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meta.c

// meta.c: meta backend ("dynamic backend loader")
// This file is part of scanbuttond.
// Copyleft )c( 2005-2006 by Bernhard Stiftner
//
// This program 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 of the
// License, or (at your option) any later version.
//
// This program 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.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <syslog.h>
#include <dlfcn.h>
#include <errno.h>
#include "scanbuttond/common.h"
#include "scanbuttond/scanbuttond.h"
#include "scanbuttond/libusbi.h"
#include "meta.h"

#define MAX_CONFIG_LINE 255
#define MAX_SCANNERS_PER_BACKEND 16

static char* backend_name = "Dynamic Module Loader";
static char* config_file = STRINGIFY(CFG_DIR) "/meta.conf";
static char* lib_dir = STRINGIFY(LIB_DIR);

libusb_handle_t* libusb_handle;
scanner_t* meta_scanners = NULL;
backend_t* meta_backends = NULL;


const char* scanbtnd_get_backend_name(void)
{
      return backend_name;
}


void meta_attach_scanner(scanner_t* scanner, backend_t* backend)
{
      scanner_t* dev = (scanner_t*)malloc(sizeof(scanner_t));
      dev->vendor = scanner->vendor;
      dev->product = scanner->product;
      dev->connection = scanner->connection;
      dev->internal_dev_ptr = scanner->internal_dev_ptr;
      dev->sane_device = scanner->sane_device;
      dev->meta_info = (void*)backend;
      dev->lastbutton = scanner->lastbutton;
      dev->num_buttons = scanner->num_buttons;
      dev->is_open = scanner->is_open;
      dev->next = meta_scanners;
      meta_scanners = dev;
      syslog(LOG_INFO, "meta-backend: attached scanner \"%s %s\"",
               scanner->vendor, scanner->product);
}


void meta_attach_scanners(scanner_t* devices, backend_t* backend)
{
      scanner_t* dev = devices;
      int count = 0;
      while (dev != NULL) {
            if (count >= MAX_SCANNERS_PER_BACKEND) {
                  syslog(LOG_WARNING, "meta-backend: refusing to attach scanner \"%s %s\": Too many scanners!",
                           dev->vendor, dev->product);
                  return;
            }
            meta_attach_scanner(dev, backend);
            dev = dev->next;
            count++;
      }
}


void meta_detach_scanner(scanner_t* scanner, scanner_t* prev_scanner)
{
      syslog(LOG_INFO, "meta-backend: detaching scanner: \"%s %s\"",
               scanner->vendor, scanner->product);
      if (prev_scanner != NULL)
            prev_scanner->next = scanner->next;
      else if (scanner == meta_scanners)
            meta_scanners = scanner->next;
      else
            syslog(LOG_WARNING, "meta-backend: detach scanner: invalid arguments!");
      free(scanner);
}


void meta_detach_scanners(void)
{
      while (meta_scanners != NULL) {
            meta_detach_scanner(meta_scanners, NULL);
      }
}


int meta_attach_backend(backend_t* backend)
{
  // don't load another meta backend
      if (strcmp(backend->scanbtnd_get_backend_name(), scanbtnd_get_backend_name())==0) {
            syslog(LOG_WARNING, "meta-backend: refusing to load another meta backend!");
            return -1;
      }
      syslog(LOG_INFO, "meta-backend: attaching backend: %s",
               backend->scanbtnd_get_backend_name());
      backend->next = meta_backends;
      meta_backends = backend;
      backend->scanbtnd_init();
      return 0;
}


void meta_detach_backend(backend_t* backend, backend_t* prev_backend)
{
      if (prev_backend != NULL)
            prev_backend->next = backend->next;
      else if (backend == meta_backends)
            meta_backends = backend->next;
      else
            syslog(LOG_WARNING, "meta-backend: detach backend: invalid arguments!");
      backend->scanbtnd_exit();
      unload_backend(backend);
}


void meta_detach_backends(void)
{
      while (meta_backends != NULL) {
            meta_detach_backend(meta_backends, NULL);
      }
}


backend_t* meta_lookup_backend(scanner_t* scanner)
{
      return (backend_t*)scanner->meta_info;
}


void meta_strip_newline(char* str)
{
      int len = strlen(str);
      if (len == 0) return;
      if (str[len-1] != '\n') return;
      str[len-1] = 0;
}


int scanbtnd_init(void)
{
      meta_scanners = NULL;
      meta_backends = NULL;

      syslog(LOG_INFO, "meta-backend: init");
      libusb_handle = libusb_init();

      // read config file
      char lib[MAX_CONFIG_LINE];
      backend_t* backend;
      FILE* f = fopen(config_file, "r");
      if (f == NULL) {
            syslog(LOG_ERR, "meta-backend: config file \"%s\" not found.",
                     config_file);
            return -1;
      }
      while (fgets(lib, MAX_CONFIG_LINE, f)) {
            meta_strip_newline(lib);
            if (strlen(lib)==0) continue;
            char* libpath = (char*)malloc(strlen(lib) + strlen(lib_dir) + 2);
            strcpy(libpath, lib_dir);
            strcat(libpath, "/");
            strcat(libpath, lib);
            backend = load_backend(libpath);
            free(libpath);
            if (backend != NULL && meta_attach_backend(backend)==0) {
                  meta_attach_scanners(backend->scanbtnd_get_supported_devices(),
                        backend);
            }
      }
      fclose(f);

      return 0;
}


int scanbtnd_rescan(void)
{
      backend_t* backend;

      meta_detach_scanners();
      meta_scanners = NULL;

      backend = meta_backends;
      while (backend != NULL) {
            backend->scanbtnd_rescan();
            meta_attach_scanners(backend->scanbtnd_get_supported_devices(),
                                           backend);
            backend = backend->next;
      }

      return 0;
}


const scanner_t* scanbtnd_get_supported_devices(void)
{
      return meta_scanners;
}


int scanbtnd_open(scanner_t* scanner)
{
  // if devices have been added/removed, return -ENODEV to
  // make scanbuttond update its device list
      if (libusb_get_changed_device_count() != 0) {
            return -ENODEV;
      }
      backend_t* backend = meta_lookup_backend(scanner);
      if (backend == NULL) return -1;
      return backend->scanbtnd_open(scanner);
}


int scanbtnd_close(scanner_t* scanner)
{
      backend_t* backend = meta_lookup_backend(scanner);
      if (backend == NULL) return -1;
      return backend->scanbtnd_close(scanner);
}


int scanbtnd_get_button(scanner_t* scanner)
{
      backend_t* backend = meta_lookup_backend(scanner);
      if (backend == NULL) return 0;
      return backend->scanbtnd_get_button(scanner);
}


const char* scanbtnd_get_sane_device_descriptor(scanner_t* scanner)
{
      backend_t* backend = meta_lookup_backend(scanner);
      if (backend == NULL) return NULL;
      return backend->scanbtnd_get_sane_device_descriptor(scanner);
}


int scanbtnd_exit(void)
{
      syslog(LOG_INFO, "meta-backend: exit");
      meta_detach_scanners();
      meta_detach_backends();
      libusb_exit(libusb_handle);
      return 0;
}


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