File: main.c

package info (click to toggle)
libcddb 1.3.2-6
  • links: PTS
  • area: main
  • in suites: bullseye, buster
  • size: 2,276 kB
  • sloc: sh: 10,946; ansic: 4,721; makefile: 44
file content (593 lines) | stat: -rw-r--r-- 23,543 bytes parent folder | download | duplicates (6)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
/*
    $Id: main.c,v 1.28 2006/10/15 08:57:10 airborne Exp $

    Copyright (C) 2003, 2004, 2005 Kris Verbeeck <airborne@advalvas.be>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the
    Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA  02111-1307, USA.
*/

#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "main.h"

/* command-line option string */

#ifdef HAVE_LIBCDIO
/* Allow -i <device> parameter */
#define OPT_STRING ":c:D:e:hi:l:p:P:qs:t"
#else
#define OPT_STRING ":c:D:e:hl:p:P:qs:t"
#endif

/* other stuff */
#define ENV_HTTP_PROXY "http_proxy"
#define HTTP_PREFIX "http://"
#define HTTP_PREFIX_LEN 7

/* parsed command-line parameters */
enum { CMD_NONE = 0, CMD_DISCID, CMD_QUERY, CMD_READ, CMD_SITES, CMD_SEARCH,
       CMD_ALBUM, };
static int quiet = 0;           /* work silently, reports no errors */
static int command = 0;         /* request command */
static char *category = NULL;   /* category command-line argument */
static unsigned int discid = 0; /* disc ID command-line argument or calculated */
static int dlength = 0;         /* disc length command-line argument */
static int tcount = 0;          /* track count command-line parameter */
static int *foffset = NULL;     /* frame offset list command-line parameter */
static int use_cd = 0;          /* use CD-ROM to retrieve disc data */
static char *device = NULL;     /* device to use if use_cd == 1. NULL means 
                                   to find a suitable CD-ROM drive. */
static int use_time = 0;        /* use track times (in seconds) instead of frame offsets */
static char *charset = NULL;    /* requested character set encoding */
static char *searchstr = NULL;  /* text search string */
static char *artist = NULL;     /* artist's name */
static char *title = NULL;      /* album title */

/* print usage message */
static void usage(void)
{
    fprintf(stderr, "Usage: cddb_query [OPTION] COMMAND [ARG]\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "Available options:\n");
    fprintf(stderr, "  -c <mode>        local cache mode [on|off|only] (default = on)\n");
    fprintf(stderr, "  -D <cache dir>   directory for local cache (default = ~/.cddbslave)\n");
    fprintf(stderr, "  -e <charset>     character set encoding (default = UTF-8, see iconv -l)\n");
    fprintf(stderr, "  -h               display this help and exit\n");
#ifdef HAVE_LIBCDIO
    fprintf(stderr, "  -i <device>      use device to get disc data for commands\n");
#endif
    fprintf(stderr, "  -l <level>       log level, one of debug, info, warning, error or\n");
    fprintf(stderr, "                   critical (default = warning)\n");
    fprintf(stderr, "  -p <port>        port of CDDB server (default = 888)\n");
    fprintf(stderr, "  -P <protocol>    server protocol [cddbp|http|proxy] (default = cddbp)\n");
    fprintf(stderr, "  -q               quiet, do not print any error or log messages\n");
    fprintf(stderr, "  -s <server>      name of CDDB server (default = freedb.org)\n");
    fprintf(stderr, "  -t               use track times (in seconds) instead of frame offsets\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "Available commands:\n");
    fprintf(stderr, "  calc <len> <n> <fo_1> ... <fo_n>\n");
    fprintf(stderr, "                   calculate disc ID\n");
    fprintf(stderr, "  query <len> <n> <fo_1> ... <fo_n>\n");
    fprintf(stderr, "                   query CDDB server and list all matching entries\n");
    fprintf(stderr, "  read <cat> <id>  retrieve disc details from CDDB server\n");
    fprintf(stderr, "  search <str>     perform a text search against the CDDB database\n");
    fprintf(stderr, "  album <artist> <title>\n");
    fprintf(stderr, "                   perform a text search against the CDDB database (only\n");
    fprintf(stderr, "                   works on freedb2.org servers)\n");
    fprintf(stderr, "  sites            retrieve a list of mirror sites\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "Command arguments\n");
    fprintf(stderr, "  <cat>            disc category (see below)\n");
    fprintf(stderr, "  <fo_i>           without -t: frame offset of track i\n");
    fprintf(stderr, "                   with -t:    length of track i in seconds\n");
    fprintf(stderr, "  <id>             disc ID in hexadecimal\n");
    fprintf(stderr, "  <len>            disc length in seconds\n");
    fprintf(stderr, "  <n>              track count\n");
    fprintf(stderr, "  <str>            search string\n");
    fprintf(stderr, "\n");
#ifdef HAVE_LIBCDIO
    fprintf(stderr, "If you do not specify any arguments for a command, the program\n");
    fprintf(stderr, "will try to retrieve the needed disc data from a CD in your CD-ROM\n");
    fprintf(stderr, "drive.\n");
#endif
    fprintf(stderr, "\n");
    fprintf(stderr, "Available CDDB categories are:\n");
    fprintf(stderr, "  data, folk, jazz, misc, rock, country, blues, newage, reggae,\n");
    fprintf(stderr, "  classical, and soundtrack\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "Examples:\n");
    fprintf(stderr, "  To calculate the disc ID of the CD 'Mezzanine' from Massive Attack:\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "\tcddb_query calc 3822 11 150 28690 51102 75910 102682 \\\n");
    fprintf(stderr, "\t           121522 149040 175772 204387 231145 268065\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "  To query for matches of the CD 'Mezzanine' from Massive Attack:\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "\tcddb_query query 3822 11 150 28690 51102 75910 102682 \\\n");
    fprintf(stderr, "\t           121522 149040 175772 204387 231145 268065\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "  To read the details of the CD 'Mezzanine' from Massive Attack:\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "\tcddb_query read misc 0x920ef00b\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "  To search for all CDs with the string 'Mezzanine':\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "\tcddb_query search Mezzanine\n");
    fprintf(stderr, "  or\n");
    fprintf(stderr, "\tcddb_query album '' Mezzanine\n");
}

