Help using sprintf, wanting to make 2 byte lengths and 4 byte lengths to hex string?

[jt]

Here is my code:

unsigned long listenip;
short tlen;

sprintf(tmp,"len:%x listenip:%x",htonl(tlen),listenip);

If the value on "tlen" is less than 2 bytes and the value on "listenip" is
less than 4 bytes, how can I make it fill with preciding 0 zeros?

Thanks,
JT

[baumann]

jt wrote:

Here is my code:

unsigned long listenip;
short tlen;

sprintf(tmp,"len:%x listenip:%x",htonl(tlen),listenip); since tlen is less than 2 bytes, you should use htons() instead.

sprintf(tmp,"len:%02x listenip:%04x",htonl(tlen),listenip);
above should work for your purpose.


If the value on "tlen" is less than 2 bytes and the value on "listenip" is less than 4 bytes, how can I make it fill with preciding 0 zeros?

Thanks,
JT

[Dave Thompson]

On 17 May 2005 18:03:40 -0700, "baumann@pan" <ba*********@gmail.com>
wrote:

jt wrote:

Here is my code:

unsigned long listenip;
short tlen;

sprintf(tmp,"len:%x listenip:%x",htonl(tlen),listenip); since tlen is less than 2 bytes, you should use htons() instead.

is _exactly_ 2 bytes, on "normal" systems with 8-bit byte and 16-bit
short, which is not absolutely everywhere but does include the places
sockets functions like these (and maybe Unix I/O in general) are
likely to be available and work as expected.
sprintf(tmp,"len:%02x listenip:%04x",htonl(tlen),listenip);
above should work for your purpose.

htons, as you said; and %04lx (ell ecks) for the listenip; x with no
modifier expects and prints unsigned int which can be as little as 16
bits (2 bytes) and is on some systems, at least one of them socketed.

- David.Thompson1 at worldnet.att.net

[Keith Thompson]

Dave Thompson <da*************@worldnet.att.net> writes:

On 17 May 2005 18:03:40 -0700, "baumann@pan" <ba*********@gmail.com>
wrote:

[...]

since tlen is less than 2 bytes, you should use htons() instead.

is _exactly_ 2 bytes, on "normal" systems with 8-bit byte and 16-bit
short, which is not absolutely everywhere but does include the placesn
sockets functions like these (and maybe Unix I/O in general) are
likely to be available and work as expected.

I've used Unix systems where short is 32 bits, and others where it's
64 bits (both Crays). Along with CHAR_BIT==8 and the lack of extended
integer types, this implies that there is no 16-bit integer type,
which makes some of the network stuff interesting (it uses bit
fields).

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.