Commit 44279f2c authored by Sven Gestegård Robertz's avatar Sven Gestegård Robertz
Browse files

added bibliography to tex file and small changes

parent 6554806c
......@@ -8,9 +8,9 @@
\begin{document}
\title{Labcomm tech report}
\author{Anders Blomdell and Sven Gesteg\aa{}rd Robertz }
\date{embryo of draft, \today}
\date{draft, \today}
\maketitle
\maketitle
\begin{abstract}
......@@ -20,7 +20,7 @@ processor, and network used (e.g., byte order, etc). It is primarily intended
for situations where the overhead of communication has to be kept at a minimum,
hence LabComm only requires one-way communication to operate. The one-way
operation also has the added benefit of making LabComm suitable as a storage
format.
format.
LabComm provides self-describing channels, as communication starts with the
transmission of an encoded description of all possible sample types that can
......@@ -35,7 +35,7 @@ encoding and decoding types and samples, and interaction with
application code.
The LabComm compiler accepts type and sample declarations in a small language
that is similar to C or Java type-declarations.
that is similar to C or Java type-declarations.
\end{abstract}
\section{Introduction}
......@@ -43,20 +43,21 @@ that is similar to C or Java type-declarations.
%[[http://asn1.org|ASN1]].
LabComm has got it's inspiration from Sun RPC~\cite{SunRPC}
and ASN1~\cite{ANS1}. LabComm is primarily intended for situations
and ASN1~\cite{ASN1}. LabComm is primarily intended for situations
where the overhead of communication has to be kept at a minimum, hence LabComm
only requires one-way communication to operate. The one-way operation also has
the added benefit of making LabComm suitable as a storage format.
the added benefit of making LabComm suitable as a storage format.
Two-way comminication adds complexity, in particular for hand-shaking
during establishment of connections, and the LabComm library provides
support for (for instance) avoiding deadlocks during such hand-shaking.
\pagebreak
\section{Communication model}
LabComm provides self-describing communication channels, by always transmitting
a machine readable description of the data before actual data is
sent\footnote{Sometimes referred to as \emph{in-band} self-describing}.
sent\footnote{Sometimes referred to as \emph{in-band} self-describing}.
Therefore, communication on a LabComm channel has two phases
\begin{enumerate}
......@@ -70,9 +71,9 @@ During operation, LabComm will ensure (i.e., monitor) that a communication
channel is fully configured, meaning that both ends agree on what messages that
may be passed over that channel. If an unregistered sample type is sent or
received, the LabComm encoder or decoder will detect it and take action.
In more dynamic applications, it is possible to reconfigure a channel in order to add,
remove, or change the set of registerd sample types.
remove, or change the set of registered sample types. This is discussed
in Section~\ref{sec:reconfig}.
The roles in setting up, and maintaining, the configuration of a channel are as follows:
......@@ -86,7 +87,7 @@ The roles in setting up, and maintaining, the configuration of a channel are as
\paragraph{The transmitter (encoder)}
\begin{itemize}
\item ensures that the signature of a sample is transmitted on the channel before samples are
\item ensures that the signature of a sample is transmitted on the channel before samples are
written to that channel
\end{itemize}
......@@ -97,7 +98,21 @@ The roles in setting up, and maintaining, the configuration of a channel are as
\item if an unhandled signature is received, pauses the channel and informs the application
\end{itemize}
The fundamental communication model applies to all LabComm channels and
deals with the individual unidirectional channels. In addition to that,
the labcomm libraries support the implementation of higher-level
handshaking and establishment of bidirectional channels both through
means of interacting with the underlying transport layer (e.g., for
marking packets containing signatures as \emph{important}, for
transports that handle resending of dropped packets selectively), or
requesting retransmission of signatures.
In order to be both lean and generic, LabComm does not provide a
complete protocol for establishing and negotiating bidirectional
channels, but does provide support for building such protocols on top
of LabComm.
\subsection{Reconfiguration}
\label{sec:reconfig}
The fundamental communication model can be generalized to the life-cycle
of a concrete communication channel, including the transport layer,
......@@ -113,6 +128,21 @@ back from phase 3 to phase 2. That allows dynamic behaviour, as a sample
type can be added or redefined at run-time. It also facilitates error
handling in two-way channels.
One example of this, more dynamic, view of a labcomm channel is that the
action taken when an unregistered sample is sent or received is to
revert back to the configuration phase and redo the handshaking to
ensure that both sides agree on the set of sample types (i.e.,
signatures) that are currently configured for the channel.
From the system perspective, the LabComm protocol is involved in
phases 2 and 3. The establishement of the \emph{transport-layer}
channels is left to external application code. In the Labcomm library,
that application code is connected to the LabComm routines through
the \emph{reader} and \emph{writer} interfaces,
with default implementations for sockets or file descriptors (i.e.,
files and streams).
