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<h1>[TN#010] Using libatalk from third party apps</h1>

<dl>
<dt><strong>Author</strong></dt>
<dd>Ralph Böhme</dd>
<dt><strong>Published on</strong></dt>
<dd>July 12, 2012</dd>
</dl>

<p>Third party developers wishing to add Netatalk 3 support to their applications have two choices</p>
<ol>
<li>Directly integrate libatalk from the Netatalk source tree</li>
<li>Link with libatalk which is a shared library in its own right starting with Netatalk 3</li>
</ol>
<p>This examples uses approach 2. Assuming Netatalk has been installed to <em>/usr/local/netatalk </em>compiling backup_demo.c is done like this:</p>
<pre>c99 -I/usr/local/netatalk/include -o backup_demo backup_demo.c -L/usr/local/netatalk/lib -latalk -Wl,-rpath=/usr/local/netatalk/lib</pre>
<p>Please note that you need at least Netatalk 3.0.1 for this to work, as in Netatalk some necessary headers are not installed correctly.</p>
<p>Example program <em>backup_demo.c</em> which copies metadata and ressource from one file to another:</p>
<pre>/*
   Copyright (c) 2012, Frank Lahm 

   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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* HAVE_CONFIG_H */

#include &lt;unistd.h&gt;
#include &lt;sys/types.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdarg.h&gt;
#include &lt;string.h&gt;
#include &lt;errno.h&gt;

#include &lt;atalk/logger.h&gt;
#include &lt;atalk/netatalk_conf.h&gt;
#include &lt;atalk/volume.h&gt;

#define ERROR(...)                              \
    do {                                        \
        _log(__VA_ARGS__);                      \
        exit(1);                                \
    } while (0)

static void _log(char *fmt, ...)
{
    int len;
    static char logbuffer[1024];
    va_list args;

    va_start(args, fmt);
    len = vsnprintf(logbuffer, 1023, fmt, args);
    va_end(args);
    logbuffer[1023] = 0;

    printf("%s\n", logbuffer);
}

int main(int argc, char **argv)
{
    const char *file, *newfile;
    struct vol *vol;
    struct adouble ad, adnew;
    struct stat st;

    if (argc != 3) {
        ERROR("usage: backup_demo FILE NEWFILE");
    }
    file = argv[1];
    newfile = argv[2];

    AFPObj obj = { 0 };

    if (afp_config_parse(&amp;obj, "ad") != 0)
        ERROR("No Netatalk 3 afp.conf found", file);

    setuplog("default:note", "/dev/tty");

    if (load_volumes(&amp;obj, NULL) != 0)
        ERROR("Couldn't load volumes");
    if ((vol = getvolbypath(&amp;obj, file)) == NULL)
        ERROR("Not a Netatalk volume for file \"%s\"", file);

    printf("Volume path \"%s\"\n", vol-&gt;v_path);
    if (vol-&gt;v_adouble == AD_VERSION2) {
        printf("Volume adouble version v2\n");
    } else if (vol-&gt;v_adouble == AD_VERSION_EA) {
        printf("Volume adouble version ea\n");
    } else {
        ERROR("Unknown adouble version");
    }

    ad_init(&amp;ad, vol);

    /* Open an existing file's metadata and ressource */
    if (ad_open(&amp;ad, file, ADFLAGS_HF | ADFLAGS_RDONLY) != 0)
        ERROR("Couldn't open metadata of \"%s\"", file);

    int ad_size = vol-&gt;v_adouble == AD_VERSION2 ? AD_DATASZ2 : AD_DATASZ_EA;
    printf("%d bytes in adouble metadata buffer ad-&gt;ad_data\n", ad_size);

    if (ad_open(&amp;ad, file, ADFLAGS_RF | ADFLAGS_RDONLY) != 0)
        ERROR("Couldn't open ressource of \"%s\"", file);

    printf("File has ressource fork of size: %d, fd: %d\n", ad.ad_rlen, ad_reso_fileno(&amp;ad));

    /* Copy over metadata and ressource to new file */
    if (lstat(newfile, &amp;st) != 0)
        ERROR("Can't stat \"%s\", must exist, create with eg touch", newfile);

    ad_init(&amp;adnew, vol);
    if (ad_open(&amp;ad, file, ADFLAGS_HF | ADFLAGS_RF | ADFLAGS_RDWR | ADFLAGS_CREATE) != 0)
        ERROR("Couldn't create metadata/ressource of \"%s\"", newfile);

    memcpy(adnew.ad_data, ad.ad_data, ad_size);
    ad_flush(&amp;adnew);
    if (vol-&gt;vfs-&gt;vfs_copyfile(vol, -1, file, newfile) != 0)
        ERROR("Couln't copy ressource to \"%s\"", newfile);

    ad_close(&amp;ad, ADFLAGS_HF | ADFLAGS_RF);
    ad_close(&amp;adnew, ADFLAGS_HF | ADFLAGS_RF);

#if 0
    /* examples setting some stuff */
    ad_setdate(&amp;ad, AD_DATE_CREATE | AD_DATE_UNIX, st.st_mtime);
    ad_setdate(&amp;ad, AD_DATE_MODIFY | AD_DATE_UNIX, st.st_mtime);
    ad_setdate(&amp;ad, AD_DATE_ACCESS | AD_DATE_UNIX, st.st_mtime);
    ad_setdate(&amp;ad, AD_DATE_BACKUP, AD_DATE_START);
    ad_flush(&amp;ad);
#endif

    return 0;
}</pre>

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