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 ;;; ppindent.el --- Indents C preprocessor directives
 
 ;; Copyright (C) 2007 Free Software Foundation, Inc.
 
 ;; Author: Craig McDaniel <craigmcd@gmail.com>
 ;; Keywords: languages, c
 ;; Maintainer: Craig McDaniel <craigmcd@gmail.com>
 
 ;; This file 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, or (at your option)
 ;; any later version.
 
 ;; This file 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 GNU Emacs; see the file COPYING. If not, write to
 ;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 ;; Boston, MA 02111-1307, USA.
 
 ;;; Commentary:
 
 ;; PPINDENT indents C-preprocessor statements depending on the current
 ;; #if..., #el.., #endif level. It only modifies lines with "#" as the
 ;; first non-blank character and therefore does not conflict with the
 ;; normal C indentation. Unlike a true indent, it inserts the
 ;; requisite number of spaces after, rather than before the "#"
 ;; character. This type of preprocesor indent is commonly used to
 ;; provide the most compatibility with different C-compilers.
 ;;
 ;; Example:
 
 ;;        #ifdef WOO
 ;;        ....
 ;;        #if defined(X) && !defined(Y)
 ;;        #ifdef Q8
 ;;        ...
 ;;        #else
 ;;        ...
 ;;        ....
 ;;        #elif defined (Z)
 ;;        ....
 ;;        #endif
 ;;        #endif
 ;;        #endif
 
 ;; After "M-x ppindent-c" becomes:
 
 ;;        #ifdef WOO
 ;;        ....
-;;        #  if defined(X) && !defined(Y)
+;;          #if defined(X) && !defined(Y)
-;;        #    ifdef Q8
+;;            #ifdef Q8
 ;;        ...
-;;        #    else
+;;            #else
 ;;        ...
 ;;        ....
-;;        #    elif defined (Z)
+;;            #elif defined (Z)
 ;;        ....
-;;        #    endif
+;;            #endif
-;;        #  endif
+;;          #endif
 ;;        #endif
 
 ;; Two functions are provided: PPINDENT-C indents as described
 ;; above. PPINDENT-H does not indent the first level, assuming that
 ;; .h/.hpp files use an #ifdef guard around the entire file.
 
 ;; You can customize PPINDENT-INCREMENT if you want to use something
 ;; other than 2 spaces for the indent.
 
 ;;; History:
 
 ;; 2007-01-19 WCM Initial version
 
 ;;; Code:
 
 (provide 'ppindent)
 
 (defgroup pp-indent nil
   "Indent C preproccessor directives."
   :group 'c)
 
 (defcustom ppindent-increment 2
   "Number of spaces per indention level.
 
 Used in C pre-processor indent functions ppindent-c and ppindent-h"
   :type 'number
   :group 'pp-indent)
 
 (defun starts-withp (str prefix)
   "str starts with prefix"
   (eql (compare-strings prefix nil nil str nil (length prefix)) t))
 
 (defun my-make-string (length init)
   "just like make-string, but makes an empty string if length is negative"
   (when (minusp length)
     (setf length 0))
   (make-string length init))
 
 (defun ppindent-aux (start)
   (let ((cnt start))
     (goto-char (point-min))
     (while (re-search-forward "^[ \t]*#[ \t]*\\(.*\\)" nil t)
       (cond ((starts-withp (match-string-no-properties 1) "if")
              (replace-match (concat (my-make-string cnt ?\s) "#\\1"))
              (incf cnt ppindent-increment))
             ((starts-withp (match-string-no-properties 1) "el")
              (when (< (- cnt ppindent-increment) start)
                (throw 'err `(,(line-number-at-pos) "Unmatched #else or #elif")))
              (replace-match (concat (my-make-string
                                          (- cnt ppindent-increment)
                                          ?\s) "#\\1")))
             ((starts-withp (match-string-no-properties 1) "endif")
              (when (< (- cnt ppindent-increment) start)
                (throw 'err `(,(line-number-at-pos) "Unmatched #endif")))
              (decf cnt ppindent-increment)
              (replace-match (concat (my-make-string cnt ?\s) "#\\1")))
             (t
              (replace-match (concat (my-make-string cnt ?\s) "#\\1")))))))
 
 (defun ppindent-buffer (start)
   (let ((result (catch 'err (save-excursion (ppindent-aux start)))))
     (when result
       (goto-line (car result))
       (error "Error: %s" (cadr result)))))
 
 (defun ppindent-c ()
   "Indent all C pre-processor statements"
   (interactive)
   (ppindent-buffer 0))
 
 (defun ppindent-h ()
   "Indent C pre-processor statements, keeping first level #ifdef unindented"
   (interactive)
   (ppindent-buffer (- ppindent-increment)))