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很少见的linux下的红外口的工具

      indicating the result of processing the command. In case of an
      error the following data is a message explaining the
      problem. This message can be used to create an error message for
      the user.<BR>

      If the command was successful, data is only sent for the
      commands that return some information. Note that a packet
      containing 0 lines of data can be a valid reply.
    </P>
    
    <!-- Writing LIRC Applications +++++++++++++++++++++++++++++++++++++++ -->
    
    <A NAME="library"></A><HR>
    
    <H2 ALIGN="CENTER">The lirc_client library</H2>
    <HR WIDTH="70%">
    
    <P>
      If you only want to make your application receive IR commands
      and if you don't want to mess with all the protocol stuff you
      can use the <em>lirc_client</em> library that comes with LIRC
      since version 0.6.0. With the help of this library your program
      can look as simple as this:
    </P>
    <PRE>
/*      &#36;Id: irexec.c,v 5.2 2000/02/02 20:28:42 columbus Exp $      */

/****************************************************************************
 ** irexec.c ****************************************************************
 ****************************************************************************
 *
 * irexec  - execute programs according to the pressed remote control buttons
 *
 * Copyright (C) 1998 Trent Piepho &lt;[e-mail]&gt;
 * Copyright (C) 1998 Christoph Bartelmus &lt;[e-mail]&gt;
 *
 */

#ifdef HAVE_CONFIG_H
# include &lt;config.h&gt;
#endif

#include &lt;errno.h&gt;
#include &lt;unistd.h&gt;
#include &lt;stdarg.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;
#include "lirc_client.h"

char *progname;

int main(int argc, char *argv[])
{
	struct lirc_config *config;

	progname=argv[0];
	if(argc&gt;2)
	{
		fprintf(stderr,"Usage: %s &lt;config file&gt;\n",progname);
		exit(EXIT_FAILURE);
	}
	if(lirc_init("irexec",1)==-1) exit(EXIT_FAILURE);

	if(lirc_readconfig(argc==2 ? argv[1]:NULL,&amp;config,NULL)==0)
	{
		char *code;
		char *c;
		int ret;

		while(lirc_nextcode(&amp;code)==0)
		{
			if(code==NULL) continue;
			while((ret=lirc_code2char(config,code,&amp;c))==0 &amp;&amp;
			      c!=NULL)
			{
#ifdef DEBUG
				printf("Execing command \"%s\"\n",c);
#endif
				system(c);
			}
			free(code);
			if(ret==-1) break;
		}
		lirc_freeconfig(config);
	}

	lirc_deinit();
	exit(EXIT_SUCCESS);
}</PRE>
    
    <P>
      Before anything else you have to include the header file for the
      lirc_client library. This is done with
    </P>
    <PRE>
#include &lt;lirc/lirc_client.h&gt;</PRE>
    <P>
      Note that our example differs in this point because it was taken
      directly from the lirc-0.6.0 source that comes with its own
      <em>lirc_client.h</em> but we have to use the one that is
      already installed on the system.
    </P>
    <P>
      The next step is to initialize the library code with
      <em>lirc_init()</em>. This function connects to lircd and does
      some internal init stuff.
    </P>
    <PRE>
int lirc_init(char *prog,int verbose);</PRE>
    <P>
      The first argument to this function is the string users will
      have to provide as <em>prog</em> token in their .lircrc config
      files. If the second argument is non-zero error messages will be
      printed to <em>stderr</em>. Otherwise no error messages will
      ever be displayed.  This function returns the file descriptor of
      the socket that is connected to lircd or -1 if an error
      occurred.
    </P>
    <P>
      The example continues by reading a config file. This is done by
      the <em>lirc_readconfig()</em> function:
    </P>
    <PRE>
int lirc_readconfig(char *file,struct lirc_config **config,
		    int (check)(char *s));</PRE>
    <P>
      If you want to load the default config file you should pass NULL
      as first argument. If you want to load some other config file
      the <em>file</em> argument should contain the complete path to
      the file. Your program should give the user the possibility to
      use an other than the default config file. You should also be
      able to load multiple config files by calling this function
      several times.<BR>

      The <em>config</em> argument is used to pass the pointer to the
      config file data structures back to your application. You will
      need it for calls to the <em>lirc_code2char()</em> function. The
      last argument is a call-back function that can be used to do
      syntax checks with the config strings. The library code will
      call the call-back function for all config strings where the
      <em>prog</em> token in the config file matches the prog string
      you provided with the <em>lirc_init()</em> function. If there is
      an error in the config string the call-back function should
      return -1, otherwise 0. If you don't need to do any syntax
      checks you can pass NULL here. The function returns -1 if an
      error occurred, 0 otherwise.
    </P>
    <P>
      The <em>lirc_nextcode()</em> function blocks until there is
      something available on the lircd socket. This way it can be used
      in the main loop of your program like in our example.
    </P>
    <PRE>
int lirc_nextcode(char **code);</PRE>
    <P>
      If an error occurs (usually this means that the socket has been
      closed by the daemon) this function returns -1. Otherwise it
      returns 0 and <em>code</em> points to the next string available
      in the data stream. This string has to be freed by your
      application using the <em>free(3)</em> function. If no complete
      string is available <em>code</em> will be NULL.<BR>

