Configure

#! /bin/sh
#
# This script is used to configure the linux kernel.
#
# It was inspired by the challenge in the original Configure script
# to ``do something better'', combined with the actual need to ``do
# something better'' because the old configure script wasn't flexible
# enough.
#
# Please send comments / questions / bug fixes to raymondc@microsoft.com.
#
# Each line in the config file is a command.
#
#	# internal comment
#
#		Lines beginning with a `#' are ignored.
#
#	: message
#
#		`:' causes the line to be echoed to the screen.
#
#	* external comment
#
#		`*' causes the line to be placed in the output
#		configuration file as a comment as well as being
#		echoed to the screen.
#
#	if condition
#		... commands ...
#	else
#		... commands ...
#	fi
#
#		This does the obvious thing.  The `else' clause is
#		optional.  Conditionals can be nested.
#
#		The `condition' can be any valid bash expression.
#		They typically involve tests against environment
#		variables set by configuration options.  For example,
#
#		if [ "$CONFIG_SCSI" = "y" ]
#			...More stuff...
#		fi
#
#		Note!  That there is no `then' keyword.
#
#	bool 'prompt' CONFIG_VARIABLE default
#
#		This prompts the user for a boolean value.
#		The prompt may not contain an apostrophe.
#		`default' should be either `y' or `n'.
#		The user's response is recorded in four places.
#
#		In .config, if `y'
#			CONFIG_VARIABLE = CONFIG_VARIABLE
#		In .config, if `n'
#			# CONFIG_VARIABLE is not set
#			
#		In autoconf.h, if `y'
#			#define CONFIG_VARIABLE 1
#		In autoconf.h, if `n'
#			#undef CONFIG_VARIABLE
#
#		In config.in, if `y'
#			bool 'prompt' CONFIG_VARIABLE y
#		In config.in, if `n'
#			bool 'prompt' CONFIG_VARIABLE n
#
#		In the environment of the Configure script, if `y'
#			CONFIG_VARIABLE = y
#		In the environment of the Configure script, if `n'
#			CONFIG_VARIABLE = n
#
#		The value is placed into the environment of the Configure
#		script so that later parts of config.in can use the `if'
#		command to inspect the results of previous queries.
#
#	int 'prompt' CONFIG_VARIABLE default
#
#		This prompts the user for an integer value.
#		The prompt may not contain an apostrophe.
#		`default' should be an integer.
#
#		The response is recorded as follows.
#
#		In .config
#			CONFIG_VARIABLE = response
#		In autoconf.h
#			#define CONFIG_VARIABLE (response)
#		In config.in
#			int 'prompt' CONFIG_VARIABLE response
#		In the environment of the Configure script
#			CONFIG_VARIABLE = response
#
# 050793 - use IFS='@' to get around a bug in a pre-version of bash-1.13
# with an empty IFS.

#
# Make sure we're really running bash.
#
# I would really have preferred to write this script in a language with
# better string handling, but alas, bash is the only scripting language
# that I can be reasonable sure everybody has on their linux machine.
#
[ -z "$BASH" ] && { echo "Configure requires bash" 1>&2; exit 1; }

# Disable filename globbing once and for all.
# Enable function cacheing.
set -f -h

#
# readln reads a line into $ans.
#
#	readln prompt default
#
function readln () {
	echo -n "$1"
	IFS='@' read ans </dev/tty || exit 1
	[ -z "$ans" ] && ans=$2
}

# bool processes a boolean argument
#
#	bool tail
#
function bool () {
	# Slimier hack to get bash to rescan a line.
	eval "set -- $1"
	ans=""
	while [ "$ans" != "y" -a "$ans" != "n" ]; do
		readln "$1 ($2) [$3] " "$3"
	done
	if [ "$ans" = "y" ]; then
		echo "$2 = $2" >>$CONFIG
		echo "#define $2 1" >>$CONFIG_H
	else
		echo "# $2 is not set" >>$CONFIG
		echo "#undef $2" >>$CONFIG_H
	fi
	raw_input_line="bool '$1' $2 $ans"
	eval "$2=$ans"
}

# int processes an integer argument
#
#	int tail
#
function int () {
	# Slimier hack to get bash to rescan a line.
	eval "set -- $1"
	ans="x"
	while [ $[$ans+0] != "$ans" ]; do
		readln "$1 ($2) [$3] " "$3"
	done
	echo "$2 = $ans" >>$CONFIG
	echo "#define $2 ($ans)" >>$CONFIG_H
	raw_input_line="int '$1' $2 $ans"
	eval "$2=$ans"
}

CONFIG=.tmpconfig
CONFIG_H=include/linux/autoconf.h
trap "rm -f $CONFIG $CONFIG_H config.new ; exit 1" 1 2

#
# Make sure we start out with a clean slate.
#
> config.new
echo "#" > $CONFIG
echo "# Automatically generated make config: don't edit" >> $CONFIG
echo "#" >> $CONFIG

echo "/*" > $CONFIG_H
echo " * Automatically generated C config: don't edit" >> $CONFIG_H
echo " */" >> $CONFIG_H

stack=''
branch='t'

while IFS='@' read raw_input_line
do
	# Slimy hack to get bash to rescan a line.
	read cmd rest <<-END_OF_COMMAND
		$raw_input_line
	END_OF_COMMAND

	if [ "$cmd" = "*" ]; then
		if [ "$branch" = "t" ]; then
			echo "$raw_input_line"
			echo "# $rest" >>$CONFIG
			if [ "$prevcmd" != "*" ]; then
				echo >>$CONFIG_H
				echo "/* $rest" >>$CONFIG_H
			else
				echo " * $rest" >>$CONFIG_H
			fi
			prevcmd="*"
		fi
	else
		[ "$prevcmd" = "*" ] && echo " */" >>$CONFIG_H
		prevcmd=""
		case "$cmd" in
		:)	[ "$branch" = "t" ] && echo "$raw_input_line" ;;
		int)	[ "$branch" = "t" ] && int "$rest" ;;
		bool)	[ "$branch" = "t" ] && bool "$rest" ;;
		exec)	[ "$branch" = "t" ] && ( sh -c "$rest" ) ;;
		if)	stack="$branch $stack"
			if [ "$branch" = "t" ] && eval "$rest"; then
				branch=t
			else
				branch=f
			fi ;;
		else)	if [ "$branch" = "t" ]; then
				branch=f
			else
				read branch rest <<-END_OF_STACK
					$stack
				END_OF_STACK
			fi ;;
		fi)	[ -z "$stack" ] && echo "Error!  Extra fi." 1>&2
			read branch stack <<-END_OF_STACK
				$stack
			END_OF_STACK
			;;
		esac
	fi
	echo "$raw_input_line" >>config.new
done
[ "$prevcmd" = "*" ] && echo " */" >>$CONFIG_H

[ -z "$stack" ] || echo "Error!  Untermiated if." 1>&2

mv config.in config.old
mv config.new config.in

echo
echo "The linux kernel is now hopefully configured for your setup."
echo "Check the top-level Makefile for additional configuration,"
echo "and do a 'make dep ; make clean' if you want to be sure all"
echo "the files are correctly re-made"
echo

exit 0