Pthread producer consumer example in C

This code creates two threads then passes data from one to the other in sequence. To compile, save the code as main.c (or whatever you want) and then use the command:

 gcc -lpthread main.c -o main 

or you can create a make file containing the lines:

main: main.c      gcc -lpthread main.c -o main

You can then just use the command “make” to compile the code, this is useful if you want to change the program thus needing to compile it multiple times.

/*pthread example. Copyright (c) 2006-2007 Richard Palethorpe  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE  Website: richiejp.wordpress.com email: richiejp@gmail.com*/  #include  #include  #include   void* producer(void*); void* consumer(void*);  /*This data structure contains information that needs to be shared between threads. It is passed to the producer and consumer threads' starter functions. The alternative to this is to use global variables.*/ struct Context{         pthread_cond_t* cond;         pthread_mutex_t* mutex;         /*This is used to hold a character while it is passed from one thread to         another. Only the thread which owns the mutex lock should access it.*/         char holder;         int error; };  int main(){         volatile struct Context context;         context.cond = (pthread_cond_t*)malloc(sizeof(pthread_cond_t));         context.mutex = (pthread_mutex_t*)malloc(sizeof(pthread_mutex_t));         context.error = 0;          pthread_cond_init(context.cond, NULL);         pthread_mutex_init(context.mutex, NULL);          pthread_t prod;         pthread_t cons;          puts("createing first thread");         if(pthread_create(&prod, NULL, producer, (void*)&context) != 0){                 puts("Could not create producer thread");                  pthread_mutex_destroy(context.mutex);                 pthread_cond_destroy(context.cond);                  return(EXIT_FAILURE);         }          puts("createing second thread");         if(pthread_create(&cons, NULL, consumer, (void*)&context) != 0){                 puts("Could not create consumer thread");                  pthread_mutex_lock(context.mutex);                 context.error = 1;                 pthread_mutex_unlock(context.mutex);                 pthread_cond_signal(context.cond);                  pthread_join(prod, NULL);                  pthread_mutex_destroy(context.mutex);                 pthread_cond_destroy(context.cond);;                  return(EXIT_FAILURE);         }          pthread_join(prod, NULL);         pthread_join(cons, NULL);          pthread_mutex_destroy(context.mutex);         pthread_cond_destroy(context.cond);          free(context.cond);         free(context.mutex);          return(EXIT_SUCCESS); }  void* producer(void* _context){         puts("in producer");         struct Context* context = (struct Context*)_context;          char data[] = "Some data to send to the consumer\n";          pthread_mutex_lock(context->mutex);         int i;         for(i = 0; i  sizeof data; i++){                 if(!context->error){                         context->holder = data[i];                          pthread_cond_signal(context->cond);                         pthread_cond_wait(context->cond, context->mutex);                 }else{                         pthread_mutex_unlock(context->mutex);                          return NULL;                 }         }          pthread_cond_signal(context->cond);         pthread_mutex_unlock(context->mutex);          return NULL; }  void* consumer(void* _context){         puts("in consumer");         struct Context* context = (struct Context*)_context;          printf("Recieving data: ");           pthread_mutex_lock(context->mutex);         while(context->holder != ''){                 if(!context->error){                         putc((unsigned int)context->holder, stdout);                          pthread_cond_signal(context->cond);                         pthread_cond_wait(context->cond, context->mutex);                 }else{                         pthread_cond_signal(context->cond);                         pthread_mutex_unlock(context->mutex);                          return NULL;                 }         }          pthread_cond_signal(context->cond);         pthread_mutex_unlock(context->mutex);          return NULL; }