##### http://autoconf-archive.cryp.to/adl_normalize_path.html
#
# SYNOPSIS
#
#   adl_NORMALIZE_PATH(VARNAME, [REFERENCE_STRING])
#
# DESCRIPTION
#
#   Perform some cleanups on the value of $VARNAME (interpreted as a
#   path):
#
#     - empty paths are changed to '.'
#     - trailing slashes are removed
#     - repeated slashes are squeezed except a leading doubled slash '//'
#       (which might indicate a networked disk on some OS).
#
#   REFERENCE_STRING is used to turn '/' into '\' and vice-versa: if
#   REFERENCE_STRING contains some backslashes, all slashes and
#   backslashes are turned into backslashes, otherwise they are all
#   turned into slashes.
#
#   This makes processing of DOS filenames quite easier, because you
#   can turn a filename to the Unix notation, make your processing, and
#   turn it back to original notation.
#
#     filename='A:\FOO\\BAR\'
#     old_filename="$filename"
#     # Switch to the unix notation
#     adl_NORMALIZE_PATH([filename], ["/"])
#     # now we have $filename = 'A:/FOO/BAR' and we can process it as if
#     # it was a Unix path.  For instance let's say that you want
#     # to append '/subpath':
#     filename="$filename/subpath"
#     # finally switch back to the original notation
#     adl_NORMALIZE_PATH([filename], ["$old_filename"])
#     # now $filename equals to 'A:\FOO\BAR\subpath'
#
#   One good reason to make all path processing with the unix
#   convention is that backslashes have a special meaning in many
#   cases. For instance
#
#     expr 'A:\FOO' : 'A:\Foo'
#
#   will return 0 because the second argument is a regex in which
#   backslashes have to be backslashed. In other words, to have the two
#   strings to match you should write this instead:
#
#     expr 'A:\Foo' : 'A:\\Foo'
#
#   Such behavior makes DOS filenames extremely unpleasant to work
#   with. So temporary turn your paths to the Unix notation, and revert
#   them to the original notation after the processing. See the macro
#   adl_COMPUTE_RELATIVE_PATHS for a concrete example of this.
#
#   REFERENCE_STRING defaults to $VARIABLE, this means that slashes
#   will be converted to backslashes if $VARIABLE already contains some
#   backslashes (see $thirddir below).
#
#     firstdir='/usr/local//share'
#     seconddir='C:\Program Files\\'
#     thirddir='C:\home/usr/'
#     adl_NORMALIZE_PATH([firstdir])
#     adl_NORMALIZE_PATH([seconddir])
#     adl_NORMALIZE_PATH([thirddir])
#     # $firstdir = '/usr/local/share'
#     # $seconddir = 'C:\Program Files'
#     # $thirddir = 'C:\home\usr'
#
# LAST MODIFICATION
#
#   2006-10-22
#
# COPYLEFT
#
#   Copyright (c) 2006 Alexandre Duret-Lutz <adl@gnu.org>
#
#   This program 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 2 of the
#   License, or (at your option) any later version.
#
#   This program 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 this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
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#   owner gives unlimited permission to copy, distribute and modify the
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#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([adl_NORMALIZE_PATH],
[case ":[$]$1:" in
# change empty paths to '.'
  ::) $1='.' ;;
# strip trailing slashes
  :*[[\\/]]:) $1=`echo "[$]$1" | sed 's,[[\\/]]*[$],,'` ;;
  :*:) ;;
esac
# squeze repeated slashes
case ifelse($2,,"[$]$1",$2) in
# if the path contains any backslashes, turn slashes into backslashes
 *\\*) $1=`echo "[$]$1" | sed 's,\(.\)[[\\/]][[\\/]]*,\1\\\\,g'` ;;
# if the path contains slashes, also turn backslashes into slashes
 *) $1=`echo "[$]$1" | sed 's,\(.\)[[\\/]][[\\/]]*,\1/,g'` ;;
esac])