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%
% Copyright (c) 1999 University of Utah and the Flux Group.
% All rights reserved.
%
% The University of Utah grants you the right to copy and reproduce this
% document or portions thereof for academic, research, evaluation, and
% personal use only, provided that (1) the title page appears prominently,
% and (2) these copyright and permission notices are retained in all copies.
% To arrange for alternate terms, contact the University of Utah at
% csl-dist@cs.utah.edu or +1-801-585-3271.
%
\label{memfs}
The memfs library contains an implementation of a trivial memory-based
filesystem. It exports the standard \oskit{} filesystem interface,
and depends on the underlying osenv interfaces. (See
Chapter~\ref{fs}).
The header file \texttt{<oskit/fs/memfs.h>} must be included to use
the memfs, and its derivative cousin, the bmodfs. When first
instantiated, a memfs filesystem is empty, and may be populated using
the standard file access mechanisms. A special function,
oskit_memfs_file_set_contents is provided for convenience to replace
the contents of a MEMFS filesystem. Clients who wish to strictly use
the \oskit{} filesystem interface to guarantee portability to other
filesystems should not use this function.
\api{oskit_memfs_init}{initialize MEMFS filesystem}
\begin{apisyn}
\cinclude{oskit/fs/memfs.h}
\funcproto oskit_error_t oskit_memfs_init(oskit_osenv_t *osenv,
! oskit_filesystem_t **out_fs);
\end{apisyn}
\begin{apidesc}
Initialize the MEMFS filesystem.
\end{apidesc}
\begin{apiret}
Returns handle to an empty MEMFS filesystem.
\end{apiret}
\api{oskit_memfs_file_set_contents}{replace contents of a MEMFS file}
\begin{apisyn}
\cinclude{oskit/fs/memfs.h}
\funcproto oskit_error_t
oskit_memfs_file_set_contents(oskit_file_t *file,
void *data, oskit_off_t size, oskit_off_t allocsize,
oskit_bool_t can_sfree, oskit_bool_t inhibit_resize);
\end{apisyn}
\begin{apidesc}
This function changes the indicated MEMFS file to use the memory
from [\emph{data} - \emph{data}+\emph{size}-1] as its contents.
\emph{File} must be a regular MEMFS file and not a directory.
\emph{Allocsize} indicates the total amount of memory available
for the file to use when growing and must be greater than or
equal to \emph{size}.
If an attempt is made to grow the file to a size greater than
\emph{allocsize}, new memory will be allocated with
\texttt{smemalign} and the file contents copied to the new memory.
If \emph{inhibit_resize} is true, attempts to change the size of
the file hereafter will fail with \texttt{OSKIT_EPERM}.
If \emph{can_sfree} is true, \texttt{sfree} is called on the
data buffer if the file grows beyond \emph{allocsize},
is truncated to zero-length or is removed.
\end{apidesc}
\begin{apiparm}
\item[file]
File in the memfs filesystem whose contents are being replaced.
\item[data]
Pointer to memory to be used as the new file contents.
\item[size]
The new size of the file.
\item[allocsize]
Size of writable memory available for the file.
\item[can_sfree]
If true, indicates that the memory pointed to by \emph{data}
can be released with \texttt{sfree} when the file grows
beyond \emph{allocsize}, is truncated to zero-length, or
is removed.
\item[inhibit_resize]
If true, fails any attempt to change the size of the file.
\end{apiparm}
\begin{apiret}
Returns zero on success, an error code otherwise.
\end{apiret}
\begin{apidep}
\item osenv_mem_alloc \ref{dev}
\item osenv_mem_free \ref{dev}
\item osenv_log \ref{dev}
\item osenv_assert \ref{dev}
\item memcpy \ref{memcpy}
\item memset \ref{memset}
\end{apidep}
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