/* print error message */
static void prt_error(const char *fmt, va_list ap)
{
    if (!quiet) {
        fprintf(stderr, "\nerror: ");
        vfprintf(stderr, fmt, ap);
        fprintf(stderr, "\n\n");
    }
}

/* print error message and die */
void error_exit(int err, const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    prt_error(fmt, ap);
    va_end(ap);
    exit(err);
}

/* print error message, program usage and die */
static void error_usage(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    prt_error(fmt, ap);
    va_end(ap);
    if (!quiet) {
        usage();
    }
    exit(GENERIC_ERROR);
}

#define CMD_STR(c) ((c) == CMD_DISCID ? "calc" : "query")
static void parse_disc_data(int cmd, int argc, char **argv, int idx)
{
    if (argc >= idx + 3) {
        /* at least two extra arguments are needed */
        sscanf(argv[idx+1], "%d", &dlength);
        sscanf(argv[idx+2], "%d", &tcount);
        if (argc == idx + tcount + 3) {
            /* parse frame offsets */
            if (tcount > 0) {
                int i;
                foffset = calloc(tcount, sizeof(int));
                for (i = 0; i < tcount; i++) {
                    sscanf(argv[idx+3+i], "%d", &foffset[i]);
                }
            }
        } else {
            error_usage("track count is %d, but %d frame offset(s) specified", tcount, (argc - idx - 3));
        }
    } else {
        error_usage("the %s command requires at least two arguments", CMD_STR(cmd));
    }
}

static void init_protocol(cddb_conn_t *conn, const char *proto)
{
    int len, port;
    char *aux, *host, *portstr, *password;

