how to organize my main file ?

[pereges]

By main file, I mean the one which contains the main routine. Can some
one please provide suggestions as to how I can improve the
organization of main file ? I have just though about a rough skeleton.

In my ray tracing project, I have to carry out following task (in
sequence)

1. Read the mesh from an ascii file and store it in the mesh data
structure.
2. Create a ray list and store it in a ray list.
3. Create the binary space partitioning tree for fast mesh traversal.
4. Trace all the rays and calculate the scattered and incident
electric fields.

I'm thinking of writing a function for every task.

#include "main.h"

static mesh *m; /* pointer to the mesh */
static bsptree *tree; /* pointer to the bsp tree */
static ray *raylist; /* pointer to the ray list */

/* function prototypes */

int read_mesh(char *);
int init_plane_wave (void);
int create_bsp_tree (void);
int calc_e_fields (void);
/* Provide the name of the ascii file(from which mesh is to be read)
as a command line argument eg. main sphere.dat */

int main(int argc char *argv[])
{
if(argc < 2)
{
fprintf(stderr, "Insufficie nt argumens\n");
return -1;
}

if(argc 2)
{
fprintf(stderr, "Too many arguments\n");
return -1;
}

if(read_mesh(ar gv[1])
return -1;
if(init_plane_w ave())
return -1;
if(create_bsp_t ree())
return -1;
if(calc_e_field s())
return -1;

return 0;
}

/* I decided to make the above data structures as static global
because they are needed throughout the program */

int read_mesh(char *filename)
{
FILE *fp;

fp = fopen(filename, "r");
if(fp == NULL)
{
fprintf(stderr, "Error while opening the file %s\n", filename);
return -1;
}
m = malloc(sizeof *m);
if(m == NULL)
{
fprintf(stderr, "Couldn't allocate memory for the mesh\n");
return -1;
}
/* parse_dat_file returns -1 if error occured while parsing file */
if(parse_dat_fi le(fp, &m))
return -1;
}

/* This function will initiailize the plane as in read the
specification related to a plane wave like frequency, electric field
at reference point, direction of the plane wave etc. It will allocate
memory for the ray list. After this it will call init_rays which
initializes a set of parallel rays. A plane wave is being simulated by
a dense grid of parallel rays */

int init_plane_wave (void)
{
...
...
}

/* This function will read the maximum allowable depth for the tree ,
allocate memory for it*/

int create_bsp_tree (void)
{

}

/* This function will call the raytrace function and after that it
will perform some calculations to find out the scattered and incident
electric fields */

int calc_e_fields (void)
{

}

[rahul]

On Jun 18, 9:25 am, pereges <Brol...@gmail. comwrote:

>
Can you please given an example of these three functions ? what are
they used for ? :

void (*trace) (const char *msg);
void (*err_warn ) (int err, int line, const char *msg);
void (*err_fatal) (int err, int line, const char *msg);

How to differentiate between a fatal error and a warning ?

Where did you get these functions? These functions are not there in
the Standard C Library.
<off-topic>
Richard Stevens have used similar functions in his Unix Network
Programming Books. May be you got these functions from there. When you
issue a warning, a diagnostic is sent to stderr or logged and the
process continues. In case of fatal errors, you display/log an error
message and the process terminates.
</off-topic>

[Richard Heathfield]

rahul said:

On Jun 18, 9:25 am, pereges <Brol...@gmail. comwrote:

>>
Can you please given an example of these three functions ? what are
they used for ? :

void (*trace) (const char *msg);
void (*err_warn ) (int err, int line, const char *msg);
void (*err_fatal) (int err, int line, const char *msg);

How to differentiate between a fatal error and a warning ?

Where did you get these functions?

Nowhere. They're not functions. They're function pointers.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[santosh]

pereges wrote:

<snip>

Can you please given an example of these three functions ? what are
they used for ? :

void (*trace) (const char *msg);

I guess that this is used to print a backtrace, preceded by the
customised message.

void (*err_warn ) (int err, int line, const char *msg);

This is to print a warning - the line where it occured, and the text
pointed by 'msg', with perhaps other information. You might call it
like this:

err_warn(errno, __LINE__, "Custom message.");

void (*err_fatal) (int err, int line, const char *msg);

Same as above except that it should terminate the program (or call a
function that does so) after printing the diagnostics.

How to differentiate between a fatal error and a warning ?

That's context specific. Generally failure to obtain critical resources
like files and memory are fatal, while things like network packet loss,
or failure of a non-essential component could just be regarded as
insufficient to terminate the program. In general any exception after
which you can still proceed with all or most of the functionality of
the program intact can be just a "warning" while a fatal error is one
that forces you to stop.

[Richard Heathfield]

santosh said:

pereges wrote:

<snip>

>Can you please given an example of these three functions ? what are
they used for ? :

void (*trace) (const char *msg);

I guess that this is used to print a backtrace, preceded by the
customised message.

You're sure it isn't used to point at a function, then?

(Ditto, twice, for the other two.)

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Herbert Rosenau]

On Tue, 17 Jun 2008 16:33:24 UTC, pereges <Br*****@gmail. comwrote:

Note that a -1 return value from main isn't guaranteed to be

meaningful,

whereas EXIT_FAILURE is.

