From 12aa2c32d527fef5fd5641e19160f0ea3ee59f72 Mon Sep 17 00:00:00 2001
From: Mart Lubbers <mart@martlubbers.net>
Date: Thu, 15 Jun 2017 10:46:17 +0200
Subject: [PATCH] add interpreter part

---
 conclusion.tex    |  5 ++++-
 results.mtask.tex | 51 +++++++++++++++++++++++++++++++++++++++++++----
 thesis.tex        |  3 +--
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/conclusion.tex b/conclusion.tex
index 94b75ff..729f479 100644
--- a/conclusion.tex
+++ b/conclusion.tex
@@ -56,7 +56,10 @@ of the client software. However, it could be implemented as a compile-time
 option and exchanged during the handshake so that the server knows the
 multithreading capabilities of the client.
 
-\todo{Parametric lenses on devices share?}
+Hardly any work has been done in the interpreter. The current interpreter is a
+no nonsense stack machine. A lot of improvements can be done in this part. For
+example, precomputed \emph{gotos} can improve jumping to the correct part of
+the code corresponding to the correct instruction.
 
 \subsection{Resources}
 Resource analysis during compilation can be useful to determine if an
diff --git a/results.mtask.tex b/results.mtask.tex
index 2ad243a..9c16fc5 100644
--- a/results.mtask.tex
+++ b/results.mtask.tex
@@ -324,7 +324,50 @@ position in the program memory.
 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}
diff --git a/thesis.tex b/thesis.tex
index d6d6e71..2c89d51 100644
--- a/thesis.tex
+++ b/thesis.tex
@@ -61,8 +61,7 @@
 \chapter{Conclusion \& Discussion}\label{chp:conclusion}
 \input{conclusion}
 
-\appendix%
-\label{chp:appendix}
+\appendix\label{chp:appendix}
 
 \chapter{Communication protocol}\label{app:communication-protocol}
 \input{appendix-protocol}
-- 
2.20.1