Date: Mon, 28 May 2007 16:39:11 -0600
From: Michael Fuhr <mike@fuhr.org>
To: "Y. Ming Lam" <ymlam@rogers.com>
Cc: pgsql-interfaces@postgresql.org
Subject: Re: PQgetvalue failed to get non-text data under binary format
Message-ID: <20070528223911.GA66138@winnie.fuhr.org>
References: <46512118.2040105@rogers.com>
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In-Reply-To: <46512118.2040105@rogers.com>

On Mon, May 21, 2007 at 12:33:28AM -0400, Y. Ming Lam wrote:
> I am new to PostgreSQL and tried using the libpq C library.  I can read 
> a test table using PQgetvalue for text format, i.e. format = 0.  
> However, when I experiment with using binary output format, I was unable 
> to read anything else except result set fiend that is in char(x), 
> varchar(x), i.e., character string data.
[...]
> What I got is as follow:
> 
> + + + printing resultset, 2 rows, 8 columns
> id: 167772160 name: Amy Who salary: 0.000000
> id: 16777216 name: David Smith salary: 0.000000
> 
> Which supposed to return:
> id: 10 name: Amy Who salary: 150000.00
> id: 1  name: David Smith salary: 350000.00

For numeric types you'll need to convert binary values from network
byte order to host byte order (e.g., using ntohl() for 32-bit
values).  Notice that 167772160 = 0x0a000000 and 16777216 = 0x01000000,
which are the values you're expecting except for the reversed byte
order.

-- 
Michael Fuhr