Thread: Consumer program

Hi everyone, iam working on this program called consumer.c

This program is to demonstrate a modified version of the classical Producer/Consumer problem. This problem is as follows:

There is a store where both Workers (Producers) and Customers
(Consumers) exist. There is a cabinet in this store which all people can
access. However, when one person is using the cabinet, no one else can.

Workers produce objects to place within the cabinet, while Customers
buy those objects, thus removing them. If there is nothing in the
cabinet, then the Customer must wait until a Worker has created an object
and placed that object into the cabinet. However, if the cabinet is full,
then the Worker must wait until an object is bought before he/she can
restock the cabinet.

How can we simulate this behavior?
This are some errors i have so far, can you guys tell me if i am in the right direction. I hope i am but right now i am having some problems this are the errors i get (thanks you for your help):

Code:

user@linux-p3nb:~/program> gcc -o consumer consumer.c
consumer.c: In function ‘producer’:
consumer.c:6: error: ‘item’ undeclared (first use in this function)
consumer.c:6: error: (Each undeclared identifier is reported only once
consumer.c:6: error: for each function it appears in.)
consumer.c:7: error: expected ‘while’ before ‘wait’
consumer.c:8: error: ‘mutex’ undeclared (first use in this function)
consumer.c:11: error: ‘full’ undeclared (first use in this function)
consumer.c: In function ‘consumer’:
consumer.c:17: error: ‘full’ undeclared (first use in this function)
consumer.c:18: error: expected ‘while’ before ‘wait’
consumer.c:19: error: ‘item’ undeclared (first use in this function)
consumer.c:20: error: ‘mutex’ undeclared (first use in this function)
consumer.c:21: error: ‘empty’ undeclared (first use in this function)
consumer.c: At top level:
consumer.c:26: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘event_counter’
consumer.c:39: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘in’
consumer.c:41: error: redefinition of ‘producer’
consumer.c:4: error: previous definition of ‘producer’ was here
consumer.c: In function ‘producer’:
consumer.c:42: error: expected declaration specifiers or ‘...’ before numeric constant
consumer.c:44: error: ‘item’ undeclared (first use in this function)
consumer.c:45: error: expected ‘while’ before ‘sequence’
consumer.c:46: error: ‘out’ undeclared (first use in this function)
consumer.c:46: error: ‘num_buffers’ undeclared (first use in this function)
consumer.c:48: error: ‘in’ undeclared (first use in this function)
consumer.c: At top level:
consumer.c:52: error: redefinition of ‘consumer’
consumer.c:15: error: previous definition of ‘consumer’ was here
consumer.c: In function ‘consumer’:
consumer.c:53: error: expected declaration specifiers or ‘...’ before numeric constant
consumer.c:55: error: invalid lvalue in increment
consumer.c:56: error: expected ‘while’ before ‘in’
consumer.c:57: error: ‘item’ undeclared (first use in this function)
consumer.c:58: error: ‘out’ undeclared (first use in this function)
consumer.c:61:2: warning: no newline at end of file
user@linux-p3nb:~/program>

I am new to c programming and i got this example from a book and iam trying to get it running so it can be the base of my program. The problem is that i want to be sure of what iam doing and understanding it. I think the problem that i currently have is in the functions i have to declare the variables outside main or something... so that the functions can be read. Help me out please. Thanks for your help.

this is my code:

Code:

#include<stdio.h>

void producer ( void )
{
do
produce ( item );
wait ( empty ); // empty is semaphore
wait ( mutex ); // mutex is semaphore
put ( item );
signal ( mutex );
signal ( full );
while ( 1 );
}
void consumer ( void )
{
do
wait ( full );
wait ( mutex );
remove ( item );
signal ( mutex );
signal ( empty );
consume ( item );
while ( 1 );
}

class event_counter
{
int ec; // Event counter
public:
event_counter ( void ) // Default constructor
{
ec = 0;
}
int read ( void ) const { return ( ec ); }
void advance ( void ) { ec++; }
void await ( const int v ) { while ( ec < v ); }
};

extern event_counter in, out; // Shared event counters
void producer ( void )
{
int sequence ( 0 );
do
produce ( item );
sequence++;
out.await ( sequence - num_buffers );
put ( item );
in.advance();
while ( 1 );
}
void consumer ( void )
{
int sequence ( 0 );
do
sequence++;
in.await ( sequence );
remove ( item );
out.advance();
consume ( item );
while ( 1 );
}

So where is
- the indentation
- a whole bunch of { } around blocks of statements

Just another "write the whole thing and dump it on a message board for some other sap to fix" post.

