- Added messagepipe.c

- Added initial version of sicsget. This is a more generalised way of
  reading and writing SICS data wherever it is. The thing is extendable if
  reading something the current way is to slow. This has both a C interface
  and an interpreter interface.

messagepipe.c

@@ -0,0 +1,118 @@
+/**
+ * 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);
+    }
+  }
+}