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vringbuffer.c

/*
  Kjetil Matheussen, 2010.
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/



/*
  vringbuffer is convenient to use when sending data from a realtime
  thread to a non-realtime thread.
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>




/*
  Increaser:
    while true:
      if (ringbuffer_size(used)>...)
         buffer=my_calloc(1,sizeof(buffer))
         write_ringbuffer(free_new,buffer)
      sleep(...)
  ->
  Increaser:
    while true:
      if (ringbuffer_size(used)>...)
         buffer=my_calloc(1,sizeof(buffer))
         increase_vringbuffer(vringbuffer_t *vrb,1,&buffer)
      sleep(...)
 

  Disk:
    while true:
      buffer=read_ringbuffer(used)
      write_to_disk(buffer)
      write_ringbuffer(free_used,buffer)
  ->
  Disk:
    while true:
      buffer=read_vringbuffer(vringbuffer)
      write_to_disk(buffer)
      return_vringbuffer(vringbuffer,buffer)


  Process(data):
    if(ringbuffer_size(free_new)>0)
       buffer = read_ringbuffer(free_new)
    else
       buffer = read_ringbuffer(free_used)
    fill_buffer(buffer,data)
    write_ringbuffer(used,buffer)
  ->
  Process(data):
    buffer = read_vringbuffer(vringbuffer);
    fill_buffer(buffer,data);
    return_buffer(vringbuffer,buffer)
    

vringbuffer_t *vringbuffer_create (int num_elements_during_startup, int max_num_elements);

void  vringbuffer_increase        (vringbuffer_t *vrb, int num_elements, void **elements);

int   vrginbuffer_size            (vringbuffer_t *vrb);

void* vringbuffer_get_reading     (vringbuffer_t *vrb);
void  vringbuffer_return_reading  (vringbuffer_t *vrb, void *data);
int   vringbuffer_reading_size    (vringbuffer_t *vrb);

void* vringbuffer_get_writing     (vringbuffer_t *vrb);
void  vrginbuffer_return_writing  (vringbuffer_t *vrb, void *data);
int   vringbuffer_writing_size    (vringbuffer_t *vrb);
*/


#include "vringbuffer.h"


////////////////// Implementation ///////////////////////////////////


static void* my_malloc(size_t size1,size_t size2){
  size_t size=size1*size2;
  void* ret=malloc(size);
  if(ret==NULL){
    fprintf(stderr,"\nOut of memory. Try a smaller buffer.\n");
    return NULL;
  }

  // Touch all pages. (earlier all memory was nulled out, but that puts a strain on the memory bus)
  {
    long pagesize = sysconf(_SC_PAGESIZE);
    char *cret=ret;
    long i=0;
    for(i=0;i<size;i+=pagesize)
      cret[i]=0;
  }

  return ret;
}

static void sem_post_if_waiting(sem_t *sem){
  int semval;
  sem_getvalue(sem,&semval);
  if(semval<=0)
    sem_post(sem);
}



static bool vringbuffer_increase_writer1(vringbuffer_t *vrb,int num_elements,bool first_call){

  if(num_elements+vrb->curr_num_elements > vrb->max_num_elements)
    num_elements = vrb->max_num_elements - vrb->curr_num_elements;

  if(num_elements==0)
    return true;

  pthread_mutex_lock(&vrb->increase_lock);{
    int i;

    vringbuffer_list_t *element=my_malloc(1,sizeof(vringbuffer_list_t) + (num_elements*vrb->element_size));
    element->next=vrb->allocated_mem;
    vrb->allocated_mem=element;

    char *das_buffer=(char*)(element+1);
    
    if(das_buffer==NULL)
      return false;

    if(first_call){
      // Make sure at least a certain amount of the buffer is in a cache.
      // Might create a less shocking startup.
      int num=8;
      if(num>num_elements)
        num=num_elements;
      memset(das_buffer,0,num*vrb->element_size);
    }
    
      for(i=0;i<num_elements;i++){
        char *pointer =  das_buffer + (i*vrb->element_size);
        jack_ringbuffer_write(vrb->for_writer1,
                              (char*)&pointer,
                              sizeof(char*));
      }

      vrb->curr_num_elements += num_elements;

  }pthread_mutex_unlock(&vrb->increase_lock);
  
  return true;
}


vringbuffer_t* vringbuffer_create   (int num_elements_during_startup, int max_num_elements,size_t element_size){
  //fprintf(stderr,"Creating %d %d %d\n",num_elements_during_startup,max_num_elements,element_size);
  vringbuffer_t *vrb=calloc(1,sizeof(struct vringbuffer_t));

  vrb->for_writer1 = jack_ringbuffer_create(sizeof(void*) * max_num_elements);
  vrb->for_writer2 = jack_ringbuffer_create(sizeof(void*) * max_num_elements);
  vrb->for_reader  = jack_ringbuffer_create(sizeof(void*) * max_num_elements);

  vrb->element_size = element_size;
  vrb->max_num_elements = max_num_elements;

  vrb->please_stop=false;

  pthread_mutex_init(&vrb->increase_lock,NULL);

  if(vringbuffer_increase_writer1(vrb,num_elements_during_startup,true)==false)
    return NULL;

  return vrb;
}

void vringbuffer_stop_callbacks(vringbuffer_t* vrb){
  vrb->please_stop=true;

