Byte Array redux

0

I am continuing to experiment with the coding patterns used in my numerics dll project and releasing TForge 0.60.

First of all TForge is a modern cryptographic library for Delphi and Lazarus/FPC (which I am currently working on) implemented as a set of runtime packages. The current release contains only one package (also named TForge); it is core package of the whole TForge project and is required by other packages (to be released later).

The purpose of the release is to introduce a new type – ByteArray; the type is an enhanced version of the standard RTL TBytes type. If you want to test the ByteArray you need to build tforge package; the release containes tforge packages for Delphi XE and Lazarus.

The release includes ByteArrayDemo console application which demonstrates functionality of the ByteArray type. For example, you can concatenate byte arrays:

var
  A1, A2: ByteArray;

begin
  A1:= ByteArray(1);
  A2:= TBytes.Create(2, 3, 4);
  Writeln('A1 + A2 = ', (A1 + A2).ToString); // 1, 2, 3, 4

perform bitwise boolean operations (xor is most useful):

var
  A1, A2: ByteArray;

begin
  A1:= ByteArray(1);
  A2:= TBytes.Create(2, 3, 4);
  Writeln('A1 xor A2 = ', (A1 xor A2).ToString); // 3 (= 1 xor 2, min array length used)

use fluent coding style (which appears to be very handy once one gets accustomed to it):

begin
  Writeln(ByteArray.FromText('ABCDEFGHIJ').Insert(3,
    ByteArray.FromText(' 123 ')).Reverse.ToText); // JIHGFED 321 CBA

and so on. It was fun to code ByteArray; I am using it more and more now as a TBytes replacement because of better usability.

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Why PDWORD is not a pointer to DWORD

2

Once upon a time the Delphi team lead decided that Delphi should contain declarations of C++ types like unsigned long for the sake of better C++ compatibility. So he has written

type
  CppULongInt = LongWord;

No, that is not good thought the team lead. Delphi’s LongWord is a 32-bit type while the C++’s unsigned long is a platform-dependent type. So let us declare CppULongInt as a distinct type instead of an alias type:

type
  CppULongInt = type LongWord;

That is better. Now how about DWORD type? It is declared in Windows headers as

  typedef unsigned long       DWORD;

So for compatibility sake we will declare DWORD as

type
  DWORD = CppULongInt;

Great, thought the Delphi team lead. He call two juniors (let us call them DevA and DevB) and said:

DevA, create a branch (BranchA) in the Delphi project, declare type DWORD = CppULongInt; and fix all bugs that may appear after;
DevB, create a branch (BranchB) in the Delphi project, declare type PDWORD = ^CppULongInt; and fix all bugs that may appear after;

After you both are ready we will merge the branches and declare PDWORD type as it should be:

type
  PDWORD = ^DWORD;

In a due time the happy DevB came to the Delphi team lead and said: “I did everything as you said Sir!. Now type DWORD = CppULongInt;, and everything is fine!”.

But the second guy DevA was not happy. He said: “Sir, we have tons of code like that:

procedure Foo(var Value: DWord);
begin
  Value:= 0;
end;

var
  D: Longword;

begin
  Foo(D);

If I declare

type
  DWORD = CppULongInt;

Then it does not compile. What should I do?”

-“Nothing”, said the Delphi team lead. “The BranchB will be the main trunk now”.

Disclaimer: the tale was written after reading this SO question