From 6a6c1b118901d32217282dd6c4ca8f31973ffe31 Mon Sep 17 00:00:00 2001
From: Sven Gestegard Robertz <sven.robertz@cs.lth.se>
Date: Sat, 10 Jan 2015 14:40:03 +0100
Subject: [PATCH] updated grammar appendix
---
doc/tech_report.tex | 97 +++++++++++++++++++++++++++------------------
1 file changed, 58 insertions(+), 39 deletions(-)
diff --git a/doc/tech_report.tex b/doc/tech_report.tex
index 5bc57db..b482231 100644
--- a/doc/tech_report.tex
+++ b/doc/tech_report.tex
@@ -289,6 +289,7 @@ With the following `example.lc` file:
and this \verb+example_encoder.c+ file
\lstinputlisting[basicstyle=\footnotesize,language=C]{../examples/wiki_example/example_encoder.c}
+\newpage
Running \verb+./example_encoder one two+, will yield the following result in example.encoded:
\begin{verbatim}
@@ -306,7 +307,9 @@ 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:
<number_of_fields: 2>
@@ -379,37 +382,25 @@ VariableSize : Exp;
\section{The LabComm protocol}
\label{sec:ProtocolGrammar}
+Each LabComm2014 packet has the layout
+\begin{verbatim}
+<id> <length> <data...>
+\end{verbatim}
+where \verb+length+ is the number of bytes of the \verb+data+ part
+(i.e., excluding the \verb+id+ and \verb+length+ fields), and
+the \verb+id+ gives the layout of the \verb+data+ part as defined
+in \ref{sec:ConcreteGrammar}
+\subsection{Data encoding}
+LabComm primitive types are encoded as fixed width values, sent in
+network order. Type fields, user IDs, number of indices and lengths are
+sent in a variable length (\emph{varint}) form. A varint integer value
+is sent as a sequence of bytes where the lower seven bits contain a
+chunk of the actual number and the high bit indicates if more chunks
+follow. The sequence of chunks are sent with the least significant chunk
+first.
+
+The built-in data types are encoded as follows:
\begin{verbatim}
-<packet> := ( <type_decl> | <sample_decl> | <sample_data> )*
-<type_decl> := 0x01 ''(packed)'' <user_id> <string> <type>
-<sample_decl> := 0x02 ''(packed)''<user_id> <string> <type>
-<user_id> := 0x40..0xffffffff ''(packed)''
-<string> := <string_length> <char>*
-<string_length> := 0x00..0xffffffff ''(packed)''
-<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> |
- <double_type> | <string_type> )
-<boolean_type> := 0x20 ''(packed)''
-<byte_type> := 0x21 ''(packed)''
-<short_type> := 0x22 ''(packed)''
-<integer_type> := 0x23 ''(packed)''
-<long_type> := 0x24 ''(packed)''
-<float_type> := 0x25 ''(packed)''
-<double_type> := 0x26 ''(packed)''
-<string_type> := 0x27 ''(packed)''
-<array_decl> := 0x10 ''(packed)'' <number_of_indices> <indices> <type>
-<number_of_indices> := 0x00..0xffffffff ''(packed)''
-<indices> := ( <variable_index> | <fixed_index> )*
-<variable_index> := 0x00 ''(packed)''
-<fixed_index> := 0x01..0xffffffff ''(packed)''
-<struct_decl> := 0x11 ''(packed)'' <number_of_fields> <field>*
-<number_of_fields> := 0x00..0xffffffff ''(packed)''
-<field> := <string> <type>
-<sample_data> := <user_id> <packed_sample_data>
-<packed_sample_data> := is sent in network order, sizes are as follows:
-
||Type ||Encoding/Size ||
||---------------||------------------------------------------------------||
||boolean || 8 bits ||
@@ -419,18 +410,46 @@ VariableSize : Exp;
||long || 64 bits ||
||float || 32 bits ||
||double || 64 bits ||
-||string || length ''(packed)'', followed by UTF8 encoded string ||
-||array || each variable index ''(packed)'', ||
+||string || length (varint), followed by UTF8 encoded string ||
+||array || each variable index (varint), ||
|| || followed by encoded elements ||
||struct || concatenation of encoding of each element ||
|| || in declaration order ||
\end{verbatim}
-Type fields, user IDs, number of indices and lengths are sent in a packed, or
-variable length, form. An integer is sent as a sequence of bytes where the
-lower seven bits contain a chunk of the actual number and the high bit
-indicates if more chunks follow. The sequence of chunks are sent with the least
-significant chunk first. (The numbers encoded in this form are indicated above
-with \textit{(packed)}.)
+\subsection{Protocol grammar}
+\label{sec:ConcreteGrammar}
+\begin{verbatim}
+<packet> := ( <version> | <type_decl> | <sample_decl> | <sample_data> )*
+<version> := 0x01 <length> <string>
+<sample_def> := 0x02 <length> <user_id> <string> <type>
+<type_def> := 0x03 <length> <user_id> <string> <type>
+<user_id> := 0x40..0xffffffff
+<string> := <string_length> <char>*
+<string_length> := 0x00..0xffffffff
+<char> := any UTF-8 char
+<type> := <length> ( <basic_type> | <user_id> | <array_decl> | <struct_decl> )
+<basic_type> := ( <boolean_type> | <byte_type> | <short_type> |
+ <integer_type> | <long_type> | <float_type> |
+ <double_type> | <string_type> )
+<boolean_type> := 0x20
+<byte_type> := 0x21
+<short_type> := 0x22
+<integer_type> := 0x23
+<long_type> := 0x24
+<float_type> := 0x25
+<double_type> := 0x26
+<string_type> := 0x27
+<array_decl> := 0x10 <number_of_indices> <indices> <type>
+<number_of_indices> := 0x00..0xffffffff
+<indices> := ( <variable_index> | <fixed_index> )*
+<variable_index> := 0x00
+<fixed_index> := 0x01..0xffffffff
+<struct_decl> := 0x11 <number_of_fields> <field>*
+<number_of_fields> := 0x00..0xffffffff
+<field> := <string> <type>
+<sample_data> := <user_id> <packed_sample_data>
+<packed_sample_data> := is sent in network order, encoded :
+\end{verbatim}
\end{document}
--
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