;;; dwarf-mode.el --- Browser for DWARF information.

;; Version: 1.2

;; Copyright (C) 2012-2016 Free Software Foundation, Inc.

;; This file is not part of GNU Emacs, but is distributed under the
;; same terms:

;; 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/>.

;;; Code:

(defvar dwarf-objdump-program "objdump")

(defconst dwarf-font-lock-keywords
  '(
    ;; Name and linkage name.
    ("DW_AT_[a-z_]*name\\s *: .*:\\(.*\\)\\s *$"
     (1 font-lock-function-name-face))

    ("Compilation Unit @ offset 0x[0-9a-f]+"
     (0 font-lock-string-face))
    ))

(defvar dwarf-file nil
  "Buffer-local variable holding the file name passed to objdump.")

;; Expand a "..." to show all the child DIES.  NEW-DEPTH controls how
;; deep to display the new dies; `nil' means display all of them.
(defun dwarf-do-insert-substructure (new-depth die)
  (let ((inhibit-read-only t))
    (beginning-of-line)
    (delete-region (point) (progn
			     (end-of-line)
			     (forward-char)
			     (point)))
    (save-excursion
      (apply #'call-process dwarf-objdump-program nil (current-buffer) nil
	     "-Wi" (concat "--dwarf-start=0x" die)
	     (expand-file-name dwarf-file)
	     (if new-depth (list (concat "--dwarf-depth="
					 (int-to-string new-depth))))))
    (set-buffer-modified-p nil)))

(defun dwarf-insert-substructure-button (die)
  (beginning-of-line)
  (unless (looking-at "^ <\\([0-9]+\\)>")
    (error "Unrecognized line."))
  (let ((new-depth (1+ (string-to-number (match-string 1)))))
    (dwarf-do-insert-substructure new-depth die)))

(defun dwarf-insert-substructure (arg)
  "Expand a `...' to show children of the current DIE.
By default, expands just one level of children.
A prefix argument means expand all children."
  (interactive "P")
  (beginning-of-line)
  (unless (looking-at "^ <\\([0-9]+\\)><\\([0-9a-f]+\\)>")
    (error "Unrecognized line."))
  (let ((die (match-string 2)))
    (if arg
	(dwarf-do-insert-substructure nil die)
      (dwarf-insert-substructure-button die))))

;; Called when a button is pressed.
;; Either follows a DIE reference, or expands a "...".
(defun dwarf-die-button-action (button)
  (let* ((die (button-get button 'die))
	 ;; Note that the first number can only be decimal.
	 (die-rx (concat "^\\s *\\(<[0-9]+>\\)?<"
			 die ">[^<]"))
	 (old (point))
	 (is-ref (button-get button 'die-ref)))
    (if is-ref
	(progn
	  (goto-char (point-min))
	  (if (re-search-forward die-rx nil 'move)
	      (push-mark old)
	    (goto-char old)
	    (error "Could not find DIE <0x%s>" die)))
      (dwarf-insert-substructure-button die))))

;; Button definition.
(define-button-type 'dwarf-die-button
  'follow-link t
  'action #'dwarf-die-button-action)

;; Helper regexp to match a DIE reference.
(defconst dwarf-die-reference "\\(<0x\\([0-9a-f]+\\)>\\)")

;; Helper regexp to match a `...' indicating that there are hidden
;; children.
(defconst dwarf-die-more "^ <[0-9]+><\\([0-9a-z]+\\)>: \\([.][.][.]\\)")

;; jit-lock callback function to fontify a region.  This applies the
;; buttons, since AFAICT there is no good way to apply buttons via
;; font-lock.
(defun dwarf-fontify-region (start end)
  (save-excursion
    (let ((beg-line (progn (goto-char start) (line-beginning-position)))
	  (end-line (progn (goto-char end) (line-end-position))))
      (goto-char beg-line)
      (while (re-search-forward dwarf-die-reference end-line 'move)
	(let ((b-start (match-beginning 1))
	      (b-end (match-end 1))
	      (hex (match-string-no-properties 2)))
	  (make-text-button b-start b-end :type 'dwarf-die-button
			    'die hex 'die-ref t)))
      ;; This is a bogus approach.  Why can't we make buttons from the
      ;; font-lock defaults?
      (goto-char beg-line)
      (while (re-search-forward dwarf-die-more end-line 'move)
	(let ((hex (match-string-no-properties 1))
	      (b-start (match-beginning 2))
	      (b-end (match-end 2)))
	  (make-text-button b-start b-end :type 'dwarf-die-button
			    'die hex 'die-ref nil))))))

;; Run objdump and insert the contents into the buffer.  The arguments
;; are the way they are because this is also called as a
;; revert-buffer-function.
(defun dwarf-do-refresh (&rest ignore)
  (let ((inhibit-read-only t))
    (erase-buffer)
    (save-excursion
      (call-process dwarf-objdump-program
		    nil (current-buffer) nil
		    "-Wi" "--dwarf-depth=1"
		    (expand-file-name dwarf-file)))
    (set-buffer-modified-p nil)))

(define-derived-mode dwarf-mode special-mode "DWARF"
  "Major mode for browsing DWARF output.

\\{dwarf-mode-map}"

  (set (make-local-variable 'font-lock-defaults) '(dwarf-font-lock-keywords))
  ;; FIXME: we could be smarter and check the file time.
  (set (make-local-variable 'revert-buffer-function) #'dwarf-do-refresh)
  (jit-lock-register #'dwarf-fontify-region))

(define-key dwarf-mode-map [(control ?m)] #'dwarf-insert-substructure)

;;;###autoload
(defun dwarf-browse (file)
  "Invoke `objdump' and put output into a `dwarf-mode' buffer.
This is the main interface to `dwarf-mode'."
  (interactive "fFile name: ")
  (let* ((base-name (file-name-nondirectory file))
	 (buffer (generate-new-buffer (concat "*DWARF for " base-name "*"))))
    (pop-to-buffer buffer)
    (dwarf-mode)
    (set (make-local-variable 'dwarf-file) file)
    (dwarf-do-refresh)))

(provide 'dwarf-mode)

;;; dwarf-mode.el ends here