  if(vrb->autoincrease_callback!=NULL){
    sem_post(&vrb->autoincrease_trigger);
    pthread_join(vrb->autoincrease_thread, NULL);
    vrb->autoincrease_callback=NULL;
  }

  if(vrb->receiver_callback!=NULL){
    sem_post(&vrb->receiver_trigger);
    pthread_join(vrb->receiver_thread, NULL);
    vrb->receiver_callback=NULL;
  }
}

void vringbuffer_delete(vringbuffer_t* vrb){
  vringbuffer_stop_callbacks(vrb);

  while(vrb->allocated_mem!=NULL){
    vringbuffer_list_t *next=vrb->allocated_mem->next;
    free(vrb->allocated_mem);
    vrb->allocated_mem=next;
  }

  jack_ringbuffer_free(vrb->for_writer1);
  jack_ringbuffer_free(vrb->for_writer2);
  jack_ringbuffer_free(vrb->for_reader);

  free(vrb);
}


static void *autoincrease_func(void* arg){
  vringbuffer_t *vrb=arg;
  vrb->autoincrease_callback(vrb,true,0,0);
  sem_post(&vrb->autoincrease_started);
  while(vrb->please_stop==false){
    int reading_size = vringbuffer_reading_size(vrb);
    int writing_size = vringbuffer_writing_size(vrb);

    int num_new_elements = vrb->autoincrease_callback(vrb,false,reading_size,writing_size);
    if(num_new_elements>0)
      vringbuffer_increase_writer1(vrb,num_new_elements,false);

    if(vrb->autoincrease_interval==0)
      sem_wait(&vrb->autoincrease_trigger);
    else
      usleep(vrb->autoincrease_interval);
  }

  return NULL;
}


void vringbuffer_trigger_autoincrease_callback(vringbuffer_t *vrb){
  sem_post_if_waiting(&vrb->autoincrease_trigger);
}

void    vringbuffer_set_autoincrease_callback  (vringbuffer_t *vrb, Vringbuffer_autoincrease_callback callback, useconds_t interval){
  vrb->autoincrease_callback = callback;
  vrb->autoincrease_interval = interval;

  sem_init(&vrb->autoincrease_trigger,0,0);

  sem_init(&vrb->autoincrease_started,0,0);
  pthread_create(&vrb->autoincrease_thread, NULL, autoincrease_func, vrb);
  sem_wait(&vrb->autoincrease_started);
  
}

void  vringbuffer_increase          (vringbuffer_t *vrb, int num_elements, void **elements){
  if(num_elements+vrb->curr_num_elements > vrb->max_num_elements)
    num_elements = vrb->max_num_elements - vrb->curr_num_elements;

  if(num_elements==0)
    return;

  pthread_mutex_lock(&vrb->increase_lock);{
    jack_ringbuffer_write(vrb->for_writer1,(char*)elements,sizeof(void*) * num_elements);
    vrb->curr_num_elements += num_elements;
  }pthread_mutex_unlock(&vrb->increase_lock);
}


/* Non-realtime */

void* vringbuffer_get_reading       (vringbuffer_t *vrb){
  void *ret=NULL;
  jack_ringbuffer_read(vrb->for_reader,(char*)&ret,sizeof(void*));
  return ret;
}

void  vringbuffer_return_reading  (vringbuffer_t *vrb, void *data){
  jack_ringbuffer_write(vrb->for_writer2,(char*)&data,sizeof(void*));
}

int vringbuffer_reading_size    (vringbuffer_t *vrb){
  return (jack_ringbuffer_read_space(vrb->for_reader)/sizeof(void*));
}


static void *receiver_func(void* arg){
  vringbuffer_t *vrb=arg;
  vrb->receiver_callback(vrb,true,NULL);
  sem_post(&vrb->receiver_started);

  while(vrb->please_stop==false){
    sem_wait(&vrb->receiver_trigger);
    while(vringbuffer_reading_size(vrb) > 0){
      void *buffer=vringbuffer_get_reading(vrb);
      vrb->receiver_callback(vrb,false,buffer);
      vringbuffer_return_reading(vrb,buffer);
    }    
  }

  return NULL;
}

void vringbuffer_set_receiver_callback(vringbuffer_t *vrb,Vringbuffer_receiver_callback receiver_callback){
  vrb->receiver_callback=receiver_callback;

  sem_init(&vrb->receiver_trigger,0,0);

  sem_init(&vrb->receiver_started,0,0);
  pthread_create(&vrb->receiver_thread, NULL, receiver_func, vrb);
  sem_wait(&vrb->receiver_started);
}


/* Realtime */

void* vringbuffer_get_writing       (vringbuffer_t *vrb){
  void *ret=NULL;
  if(jack_ringbuffer_read(vrb->for_writer2,(char*)&ret,sizeof(void*))==0) // Checking writer2 first since that memory is more likely to already be in the cache.
    jack_ringbuffer_read(vrb->for_writer1,(char*)&ret,sizeof(void*));
  return ret;
}

void vringbuffer_return_writing     (vringbuffer_t *vrb, void *data){
  jack_ringbuffer_write(vrb->for_reader,(char*)&data,sizeof(void*));
  if(vrb->receiver_callback!=NULL)
    sem_post_if_waiting(&vrb->receiver_trigger);
}

int vringbuffer_writing_size  (vringbuffer_t *vrb){
  return
    (  (jack_ringbuffer_read_space(vrb->for_writer1) + jack_ringbuffer_read_space(vrb->for_writer2))
       / sizeof(void*));
}


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