfaces, the implementation of which will be used in other classes.

Programming

Free Pascal: call stack and procedures names at runtime

Submitted by st on Wed, 27/05/2015 - 11:37

Here is an example how to get N-2 calling procedure information.

Warning: code seeking debugging info is slow so be aware to use it in loops.

Make sure to compile with following options:

Programming

Free Pascal

Crack C# namespaces in 30 seconds

Submitted by st on Mon, 20/04/2015 - 15:58

The namespaces conception in C# seems to be exhaustive and insufficient at the same time compared with a strong module notation in Oberon-2 and even with a modular programming approaches in Free Pascal/Delphi.

Why insufficient? You cannot declare constants and functions within namespaces but you should add a class with constant field or static method for it.

Why exhaustive? The using directive with such introduced classes is the source of unexpected errors. Here is an example below.

Programming

FGL extension for FPC 2.6.4

Submitted by st on Thu, 09/04/2015 - 11:17

As Free Pascal 2.6.4 distribution does not include generic tree implementation (there are some limitation of compiler), I use my own named FGLExt for different purposes.

Here are 2 files in repository:

Programming

Free Pascal

Firebird: bulk insert and bulk export

Submitted by st on Fri, 02/08/2013 - 16:50

Firebird doesn't support INSERT BULK command or bcp.exe utility. But the external tables can be a good replacement. Simple example is below.

Check that firebird.conf file allow to create external tables. Write or uncomment line like

ExternalFileAccess = Full

Programming

Firebird

Delphi / Free Pascal: very simple "old school" mutex

Submitted by st on Mon, 22/07/2013 - 16:28

The code below show how to implement very simple but cross-platform "old school" mutex (mutually exclusive semaphore)

Programming

Delphi |
Free Pascal

Nullables in Free Pascal and Delphi

Submitted by st on Wed, 30/01/2013 - 00:44

An example of generic implementation of nullable value types in FreePascal (easy to adapt for Delphi).

Programming

Delphi |
Free Pascal

Fast inserting a file into a table

Submitted by st on Sat, 01/12/2012 - 11:15

How to insert fast a file (i.e. binary one) from disk to a SQL Server table?

Certainly the SQL Server account should have a corresponding permissions to access the file on the disk. For example I take the file C:\WINDOWS\system32\oembios.bin having the size about 12 MB. For really big files you'd better switch to the FILESTREAM approach.

Programming

SQL Server

SQL: generate date/time series

Submitted by st on Fri, 27/04/2012 - 20:31

There are many examples of user defined table functions generating the series of dates(times) between two specified values. Usually, in OLAP you can see a table filled by the date/time series, too. Such table avoid to generate the values "on the fly".

However, in some cases you may be unable to use an UDF or a table. Fortunately, "pure SQL" method still works.

Suppose, the start and finish dates are specified as entry parameters. The transact SQL code below generates the series "moth by month".

Programming

Programming