    if (!*optarg) {
        error_usage("-P, server protocol missing");
    }
    if (strcmp(optarg, "cddbp") == 0) {
        /* Enable the CDDBP protocol, i.e. disable the usage of HTTP.
           This is the default so actually this function call is not
           needed. */
        cddb_http_disable(conn);
    } else if (strcmp(optarg, "http") == 0) {
        /* Enable the HTTP protocol.  We will also set the server port
           to 80, i.e. the default HTTP port. */
        cddb_http_enable(conn);
        cddb_set_server_port(conn, 80);
    } else if (strcmp(optarg, "proxy") == 0) {
        /* Enable the HTTP protocol through a proxy server.  Enabling
           the proxy will automatically enable HTTP.  We will also set
           the server port to 80, i.e. the default HTTP port.  */
        cddb_http_proxy_enable(conn);
        cddb_set_server_port(conn, 80);
        /* We will retrieve the proxy settings from the environment
           variable 'http_proxy'.  If these do not exist, an error
           will be signaled. */
        aux = getenv(ENV_HTTP_PROXY);
        if (aux == NULL) {
            error_exit(GENERIC_ERROR, "environment variable 'http_proxy' not set");
        }
        /* Check the prefix.  It should be 'http://'. */
        if (strncmp(aux, HTTP_PREFIX, HTTP_PREFIX_LEN) != 0) {
            error_exit(GENERIC_ERROR, "environment variable 'http_proxy' invalid");
        }
        host = aux + HTTP_PREFIX_LEN;
        /* Check if a proxy username:password pair is provided */
        aux = strchr(host, '@');
        if (aux != NULL) {
            *aux = '\0';
            password = strchr(host, ':');
            if (password != NULL) {
                *password = '\0';
                password++;
            }
            cddb_set_http_proxy_credentials(conn, host, password);
            host = aux + 1;
        }
        /* Check if a proxy port is specified. */
        portstr = strchr(host, ':');
        if (portstr == NULL) {
            /* No port, set proxy server name and use default port 80. */
            cddb_set_http_proxy_server_name(conn, host);
            cddb_set_http_proxy_server_port(conn, 80);
        } else {
            /* A proxy port is present.  Parse it and initialize the
               connection structure with it. */
            portstr++;          /*  Skip colon. */
            port = strtol(portstr, &aux, 10);
            if (*aux != '\0' && *aux != '/') {
                error_exit(GENERIC_ERROR, "environment variable 'http_proxy' port invalid");
            }
            len = portstr - host - 1;
            aux = malloc(len + 1);
            strncpy(aux, host, len);
            aux[len] = '\0';
            cddb_set_http_proxy_server_name(conn, aux);
            cddb_set_http_proxy_server_port(conn, port);
        }
    } else {
        error_usage("-P, invalid server protocol '%s'", optarg);
    }
}

static void parse_cmdline(int argc, char **argv, cddb_conn_t *conn)
{
    int arg, port;
    char *aux;

    opterr = 0;
    while ((arg = getopt(argc, argv, OPT_STRING)) != -1) {
        switch ((char)arg) {
        case ':':               /* missing option argument */
            error_usage("-%c, option needs argument", optopt);
            break;
        case '?':               /* help */
        case 'h':               /* help */
            usage();
            exit(0);
            break;
        case 'c':               /* local cache settings */
            if (!*optarg) {
                error_usage("-c, cache mode missing");
            }
            if (strcmp(optarg, "on") == 0) {
                /* Enable the usage of the local CDDB cache (default).
                   This cache can be used to speed things up
                   drastically. */
                cddb_cache_enable(conn);
            } else if (strcmp(optarg, "off") == 0) {
                /* Disable the usage of the local CDDB cache. */
                cddb_cache_disable(conn);
            } else if (strcmp(optarg, "only") == 0) {
                /* Only use the local CDDB cache.  Never try reading
                   any data from the network. */
                cddb_cache_only(conn);
            } else {
                error_usage("-c, invalid cache mode '%s'", optarg);
            }
            break;
        case 'D':               /* local cache directory */
            if (!*optarg) {
                error_usage("-D, cache directory missing");
            }
            /* Set the location of the local CDDB cache directory.
               The default location of this directory is
               ~/.cddbslave. */
            cddb_cache_set_dir(conn, optarg);
            break;
        case 'e':
            if (!*optarg) {
                error_usage("-e, character set encoding missing");
            }
            charset = strdup(optarg);
            break;
        case 'i':               /* device for arguments */
            if (!*optarg) {
                error_usage("-i, device name missing");
            }
            use_cd = 1;
            device = strdup(optarg);
            break;
        case 'l':               /* log level */
            if (!*optarg) {
                error_usage("-l, log level missing");
            }
            if (strcmp(optarg, "debug") == 0) {
                cddb_log_set_level(CDDB_LOG_DEBUG);
            } else if (strcmp(optarg, "info") == 0) {
                cddb_log_set_level(CDDB_LOG_INFO);
            } else if (strcmp(optarg, "warning") == 0) {
                cddb_log_set_level(CDDB_LOG_WARN);
            } else if (strcmp(optarg, "error") == 0) {
                cddb_log_set_level(CDDB_LOG_ERROR);
            } else if (strcmp(optarg, "critical") == 0) {
                cddb_log_set_level(CDDB_LOG_CRITICAL);
            } else {
                error_usage("-l, invalid log level '%s'", optarg);
            }
            break;
        case 'p':               /* server port */
            if (!*optarg || *optarg == '\0') {
                error_usage("-p, server port missing");
            }
            port = strtol(optarg, &aux, 10);
            if (*aux != '\0') {
                error_usage("-p, invalid server port '%s'", optarg);
            }
            /* Initialize the CDDB server port.  This step can also be
               skipped if the default port (888) is good enough.  This
               default also matches the port of the FreeDB server. */
            cddb_set_server_port(conn, port);
            break;
        case 'P':               /* server protocol */
            init_protocol(conn, optarg);
            break;
        case 'q':               /* quiet */
            cddb_log_set_level(CDDB_LOG_NONE);
            quiet = 1;
            break;
        case 's':               /* server name */
            if (!*optarg) {
                /* server name missing */
                error_usage("-s, server name missing");
            }
            /* Initialize the CDDB server name.  Actually this call is
               optional because the default is 'freedb.org'.  So if
               the default is OK for you, then you can skip this
               step. */
            cddb_set_server_name(conn, optarg);
            break;
        case 't':               /* use track time */
            use_time = 1;
            break;
        }
    }

