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;;; format-spec.el --- functions for formatting arbitrary formatting strings
;; Copyright (C) 1999-2015 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: tools
;; This file is part of GNU Emacs.
;; GNU Emacs 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 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs 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. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
(eval-when-compile (require 'cl))
(defun format-spec (format specification)
"Return a string based on FORMAT and SPECIFICATION.
FORMAT is a string containing `format'-like specs like \"bash %u %k\",
while SPECIFICATION is an alist mapping from format spec characters
to values. Any text properties on a %-spec itself are propagated to
the text that it generates."
(with-temp-buffer
(insert format)
(goto-char (point-min))
(while (search-forward "%" nil t)
(cond
;; Quoted percent sign.
((eq (char-after) ?%)
(delete-char 1))
;; Valid format spec.
((looking-at "\\([-0-9.]*\\)\\([a-zA-Z]\\)")
(let* ((num (match-string 1))
(spec (string-to-char (match-string 2)))
(val (assq spec specification)))
(unless val
(error "Invalid format character: `%%%c'" spec))
(setq val (cdr val))
;; Pad result to desired length.
(let ((text (format (concat "%" num "s") val)))
;; Insert first, to preserve text properties.
(insert-and-inherit text)
;; Delete the specifier body.
(delete-region (+ (match-beginning 0) (length text))
(+ (match-end 0) (length text)))
;; Delete the percent sign.
(delete-region (1- (match-beginning 0)) (match-beginning 0)))))
;; Signal an error on bogus format strings.
(t
(error "Invalid format string"))))
(buffer-string)))
(defun format-spec-make (&rest pairs)
"Return an alist suitable for use in `format-spec' based on PAIRS.
PAIRS is a list where every other element is a character and a value,
starting with a character."
(let (alist)
(while pairs
(unless (cdr pairs)
(error "Invalid list of pairs"))
(push (cons (car pairs) (cadr pairs)) alist)
(setq pairs (cddr pairs)))
(nreverse alist)))
(provide 'format-spec)
;;; format-spec.el ends here
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