Write it in small amounts and compile often. Then it will tell you you're screwing up when you've only made a few mistakes rather than a whole lot of mistakes.

Iam doing this program in C, and now i have broken it up into a smaller program.

Code:

 
#include<stdio.h>

int main()
{

	void producer ( void )
	{
	do
	produce ( item );
	wait ( empty ); // empty is semaphore
	wait ( mutex ); // mutex is semaphore
	put ( item );
	signal ( mutex );
	signal ( full );
	while ( 1 );
	}
	
	class event_counter
	{
	int ec; // Event counter
	public:
	event_counter ( void ) // Default constructor
	{
	ec = 0;
	}
	int read ( void ) const { return ( ec ); }
	void advance ( void ) { ec++; }
	void await ( const int v ) { while ( ec < v ); }
	};

	extern event_counter in, out; // Shared event counters
	void producer ( void )
	{
	int sequence ( 0 );
	do
	produce ( item );
	sequence++;
	out.await ( sequence - num_buffers );
	put ( item );
	in.advance();
	while ( 1 );
	}	

}

this are my errors, what is wrong and how can i fix it?

Code:

consumer.c:2: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘wait’
consumer.c: In function ‘producer’:
consumer.c:10: error: ‘item’ undeclared (first use in this function)
consumer.c:10: error: (Each undeclared identifier is reported only once
consumer.c:10: error: for each function it appears in.)
consumer.c:11: error: expected ‘while’ before ‘wait’
consumer.c:12: error: ‘mutex’ undeclared (first use in this function)
consumer.c:15: error: ‘full’ undeclared (first use in this function)
consumer.c: In function ‘consumer’:
consumer.c:21: error: ‘full’ undeclared (first use in this function)
consumer.c:22: error: expected ‘while’ before ‘wait’
consumer.c:23: error: ‘item’ undeclared (first use in this function)
consumer.c:24: error: ‘mutex’ undeclared (first use in this function)
consumer.c:25: error: ‘empty’ undeclared (first use in this function)
consumer.c: In function ‘main’:
consumer.c:30: error: ‘class’ undeclared (first use in this function)
consumer.c:30: error: expected ‘;’ before ‘event_counter’
consumer.c:43: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘in’
consumer.c:43: error: ‘in’ undeclared (first use in this function)
consumer.c:43: error: ‘out’ undeclared (first use in this function)
consumer.c:56: error: redefinition of ‘consumer’
consumer.c:19: error: previous definition of ‘consumer’ was here
consumer.c: In function ‘consumer’:
consumer.c:57: error: expected declaration specifiers or ‘...’ before numeric constant
consumer.c:59: error: invalid lvalue in increment
consumer.c:60: error: expected ‘while’ before ‘in’
consumer.c:61: error: ‘item’ undeclared (first use in this function)
consumer.c:66:2: warning: no newline at end of file

Use more indent levels

Code:

void producer ( void )
{
	do {
	produce ( item );
	wait ( empty ); // empty is semaphore
	wait ( mutex ); // mutex is semaphore
	put ( item );
	signal ( mutex );
	signal ( full );
	} while ( 1 );
}

Extra { } in red.
Also, functions must be declared outside other functions.

Start a new file with just a blank main() and compile it.
Then add ONE function to it and compile again. DO NOT add more code until that first one compiles OK.
Add each remaining function in turn until you have the whole code, which compiles.

Thanks for your help. Iam only working with the function as you sayed, iam getting some errors... can you guys help me out.

Code:

#include<stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>

int main()

{
	void producer ( void )
  {
	do 
	produce ( item );
	wait ( empty ); // empty is semaphore
	wait ( mutex ); // mutex is semaphore
	put ( item );
	signal ( mutex );
	signal ( full );
         while ( 1 );
  }
}

Code:

part1.c: In function ‘producer’:
part1.c:12: error: ‘item’ undeclared (first use in this function)
part1.c:12: error: (Each undeclared identifier is reported only once
part1.c:12: error: for each function it appears in.)
part1.c:13: error: expected ‘while’ before ‘wait’
part1.c:14: error: ‘mutex’ undeclared (first use in this function)
part1.c:16: error: too few arguments to function ‘signal’
part1.c:17: error: ‘full’ undeclared (first use in this function)
part1.c:17: error: too few arguments to function ‘signal’

When did you come over all helpless (see your previous posts).
I mean, you managed to declare variables before using them, write functions etc etc.

This is just pseudo-code slapped into a compiler!

Just read the damn error messages and pay attention.