io-multiplex/fd-wait.lisp

   1 ;;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; Indent-tabs-mode: NIL -*-
   2 ;;;
   3 ;;; fd-wait.lisp --- Wait for events on single FDs.
   4 ;;;
   5 ;;; Copyright (C) 2006-2007, Stelian Ionescu  <sionescu@common-lisp.net>
   6 ;;;
   7 ;;; This code is free software; you can redistribute it and/or
   8 ;;; modify it under the terms of the version 2.1 of
   9 ;;; the GNU Lesser General Public License as published by
  10 ;;; the Free Software Foundation, as clarified by the
  11 ;;; preamble found here:
  12 ;;;     http://opensource.franz.com/preamble.html
  13 ;;;
  14 ;;; This program is distributed in the hope that it will be useful,
  15 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;;; GNU General Public License for more details.
  18 ;;;
  19 ;;; You should have received a copy of the GNU Lesser General
  20 ;;; Public License along with this library; if not, write to the
  21 ;;; Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
  22 ;;; Boston, MA 02110-1301, USA
  23
  24 (in-package :io.multiplex)
  25
  26 ;;; FIXME: Until a way to autodetect platform features is implemented
  27 #+(or darwin freebsd)
  28 (define-constant nix::pollrdhup 0)
  29
  30 (define-condition poll-error (error)
  31   ((fd :initarg :fd :reader poll-error-fd)
  32    (identifier :initarg :identifier :initform "Unknown error"
  33                :reader poll-error-identifier))
  34   (:report (lambda (condition stream)
  35              (format stream "Error caught while polling file descriptor ~A: ~A"
  36                      (poll-error-fd condition)
  37                      (poll-error-identifier condition))))
  38   (:documentation
  39    "Signaled when an error occurs while polling for I/O readiness
  40 of a file descriptor."))
  41
  42 (defun compute-poll-flags (type)
  43   (ecase type
  44     (:read (logior nix:pollin nix:pollrdhup nix:pollpri))
  45     (:write (logior nix:pollout nix:pollhup))
  46     (:read-write (logior nix:pollin nix:pollrdhup nix:pollpri
  47                          nix:pollout nix:pollhup))))
  48
  49 (defun process-poll-revents (revents fd)
  50   (let ((readp nil) (writep nil))
  51     (flags-case revents
  52       ((nix:pollin nix:pollrdhup nix:pollpri)
  53        (setf readp t))
  54       ((nix:pollout nix:pollhup) (setf writep t))
  55       ((nix:pollerr) (error 'poll-error :fd fd))
  56       ((nix:pollnval) (error 'poll-error :fd fd
  57                               :identifier "Invalid file descriptor")))
  58     (values readp writep)))
  59
  60 (defun wait-until-fd-ready (fd event-type &optional timeout)
  61   "Poll file descriptor `FD' for I/O readiness. `EVENT-TYPE' must be
  62 :READ, :WRITE or :READ-WRITE which means \"either :READ or :WRITE\".
  63 `TIMEOUT' must be either a non-negative integer measured in seconds,
  64 or `NIL' meaning no timeout at all."
  65   (flet ((poll-error (unix-err)
  66            (error 'poll-error :fd fd
  67                   :identifier (osicat-sys:system-error-identifier unix-err))))
  68     (with-foreign-object (pollfd 'nix::pollfd)
  69       (nix:bzero pollfd nix::size-of-pollfd)
  70       (with-foreign-slots ((nix::fd nix::events nix::revents)
  71                            pollfd nix::pollfd)
  72         (setf nix::fd fd
  73               nix::events (compute-poll-flags event-type))
  74         (handler-case
  75             (let ((ret (nix:repeat-upon-condition-decreasing-timeout
  76                            ((nix:eintr) tmp-timeout timeout)
  77                          (nix:poll pollfd 1 (timeout->milisec timeout)))))
  78               (when (zerop ret)
  79                 (return-from wait-until-fd-ready (values nil nil))))
  80           (nix:posix-error (err) (poll-error err)))
  81         (process-poll-revents nix::revents fd)))))
  82
  83 (defun fd-ready-p (fd &optional (event-type :read))
  84   "Tests file-descriptor `FD' for I/O readiness. `EVENT-TYPE'
  85 must be :READ, :WRITE or :READ-WRITE which means \"either :READ
  86 or :WRITE\"."
  87   (multiple-value-bind (readp writep)
  88       (wait-until-fd-ready fd event-type 0)
  89     (ecase event-type
  90       (:read readp)
  91       (:write writep)
  92       (:read-write (or readp writep)))))
  93
  94 (defun fd-readablep (fd)
  95   (nth-value 0 (wait-until-fd-ready fd :read 0)))
  96
  97 (defun fd-writablep (fd)
  98   (nth-value 1 (wait-until-fd-ready fd :write 0)))