, sdsval :: BCValue
}
:: BCState =
- { freshl :: [Int]
- , freshs :: [Int]
+ { freshl :: Int
+ , freshs :: Int
, sdss :: [BCShare]
}
\begin{lstlisting}[label={lst:controlflow},%
caption={Bytecode view for \texttt{arith}}]
-freshlabel = get >>= \st=:{freshl=[fr:frs]}->put {st & freshl=frs} >>| pure fr
+freshlabel = get >>= \st=:{freshl}->put {st & freshl=freshl+1} >>| pure freshl
instance If ByteCode Stmt Stmt Stmt where If b t e = BCIfStmt b t e
instance If ByteCode e Stmt Stmt where If b t e = BCIfStmt b t e
\begin{lstlisting}[label={lst:shareview},%
caption={Bytecode view for \texttt{arith}}]
-freshshare = get >>= \st=:{freshl=[fr:frs]}->put {st & freshl=frs} >>| pure fr
+freshshare = get >>= \st=:{freshs}->put {st & freshs=freshs+1} >>| pure freshs
instance sds ByteCode where
sds f = {main = BC (freshshare
20 : BCDigitalWrite (Digital D0)
\end{lstlisting}
-\todo{add more elaborate example?}
-
-\section{Interpretation}
-\todo{details about the interpreter on the client}
+\section{Interpreter}
+The client contains an interpreter to execute a \gls{Task}'s bytecode.
+
+First some preparatory work is done. The stack will be initialized and the
+program counter and stack pointer are set to zero and the bottom respectively.
+Then the interpreter executes one step at the time while the program counter is
+smaller than the program length. The code for this is listed in
+Listing~\ref{lst:interpr}. One execution step is basically a big switch
+statement going over all possible bytecode instructions. Some instructions are
+detailed upon in the listing. The \CI{BCPush} instruction is a little more
+complicated in real life because some decoding will take place as not all
+\CI{BCValue}'s are of the same length.
+
+\begin{lstlisting}[language=C,label={lst:interpr},%
+ caption={Rough code outline for interpretation}]
+#define f16(p) program[pc]*265+program[pc+1]
+
+void run_task(struct task *t){
+ uint8_t *program = t->bc;
+ int plen = t->tasklength;
+ int pc = 0;
+ int sp = 0;
+ while(pc < plen){
+ switch(program[pc++]){
+ case BCNOP:
+ break;
+ case BCPUSH:
+ stack[sp++] = pc++ //Simplified
+ break;
+ case BCPOP:
+ sp--;
+ break;
+ case BCSDSSTORE:
+ sds_store(f16(pc), stack[--sp]);
+ pc+=2;
+ break;
+ // ...
+ case BCADD: trace("add");
+ stack[sp-2] = stack[sp-2] + stack[sp-1];
+ sp -= 1;
+ break;
+ // ...
+ case BCJMPT: trace("jmpt to %d", program[pc]);
+ pc = stack[--sp] ? program[pc]-1 : pc+1;
+ break;
+}
+\end{lstlisting}