Converting C struct to Perl

[kardon33]

Hi i didnt know to post this into the C threads or Perl but what i need is to convert the comand: (typedef struct {}) in C to somthing that does the same thing in Perl.

[kardon33]

I have 2 pieces of code that i do not know what it means. Could someone please explain what it is saying and if anyone could could you show me a way to do it in PERL?

#ifndef _ARTNET_H_
#define _ARTNET_H_

#define uchar unsigned char
#define ushort unsigned short int
#define ulong unsigned int

[miller]

Give us the full command or piece of code that you're trying to convert.

- Miller

[RedSon]

I have 2 pieces of code that i do not know what it means. Could someone please explain what it is saying and if anyone could could you show me a way to do it in PERL?

#ifndef _ARTNET_H_
#define _ARTNET_H_

#define uchar unsigned char
#define ushort unsigned short int
#define ulong unsigned int

The first two lines can be read as "if _ARTNET_H_ is not defined then define _ARTNET_H_"

The second line can be read as "define uchar as a synonym to unsigned char" and "define ushort to be a synonym to unsigned short int" and "define ulong to be a synonym to unsigned int".

As for a PERL interpretation you will have to ask the PERL forum. Or I can just move this post over there.

[kardon33]

ok thanks that helps alot.

[RedSon]

Merge me !

[kardon33]

typedef struct {
    uchar IP[4];    // IP address
    ushort Port;    // UDP port    BYTE-SWAPPED MANUALLY
} T_Addr;

[kardon33]

#define uchar unsigned char
#define ushort unsigned short int
#define ulong unsigned int
 
typedef struct S_ArtDmx {
    uchar ID[8];                
    ushort OpCode;                  
    uchar VersionH;               
    uchar Version;                  
    uchar Sequence;            
    uchar Physical;               
    ushort Universe;             
    ushort Length;            
    uchar Data[MaxDataLength];
} T_ArtDmx;

Could some one help me convert that to PERL?

[miller]

If you're just creating is a struct, then the perl equivalent would be a hash. If you're sending this information over the net and need to receive it, then you're going to need pack and unpack.

- Miller

[kardon33]

Ok thank you that helps, but one question what is the diffrence between hash and pack/unpack

[KevinADC]

Ok thank you that helps, but one question what is the diffrence between hash and pack/unpack

a hash (in perl) is essentially an array, pack/unpack are functions.

[kardon33]

If you're just creating is a struct, then the perl equivalent would be a hash. If you're sending this information over the net and need to receive it, then you're going to need pack and unpack.

- Miller

You say i need to use pack if i am going to be sending the info over the net, well could you explain to me that why i could not use hash over the net to send it?

[kardon33]

I think i have the idea to the pack and unpack functions i am using but it still is not working write. First here is the code i need to transfer to PERL.

#define uchar unsigned char
#define ushort unsigned short int
#define ulong unsigned int

Im at the understanding that is saying i need to define the varible uchar and the others as an unsigned char. In PERL i think i do that by using pack with the C operator so the code i have looks like,

$uchar = "2131Adam2113";
pack 'C', $uchar;
print $uchar;

But for some reason i get the output of 2131Adam2113 instead of just char like Adam???

[miller]

A hash is an perl internal data structure. It's essentially just an associative array.

Whenever you send a C struct across the net, it often must be serialized in some way. And then the receiving end must decrypt the serialization and turn it back into a C struct.

pack and unpack are the functions that are most often used to serialize data in perl for network programming.

- Miller

[kardon33]

thanks i actually just found that out before u replied.