Initial revision

costa.w

@@ -0,0 +1,68 @@
+\subsection{The Command Stack}
+This is a helper class to the connection class. 
+Each connection to a client has a command stack associated with it. The
+command stack is a stack of command strings as generated by the SICS
+clients. Commands are added to the top of the command queue by the network
+ reader. Each time the task associated with a connection runs one command
+is popped from the command stack and executed. During execution the command
+stack must be locked in order to prevent commands being accepted by tasks
+busy waiting for some other process to finish. 
+
+Correspondingly, the interface to the command stack looks like this:
+
+@d costaint @{
+     typedef struct __costa *pCosta;
+
+/*----------------------------- live & death ----------------------------*/
+     pCosta CreateCommandStack(void);
+     void   DeleteCommandStack(pCosta self);
+     int    SetCommandStackMaxSize(pCosta self, int iNewSize);
+/*----------------------------------------------------------------------*/
+     int CostaTop(pCosta self, char *pCommand);
+     int CostaBottom(pCosta self, char *pCommand);
+     int CostaPop(pCosta self,char **pPtr);
+/*----------------------------------------------------------------------*/
+     void CostaLock(pCosta self);
+     void CostaUnlock(pCosta self);
+@}   
+
+Internally, two data structure need to be defined, the first for the 
+list implementing the command stack, the second for the command stack
+itself.
+
+@d costadat @{
+
+/*------------------------------------------------------------------------*/
+  typedef struct __costa {
+                          int iLock;
+                          int iList;
+                          int iMaxSize;
+                          int iCount;
+                         } Costa;
+@}
+
+
+@o costa.h @{
+/*-------------------------------------------------------------------------
+                             C O S T A
+
+  A command stack implementation for SICS. To be used by each connection.
+
+  Mark Koennecke, September 1997
+
+  copyright: see implementation file.
+
+----------------------------------------------------------------------------*/
+#ifndef SICSCOSTA
+#define SICSCOSTA
+@<costaint@>
+#endif
+@}
+
+@o costa.i @{
+/*---------------------------------------------------------------------------
+                          C O S T A
+  Internal data structures for the command stack.
+--------------------------------------------------------------------------*/
+@<costadat@>
+@}