Implement ob_substvars().

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/control.sh b/lib/control.sh
index 15093a0..5190155 100644
--- a/lib/control.sh
+++ b/lib/control.sh
@@ -23,6 +23,8 @@ _OB_CONTROL_SM='true'
 ob_use messages
 ob_use locale
 
+_OB_SUBSTVARS_MAX_DEPTH=50
+
 OB_CONTROL_NAME=
 OB_CONTROL_VALUE=
 
@@ -169,6 +171,58 @@ ob_set_substvar()
 	return ${?}
 }
 
+ob_substvars()
+{
+	_ob_local _obsv_string _obsv_depth \
+		_obsv_lhs _obsv_name _obsv_rhs _obsv_old_rhs _obsv_value
+
+	if [ ${#} -eq 1 ]; then
+		_obsv_string="${1}"
+	else
+		_ob_return 125
+		return ${?}
+	fi
+
+	# Logic inspired by that of dpkg's Dpkg::Substvars::substvars() subroutine.
+
+	_obsv_depth=0
+
+	while true; do
+		_obsv_lhs="${_obsv_string%%\$\{*}"
+		if [ ${#_obsv_lhs} -eq ${#_obsv_string} ]; then
+			# No "${" was found.
+			break
+		fi
+		_obsv_string="${_obsv_string#*\$\{}"
+		_obsv_name="${_obsv_string%%\}*}"
+		_obsv_rhs="${_obsv_string#*\}}"
+
+		if [ ${#_obsv_rhs} -lt ${#_obsv_old_rhs} ]; then
+			# Reset the nesting counter if we've advanced the right side of the
+			# matched space.
+			_obsv_depth=0
+		fi
+		if [ ${_obsv_depth} -ge ${_OB_SUBSTVARS_MAX_DEPTH} ]; then
+			# Warn of possible recursion.
+			ob_warn "$(ob_get_msg 'substvar_deep_nesting')"
+			_ob_return 1
+			return ${?}
+		fi
+		_obsv_old_rhs="${_obsv_rhs}"
+
+		# Perform the substitution.
+		_obsv_name="$(echo "${_obsv_name}" | tr 'a-z-' 'A-Z_')"
+		_obsv_value="$(eval echo \"\$\{"_OB_SUBSTVAR_${_obsv_name}"\}\")"
+		_obsv_string="${_obsv_lhs}${_obsv_value}${_obsv_rhs}"
+		_obsv_depth=$(($_obsv_depth + 1))
+	done
+
+	printf '%s\n' "${_obsv_string}"
+
+	_ob_return 0
+	return ${?}
+}
+
 _ob_parse_control_error()
 {
 	_ob_local _obpcoe_file _obpcoe_line_nr _obpcoe_msg_id \