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1 ;; -*-Emacs-Lisp-*-
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2 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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3 ;;
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4 ;; File: efs-ovwrt.el
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5 ;; Release: $efs release: 1.15 $
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6 ;; Version: $Revision: 1.1 $
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7 ;; RCS:
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8 ;; Description: Utilities for overwriting functions with new definitions.
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9 ;; Author: Andy Norman <ange@hplb.hpl.hp.com>
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10 ;; Modified: Sun Nov 27 18:40:20 1994 by sandy on gandalf
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11 ;;
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12 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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13
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14 ;;; Although used by efs, these utilities could be of general use to other
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15 ;;; packages too. Keeping them separate from the main efs program
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16 ;;; makes it easier for other programs to require them.
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17
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18 (provide 'efs-ovwrt)
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19
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20 (defconst efs-ovwrt-version
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21 (concat (substring "$efs release: 1.15 $" 14 -2)
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22 "/"
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23 (substring "$Revision: 1.1 $" 11 -2)))
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24
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25 (defvar efs-overwrite-fmt
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26 "Note: This function has been modified to work with %s.")
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27
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28 ;; Make the byte compiler happy.
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29 (defvar file-name-handler-alist)
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30 (defvar inhibit-file-name-handlers)
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31 (defvar inhibit-file-name-operation)
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32
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33 (defun efs-safe-documentation (fun)
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34 "A documentation function that isn't quite as fragile."
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35 (condition-case ()
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36 (documentation fun)
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37 (error nil)))
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38
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39 (defun efs-overwrite-fn (package fun &optional newfun)
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40 "Overwrites a function with a new definition from PACKAGE.
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41 PACKAGE should be a string. The the function to be overwritten is FUN.
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42 The new definition is obtained from the optional NEWFUN. If ommitted,
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43 NEWFUN is taken to be PACKAGE-FUN. The original definition is stored in
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44 PACKAGE-real-FUN. The original documentation is placed on the new
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45 definition suitably augmented."
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46 (let* ((name (symbol-name fun))
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47 (saved (intern (concat package "-real-" name)))
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48 (new (or newfun (intern (concat package "-" name))))
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49 (nfun (symbol-function new))
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50 (exec-directory (if (or (equal (nth 3 command-line-args) "dump")
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51 (equal (nth 4 command-line-args) "dump"))
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52 "../etc/"
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53 exec-directory)))
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54
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55 (while (symbolp nfun)
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56 (setq nfun (symbol-function nfun)))
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57
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58 ;; Interpose the new function between the function symbol and the
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59 ;; original definition of the function symbol AT TIME OF FIRST LOAD.
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60 ;; We must only redefine the symbol-function of FUN the very first
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61 ;; time, to avoid blowing away stuff that overloads FUN after this.
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62
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63 ;; We direct the function symbol to the new function symbol
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64 ;; rather than function definition to allow reloading of this file or
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65 ;; redefining of the individual function (e.g., during debugging)
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66 ;; later after some other code has been loaded on top of our stuff.
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67
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68 (or (fboundp saved)
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69 (progn
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70 (fset saved (symbol-function fun))
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71 (fset fun new)))
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72
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73 ;; Rewrite the doc string on the new function. This should
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74 ;; be done every time the file is loaded (or a function is redefined),
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75 ;; because the underlying overloaded function may have changed its doc
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76 ;; string.
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77
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78 (let* ((doc-str (efs-safe-documentation saved))
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79 (ndoc-str (concat doc-str (and doc-str "\n")
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80 (format efs-overwrite-fmt package))))
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81
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82 (cond ((listp nfun)
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83 ;; Probe to test whether function is in preloaded read-only
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84 ;; memory, and if so make writable copy:
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85 (condition-case nil
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86 (setcar nfun (car nfun))
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87 (error
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88 (setq nfun (copy-sequence nfun)) ; shallow copy only
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89 (fset new nfun)))
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90 (let ((ndoc-cdr (nthcdr 2 nfun)))
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91 (if (stringp (car ndoc-cdr))
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92 ;; Replace the existing docstring.
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93 (setcar ndoc-cdr ndoc-str)
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94 ;; There is no docstring. Insert the overwrite msg.
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95 (setcdr ndoc-cdr (cons (car ndoc-cdr) (cdr ndoc-cdr)))
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96 (setcar ndoc-cdr (format efs-overwrite-fmt package)))))
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97 (t
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98 ;; it's an emacs19 compiled-code object
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99 (let ((new-code (append nfun nil))) ; turn it into a list
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100 (if (nthcdr 4 new-code)
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101 (setcar (nthcdr 4 new-code) ndoc-str)
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102 (setcdr (nthcdr 3 new-code) (cons ndoc-str nil)))
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103 (fset new (apply 'make-byte-code new-code))))))))
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104
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105
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106 ;;; end of efs-ovwrt.el
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