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) 2006-2008, 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 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 (define-condition poll-timeout (condition)
  43   ((fd :initarg :fd :reader poll-timeout-fd)
  44    (event-type :initarg :event-type :reader poll-timeout-event-type))
  45   (:report (lambda (condition stream)
  46              (format stream "Timeout occurred while polling file descriptor ~A for event ~S"
  47                      (poll-timeout-fd condition)
  48                      (poll-timeout-event-type condition))))
  49   (:documentation
  50    "Signaled when a timeout occurs while polling for I/O readiness
  51 of a file descriptor."))
  52
  53 (defun compute-poll-flags (type)
  54   (ecase type
  55     (:read (logior pollin pollrdhup pollpri))
  56     (:write (logior pollout pollhup))
  57     (:read-write (logior pollin pollrdhup pollpri pollout pollhup))))
  58
  59 (defun process-poll-revents (revents fd)
  60   (let ((readp nil) (writep nil))
  61     (flags-case revents
  62       ((pollin pollrdhup pollpri)
  63        (setf readp t))
  64       ((pollout pollhup) (setf writep t))
  65       ((pollerr) (error 'poll-error :fd fd))
  66       ((pollnval) (error 'poll-error :fd fd
  67                          :identifier "Invalid file descriptor")))
  68     (values readp writep)))
  69
  70 (defun wait-until-fd-ready (file-descriptor event-type &optional timeout errorp)
  71   "Poll file descriptor `FILE-DESCRIPTOR' for I/O readiness. `EVENT-TYPE' must be
  72 :READ, :WRITE or :READ-WRITE which means \"either :READ or :WRITE\".
  73 `TIMEOUT' must be either a non-negative integer measured in seconds,
  74 or `NIL' meaning no timeout at all. If `ERRORP' is not NIL and a timeout
  75 occurs, then a condition of type `POLL-TIMEOUT' is signaled.
  76 Returns two boolean values indicating readbility and writability of `FILE-DESCRIPTOR'."
  77   (flet ((poll-error (unix-err)
  78            (error 'poll-error :fd file-descriptor
  79                   :identifier (osicat-sys:system-error-identifier unix-err))))
  80     (with-foreign-object (pollfd 'pollfd)
  81       (bzero pollfd size-of-pollfd)
  82       (with-foreign-slots ((fd events revents) pollfd pollfd)
  83         (setf fd file-descriptor
  84               events (compute-poll-flags event-type))
  85         (handler-case
  86             (let ((ret (nix:repeat-upon-condition-decreasing-timeout
  87                            ((nix:eintr) tmp-timeout timeout)
  88                          (poll pollfd 1 (timeout->milisec timeout)))))
  89               (when (zerop ret)
  90                 (if errorp
  91                     (error 'poll-timeout :fd file-descriptor :event-type event-type)
  92                     (return-from wait-until-fd-ready (values nil nil)))))
  93           (nix:posix-error (err) (poll-error err)))
  94         (process-poll-revents revents file-descriptor)))))
  95
  96 (defun fd-ready-p (fd &optional (event-type :read))
  97   "Tests file-descriptor `FD' for I/O readiness. `EVENT-TYPE'
  98 must be :READ, :WRITE or :READ-WRITE which means \"either :READ
  99 or :WRITE\"."
 100   (multiple-value-bind (readp writep)
 101       (wait-until-fd-ready fd event-type 0)
 102     (ecase event-type
 103       (:read readp)
 104       (:write writep)
 105       (:read-write (or readp writep)))))
 106
 107 (defun fd-readablep (fd)
 108   (nth-value 0 (wait-until-fd-ready fd :read 0)))
 109
 110 (defun fd-writablep (fd)
 111   (nth-value 1 (wait-until-fd-ready fd :write 0)))