plugin_fifo.c

/* $Id$
 * $URL$
 *
 * Fifo plugin
 *
 * Copyright (C) 2008 Michael Vogt <michu@neophob.com>
 * Copyright (C) 2010 Mattia Jona-Lasinio <mjona@users.sourceforge.net>
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 The LCD4Linux Team <lcd4linux-devel@users.sourceforge.net>
 *
 * This file is part of LCD4Linux.
 *
 * LCD4Linux 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 2, or (at your option)
 * any later version.
 *
 * LCD4Linux 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 this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/*
 * Configuration parameters:
 *
 * - FifoPath 'string'	: use <string> as the fifo complete file path
 *			  If absent use  /tmp/lcd4linux.fifo)
 *
 * - FifoBufSize num	: if the plugin is unable to determine the display size then
 *			  set the size of the internal buffer to <num> characters
 *			  otherwise use the display size (number of columns).
 *			  If no display size is available and no FifoBufSize parameter
  *			  is specified then arbitrarily set the internal buffer size
 *			  to 80 characters.
 */

#include "config.h"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <signal.h>

#include "debug.h"
#include "plugin.h"
#include "cfg.h"

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif

#define FIFO_MAXPATH		256
#define FIFO_DEFAULT_PATH	/tmp/lcd4linux.fifo
#define FIFO_DEFAULT_BUFSIZE	80
#define str(s) #s
#define string(s) str(s)

struct FifoData {
    char *path;
    char *msg;
    int msglen;
    int input;
    int created;
};

static struct FifoData fd = {
    .path = NULL,
    .msg = NULL,
    .msglen = -1,
    .input = -1,
    .created = -1,
};


static int confFifo(struct FifoData *p)
{
    char *path, *disp, *sect, *fifosect = "Plugin:FIFO";
    unsigned int pathlen;

    info("[FIFO] Reading config file '%s'", cfg_source());

    path = cfg_get(fifosect, "FifoPath", string(FIFO_DEFAULT_PATH));
    pathlen = strlen(path);
    if (pathlen == 0) {
	info("[FIFO] Invalid '%s.FifoPath' entry from '%s'. "
	     "Assuming " string(FIFO_DEFAULT_PATH), fifosect, cfg_source());
	free(path);
	path = strdup(string(FIFO_DEFAULT_PATH));
	pathlen = strlen(path);
    }
    if (pathlen > FIFO_MAXPATH) {
	error("[FIFO] Error: Too long '%s.FifoPath' entry from '%s'. "
	      "(MAX " string(FIFO_MAXPATH) " chars)", fifosect, cfg_source());
	free(path);
	return (-1);
    }
    info("[FIFO] Read '%s.FifoPath' value is '%s'", fifosect, path);

    disp = cfg_get(NULL, "Display", NULL);
    if (disp == NULL) {
	error("[FIFO] Error: Could not get the Display name from '%s'", cfg_source());
	free(path);
	return (-1);
    }
    if ((sect = malloc(1 + strlen("Display:") + strlen(disp))) == NULL) {
	error("[FIFO] Error: Memory allocation failed");
	free(disp);
	free(path);
	return (-1);
    }
    strcpy(sect, "Display:");
    strcat(sect, disp);
    info("[FIFO] Using display '%s'.", disp);
    free(disp);

    disp = cfg_get(sect, "Size", NULL);
    if (disp != NULL) {
	info("[FIFO] Getting the buffer size from '%s.Size'", sect);
	if (sscanf(disp, "%dx%*d", &p->msglen) != 1) {
	    info("[FIFO] Could not determine the display size. " "Assuming " string(FIFO_DEFAULT_BUFSIZE));
	    p->msglen = FIFO_DEFAULT_BUFSIZE;
	}
	free(disp);
    } else {
	info("[FIFO] Could not find a '%s.Size' entry.", sect);
	if (cfg_number(fifosect, "FifoBufSize", FIFO_DEFAULT_BUFSIZE, 0, -1, &p->msglen) > 0) {
	    info("[FIFO] Getting the buffer size from '%s.FifoBufSize'", fifosect);
	} else {
	    info("[FIFO] Could not find a valid '%s.FifoBufSize' entry. "
		 "Assuming " string(FIFO_DEFAULT_BUFSIZE), fifosect);
	    p->msglen = FIFO_DEFAULT_BUFSIZE;
	}
    }
    info("[FIFO] Read buffer size is '%d'", p->msglen);
    free(sect);

