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token.tex

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+\subsection{Token Management}
+In SICS any client can issue commands to the SICS server. This
+is a potential cause for trouble with users issuing conflicting
+commands without knowing. In order to deal with this problem a
+token mechanism has been developed. A connection can grab a
+token and then has full control over the SICS server. Any other
+connection will not be priviledged to do anything useful, except
+looking at things. A token can be released manually with a
+special command or is automatically released when the connection
+dies. Another command exists which allows a SICS manager to
+force his way into the SICS server.
+
+This token scheme is implemented using the signal system of the
+task management facility and the connection object. The connection
+object has a field called iGrap which is true if the connection is the
+ultimate and only control connection. This field will be modified
+either directly through commands or via the signal system of the SICS
+task manager. This must be so as all connections need to be notified
+if one connection has grabbed control. 
+
+This object implements the user interface to the token system.
+It checks privileges and issues the necessary signals. No own
+data structure is needed. Just a wrapper function is
+implemented.
+
+\begin{flushleft} \small
+\begin{minipage}{\linewidth} \label{scrap1}
+\verb@"token.h"@ {\footnotesize ? }$\equiv$
+\vspace{-1ex}
+\begin{list}{}{} \item
+\mbox{}\verb@@\\
+\mbox{}\verb@/*---------------------------------------------------------------@\\
+\mbox{}\verb@                    S I C S  T O K E N@\\
+\mbox{}\verb@                    @\\
+\mbox{}\verb@   This is the header file for the SICS token management@\\
+\mbox{}\verb@   functions. It implements the token command.@\\
+\mbox{}\verb@   @\\
+\mbox{}\verb@   Mark Koenencke, January 1998@\\
+\mbox{}\verb@   @\\
+\mbox{}\verb@   copyright: see copyright.h@\\
+\mbox{}\verb@   @\\
+\mbox{}\verb@----------------------------------------------------------------*/@\\
+\mbox{}\verb@#ifndef SICSTOKEN@\\
+\mbox{}\verb@#define SICSTOKEN@\\
+\mbox{}\verb@  int TokenInit(SConnection *pCon, SicsInterp *pSics, @\\
+\mbox{}\verb@                void *pData, int argc, char *argv[]);@\\
+\mbox{}\verb@  /*@\\
+\mbox{}\verb@      The Token Factory function.@\\
+\mbox{}\verb@  */                  @\\
+\mbox{}\verb@  int TokenWrapper(SConnection *pCon, SicsInterp *pSics, @\\
+\mbox{}\verb@                void *pData, int argc, char *argv[]);@\\
+\mbox{}\verb@    @\\
+\mbox{}\verb@   /* @\\
+\mbox{}\verb@   The wrapper function for the token command.@\\
+\mbox{}\verb@   */               @\\
+\mbox{}\verb@   @\\
+\mbox{}\verb@   int TokenGrabActive(void);@\\
+\mbox{}\verb@   /*@\\
+\mbox{}\verb@      Returns 1, if a token grab is active, else 0@\\
+\mbox{}\verb@   */  @\\
+\mbox{}\verb@   @\\
+\mbox{}\verb@   void TokenRelease(void);@\\
+\mbox{}\verb@   /* @\\
+\mbox{}\verb@     Releases a Token Grab@\\
+\mbox{}\verb@   */   @\\
+\mbox{}\verb@#endif                       @\\
+\mbox{}\verb@@$\diamond$
+\end{list}
+\vspace{-2ex}
+\end{minipage}\\[4ex]
+\end{flushleft}
+The functions are:
+\begin{description}
+\item[TokenInit] is the installation routine which configures the
+token system into SICS. Called from the initialisation script.
+\item[TokenWrapper] is the interpreter interface function for the
+token system. Implements the active run time commands.
+\item[TokenGrapActive] returns true (1) if a connection has grabbed
+control or false (0) otherwise.
+\item[TokenRelease] releases the current control token.   
+\end{description}
+