#!@GUILE@ -ds
!#
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2017 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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 Guix 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 Guix.  If not, see <http://www.gnu.org/licenses/>.

;;;
;;; List files being used at run time; these files are garbage collector
;;; roots.  This is equivalent to `find-runtime-roots.pl' in Nix.
;;;

(use-modules (ice-9 ftw)
             (ice-9 regex)
             (ice-9 rdelim)
             (ice-9 popen)
             (srfi srfi-1)
             (srfi srfi-26)
             (rnrs io ports))

(define %proc-directory
  ;; Mount point of Linuxish /proc file system.
  "/proc")

(define %store-directory
  (or (getenv "NIX_STORE_DIR")
      "@storedir@"))

(define (proc-file-roots dir file)
  "Return a one-element list containing the file pointed to by DIR/FILE,
or the empty list."
  (or (and=> (false-if-exception (readlink (string-append dir "/" file)))
             list)
      '()))

(define proc-exe-roots (cut proc-file-roots <> "exe"))
(define proc-cwd-roots (cut proc-file-roots <> "cwd"))

(define (proc-fd-roots dir)
  "Return the list of store files referenced by DIR, which is a
/proc/XYZ directory."
  (let ((dir (string-append dir "/fd")))
    (filter-map (lambda (file)
                  (let ((target (false-if-exception
                                 (readlink (string-append dir "/" file)))))
                    (and target
                         (string-prefix? "/" target)
                         target)))
                (scandir dir string->number))))

(define (proc-maps-roots dir)
  "Return the list of store files referenced by DIR, which is a
/proc/XYZ directory."
  (define %file-mapping-line
    (make-regexp "^.*[[:blank:]]+/([^ ]+)$"))

  (call-with-input-file (string-append dir "/maps")
    (lambda (maps)
      (let loop ((line  (read-line maps))
                 (roots '()))
        (cond ((eof-object? line)
               roots)
              ((regexp-exec %file-mapping-line line)
               =>
               (lambda (match)
                 (let ((file (string-append "/"
                                            (match:substring match 1))))
                   (loop (read-line maps)
                         (cons file roots)))))
              (else
               (loop (read-line maps) roots)))))))

(define (proc-environ-roots dir)
  "Return the list of store files referenced by DIR/environ, where DIR is a
/proc/XYZ directory."
  (define split-on-nul
    (cute string-tokenize <>
          (char-set-complement (char-set #\nul))))

  (define (rhs-file-names str)
    (let ((equal (string-index str #\=)))
      (if equal
          (let* ((str (substring str (+ 1 equal)))
                 (rx  (string-append (regexp-quote %store-directory)
                                     "/[0-9a-z]{32}-[a-zA-Z0-9\\._+-]+")))
            (map match:substring (list-matches rx str)))
          '())))

  (define environ
    (string-append dir "/environ"))

  (append-map rhs-file-names
              (split-on-nul
               (call-with-input-file environ
                 get-string-all))))

(define (lsof-roots)
  "Return the list of roots as found by calling `lsof'."
  (define parent (getpid))

  (catch 'system-error
    (lambda ()
      (let ((pipe (catch 'system-error
                    (lambda ()
                      (open-pipe* OPEN_READ "lsof" "-n" "-w" "-F" "n"))
                    (lambda args
                      ;; In Guile 2.0.5, when (ice-9 popen) was still written
                      ;; in Scheme, 'open-pipe*' would leave the child process
                      ;; behind it when 'execlp' failed (that was mostly
                      ;; harmless though, because the uncaught exception would
                      ;; cause it to terminate after printing a backtrace.)
                      ;; Make sure that doesn't happen.
                      (if (= (getpid) parent)
                          (apply throw args)
                          (begin
                            (format (current-error-port)
                                    "failed to execute 'lsof': ~a~%"
                                    (strerror (system-error-errno args)))
                            (primitive-exit 1)))))))
        (define %file-rx
          (make-regexp "^n/(.*)$"))

        ;; We're going to read it all.
        (setvbuf pipe _IOFBF 16384)

        (let loop ((line  (read-line pipe))
                   (roots '()))
          (cond ((eof-object? line)
                 (begin
                   (close-pipe pipe)
                   roots))
                ((regexp-exec %file-rx line)
                 =>
                 (lambda (match)
                   (loop (read-line pipe)
                         (cons (string-append "/"
                                              (match:substring match 1))
                               roots))))
                (else
                 (loop (read-line pipe) roots))))))
    (lambda _
      '())))

(let ((proc (format #f "~a/~a" %proc-directory (getpid))))
  (for-each (cut simple-format #t "~a~%" <>)
            (delete-duplicates
             (let ((proc-roots (if (file-exists? proc)
                                   (append (proc-exe-roots proc)
                                           (proc-cwd-roots proc)
                                           (proc-fd-roots proc)
                                           (proc-maps-roots proc)
                                           (proc-environ-roots proc))
                                   '())))
               (append proc-roots (lsof-roots))))))
