Lazarus

Free Pascal => General => Topic started by: trn76 on October 30, 2020, 04:39:38 pm

Title: Alias / Absolute (avoid variants) inside Records?
Post by: trn76 on October 30, 2020, 04:39:38 pm

How can I use Alias / Absolute (avoid variant in records) inside Records? ...or some other neat solution, that would make my day now that I've had some more coffe'!

Code: Pascal  [Select][+][-]

1. ..
2.  
3. type
4.  
5.   Thead_info       = packed array [0..10-1] of cuchar;
6.   Thead_archive    = packed array [0..31-1] of cuchar;
7.   Thead_filename   = packed array [0..256-1] of cuchar;
8.   Thead_comment    = packed array [0..256-1] of cuchar;
9.  
10.   PPack = ^TPack;
11.   TPack = record
12.  
13.     crc           : cuint;
14.     sum           : cuint;
15.  
16.     pack_size     : cuint;
17.     unpack_size   : cuint;
18.  
19.     mode          : cint;
20.  
21.     year          : cuint;
22.     month         : cuint;
23.     day           : cuint;
24.     hour          : cuint;
25.     minute        : cuint;
26.     second        : cuint;
27.  
28.     attributes    : cuint8;
29.     //pack_mode     : cuint8;       // <--- replace this
30.  
31.     head_info     : Thead_info;
32.     head_archive  : Thead_archive;
33.     head_filename : Thead_filename;
34.     head_comment  : Thead_comment;
35.  
36.     total_pack    : cuint;
37.     total_unpack  : cuint;
38.     total_files   : cuint;
39.     merge_size    : cuint;
40.  
41.     filFile       : file;
42.     filName       : string;
43.     filError      : cuint;
44.     filList       : PStringArray;
45.  
46.     nodeList      : Pnode;
47.  
48.     pack_mode     : cuint8 absolute head_archive[11];    // <--- with this ?
49.  
50.   end;
51.  

Yes I could do this:

Code: Pascal  [Select][+][-]

1. procedure something;
2. var pack: TPack;
3.     mode: cuint8;
4. begin
5.   // access
6.   mode := pack.head_archive[11] and $1F;
7.   // but this is cleaner:
8.   mode := pack.pack_mode and $1F;
9. end;
10.  

...hope you get my drift :)

Title: Re: Alias / Absolute (avoid variants) inside Records?
Post by: ASerge on October 30, 2020, 06:44:45 pm

Code: Pascal  [Select][+][-]

1. {$MODE OBJFPC}
2. {$MODESWITCH ADVANCEDRECORDS}
3.  
4. type
5.   TheadArchive = array[0..31-1] of UInt8;
6.  
7.   TPack = record
8.   strict private
9.     function GetPackMode: UInt8; inline;
10.   public
11.     Attributes: Int8;
12.     HeadArchive: TheadArchive;
13.     filError: Cardinal;
14.     property PackMode: UInt8 read GetPackMode;
15.   end;
16.  
17. function TPack.GetPackMode: UInt8;
18. begin
19.   Result := HeadArchive[11];
20. end;
21.  
22. var
23.   Pack: TPack;
24.   Mode: UInt8;
25. begin
26.   Mode := Pack.HeadArchive[11] and $1F;
27.   Mode := Pack.PackMode and $1F;
28. end.

Code: ASM  [Select][+][-]

1. # [29] Mode := Pack.HeadArchive[11] and $1F;
2.         movw    U_$P$PROJECT1_$$_PACK+12(%rip),%ax
3.         andw    $31,%ax
4. # Var Mode located in register al
5. .Ll6:
6. # [30] Mode := Pack.PackMode and $1F;
7.         movw    U_$P$PROJECT1_$$_PACK+12(%rip),%ax
8.         andw    $31,%ax
9. # Var Mode located in register al

Title: Re: Alias / Absolute (avoid variants) inside Records?
Post by: bytebites on October 30, 2020, 06:48:53 pm

Code: Pascal  [Select][+][-]

1. {$ModeSwitch advancedrecords}  
2. type
3.      TPack = record
4. ....
5.       filError      : cuint;
6.       filList       : PStringArray;
7.  
8.       nodeList      : Pnode;
9.  
10.       //pack_mode     : cuint8; absolute head_archive[11];    // <--- with this ?
11.       function packmode:cuint8;
12.     end;
13.  
14. ...
15.  
16. function TPack.packmode: cuint8;
17. begin
18.   result:=pack_size and $1f;
19. end;  
20.  

Title: Re: Alias / Absolute (avoid variants) inside Records?
Post by: marcov on October 30, 2020, 07:16:14 pm

property packmode : cuint8 read head_archive[11];