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File linking and unlinking skeletons

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Daniel Hillerström 5 years ago
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2 changed files with 186 additions and 21 deletions
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  1. 5
      macros.tex
  2. 202
      thesis.tex

5
macros.tex
View File

@ -425,6 +425,11 @@
\newcommand{\fileIO}{\dec{fileIO}}
\newcommand{\ULink}{\dec{Link}}
\newcommand{\UUnlink}{\dec{Unlink}}
\newcommand{\flink}{\dec{flink}}
\newcommand{\funlink}{\dec{funlink}}
\newcommand{\remove}{\dec{remove}}
\newcommand{\FileLU}{\dec{FileLU}}
\newcommand{\fileLU}{\dec{fileLU}}
%%
%% Some control operators

202
thesis.tex
View File

@ -6219,25 +6219,6 @@ implementation of $\fileRW$.
\]
%
% The composition of $\fileRW$ and $\fileAlloc$ give a semantics to file
% i/o.
% %
% \[
% \bl
% \fileIO : (\UnitType \to \alpha \eff \{\dec{FileCO};\dec{FileRW}\}) \to \alpha \eff \State~\FileSystem \\
% \fileIO~m \defas \dec{fileCO}\,(\lambda\Unit. \dec{fileRW}\,m)
% \el
% \]
% %
% The two handlers may as well be implemented as a single monolithic
% handler, since they implement different operations, return the same
% value, and make use of the same state cell. In practice a monolithic
% handler may have better performance. However, a sufficient clever
% compiler would be able to use the fusion technique of \citet{WuS15} to
% fuse the two handlers into one, and thus allow modular composition
% without remorse.
\paragraph{Stream redirection}
%
The processes we have defined so far use the $\echo$ utility to write
@ -6384,13 +6365,127 @@ the file system such that it can be used as the initial file system
state on the next start of the operating system.
\subsubsection{File linking and unlinking}
%
At this point the implementation of \fsname{} is almost feature
complete. We are missing two dual file operations: linking and
unlinking. The former enables us to make shallow copies of files and
the latter enables us to remove copies. The interface is given below.
%
\[
\dec{FileLU} \defas \{\ULink : \Record{\String;\String} \opto \UnitType; \UUnlink : \String \opto \UnitType\}
\]
%
The $\ULink$ operation is parameterised by two strings. The first
string is intended to be the name of the original file and the second
string is the name of the copy. The $\UUnlink$ operation takes a
single string argument, which is the name of the file to be removed.
%
\[
\bl
\flink : \Record{\String;\String;\FileSystem} \to \FileSystem \eff \{\Fail : \UnitType \opto \Zero\}\\
\flink\,\Record{src;dest;fs} \defas
\bl
\If\;\dec{has}\,\Record{dest;fs.dir}\;\Then\;fs\\
\Else\;
\bl
\Let\;ino \revto \lookup~\Record{src;fs.dir}\;\In\\
\Let\;dir' \revto \Record{dest;ino} \cons fs.dir\;\In\\
\Let\;inode \revto \lookup~\Record{ino;fs.ilist}\;\In\\
\Let\;inode' \revto \Record{inode\;\With\;lno = inode.lno + 1}\;\In\\
\Let\;ilist' \revto \modify\,\Record{ino;inode';fs.ilist}\;\In\\
\Record{fs\;\With\;dir = dir';ilist = ilist'}
\el
\el
\el
\]
%
\[
\remove : \Record{\alpha;\Record{\alpha;\beta}} \to \Record{\alpha;\beta}
\]
%
\[
\bl
\funlink : \Record{\String;\FileSystem} \to \FileSystem \eff \{\Fail : \UnitType \opto \Zero\}\\
\funlink\,\Record{fname;fs} \defas
\bl
\If\;\dec{has}\,\Record{fname;fs.dir}\;\Then\\
\quad
\bl
\Let\;ino \revto \lookup\,\Record{fname;fs.dir}\;\In\\
\Let\;dir' \revto \remove\,\Record{fname;fs.dir}\;\In\\
\Let\;inode \revto \lookup\,\Record{ino;fs.ilist}\;\In\\
\Let\;\Record{ilist';dreg'} \revto
\bl
\If\;inode.lno > 1\;\Then\\
\quad\bl
\Let\;inode' \revto \Record{inode\;\With\;lno = inode.lno - 1}\\
\In\;\Record{\modify\,\Record{ino;inode';fs.ilist};fs.dreg}
\el\\
\Else\;
\Record{\bl\remove\,\Record{ino;fs.ilist};\\
