#include <pthread.h>
#include <iostream>
#include <stdlib.h>


using namespace std;


#define BUFFER_LENGTH   10      // Buffer length
#define DELAY_RUNTIME   10      // Run-time of program (in seconds)
#define DELAY_PRODUCER  100000  // Delay for producer thread (in microseconds)
#define DELAY_CONSUMER  200000  // Delay for producer thread (in microseconds)
#define DELAY_ARITHM    200     // Delay for arithmetic operations (in microseconds)


int in = 0;                     // First empty slot
int out = 0;                    // First non-empty slot
int counter = 0;                // Number of items in queue
bool finish = false;


void print_queue( char *s );    // print the queue stored in the buffer
void *producer( void* );        // the producer thread
void *consumer( void* );        // the consumer thread
void inc( int &c );             // increment a variable
void dec( int &c );             // decrement a variable


int main( int argc, char *argv[] )
{
    pthread_t tid_prod; /* the producer thread identifier */
    pthread_t tid_cons; /* the consumer thread identifier */
    pthread_attr_t attr; /* set of attributes for the thread */


    /* get the default attributes */
    pthread_attr_init( &attr );

    print_queue( "strt" );

    /* create the thread */
    pthread_create( &tid_prod, &attr, producer, NULL );
    pthread_create( &tid_cons, &attr, consumer, NULL );

    sleep( DELAY_RUNTIME );
    finish = true;
    usleep( 100 );

    /* now wait for the thread to exit */
    pthread_cancel( tid_prod );
    pthread_cancel( tid_cons );

    return 0;
}  // main


void print_queue( char *s )
{
    int i;

    cout << s << ".  queue: ";
    /*if( in == out )
    {
        for( i = 0; i < BUFFER_LENGTH; i++ )
            cout << ".";
    }
    else */if( out < in || counter == 0 )
    {
        for( i = 0; i < out; ++i )
            cout << ".";
        for( i = out; i < in; ++i )
            cout << "X";
        for( i = in; i < BUFFER_LENGTH; ++i )
            cout << ".";
    }
    else
    {
        for( i = 0; i < in; ++i )
            cout << "X";
        for( i = in; i < out; ++i )
            cout << ".";
        for( i = out; i < BUFFER_LENGTH; ++i )
            cout << "X";
    }
    cout << "  in: " << in;
    cout << "  out: " << out;
    cout << "  nr of items: " << (in + BUFFER_LENGTH - out) % BUFFER_LENGTH;
    cout << "  counter: " << counter;
    cout << endl;
}  // print_queue


void *producer( void* arg )
{
    while( !finish )
    {
        while( counter == BUFFER_LENGTH )
        {}  // wait
        in = (in + 1) % BUFFER_LENGTH;
        inc( counter );
        print_queue( "prod" );
        usleep( DELAY_PRODUCER );
    }

    pthread_exit( 0 );
}  // producer


void *consumer( void *arg )
{
    while( !finish )
    {
        while( counter == 0 )
        {}  // wait
        out = (out + 1) % BUFFER_LENGTH;
        dec( counter );
        print_queue( "prod" );
        print_queue( "cons" );
        usleep( DELAY_CONSUMER );
    }

    pthread_exit( 0 );
}  // consumer


void inc( int &c )
{
    int tmp;

    tmp = c;
    tmp++;
    usleep( DELAY_ARITHM );
    c = tmp;
}


void dec( int &c )
{
    int tmp;

    tmp = c;
    tmp--;
    usleep( DELAY_ARITHM );
    c = tmp;
}