From 36cf5f8c449b67665b240e51731f903ebe146e8e Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Mon, 22 Feb 2016 15:43:21 -0500
Subject: Add basic eshld

---
(limited to 'eshld')

diff --git a/eshld/link.esh b/eshld/link.esh
new file mode 100644
index 0000000..d01fc4d
--- /dev/null
+++ b/eshld/link.esh
@@ -0,0 +1,102 @@
+# Eggshell Linker entry point
+#
+# Copyright (C) 2015  Patrick "P. J." McDermott
+#
+# This file is part of the Eggshell Linker.
+#
+# The Eggshell Linker 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 Linker 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 Linker  If not, see
+# <http://www.gnu.org/licenses/>.
+
+interpreter=
+entry_point=
+output=
+make_executable=
+
+die()
+{
+	local fmt="${1}"
+	shift 1
+
+	printf "eshld: ${fmt}\n" "${@}" >&2
+	exit 2
+}
+
+link_begin()
+{
+	local interp="${1}"
+	local entry="${2}"
+	local out="${3}"
+	local mkexec="${4}"
+	shift 4
+
+	interpreter="${interp}"
+	entry_point="${entry}"
+	output="${out}"
+	make_executable=${mkexec}
+
+	# Open output file.
+	if ! exec 3>"${output}~"; then
+		die 'Cannot open file "%s"' "${output}~"
+	fi
+
+	# Write magic number and interpreter path.
+	if ${make_executable}; then
+		printf '#!%s\n' "${interpreter}" >&3
+	fi
+
+	# Write __init() function.
+	cat >&3 <<-'EOF'
+		__init_funcs=''
+		__init()
+		{
+			__init_funcs="${__init_funcs} ${1}"
+		}
+		EOF
+
+}
+
+link_file()
+{
+	local input="${1}"
+
+	if ! cat "${input}" >&3; then
+		die 'Cannot read file "%s"' "${input}"
+	fi
+}
+
+link_end()
+{
+	# Add call to init functions.
+	cat >&3 <<-'EOF'
+		for __func in ${__init_funcs}; do
+			${__func}
+		done
+		EOF
+
+	# Add call to entry point.
+	if ${make_executable}; then
+		printf '%s "${@}"\n' "${entry_point}" >&3
+	fi
+
+	# Close output file, make it executable, and set its name.
+	exec 3>&-
+	if ${make_executable}; then
+		if ! chmod a+x "${output}~"; then
+			die 'Cannot set mode of file "%s"' "${output}~"
+		fi
+	fi
+	if ! mv "${output}~" "${output}"; then
+		die 'Cannot rename file to "%s"' "${output}"
+	fi
+}
diff --git a/eshld/main.esh b/eshld/main.esh
new file mode 100644
index 0000000..775179f
--- /dev/null
+++ b/eshld/main.esh
@@ -0,0 +1,113 @@
+# Eggshell Linker entry point
+#
+# Copyright (C) 2015  Patrick "P. J." McDermott
+#
+# This file is part of the Eggshell Linker.
+#
+# The Eggshell Linker 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 Linker 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 Linker  If not, see
+# <http://www.gnu.org/licenses/>.
+
+set -u
+
+VERSION='0.1.0'
+
+usage()
+{
+	printf 'Usage: %s [option ...] <file>...\n' "${0}"
+}
+
+help()
+{
+	usage
+	cat <<EOF
+Options:
+  -h           Display this information
+  -V           Display linker version information
+  -I <interp>  Use <interp> as the interpreter for your program, instead of the
+               default of "/bin/sh"
+  -e <entry>   Use <entry> as the function for beginning execution of your
+               program, instead of the default of "main"
+  -o <output>  Use <output> as the name of the program produced by eshld,
+               instead of the default of "out.sh"
+EOF
+}
+
+version()
+{
+	cat <<EOF
+eshld ${VERSION}
+Copyright (C) 2015  Patrick "P. J." McDermott
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
+EOF
+}
+
+main()
+{
+	local opt=
+	local interpreter=
+	local entry_point=
+	local output=
+	local make_executable=
+	local input=
+
+	interpreter='/bin/sh'
+	entry_point='main'
+	output='out.sh'
+	make_executable=true
+
+	while getopts 'hVI:e:o:' opt; do
+		case "${opt}" in
+			'h')
+				help
+				return 0
+				;;
+			'V')
+				version
+				return 0
+				;;
+			'I')
+				interpreter="${OPTARG}"
+				;;
+			'e')
+				entry_point="${OPTARG}"
+				;;
+			'o')
+				output="${OPTARG}"
+				;;
+		esac
+	done
+	shift $(($OPTIND - 1))
+
+	if [ ${#} -lt 1 ]; then
+		usage >&2
+		return 1
+	fi
+
+	if ! link_begin "${interpreter}" "${entry_point}" "${output}" \
+			${make_executable}; then
+		return 1
+	fi
+	for input in "${@}"; do
+		if ! link_file "${input}"; then
+			return 1
+		fi
+	done
+	if ! link_end; then
+		return 1
+	fi
+
+	return 0
+}
--
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