io.multiplex/backend-poll.lisp

   1 ;;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; indent-tabs-mode: nil -*-
   2 ;;;
   3 ;;; --- poll(2) multiplexer implementation.
   4 ;;;
   5
   6 (in-package :io.multiplex)
   7
   8 (defconstant +poll-priority+ 2)
   9
  10 (define-multiplexer poll-multiplexer +poll-priority+ (multiplexer)
  11   ((fd-set :initform (allocate-pollfd-set) :accessor fd-set-of)
  12    (fd-set-size :initform 5 :accessor fd-set-size-of)
  13    (fd-count :initform 0 :accessor fd-count-of)))
  14
  15 (defun allocate-pollfd-set (&optional (count 5))
  16   (let ((fds (foreign-alloc 'nix::pollfd :count count)))
  17     (nix:bzero fds (* nix::size-of-pollfd count))
  18     (values fds)))
  19
  20 (defmethod print-object ((mux poll-multiplexer) stream)
  21   (print-unreadable-object (mux stream :type nil :identity nil)
  22     (format stream "poll(2) multiplexer")))
  23
  24 (defmethod close-multiplexer progn ((mux poll-multiplexer))
  25   (foreign-free (fd-set-of mux))
  26   (setf (fd-set-of mux) nil))
  27
  28 (defvar *pollfd-table* (make-hash-table :test #'eql))
  29
  30 (defun calc-pollfd-flags (readp writep)
  31   (let ((flags 0))
  32     (when readp (setf flags (logior nix:pollin nix:pollrdhup nix:pollpri)))
  33     (when writep (setf flags (logior flags nix:pollout nix:pollhup)))
  34     (values flags)))
  35
  36 (defun set-pollfd-entry (fd-set index fd readp writep)
  37   (with-foreign-slots ((nix::fd nix::events nix::revents)
  38                        (mem-aref fd-set 'nix::pollfd index)
  39                        nix::pollfd)
  40     (setf nix::fd fd
  41           nix::revents 0
  42           nix::events (calc-pollfd-flags readp writep))))
  43
  44 (defun extend-pollfd-set (fd-set size)
  45   (let* ((new-size (+ size 5))
  46          (new-fd-set (foreign-alloc 'nix::pollfd :count new-size)))
  47     (nix:memcpy new-fd-set fd-set (* size nix::size-of-pollfd))
  48     (foreign-free fd-set)
  49     (values new-fd-set new-size)))
  50
  51 (defmethod monitor-fd ((mux poll-multiplexer) fd-entry)
  52   (let ((fd (fd-entry-fd fd-entry))
  53         (readp (fd-entry-read-handler fd-entry))
  54         (writep (fd-entry-write-handler fd-entry)))
  55     (with-accessors ((fd-set fd-set-of) (size fd-set-size-of)
  56                      (count fd-count-of)) mux
  57       (when (= count size)
  58         (setf (values fd-set size) (extend-pollfd-set fd-set size)))
  59       (set-pollfd-entry fd-set count fd readp writep)
  60       (setf (gethash fd *pollfd-table*) count)
  61       (incf count))))
  62
  63 (defmethod update-fd ((mux poll-multiplexer) fd-entry event-type edge-change)
  64   (declare (ignore event-type edge-change))
  65   (let* ((fd (fd-entry-fd fd-entry))
  66          (pos (gethash fd *pollfd-table*))
  67          (readp (fd-entry-read-handler fd-entry))
  68          (writep (fd-entry-write-handler fd-entry)))
  69     (with-accessors ((fd-set fd-set-of)) mux
  70       (set-pollfd-entry fd-set pos fd readp writep))))
  71
  72 (defun shrink-pollfd-set (fd-set count size pos)
  73   (let* ((new-size (if (> 5 (- size count)) (- size 5) size))
  74          (new-fd-set (foreign-alloc 'nix::pollfd :count new-size)))
  75     (when (plusp pos)
  76       (nix:memcpy new-fd-set fd-set (* pos nix::size-of-pollfd)))
  77     (when (< pos count)
  78       (nix:memcpy new-fd-set fd-set (* (- count pos) nix::size-of-pollfd)))
  79     (foreign-free fd-set)
  80     (values new-fd-set new-size)))
  81
  82 (defmethod unmonitor-fd ((mux poll-multiplexer) fd-entry)
  83   (let* ((fd (fd-entry-fd fd-entry))
  84          (pos (gethash fd *pollfd-table*)))
  85     (with-accessors ((fd-set fd-set-of) (size fd-set-size-of)
  86                      (count fd-count-of)) mux
  87       (setf (values fd-set size) (shrink-pollfd-set fd-set (1- count) size pos))
  88       (remhash fd *pollfd-table*)
  89       (decf count))))
  90
  91 (defmethod harvest-events ((mux poll-multiplexer) timeout)
  92   (with-accessors ((fd-set fd-set-of) (size fd-set-size-of)
  93                    (count fd-count-of)) mux
  94     ;; if there are no fds set and timeout is NULL
  95     ;; poll() blocks forever
  96     (when (and (zerop count)
  97                (null timeout))
  98       (warn "Non fds to monitor and no timeout set !")
  99       (return* nil))
 100     ;; FIXME: when does poll() return EBADF ?
 101     (nix:repeat-upon-condition-decreasing-timeout
 102         ((nix:eintr) tmp-timeout timeout)
 103       (nix:poll fd-set count (timeout->milisec tmp-timeout)))
 104     (harvest-pollfd-events fd-set count)))
 105
 106 (defun harvest-pollfd-events (fd-set count)
 107   (macrolet ((pollfd-slot (name index)
 108                `(foreign-slot-value (mem-aref fd-set 'nix::pollfd ,index)
 109                                     'nix::pollfd ,name)))
 110     (loop :for i :below count
 111           :for event := ()
 112           :for fd := (pollfd-slot 'nix::fd i)
 113           :for revents := (pollfd-slot 'nix::revents i)
 114        :do (flags-case revents
 115              ((nix:pollout nix:pollhup)              (push :write event))
 116              ((nix:pollin nix:pollrdhup nix:pollpri) (push :read event))
 117              ((nix:pollerr nix:pollnval)             (push :error event)))
 118        :when event :collect (list fd event))))