From e6e3feb7b2a88b68e882e0572cc09e82b52da6e1 Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Mon, 01 Sep 2014 14:21:42 -0400
Subject: lib/substvars.sh: New file

---
diff --git a/lib/local.mk b/lib/local.mk
index 1a4ac0e..d593289 100644
--- a/lib/local.mk
+++ b/lib/local.mk
@@ -5,6 +5,7 @@ pkgdata_sources = \
 	lib/fd.sh \
 	lib/archplat.sh \
 	lib/deps.sh \
+	lib/substvars.sh \
 	lib/control.sh \
 	lib/feed.sh \
 	lib/pkg.sh \
diff --git a/lib/substvars.sh b/lib/substvars.sh
new file mode 100644
index 0000000..40d908b
--- /dev/null
+++ b/lib/substvars.sh
@@ -0,0 +1,103 @@
+# Functions for setting and substituting variables
+#
+# Copyright (C) 2012, 2014  Patrick "P. J." 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/>.
+
+[ "x${_SUBSTVARS_SM+set}" = 'xset' ] && return 0
+_SUBSTVARS_SM=1
+
+set_substvar()
+{
+	local name="${1}"
+	local value="${2}"
+
+	# Convert variable name to lower case and validate.
+	name="$(echo "${name}" | tr 'A-Z-' 'a-z_')"
+	case "${name:- }" in
+		*[!a-z0-9_]*)
+			error 2 "$(get_msg 'substvar_invalid')"
+			;;
+	esac
+
+	# Trim leading and trailing newline characters from value.
+	value="$(printf '%s\n' "${value}" | sed -n '
+		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.
+		  p;          # Print the results.
+		};
+		')"
+
+	# Escape single quotes in value.
+	value="$(printf '%s\n' "${value}" | sed "s/'/'\\\\''/g")"
+
+	eval "substvar_${name}='${value}'"
+
+	return 0
+}
+
+substvars()
+{
+	local string="${1}"
+	local depth=
+	local lhs=
+	local name=
+	local rhs=
+	local old_rhs=
+	local value=
+
+	# Logic inspired by that of dpkg's Dpkg::Substvars::substvars()
+	# subroutine.
+
+	depth=0
+
+	while :; do
+		lhs="${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 ${_OB_SUBSTVARS_MAX_DEPTH} ]; then
+			# Warn of possible recursion.
+			ob_warn "$(ob_get_msg 'substvar_deep_nesting')"
+			return 1
+		fi
+		old_rhs="${rhs}"
+
+		# Perform the substitution.
+		name="$(echo "${name}" | tr 'A-Z-' 'a-z_')"
+		value="$(eval printf '%s\n' "\"\$\{substvar_${name}\}\"")"
+		string="${lhs}${value}${rhs}"
+		depth=$(($depth + 1))
+	done
+
+	printf '%s\n' "${string}"
+
+	return 0
+}
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