    if (argc <= optind) {
        /* no command given */
        error_usage("command missing");
    }

    /* use CD-ROM ? */
    if (argc == optind + 1) {
        use_cd = 1;
    }

    /* process command */
    if (strcmp(argv[optind], "calc") == 0) {
        /* calculate disc ID */
        command = CMD_DISCID;
        if (!use_cd) {
            /* check disc arguments */
            parse_disc_data(CMD_DISCID, argc, argv, optind);
        }
    } else if (strcmp(argv[optind], "query") == 0) {
        /* CDDB query */
        command = CMD_QUERY;
        if (!use_cd) {
            /* check disc arguments */
            parse_disc_data(CMD_QUERY, argc, argv, optind);
        }
    } else if (strcmp(argv[optind], "read") == 0) {
        /* CDDB read */
        command = CMD_READ;
        if (!use_cd) {
            if (argc == optind + 3) {
                /* two more arguments are needed */
                category = strdup(argv[optind+1]);
                sscanf(argv[optind+2], "%x", &discid);
            } else {
                error_usage("the read command requires two arguments");
            }
        }
    } else if (strcmp(argv[optind], "sites") == 0) {
        /* CDDB sites */
        command = CMD_SITES;
        if (argc != optind + 1) {
            error_usage("the sites command expects no arguments");
        }
        use_cd = 0;
    } else if (strcmp(argv[optind], "search") == 0) {
        /* CDDB search */
        command = CMD_SEARCH;
        if (argc == optind + 2) {
            /* one more argument is needed */
            searchstr = strdup(argv[optind+1]);
        } else {
            error_usage("the search command requires one argument");
        }
        use_cd = 0;
    } else if (strcmp(argv[optind], "album") == 0) {
        /* CDDB album */
        command = CMD_ALBUM;
        if ((argc >= optind + 2) && (argc <= optind + 3)) {
            /* one or two more arguments are needed */
            artist = strdup(argv[optind+1]);
            if (argc == optind + 3) {
              title = strdup(argv[optind+2]);
            }
        } else {
            error_usage("the album command requires one or two arguments");
        }
        use_cd = 0;
    } else {
        /* unknown command */
        error_usage("unknown command '%s'", argv[optind]);
    }
}

int main(int argc, char **argv)
{
    cddb_conn_t *conn = NULL;   /* libcddb connection structure */
    cddb_disc_t *disc = NULL;   /* libcddb disc structure */

    /* Create a new connection structure.  You will have to use this
       structure in most other calls to the libcddb library.  The
       connection settings will be updated while processing the
       command-line options. */
    conn = cddb_new();

    /* If the pointer is NULL then an error occured (out of memory). */
    if (!conn) {
        error_exit(GENERIC_ERROR, "unable to create connection structure");
    }