      If you use some GUI-toolkit for your program then you probably
      won't be able to use this function in your program's main loop
      because this is already handled by the GUI-toolkit. In this
      situation you should use the call-back abilities of the toolkit
      that will notify you whenever there is some input available from
      a file descriptor (you get the file descriptor from the
      <em>lirc_init()</em> function). E.g. you can use the
      <em>gdk_input_add()</em>/<em>gdk_input_remove</em>() functions
      with gtk or the <em>QSocketNotifier</em> class with Qt. If you
      don't have such functionality in your toolkit or can't use it
      for some reason you can still use SIGIO signals for this
      purpose. Check the documentation for your GUI-toolkit and
      signal(2) for further information.<BR>

      Please note that using call-backs you still have to use some
      kind of while loop to read strings from the socket because
      several strings may be available in the data stream and you will
      only get a notification for the first one. This poses a problem
      for us because <em>lirc_nextcode()</em> blocks until there is
      something available from the socket which is not what we need
      here. You can solve this problem by setting the
      <b>O_NONBLOCK</b> flag for the socket using the
      <em>fcntl(2)</em> function. Have a look at the current xirw code
      that is available from the LIRC homepage for an implementation
      example.
    </P>
    <P>
      To get the config string that the user has provided in the
      config file in response to a button press you use the following
      function:
    </P>
    <PRE>
int lirc_code2char(struct lirc_config *config,char *code,char **string);</PRE>
    <P>
      <em>config</em> is a pointer to the config file data structure
      that you can get with <em>lirc_readconfig()</em> and
      <em>code</em> is the code transmitted to your application on the
      lircd socket. If an action should be taken <em>string</em> will
      point to the config string the user has provided in the config
      file. The user might want to take several actions on a button
      press so you have to execute this function until <em>string</em>
      is NULL, which means that no more actions shall be taken, or an
      error occurs. The function returns -1 if an error occurred, 0
      otherwise.
    </P>
    <P>
      In our example there are only two clean-up functions to be
      explained.
    </P>
    <PRE>
void lirc_freeconfig(struct lirc_config *config);</PRE>
    <P>
      This functions frees the data structures associated with
      <em>config</em>.
    </P>
    <PRE>
int lirc_deinit();</PRE>
    <P>
      <em>lirc_deinit()</em> closes the connection to lircd and does
      some internal clean-up stuff.
    </P>
    <P>
      I encourage you to use autoconf and automake for your
      projects. To check for the lirc_client library all you have to
      insert to your <em>configure.in</em> file is the following:
    </P>
    <PRE>
dnl Check for LIRC client support
dnl This really is not worth making a separate file for it.

have_lirc=yes
AC_REQUIRE_CPP
AC_CHECK_LIB(lirc_client,lirc_init,
  AC_CHECK_HEADER(lirc/lirc_client.h,true,have_lirc=no),have_lirc=no)

if test "$have_lirc" = "yes"; then
dnl  AC_DEFINE(HAVE_LIRC);
  true;
else
  AC_MSG_ERROR([*** LIRC client support not available ***]);
fi</PRE>
    <P>
      There is also a more complex m4 macro in the contrib directory
      of the current LIRC distribution if you plan to add LIRC support
      to your application without using the lirc_client library.
    </P>
    <P>
      While developing LIRC applications you might find a <A
	HREF="http://www.fi.muni.cz/~xkutale1/en/lircemu/">emulator</A>
      for lircd useful. With this emulator you don't need a remote
      control to generate LIRC events. That way you can develop LIRC
      applications even if you don't have a LIRC compatible device
      yourself.
    </P>
    
    <A NAME="bugs"></A><HR>
    <H1 ALIGN="CENTER">Known bugs</H1>
    <HR WIDTH="70%">
    
    <UL>
      <LI>
	<P>
	  If you use the <em>lirc_serial</em> or
	  <em>lirc_parallel</em> driver regularly to transmit
	  infra-red signals you might notice that your system clock
	  will slow down. During transmit the driver turns off
	  interrupts and hence some clock interrupts might get lost
	  causing system clock inaccuracy. Unfortunately in order to
	  ensure a good signal timing interrupts have to be
	  disabled. Currently no work-around is known for this problem
	  except using a program like <em>netdate</em> to synchronize
	  your system clock regularly.
	</P>
      </LI>
      <LI>
	<P>
	  The <em>lirc_serial</em> and <em>lirc_parallel</em> drivers
	  measure the time between interrupts on the serial resp.
	  parallel port to get a pulse and space representation of the
	  incoming infra-red signal. If interrupts are disabled by the
	  CPU for a rather long time (&gt;100 &micro;s, which happens
	  often e.g. during heavy IDE disk activity) some interrupts
	  might get lost and the incoming data stream becomes
	  disturbed. In this case decoding of the infra-red signal
	  will fail. This is the downside of the really simple
	  receiver circuits and can't be addressed in software except
	  keeping the time where interrupts are disabled to a minimum.
	</P>
      </LI>
    </UL>
    

<!-- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

		<BR><BR>
		<CENTER>[<A HREF="http://www.lirc.org/">LIRC homepage</A>]<BR>
		  <I>The LIRC Manual, last update: 12-Sep-2002</I></CENTER>
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