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128 lines
3.5 KiB
TeX
128 lines
3.5 KiB
TeX
\chapter{Amoeba Specific Services}
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\section{Built-in Module \sectcode{amoeba}}
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\bimodindex{amoeba}
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This module provides some object types and operations useful for
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Amoeba applications. It is only available on systems that support
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Amoeba operations. RPC errors and other Amoeba errors are reported as
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the exception \code{amoeba.error = 'amoeba.error'}.
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The module \code{amoeba} defines the following items:
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\renewcommand{\indexsubitem}{(in module amoeba)}
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\begin{funcdesc}{name_append}{path\, cap}
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Stores a capability in the Amoeba directory tree.
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Arguments are the pathname (a string) and the capability (a capability
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object as returned by
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\code{name_lookup()}).
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\end{funcdesc}
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\begin{funcdesc}{name_delete}{path}
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Deletes a capability from the Amoeba directory tree.
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Argument is the pathname.
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\end{funcdesc}
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\begin{funcdesc}{name_lookup}{path}
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Looks up a capability.
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Argument is the pathname.
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Returns a
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\dfn{capability}
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object, to which various interesting operations apply, described below.
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\end{funcdesc}
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\begin{funcdesc}{name_replace}{path\, cap}
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Replaces a capability in the Amoeba directory tree.
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Arguments are the pathname and the new capability.
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(This differs from
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\code{name_append()}
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in the behavior when the pathname already exists:
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\code{name_append()}
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finds this an error while
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\code{name_replace()}
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allows it, as its name suggests.)
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\end{funcdesc}
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\begin{datadesc}{capv}
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A table representing the capability environment at the time the
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interpreter was started.
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(Alas, modifying this table does not affect the capability environment
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of the interpreter.)
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For example,
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\code{amoeba.capv['ROOT']}
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is the capability of your root directory, similar to
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\code{getcap("ROOT")}
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in C.
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\end{datadesc}
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\begin{excdesc}{error}
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The exception raised when an Amoeba function returns an error.
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The value accompanying this exception is a pair containing the numeric
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error code and the corresponding string, as returned by the C function
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\code{err_why()}.
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\end{excdesc}
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\begin{funcdesc}{timeout}{msecs}
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Sets the transaction timeout, in milliseconds.
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Returns the previous timeout.
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Initially, the timeout is set to 2 seconds by the Python interpreter.
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\end{funcdesc}
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\subsection{Capability Operations}
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Capabilities are written in a convenient \ASCII{} format, also used by the
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Amoeba utilities
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\emph{c2a}(U)
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and
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\emph{a2c}(U).
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For example:
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\bcode\begin{verbatim}
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>>> amoeba.name_lookup('/profile/cap')
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aa:1c:95:52:6a:fa/14(ff)/8e:ba:5b:8:11:1a
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>>>
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\end{verbatim}\ecode
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%
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The following methods are defined for capability objects.
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\renewcommand{\indexsubitem}{(capability method)}
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\begin{funcdesc}{dir_list}{}
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Returns a list of the names of the entries in an Amoeba directory.
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\end{funcdesc}
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\begin{funcdesc}{b_read}{offset\, maxsize}
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Reads (at most)
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\var{maxsize}
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bytes from a bullet file at offset
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\var{offset.}
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The data is returned as a string.
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EOF is reported as an empty string.
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\end{funcdesc}
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\begin{funcdesc}{b_size}{}
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Returns the size of a bullet file.
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\end{funcdesc}
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\begin{funcdesc}{dir_append}{}
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\funcline{dir_delete}{}\
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\funcline{dir_lookup}{}\
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\funcline{dir_replace}{}
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Like the corresponding
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\samp{name_}*
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functions, but with a path relative to the capability.
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(For paths beginning with a slash the capability is ignored, since this
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is the defined semantics for Amoeba.)
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\end{funcdesc}
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\begin{funcdesc}{std_info}{}
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Returns the standard info string of the object.
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\end{funcdesc}
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\begin{funcdesc}{tod_gettime}{}
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Returns the time (in seconds since the Epoch, in UCT, as for POSIX) from
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a time server.
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\end{funcdesc}
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\begin{funcdesc}{tod_settime}{t}
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Sets the time kept by a time server.
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\end{funcdesc}
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