Re: Variable length custom data types help

Thank you for your response! That was quite enlightening.

Just to clarify in the example foo structure below where the first
member is the length, and then you say /*rest of structure here*/, by
that do you mean the individual data members of the structure that will
be in my array of strucs? I guess it can't be a pointer to the array as
you said postgres will not know that you are storing pointers. If so
that means you have a bit of wasted overhead right? I think I will just
try creating the pointer as void*, set the first 4 bytes to the length,
and then fill in the rest.

Seriously, that was an extremely helpful post!

Thanks,
Morgan

-----Original Message-----
From: Michael Fuhr [mailto:mike(at)fuhr(dot)org]
Sent: Thursday, March 31, 2005 11:17 PM
To: Morgan Kita
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: [NOVICE] Variable length custom data types help

The usual way is to create a structure:

typedef struct foo {
int32 total_length;
/* rest of structure here */
} foo;

What follows the length is irrelevant to PostgreSQL, so define it
however makes sense in your code. Just make sure that all data is
in a contiguous chunk of memory that begins with the 4-byte length
(don't embed pointers in the data, because PostgreSQL won't know
anything about them).