\section{The Labcomm language}
The LabComm language is used to describe data types, and from such data
......@@ -122,7 +152,7 @@ some exceptions. We will now introduce the language through a set of
examples.
These examples do not cover the entire language
specification (see appendix~\ref{language_grammar} for the complete
specification (see appendix~\ref{sec:LanguageGrammar} for the complete
grammar), but serve as a gentle introduction to the LabComm
language covering most common use-cases.
......@@ -152,7 +182,7 @@ language covering most common use-cases.
\begin{enumerate}
\item In contrast to C, LabComm supports both fixed and variable (denoted
by \verb+_+) sized arrays.
by~\verb+_+) sized arrays.
\item In contrast to Java, LabComm supports multidimensional arrays and not
only arrays of arrays.
......@@ -183,7 +213,8 @@ only arrays of arrays.
The LabComm system consists of a compiler for generating code from the data
descriptions, and libraries providing LabComm communication facilities in,
currently, C, Java, Python, and C\#.
currently, C, Java, Python, C\#, and RAPID\footnote{excluding variable
size samples, as RAPID has limited support for dynamic memory allocation}.
\subsection{The LabComm compiler}
......@@ -192,12 +223,12 @@ The LabComm compiler generates code for the declared samples, including marshall
demarshalling code, in the supported target languages.
The compiler itself is implemented in Java using the JastAdd~\cite{jastadd} compiler compiler.
\pagebreak
\subsection{The LabComm library}
The LabComm libraries contain functionality for the end-to-end transmission
of samples. They are divided into two layers, where the upper layer implements
the general encoding and decoding of samples, and the lower one deals with
the general encoding and decoding of samples, and the lower one deals with
the transmission of the encoded byte stream on a particular transport layer.
Thus, the LabComm communication stack looks like this:
......@@ -216,7 +247,7 @@ Thus, the LabComm communication stack looks like this:
\end{figure}
\subsubsection{LabComm actions}
(similar to ioctl())
(similar to ioctl())
The encoder/writer and decoder/reader interfaces consist of a set of actions
One example of this is that there is a a separate writer action for
......@@ -225,7 +256,7 @@ from encoded samples, e.g., to allow handshaking during channel setup.
User actions allow the application or a higher level
protocol to communicate with the underlying transport layer through the LabComm
encoder.
encoder.
One example is reliable communication, which is controlled from the application
but needs to be implemented for each transport at at the reader/writer level.
......@@ -235,7 +266,7 @@ but needs to be implemented for each transport at at the reader/writer level.
\begin{itemize}
\item a protocol for two-way connections
\item intrinsically supporting reliable communication
\item intrinsically supporting reliable communication
\item providing semantic service-descriptions
\end{itemize}
......@@ -255,7 +286,7 @@ But
With the following `example.lc` file:
\lstinputlisting[basicstyle=\footnotesize]{../examples/wiki_example/example.lc}
and this \verb+example_encoder.c+ file
and this \verb+example_encoder.c+ file
\lstinputlisting[basicstyle=\footnotesize,language=C]{../examples/wiki_example/example_encoder.c}
......@@ -275,16 +306,16 @@ Running \verb+./example_encoder one two+, will yield the following result in exa
i.e.,
\begin{verbatim}
<version> <length: 12> <string: <len: 11> <"LabComm2014">>
<sample_decl> <length: 48 <user_id: 0x40> <string: <len: 11> <"log_message">
<sample_decl> <length: 48 <user_id: 0x40> <string: <len: 11> <"log_message">
<signature_length: 34>
<struct_decl:
<struct_decl:
<number_of_fields: 2>
<string: <len: 8> <"sequence"> <type: <integer_type>>
<string: <len: 4> <"line">> <type: <array_decl
<number_indices: 1> <variable_index>
<type: <struct_decl:
<string: <len: 4> <"line">> <type: <array_decl
<number_indices: 1> <variable_index>
<type: <struct_decl:
<number_of_fields:2>
<string: <len: 4> <"last">> <type: <boolean_type>>
<string: <len: 4> <"last">> <type: <boolean_type>>
<string: <len: 4> <"data">> <type: <string_type>>
>>
>
......@@ -308,8 +339,12 @@ Java primitive types. However, it is unlikely that the entire range is actually
way of supporting the common cases is to include run-time checks for overflow in the Java encoders
and decoders.
\bibliography{refs}{}
\bibliographystyle{plain}
\appendix
\newpage
\section{The LabComm language}
\label{sec:LanguageGrammar}
......@@ -354,7 +389,7 @@ VariableSize : Exp;
<char> := any UTF-8 char
<type> := ( <basic_type> | <user_id> | <array_decl> | <struct_decl> )
<basic_type> := ( <boolean_type> | <byte_type> | <short_type> |
<integer_type> | <long_type> | <float_type> |
<integer_type> | <long_type> | <float_type> |
<double_type> | <string_type> )
<boolean_type> := 0x20 ''(packed)''
<byte_type> := 0x21 ''(packed)''
......
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