    if ((p->msg = malloc(2 + pathlen + p->msglen)) == NULL) {
	error("[FIFO] Error: Memory allocation failed");
	free(path);
	return (-1);
    }
    p->msg[0] = 0;
    p->path = p->msg + p->msglen + 1;
    strcpy(p->path, path);
    free(path);

    return (0);
}


static int makeFifo(struct FifoData *p)
{
    struct stat st;

    if (stat(p->path, &st) < 0) {
	if (errno == ENOENT) {
	    if (mkfifo(p->path, 0666) == 0) {
		p->created = 1;

		return (0);
	    }
	    error("Couldn't create FIFO \"%s\": %s\n", p->path, strerror(errno));

	    return (-1);
	}
	error("Failed to stat FIFO \"%s\": %s\n", p->path, strerror(errno));

	return (-1);
    }

    if (!S_ISFIFO(st.st_mode)) {
	error("\"%s\" already exists, but is not a FIFO", p->path);

	return (-1);
    }

    return (0);
}


static void closeFifo(struct FifoData *p)
{
    struct stat st;

    if (p->input >= 0) {
	close(p->input);
	p->input = -1;
    }

    if ((p->created >= 0) && (stat(p->path, &st) == 0)) {
	debug("Removing FIFO \"%s\"\n", p->path);
	if (unlink(p->path) < 0) {
	    error("Could not remove FIFO \"%s\": %s\n", p->path, strerror(errno));

	    return;
	}
	p->created = -1;
    }

    if (p->msg) {
	free(p->msg);
	p->msg = p->path = NULL;
	p->msglen = -1;
    }
}


static int openFifo(struct FifoData *p)
{
    if (p->created < 0) {
	error("Error: FIFO \"%s\" does not exist: %s\n", p->path, strerror(errno));

	return (-1);
    }

    if ((p->input = open(p->path, O_RDONLY | O_NONBLOCK)) < 0) {
	error("Could not open FIFO \"%s\" for reading: %s\n", p->path, strerror(errno));
	closeFifo(p);

	return (-1);
    }

    return (0);
}


static int startFifo(struct FifoData *p)
{
    int res;

    if ((res = confFifo(p)))
	return (res);

    if ((res = makeFifo(p)))
	return (res);

    if ((res = openFifo(p)))
	return (res);

    /* ignore broken pipe */
    signal(SIGPIPE, SIG_IGN);

    return (res);
}


static void readFifo(struct FifoData *p)
{
    int bytes;

    bytes = read(p->input, p->msg, p->msglen);
    if (bytes == 0)
	return;

    if (bytes > 0) {
	p->msg[bytes] = 0;
	while (bytes--)
	    if (p->msg[bytes] < 0x20)
		p->msg[bytes] = ' ';
    } else {
	error("[FIFO] Error %i: %s", errno, strerror(errno));
	strcpy(p->msg, "ERROR");
    }
}


static void runFifo(RESULT * result)
{
    static int state = 1;
    struct FifoData *p = &fd;
    char *s;

    switch (state) {
    case 1:
	/* Called for the first time. Set up everything. */
	state = startFifo(p);
	s = "";
	break;

    case 0:
	/* Init went fine. Now run in normal operation mode. */
	readFifo(p);
	s = p->msg;
	break;

    default:
	/* There was an error somewhere in init. Do nothing. */
	s = "ERROR";
	break;
    }

    /* Store the result */
    SetResult(&result, R_STRING, s);
}


/* plugin initialization */
int plugin_init_fifo(void)
{
    AddFunction("fifo::read", 0, runFifo);

    return (0);
}


void plugin_exit_fifo(void)
{
    closeFifo(&fd);
}