Why ?

That is because the standard requests it.

I have seen that everytime a C program fails, the process returns some
non zero value(Pelles C compiler reports this). So what is wrong in
returning -1 ? Is this only applicable to main function or others as
well ? I usually use

#define SUCCESS 0
#define FAILURE -1

as return values for functions other than main.

main() is the interface between the system that is calling your
program. So the standard tries to give you and any system that is able
to run programs written in C rules for the interface, that is
1. how to give parameters to the program at startup
2. values allowed to return to the system

There are systems on the maret who may fail miserably when main() or
exit() returns other values than 0 or EXIT_FAIlTURE.

I know of some systems that gets confused when main() or exit() tries
to return an int outside the range 0-255, even as they accept any
value inside that value, extending the C standard with system
dependant wider range. But the system will go into undefinded behavior
by receiving a value outside 0-255 in from main()/exit().

On other hand it is complete on you to define each and any value a
function you've ritten can return. So the function can return 42 for
success and 0 for failture or a pointer to a a data type its prototype
defines or something else you means it is the ideal value.

So there are only specified values for the external interface:

The name is main. It returns int with only 2 allowed values and owns 2
different groups of parameters where
group 1 defines zero parameters (VOID)
group 2 defines exactly 2 parameters in defined sequence
first parameter: int argc - the number of parameters given
second parameter: char **argv - an array of pointers to
strings
wheras argv[0] is either NULL or the name of the progrsm
and argv[argc] is always NULL
The names of the parameter are commonly used but not really
defined.
--
Tschau/Bye
Herbert

Visit http://www.ecomstation.de the home of german eComStation
eComStation 1.2R Deutsch ist da!

[CBFalconer]

Tor Rustad wrote:

>

.... snip ...

>
So, this would be my initial main:

#include <stdio.h>
#include "ray_track. h"

int main(int argc, char *argv[])
{
struct ray_track rt;

ray_open( &rt, argc, argv);
ray_fload_mesh( &rt, fname_mesh);
ray_create_rayl ist (&rt);
ray_create_bsp_ three(&rt);
ray_calc_scatte ring (&rt);
ray_close(&rt);

return EXIT_SUCCESS;
}

I hope not. You have not included stdlib.h, for EXIT_SUCCESS.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
** Posted from http://www.teranews.com **

[santosh]

Herbert Rosenau wrote:

<snip>

main() is the interface between the system that is calling your
program. So the standard tries to give you and any system that is able
to run programs written in C rules for the interface, that is
1. how to give parameters to the program at startup
2. values allowed to return to the system

[ ... ]

The name is main. It returns int with only 2 allowed values [ ... ]

Actually three viz. 0, EXIT_SUCCESS and EXIT_FAILURE.

<snip>

[Tor Rustad]

CBFalconer wrote:

[...]

I hope not. You have not included stdlib.h, for EXIT_SUCCESS.

Yeah, it's a good idea to compile the initial skeleton!

That exercise was left for the student... ;)

--
Tor <bw****@wvtqvm. vw | tr i-za-h a-z>

[pereges]

I'm thinking of declare m, tree, raylist as extern variables in
common.h. Now, I have heard a lot of arguments against extern but what
if its done *properly* ?Well these data structures are frequently
needed in many functions, and continously passing them everywhere is
extermely painful even when they are hardly used in a function. It has
made my code extermely obfuscated, difficult to read, too many
arguments in a function and probably even slower in cases where
recursive functions are used. Let's say mesh *m is passed to a
recursive function. Then in that case, for all the calls a seperate
copy of m will be maintained even if m was utilized in probably 1
statement. Apart from this during the error handling, it is quite easy
to call the killall function from any where in the program where the
error occured and free the data structures allocated upto that point.
No need to pass any parameters.

eg :

void killall()
{
if(m != NULL)
killlmesh();
if(tree != NULL)
killtree();
if(raylist != NULL)
killraylist();
}

[vippstar]

On Jun 18, 7:18 pm, "Herbert Rosenau" <[e-mail] :

On Tue, 17 Jun 2008 16:33:24 UTC, pereges <Brol...@gmail. comwrote:

Note that a -1 return value from main isn't guaranteed to be

meaningful,

whereas EXIT_FAILURE is.

Why ?

That is because the standard requests it.

I have seen that everytime a C program fails, the process returns some
non zero value(Pelles C compiler reports this). So what is wrong in
returning -1 ? Is this only applicable to main function or others as
well ? I usually use

#define SUCCESS 0
#define FAILURE -1

as return values for functions other than main.

main() is the interface between the system that is calling your
program. So the standard tries to give you and any system that is able
to run programs written in C rules for the interface, that is
1. how to give parameters to the program at startup
2. values allowed to return to the system

There are systems on the maret who may fail miserably when main() or
exit() returns other values than 0 or EXIT_FAIlTURE.

And EXIT_SUCCESS. Actually I don't think they will fail miserably. I
believe the standard says that simply it's not guaranteed that a
meaningful value will be returned to the caller.