sane-project-backends/backend/escl/escl_devices.c

/* sane - Scanner Access Now Easy.

   Copyright (C) 2019 Touboul Nathane
   Copyright (C) 2019 Thierry HUCHARD <thierry@ordissimo.com>

   This file is part of the SANE package.

   SANE 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 3 of the License, or (at your
   option) any later version.

   SANE 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 sane; see the file COPYING.  If not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   This file implements a SANE backend for eSCL scanners.  */

#define DEBUG_DECLARE_ONLY
#include "../include/sane/config.h"

#include "escl.h"

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <avahi-client/lookup.h>
#include <avahi-common/error.h>
#include <avahi-common/simple-watch.h>

#include "../include/sane/sanei.h"

static AvahiSimplePoll *simple_poll = NULL;

/**
 * \fn static void resolve_callback(AvahiServiceResolver *r, AVAHI_GCC_UNUSED
 * AvahiIfIndex interface, AVAHI_GCC_UNUSED AvahiProtocol protocol,
 * AvahiResolverEvent event, const char *name,
 *                            const char *type, const char *domain, const char *host_name,
 *                            const AvahiAddress *address, uint16_t port,
 *                            AvahiStringList *txt, AvahiLookupResultFlags flags,
 *                            void *userdata)
 * \brief Callback function that will check if the selected scanner follows the escl
 *  protocol or not.
 */
static void
resolve_callback(AvahiServiceResolver *r, AVAHI_GCC_UNUSED AvahiIfIndex interface,
                            AVAHI_GCC_UNUSED AvahiProtocol protocol,
                            AvahiResolverEvent event, const char *name,
                            const char __sane_unused__ *type,
                            const char __sane_unused__ *domain,
                            const char __sane_unused__ *host_name,
                            const AvahiAddress *address, uint16_t port, AvahiStringList *txt,
                            AvahiLookupResultFlags __sane_unused__ flags,
                            void __sane_unused__ *userdata)
{
    char a[AVAHI_ADDRESS_STR_MAX], *t;
    assert(r);
    switch (event) {
    case AVAHI_RESOLVER_FAILURE:
        break;
    case AVAHI_RESOLVER_FOUND:
        avahi_address_snprint(a, sizeof(a), address);
        t = avahi_string_list_to_string(txt);
        if (strstr(t, "\"rs=eSCL\"") || strstr(t, "\"rs=/eSCL\""))
            escl_device_add(port, name, a, (char*)type);
    }
}

/**
 * \fn static void browse_callback(AvahiServiceBrowser *b, AvahiIfIndex interface,
 * AvahiProtocol protocol, AvahiBrowserEvent event, const char *name,
 * const char *type, const char *domain,
 *                           AVAHI_GCC_UNUSED AvahiLookupResultFlags flags, void* userdata)
 * \brief Callback function that will browse tanks to 'avahi' the scanners
 * connected in network.
 */
static void
browse_callback(AvahiServiceBrowser *b, AvahiIfIndex interface,
                            AvahiProtocol protocol, AvahiBrowserEvent event,
                            const char *name, const char *type,
                            const char *domain,
                            AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
                            void* userdata)
{
    AvahiClient *c = userdata;
    assert(b);
    switch (event) {
    case AVAHI_BROWSER_FAILURE:
        avahi_simple_poll_quit(simple_poll);
        return;
    case AVAHI_BROWSER_NEW:
        if (!(avahi_service_resolver_new(c, interface, protocol, name,
                                                               type, domain,
                                                               AVAHI_PROTO_UNSPEC, 0,
                                                               resolve_callback, c)))
            break;
    case AVAHI_BROWSER_REMOVE:
        break;
    case AVAHI_BROWSER_ALL_FOR_NOW:
    case AVAHI_BROWSER_CACHE_EXHAUSTED:
        if (event != AVAHI_BROWSER_CACHE_EXHAUSTED)
            avahi_simple_poll_quit(simple_poll);
        break;
    }
}

/**
 * \fn static void client_callback(AvahiClient *c, AvahiClientState state,
 * AVAHI_GCC_UNUSED void *userdata)
 * \brief Callback Function that quit if it doesn't find a connected scanner,
 * possible thanks the "Hello Protocol".
 *        --> Waiting for a answer by the scanner to continue the avahi process.
 */
static void
client_callback(AvahiClient *c, AvahiClientState state,
                         AVAHI_GCC_UNUSED void *userdata)
{
    assert(c);
    if (state == AVAHI_CLIENT_FAILURE)
        avahi_simple_poll_quit(simple_poll);
}

/**
 * \fn ESCL_Device *escl_devices(SANE_Status *status)
 * \brief Function that calls all the avahi functions and then, recovers the
 * connected eSCL devices.
 *        This function is called in the 'sane_get_devices' function.
 *
 * \return NULL (the eSCL devices found)
 */
ESCL_Device *
escl_devices(SANE_Status *status)
{
    AvahiClient *client = NULL;
    AvahiServiceBrowser *sb = NULL;
    int error;

    *status = SANE_STATUS_GOOD;
    if (!(simple_poll = avahi_simple_poll_new())) {
        DBG( 1, "Failed to create simple poll object.\n");
        *status = SANE_STATUS_INVAL;
        goto fail;
    }
    client = avahi_client_new(avahi_simple_poll_get(simple_poll), 0,
                                               client_callback, NULL, &error);
    if (!client) {
        DBG( 1, "Failed to create client: %s\n", avahi_strerror(error));
        *status = SANE_STATUS_INVAL;
        goto fail;
    }
    if (!(sb = avahi_service_browser_new(client, AVAHI_IF_UNSPEC,
                                                                   AVAHI_PROTO_UNSPEC, "_uscan._tcp",
                                                                   NULL, 0, browse_callback, client))) {
        DBG( 1, "Failed to create service browser: %s\n",
                              avahi_strerror(avahi_client_errno(client)));
        *status = SANE_STATUS_INVAL;
        goto fail;
    }
    if (!(sb = avahi_service_browser_new(client, AVAHI_IF_UNSPEC,
                                                                   AVAHI_PROTO_UNSPEC,
                                                                   "_uscans._tcp", NULL, 0,
                                                                   browse_callback, client))) {
        DBG( 1, "Failed to create service browser: %s\n",
                                avahi_strerror(avahi_client_errno(client)));
        *status = SANE_STATUS_INVAL;
        goto fail;
    }
    avahi_simple_poll_loop(simple_poll);
fail:
    if (sb)
        avahi_service_browser_free(sb);
    if (client)
        avahi_client_free(client);
    if (simple_poll)
        avahi_simple_poll_free(simple_poll);
    return (NULL);
}