sics/messagepipe.c

/**
 * An implementation for a message pipe system as described in
 * 
 * http://eventuallyconsistent.net/2013/08/14/messaging-as-a-programming-model-part-2/
 *
 * A message is passed through a series of filter routines which do things.
 *
 * Rather then loops I try using recursion here.
 *
 * copyright: GPL Copyleft
 *
 * Mark Koennecke, November 2013
 */
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <messagepipe.h>

/*--------------------------------------------------------------------------------*/
typedef struct __MessagePipe {
  void *userData;
  mpUserKill killFunc;
  mpFilterFunc filterFunc;
  struct __MessagePipe *next;
  struct __MessagePipe *previous;
} MessagePipe;
/*--------------------------------------------------------------------------------*/
static int EmptyFunc(void *message, void *userData)
{
  return MPCONTINUE;
}
/*---------------------------------------------------------------------------------*/
pMP MakeMP()
{
  pMP result = NULL;

  result = malloc(sizeof(MessagePipe));
  if(result != NULL){
    memset(result,0,sizeof(MessagePipe));
    result->filterFunc = EmptyFunc;
  }
  return result;
}
/*---------------------------------------------------------------------------------*/
void KillMP(pMP self)
{
  if(self == NULL){
    return;
  }

  pMP next = self->next;
  if(self->userData != NULL && self->killFunc != NULL){
    self->killFunc(self->userData);
  }
  free(self);
  KillMP(next);
}
/*-----------------------------------------------------------------------------------*/
int AppendMPFilter(pMP self, mpFilterFunc func, void *userData, mpUserKill usKill)
{
  assert(self != NULL);
  assert(func != NULL);

  if(self->next == NULL){
    self->next = malloc(sizeof(MessagePipe));
    if(self->next != NULL){
      self->next->previous = self;
      self->next->next = NULL;
      self->next->userData = userData;
      self->next->killFunc = usKill;
      self->next->filterFunc = func;
      return 0;
    } else {
      return 1;
    }
  } else {
    return AppendMPFilter(self->next, func, userData, usKill);
  }
}
/*-----------------------------------------------------------------------------------*/
pMP PrependMPFilter(pMP self, mpFilterFunc func, void *userData, mpUserKill usKill)
{
  pMP result = NULL;

  assert(func != NULL);

  result = malloc(sizeof(MessagePipe));
  if(result != NULL){
    result->userData = userData;
    result->killFunc = usKill;
    result->filterFunc = func;
    result->next = self;
    result->previous  = NULL;
    return result;
  } else {
    /*
      we are ignoring an error here.........
    */
    return self;
  }
}

/*-----------------------------------------------------------------------------------*/
int MPprocess(pMP self, void *message)
{
  int status;

  if(self == NULL || self->filterFunc == NULL){
    return MPCONTINUE;
  } else {
    status = self->filterFunc(message, self->userData);
    if(status == MPSTOP){
      return status;
    } else {
      return MPprocess(self->next, message);
    }
  }
}