diff options
Diffstat (limited to 'hurd/translator/nsmux.mdwn')
| -rw-r--r-- | hurd/translator/nsmux.mdwn | 121 |
1 files changed, 0 insertions, 121 deletions
diff --git a/hurd/translator/nsmux.mdwn b/hurd/translator/nsmux.mdwn deleted file mode 100644 index d156772b..00000000 --- a/hurd/translator/nsmux.mdwn +++ /dev/null @@ -1,121 +0,0 @@ -[[!meta copyright="Copyright © 2009 Free Software Foundation, Inc."]] - -[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable -id="license" text="Permission is granted to copy, distribute and/or modify this -document under the terms of the GNU Free Documentation License, Version 1.2 or -any later version published by the Free Software Foundation; with no Invariant -Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled -[[GNU Free Documentation License|/fdl]]."]]"""]] - -# nsmux - -`nsmux` implements the simplest use-case of namespace-based translator -selection (see below). - -To use `nsmux` do the following: - - $ settrans -a <node> nsmux <directory> - -After this operation `<node>` will be a mirror of `<directory>` with -namespace-based translator selection functionality enabled. - -Please note that due to some details `nsmux` may complain a lot when -run as a normal user. This matter is the most urgent on the TODO -list. - -## Source - -`nsmux` translator can be obtained with the following series of -commands: - - $ git clone git://git.sv.gnu.org/hurd/incubator.git nsmux - $ cd nsmux/ - $ git checkout -b nsmux origin/nsmux - -`filter` translator can be obtained with the following series of -commands: - - $ git clone git://git.sv.gnu.org/hurd/incubator.git filter - $ cd filter/ - $ git checkout -b filter origin/filter - -The filter is not yet working. - -## Namespace-based Translator Selection - -Namespace-based translator selection is the special technique of using -"magic" filenames for both accessing the file and setting translators -on it. - -A "magic" filename is a filename which contains an unescaped sequence -of two commas: ",,". This sequence can be escaped by adding another -comma: ",,,". In the magic filename the part up to the first double -commas is interpreted as the filename itself; the remaining segments -into which the string is split by occurrences of ",," are treated as -names of translators located under `/hurd/`. - -The simplest advantage before traditional way of setting -translators is shown in the following examples. Compare this - - $ settrans -a file translator1 - $ settrans -a file translator2 - $ cat file - -to this: - - $ cat file,,translator1,,translator2 - -One simple command versus three more lengthy ones is an obvious -improvement. However, this advantage is not the only one and, -probably, not even the most important. - -What is a good candidate for the most important advantage is that -translators requested via "magic" filenames are session-bound. In -other words, by running `cat file,,translator` we set a translator -visible *only* to `cat`, while the original file remains untranslated. -Such session-specific translators are called **dynamic** and there is -no (theoretical) way for a client to get a port to a dynamic -translator requested by another client. - -Obviously, dynamic translators can be stacked, similarly to static -translators. Also, dynamic translator stacks may reside on top of -static translator stacks. - -An important operation of namespace-based translator selection is -*filtering*. Filtering basically consists in looking up a translator -by name in the stack and ignoring translators located on top of it. -Note that filtering does not mean dropping some translators: in the -current implementation a filter is expected to be a normal dynamic -translator, included in the dynamic translator stack similarly to -other translators. - -An important detail is that filtering is not limited to dynamic -translator stacks: a filter should be able to descend into static -translator stacks as well. - -Although the concept of filtering may seem purely abstract in the -simplest use-case of setting dynamic translators on top of files, the -situation changes greatly when dynamic translator stacks on top of -directories are considered. In this case, the implementation of -namespace-based translator selection is expected to be able to -propagate the dynamic translators associated with the directory down -the directory structure. That is, all files located under a directory -opened with magic syntax, are expected to be translated by the same -set of translators. In this case having the possibility to -specifically discard some of the translators set up on top of certain -files is very useful. - -Note that the implementation of propagation of dynamic translators -down directories is not fully conceived at the moment. The -fundamental problem is distinguishing between situations when the -dynamic translators are to be set on the underlying files of the -directory or on the directory itself. - -## Currently Implemented - -Currently there a working (though not heavily tested) implementation -of the simplest use-case of namespace-based translator selection in -the form of translator `nsmux`. The filter is partially implemented -and this is the immediate goal. Propagating translators down -directories is the next objective. |