lisp/format-spec.el

   1 ;;; format-spec.el --- functions for formatting arbitrary formatting strings
   2
   3 ;; Copyright (C) 1999-2016 Free Software Foundation, Inc.
   4
   5 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   6 ;; Keywords: tools
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;;; Code:
  26
  27 (eval-when-compile (require 'cl))
  28
  29 (defun format-spec (format specification)
  30   "Return a string based on FORMAT and SPECIFICATION.
  31 FORMAT is a string containing `format'-like specs like \"bash %u %k\",
  32 while SPECIFICATION is an alist mapping from format spec characters
  33 to values.  Any text properties on a %-spec itself are propagated to
  34 the text that it generates."
  35   (with-temp-buffer
  36     (insert format)
  37     (goto-char (point-min))
  38     (while (search-forward "%" nil t)
  39       (cond
  40        ;; Quoted percent sign.
  41        ((eq (char-after) ?%)
  42         (delete-char 1))
  43        ;; Valid format spec.
  44        ((looking-at "\\([-0-9.]*\\)\\([a-zA-Z]\\)")
  45         (let* ((num (match-string 1))
  46                (spec (if (featurep 'xemacs)
  47                          (char-to-int (string-to-char (match-string 2)))
  48                        (string-to-char (match-string 2))))
  49                (val (assq spec specification)))
  50           (unless val
  51             (error "Invalid format character: `%%%c'" spec))
  52           (setq val (cdr val))
  53           ;; Pad result to desired length.
  54           (let ((text (format (concat "%" num "s") val)))
  55             ;; Insert first, to preserve text properties.
  56             (insert-and-inherit text)
  57             ;; Delete the specifier body.
  58             (delete-region (+ (match-beginning 0) (length text))
  59                            (+ (match-end 0) (length text)))
  60             ;; Delete the percent sign.
  61             (delete-region (1- (match-beginning 0)) (match-beginning 0)))))
  62        ;; Signal an error on bogus format strings.
  63        (t
  64         (error "Invalid format string"))))
  65     (buffer-string)))
  66
  67 (defun format-spec-make (&rest pairs)
  68   "Return an alist suitable for use in `format-spec' based on PAIRS.
  69 PAIRS is a list where every other element is a character and a value,
  70 starting with a character."
  71   (let (alist)
  72     (while pairs
  73       (unless (cdr pairs)
  74         (error "Invalid list of pairs"))
  75       (push (cons (if (featurep 'xemacs)
  76                       (if (characterp (car pairs))
  77                           (char-to-int (car pairs))
  78                         (car pairs))
  79                     (car pairs))
  80                   (cadr pairs))
  81             alist)
  82       (setq pairs (cddr pairs)))
  83     (nreverse alist)))
  84
  85 (provide 'format-spec)
  86
  87 ;;; format-spec.el ends here