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# Functions for setting and substituting variables
#
# Copyright (C) 2012, 2014, 2019 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/>.
SUBSTVARS_MAX_DEPTH=50
SUBSTVAR_TRIM_SED='
H; # Store each input line in the hold space.
${ # At the last line of input:
g; # restore the hold space into the pattern space,
s/^[\n]*//; # remove leading newline characters,
s/[\n]*$//; # remove trailing newline characters, and
p; # print the results.
};
'
set_substvar()
{
local name="${1}"
local value="${2}"
shift 2
# Validate variable name and convert to lower case.
case "${name}" in *[!A-Za-z0-9-]* | '')
warn "$(get_msg 'substvar_invalid')" "${name}"
return 1
;;
esac
name="$(printf '%s' "${name}" | tr 'A-Z-' 'a-z_')"
# Trim leading and trailing whitespace from value.
value="$(printf '%s' "${value}" | sed -n "${SUBSTVAR_TRIM_SED}")"
eval "substvar_${name}=\"\${value}\""
return 0
}
substvars()
{
local string="${1}"
shift 1
local depth=
local lhs=
local name=
local rhs=
local old_rhs=
local value=
# Logic inspired by that of dpkg's Dpkg::Substvars::substvars()
# subroutine.
depth=0
while :; do
lhs="${string%%\$\{*}"
if [ ${#lhs} -eq ${#string} ]; then
# No "${" was found.
break
fi
string="${string#*\$\{}"
name="${string%%\}*}"
rhs="${string#*\}}"
if [ ${#rhs} -lt ${#old_rhs} ]; then
# Reset the nesting counter if we've advanced the right
# side of the matched space.
depth=0
fi
if [ ${depth} -ge ${SUBSTVARS_MAX_DEPTH} ]; then
# Warn of possible recursion.
warn "$(get_msg 'substvar_deep_nesting')"
return 1
fi
old_rhs="${rhs}"
# Validate the variable name.
case "${name}" in *[!A-Za-z0-9-]* | '')
warn "$(get_msg 'substvar_invalid')" "${name}"
# Remove the variable expansion altogether. We can't
# just leave the variable unexpanded, because the
# presence of the "${" characters would cause this
# parser to loop infinitely.
string="${lhs}${rhs}"
continue
esac
# Perform the substitution.
name_tr="$(printf '%s' "${name}" | tr 'A-Z-' 'a-z_')"
if eval "[ x\"\${substvar_${name_tr}:+set}\" = x'set' ]"
then
name_tr="substvar_${name_tr}"
else
warn "$(get_msg 'substvar_unknown')" "${name}"
string="${lhs}${rhs}"
continue
fi
value="$(eval "printf '%s' \"\${${name_tr}}\"")"
string="${lhs}${value}${rhs}"
depth=$((${depth} + 1))
done
printf '%s\n' "${string}"
return 0
}
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