    /* Check command-line parameters. */
    parse_cmdline(argc, argv, conn);

    /* Initialize requested character set for output strings */
    if (charset) {
        if (!cddb_set_charset(conn, charset)) {
            error_exit(cddb_errno(conn), "could not set character encoding");
        }
    }

    /* Use CD-ROM to get some disc data? */
    if (use_cd) {
        /* Retrieve the disc length and track offsets from the CD in
           the CD-ROM drive. */
        disc = cd_read(device);
        if (!disc) {
            error_exit(GENERIC_ERROR, "could not read CD in CD-ROM drive");
        }
    } else if (command == CMD_DISCID || command == CMD_QUERY) {
        /* The disc ID calculation and query command both need a disc
           structure.  We will initialize a new disc with the data
           provided on the command-line. */
        disc = cd_create(dlength, tcount, foffset, use_time);
        if (!disc) {
            error_exit(GENERIC_ERROR, "could not create disc structure");
        }
        /* The frame offset data is no longer needed because it is now
           also present in the disc structure. */
        FREE_NOT_NULL(foffset);
    } else if ((command == CMD_SEARCH) || (command == CMD_ALBUM)) {
        /* Create an empty disc structure for the search command.  It
           will be used to store the search results. */
        disc = cddb_disc_new();
        if (!disc) {
            error_exit(GENERIC_ERROR, "could not create disc structure");
        }
        if (command == CMD_ALBUM) {
          /* Fill out the artist and album title */
          cddb_disc_set_artist(disc, artist);
          if (title) {
            cddb_disc_set_title(disc, title);
          }
        }
    }

    /* Execute requested command. */
    switch (command) {
    case CMD_DISCID:
        /* Calculate the disc ID.  This function will initialize the
           disc ID field in the disc structure.  Afterwards you can
           retrieve the disc ID as shown below. */
        cddb_disc_calc_discid(disc);
        printf("CD disc ID is %08x\n", cddb_disc_get_discid(disc));
        break;
    case CMD_QUERY:
        /* Query the CDDB server for possibly matches. */
        do_query(conn, disc, quiet);
        break;
    case CMD_READ:
        /* If we read the disc data from a CD, then we first have to
           query the database for some extra information about the
           disc before we can read the details.  For a detailed
           description about querying see the do_query function.  Only
           the first match that is found will be used. */
        if (use_cd) {
            int matches;

            cddb_disc_calc_discid(disc);
            matches = cddb_query(conn, disc);
            if (matches == -1) {
                error_exit(cddb_errno(conn), "could not query");
            } else if (matches == 0) {
                error_exit(CDDB_ERR_DISC_NOT_FOUND, "no matching discs found");
            }
            /* Get the disc information needed for the read command.
               Afterwards we destroy the current disc because do_read
               will return a new disc. */
            category = strdup(cddb_disc_get_category_str(disc));
            discid = cddb_disc_get_discid(disc);
            cddb_disc_destroy(disc);
        }
        disc = do_read(conn, category, discid, quiet);
        if (!disc) {
            error_exit(cddb_errno(conn), "could not read disc data");
        }
        /* The category string is no longer needed because it is now
           also present in the disc structure. */
        FREE_NOT_NULL(category);
        /* Let's display the information that was read. */
        do_display(disc);
        break;
    case CMD_SITES:
        /* Display information about mirror sites. */
        do_sites(conn);
        break;
    case CMD_SEARCH:
        /* Search the CDDB database for possibly matches. */
        do_search(conn, disc, searchstr, quiet);
        break;
    case CMD_ALBUM:
        /* Search the CDDB server for possibly matches. */
        do_album(conn, disc, quiet);
        break;
    }
    /* Finally, we have to clean up.  With the cddb_disc_destroy
       function we can easily free all memory used by a single disc.
       This function will free the memory used by the individual
       tracks of the disc and also free the memory of the disc
       structure itself.  Next we destroy the connection structrue in
       a similar way.  Both functions will first check whether the
       provided pointer is not NULL before freeing it. */
    cddb_disc_destroy(disc);
    cddb_destroy(conn);

    /* Also destroy any global resources reserved by the library. */
    libcddb_shutdown();

    FREE_NOT_NULL(charset);
    FREE_NOT_NULL(device);
    FREE_NOT_NULL(category);
    FREE_NOT_NULL(searchstr);

    return 0;
}