Third party developers wishing to add Netatalk 3 support to their applications have two choices

  1. Directly integrate libatalk from the Netatalk source tree
  2. Link with libatalk which is a shared library in its own right starting with Netatalk 3

This examples uses approach 2. Assuming Netatalk has been installed to /usr/local/netatalk compiling backup_demo.c is done like this:

c99 -I/usr/local/netatalk/include -o backup_demo backup_demo.c -L/usr/local/netatalk/lib -latalk -Wl,-rpath=/usr/local/netatalk/lib

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.

Example program backup_demo.c which copies metadata and ressource from one file to another:

/*
   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 <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>

#include <atalk/logger.h>
#include <atalk/netatalk_conf.h>
#include <atalk/volume.h>

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

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

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

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

    ad_init(&ad, vol);

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

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

    if (ad_open(&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(&ad));

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

    ad_init(&adnew, vol);
    if (ad_open(&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(&adnew);
    if (vol->vfs->vfs_copyfile(vol, -1, file, newfile) != 0)
        ERROR("Couln't copy ressource to \"%s\"", newfile);

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

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

    return 0;
}
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