2 files changed, 125 insertions, 0 deletions
diff --git a/eshtrans/backend/codegen.esh b/eshtrans/backend/codegen.esh
new file mode 100644
index 0000000..dea169b
--- /dev/null
+++ b/eshtrans/backend/codegen.esh
@@ -0,0 +1,94 @@
+# Shell command language code generator
+#
+# Copyright (C) 2016  Patrick "P. J." McDermott
+#
+# This file is part of the Eggshell Compiler.
+#
+# The Eggshell Compiler 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 Eggshell Compiler 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 Eggshell Compiler.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+sc=
+
+sgetc()
+{
+	sc="$(dd bs=1 count=1 2>/dev/null; printf '.')"
+	sc="${sc%.}"
+}
+
+codegen_sub()
+{
+	local array="${1}"
+	shift 1
+
+	IFS="${RS}"
+	for t in ${array}; do
+		toktext "${t}"
+		case "${t%${US}*}" in
+			T_NEWLINE)
+				;;
+			*)
+				printf ' '
+				;;
+		esac
+	done
+	unset IFS
+}
+
+# The token stack is encoded in a string in the following grammar:
+#     Terminal symbols:
+#         TOKEN
+#     Production rules:
+#         stack  = tokens [ '<SOH>' type '<STX>' stack '<ETX>' [ tokens ] ] ;
+#         tokens = TOKEN { '<RS>' TOKEN } ;
+#         type   = 'C' ;
+# We need to recurse through this stack to get to all the tokens.
+# Each element in the stack (an array of tokens) gets run through the codegen to
+# become text that is inserted into the array below.
+sh_parse_stack()
+{
+	local array=
+
+	array=''
+	while :; do
+		sgetc
+		case "${sc}" in
+			'')
+				# EOF
+				break
+				;;
+			"${SOH}")
+				# New stack element
+				sgetc
+				case "${sc}" in
+					'C')
+						# Command substitution
+						sgetc  # STX
+						array="${array}$(\
+							sh_parse_stack)."
+						array="${array%.}"
+						;;
+				esac
+				;;
+			"${ETX}")
+				# End of stack element
+				break
+				;;
+			*)
+				# Token character
+				array="${array}${sc}"
+				;;
+		esac
+	done
+	codegen_sub "${array}"
+}
diff --git a/eshtrans/backend/main.esh b/eshtrans/backend/main.esh
new file mode 100644
index 0000000..884a2c3
--- /dev/null
+++ b/eshtrans/backend/main.esh
@@ -0,0 +1,31 @@
+# Shell command language backend interface
+#
+# Copyright (C) 2016  Patrick "P. J." McDermott
+#
+# This file is part of the Eggshell Compiler.
+#
+# The Eggshell Compiler 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 Eggshell Compiler 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 Eggshell Compiler.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+sh_codegen()
+{
+	local toks="${1}"
+	shift 1
+
+	if printf '%s' "${toks}" | sh_parse_stack; then
+		return 0
+	else
+		return 1
+	fi
+}