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# Functions for opening and closing file descriptors
#
# Copyright (C) 2013 Patrick McDermott
#
# This file is part of the ProteanOS Development Kit.
#
# The ProteanOS Development Kit is free software: you can redistribute
# it and/or modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# The ProteanOS Development Kit is distributed in the hope that it
# will be useful, but WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the ProteanOS Development Kit. If not, see
# <http://www.gnu.org/licenses/>.
# FD 3 is available as a temporary FD.
_FD_MIN=4
# Shells and the file descriptors they reserve for the user:
# * Debian Almquist Shell
# - The shell doesn't understand any file descriptor greater than 9.
# - File descriptors starting at 10 are used for I/O redirection.
# * BusyBox ash
# - File descriptors starting at 10 are used for job control and I/O
# redirection.
# * GNU Bash:
# - GNU Readline uses file descriptor 255 in interactive shells.
# - File descriptors starting at 10 are used for I/O redirection.
# * MirOS Korn Shell
# - File descriptors starting at either 10 or 24 are used for the shell's
# tty_fd and shl_dbg_fd.
# * Solaris ksh
# - The shell doesn't understand any file descriptor greater than 9.
_FD_MAX=9
FD=
fdalloc()
{
local i=
local fd=
# Find first available file descriptor.
i=${_FD_MIN}
while [ ${i} -le ${_FD_MAX} ]; do
if [ "x$(eval "printf '%s' \"\${_fd_${i}+set}\"")" != 'xset' ]
then
fd=${i}
break
fi
i=$((${i} + 1))
done
if [ "x${fd:+set}" != 'xset' ]; then
error "$(get_msg 'emfile')"
return 1
fi
FD="${fd}"
return 0
}
fopen()
{
local path="${1}"
local mode="${2}"
shift 2
case "${mode}" in
'r') mode='<' ;;
'w') mode='>' ;;
'a') mode='>>';;
'rw') mode='<>';;
*) return 125;;
esac
fdalloc || return 1
if eval "exec ${FD}${mode}\"\${path}\""; then
eval "_fd_${FD}=\"\${mode}\${path}\""
return 0
else
error "$(get_msg 'cant_fopen')"
FD=
return 1
fi
}
fclose()
{
local fd="${1}"
shift 1
# Make sure the file descriptor is open.
if [ "x$(eval "printf '%s' \"\${_fd_${fd}+set}\"")" != 'xset' ]; then
error "$(get_msg 'ebadf')"
return 1
fi
eval "exec ${fd}>&-"
unset "_fd_${fd}"
return 0
}
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