\remove\,\Record{inode.loc;fs.dreg}}
\el
\el\\
\In\;\Record{fs\;\With\;dir = dir'; ilist = ilist'; dreg = dreg'}
\el\\
\Else\; fs
\el
\el
\]
%
\[
\bl
\fileLU : (\UnitType \to \alpha \eff \FileLU) \to \alpha \eff \State~\FileSystem\\
\fileLU~m \defas
\bl
\Handle\;m\,\Unit\;\With\\
~\ba{@{~}l@{~}c@{~}l}
\Return\;res &\mapsto& res\\
\OpCase{\ULink}{\Record{src;dest}}{resume} &\mapsto&
\bl
\faild\,\Record{\Unit; \lambda\Unit.\\
\quad\bl
\Let\;fs = \flink\,\Record{src;dest;\Uget\,\Unit}\\
\In\;\Uput~fs}; resume\,\Unit
\el
\el\\
\OpCase{\UUnlink}{fname}{resume} &\mapsto&
\bl
\faild\,\Record{\Unit; \lambda\Unit.\\
\quad\bl
\Let\;fs = \funlink\,\Record{src;dest;\Uget\,\Unit}\\
\In\;\Uput~fs}; resume\,\Unit
\el
\el
\ea
\el
\el
\]
%
The composition of $\fileRW$, $\fileAlloc$, and $\fileLU$ complete the
implementation of \fsname{}.
%
\[
\bl
\fileIO : (\UnitType \to \alpha \eff \{\dec{FileCO};\dec{FileRW}\}) \to \alpha \eff \State~\FileSystem \\
\fileIO~m \defas \fileRW\,(\lambda\Unit. \fileAlloc\,(\lambda\Unit.\fileLU\,m))
\el
\]
%
The three handlers may as well be implemented as a single monolithic
handler, since they implement different operations, return the same
value, and make use of the same state cell. In practice a monolithic
handler may have better performance. However, a sufficient clever
compiler would be able to use the fusion technique of \citet{WuS15} to
fuse the two handlers into one, and thus allow modular composition
without remorse.
%
\[
\bl
\dec{cp} : \Record{\Bool;\String;\String} \to \UnitType \eff \{\ULink : \Record{\String;\String} \opto \UnitType;\dec{FileCO};\dec{FileRW}\}\\
\dec{cp}~\Record{link;src;dest} \defas
\bl
\If\;link\;\Then\;\Do\;\ULink\,\Record{src;dest}\\
\If\;link\;\Then\;\Do\;\ULink\,\Record{src;dest}\;\\
\Else\; \bl
\Case\;\Do\;\UOpen~src\\
\{ \ba[t]{@{~}l@{~}c@{~}l}
@ -6414,6 +6509,71 @@ state on the next start of the operating system.
\el
\]
\[
\ba{@{~}l@{~}l}
&\bl
\runState\,\Record{\dec{fs}_0;\fileIO\,(\lambda\Unit.\\
\quad\timeshare\,(\lambda\Unit.\\
\qquad\dec{interruptWrite}\,(\lambda\Unit.\\
\qquad\quad\sessionmgr\,\Record{\Root;\lambda\Unit.\\
\qquad\qquad\status\,(\lambda\Unit.
\ba[t]{@{}l}
\If\;\fork~\Unit\;\\
\Then\;
\bl
\su~\Alice;\,
\quoteRitchie~\redirect~\strlit{ritchie.txt};\\
\dec{cp}\,\Record{\False;\strlit{ritchie.txt};\strlit{ritchie}};\\
\dec{rm}\,\strlit{ritchie.txt}
\el\\
\Else\;
\bl
\su~\Bob;\,
\quoteHamlet~\redirect~\strlit{hamlet};\\
\dec{cp}\,\Record{\True;\strlit{hamlet};\strlit{act3}}
)}))))}
\el
\ea
\el \smallskip\\
\reducesto^+&
\bl
\Record{
\ba[t]{@{}l}
[0, 0];\\
\Record{
\ba[t]{@{}l}
dir=[\Record{\strlit{ritchie};3},\Record{\strlit{act3};2},\Record{\strlit{hamlet};2},
\Record{\strlit{stdout};0}];\\
ilist=[\Record{3;\Record{lno=1;loc=3}},
\Record{2;\Record{lno=2;loc=2}},
\Record{0;\Record{lno=1;loc=0}}];\\
dreg=[
\ba[t]{@{}l}
\Record{3;
\ba[t]{@{}l@{}l}
\texttt{"}&\texttt{UNIX is basically a simple operating system, }\\
&\texttt{but you have to be a genius to understand the simplicity.\nl{"}}},
\ea\\
\Record{2;
\ba[t]{@{}l@{}l}
\texttt{"}&\texttt{To be, or not to be,\nl{}that is the question:\nl{}}\\
&\texttt{Whether 'tis nobler in the mind to suffer\nl{}"}},
\ea\\
\Record{0; \strlit{}}]; lnext=4; inext=4}}\\
\ea
\ea
\ea\\
: \Record{\List~\Int; \FileSystem}
\el
\ea
\]
%
Alice makes a deep copy of the file \texttt{ritchie.txt} as
\texttt{ritchie}, and subsequently removes the original file, which
effectively amounts to a roundabout way of renaming a file. Bob makes
a shallow copy of the file \texttt{hamlet} as \texttt{act3}, meaning
both names share the same i-node with index $2$.
% \begin{figure}[t]
% \centering
% \begin{tikzpicture}[node distance=4cm,auto,>=stealth']

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