#!/bin/sh
# Stand-in C preprocessor for rpcgen(1) on an image that ships no compiler.
# rpcgen forks `cpp -C -D<RPC_HDR|RPC_XDR|...> <file>` for every pass; this
# covers exactly the directives the rpcsvc .x files use (#ifdef / #endif, no
# nesting, no #else, no #include, no macros) and refuses anything else so an
# unhandled directive is a visible failure and never a silently wrong header.

def=
file=
for a in "$@"; do
	case "$a" in
	-C) ;;
	-D*) def=${a#-D} ;;
	-*) ;;
	*) file=$a ;;
	esac
done

if [ -z "$file" ]; then
	file=/dev/stdin
fi

awk -v def="$def" '
/^[ \t]*#[ \t]*ifdef[ \t]/ {
	n = $0
	sub(/^[ \t]*#[ \t]*ifdef[ \t]+/, "", n)
	sub(/[ \t].*$/, "", n)
	if (depth > 0) { print "rpcsvc-cpp: nested #ifdef unsupported" > "/dev/stderr"; exit 1 }
	depth = 1
	skip = (n != def)
	next
}
/^[ \t]*#[ \t]*endif/ {
	if (depth == 0) { print "rpcsvc-cpp: unmatched #endif" > "/dev/stderr"; exit 1 }
	depth = 0
	skip = 0
	next
}
/^[ \t]*#/ {
	print "rpcsvc-cpp: unsupported directive: " $0 > "/dev/stderr"
	exit 1
}
{ if (!skip) print }
END {
	if (depth != 0) { print "rpcsvc-cpp: unterminated #ifdef" > "/dev/stderr"; exit 1 }
}
' "$file"