#!/bin/sh -
#
#   Change the indentation of a piece of source code.
#   Please refer to the usage message for details.
#
#   Copyright (C) 2007-2009 Oliver Fromme <olli@fromme.com> <olli@secnetix.de>
#   All rights reserved.  Standard 2-clause BSD license and disclaimer apply,
#   please refer to the file /usr/share/examples/etc/bsd-style-copyright on
#   FreeBSD or ask the author for a copy.


Usage()
{
	cat >&2 <<-tac
		Usage:  ${0##*/}  <old>  <new>  [<file> ...]
		Changes the indentation size from <old> to <new>.  Only the indentation is
		changed, other whitespace is left as-is.  Input may use tabs or spaces for
		indentation.  Output will always uses spaces.  You may use "unexpand -t<new>"
		to convert them back to tabs if you prefer this.  If no files are specified,
		standand input is used.  The result is written to standard output.
	tac
	exit 1
}

export TAB_OLD="$1" TAB_NEW="$2"
shift 2

case "$TAB_OLD/$TAB_NEW" in
	*[!0-9/]*|*/*/*|/*|*/|0/*|*/0)	Usage ;;
esac

expand -t$TAB_OLD "$@" |
awk '
	BEGIN {
		tab_old = ENVIRON["TAB_OLD"]
		tab_new = ENVIRON["TAB_NEW"]
	}

	{
		old = index($0, $1) - 1
		itab = int(old / tab_old)
		ispc = old % tab_old
		new = itab * tab_new + ispc
		printf "%*s%s\n", new, "", substr($0, old + 1)
	}
'

#--