Description

Its an ANSI C library that does allow communication with google calendar and contacts, useful if you need to support this in a C or C++ application.

Currently, libgcal implements:

 - authentication
 - get all events/contacts
 - atom stream parsing
 - access to individual events/contacts
 - add/delete/edit using gcal objects
 - add/delete/edit using raw XML
 - query for updated events/contacts
 - use of http proxy
 - timezone
 - contact photo download/upload
 - google data protocol 2.0
 - can be used with a C++ application
 - google hosted accounts (i.e. joe@foobar.com)

What is missing: batch commit, calendar (creation of recurrent events)

Currently libgcal is tested on Linux and Mac OSX Leopard, but should be portable to all platforms supported by its dependencies.

Dependencies: libxml, libcurl, ANSI C

Examples

Bellow you can see some examples of libgcal usage (they could have less lines, but checking for function return values is always a good programming practice).

Get all contacts

#include <stdio.h>
#include <gcalendar.h>
#include <gcontact.h>

int main(int argc, char *argv[])
{
        gcal_t gcal;
        gcal_contact_t contact;
        struct gcal_contact_array all_contacts;
        int result;
        size_t i;

        /* Create a gcal 'object' and authenticate with server */
        if (!(gcal = gcal_new(GCONTACT)))
                exit(1);
        if (argc == 3)
                result = gcal_get_authentication(gcal, argv[1], argv[2]);
        else
                result = gcal_get_authentication(gcal, "username",
                                                 "password");

        /* Get all contacts and print its name/email/updated time */
        result = gcal_get_contacts(gcal, &all_contacts);

        for (i = 0; i < all_contacts.length; ++i) {
                contact = gcal_contact_element(&all_contacts, i);
                if (!contact)
                        break;

                printf("contact: %d\ttitle:%s\temail:%s\tupdated:%s\n",
                       i,
                       gcal_contact_get_title(contact),
                       gcal_contact_get_email(contact),
                       gcal_contact_get_updated(contact));

        }

        /* Cleanup */
        gcal_cleanup_contacts(&all_contacts);
        gcal_delete(gcal);

        return 0;
}

Add/edit/delete a calendar event

#include <stdio.h>
#include <gcalendar.h>

int main(int argc, char *argv[])
{
        gcal_t gcal;
        gcal_event_t event;
        int result;

        /* Create a gcal 'object' and authenticate with server */
        if (!(gcal = gcal_new(GCALENDAR)))
                exit(1);

        if (argc == 3)
                result = gcal_get_authentication(gcal, argv[1], argv[2]);
        else
                result = gcal_get_authentication(gcal, "username",
                                                 "password");

        /* Create an event 'object' and fill in some data */
        if ((event = gcal_event_new(NULL))) {
                gcal_event_set_title(event, "A new event");
                gcal_event_set_content(event, "Here goes the description");
                gcal_event_set_start(event, "2008-06-26T16:00:00Z");
                gcal_event_set_end(event, "2008-06-26T18:00:00Z");
                gcal_event_set_where(event, "A nice place for a meeting");
        }

        /* Add a new event */
        if (!(result = gcal_add_event(gcal, event))) {

                /* Edit this event */
                gcal_event_set_title(event, "Changing the title");
                result = gcal_update_event(gcal, event);

                /* Delete this event (note: google doesn't really deletes
                 * the event, but set its status to 'cancelled' and keeps
                 * then for nearly 4 weeks).
                 */
                result = gcal_erase_event(gcal, event);
        }

        /* Cleanup */
        gcal_event_delete(event);
        gcal_delete(gcal);

        return 0;
}

Query for updated calendar events

#include <stdio.h>
#include <gcalendar.h>

int main(int argc, char *argv[])
{
        gcal_t gcal;
        struct gcal_event_array event_array;
        int result;

        /* Create a gcal 'object' and authenticate with server */
        if (!(gcal = gcal_new(GCALENDAR)))
                exit(1);

        if (argc == 3)
                result = gcal_get_authentication(gcal, argv[1], argv[2]);
        else
                result = gcal_get_authentication(gcal, "username",
                                                 "password");

        /* This will query for all updated events (fall in this category
         * added/deleted/updated events) starting for 06:00Z UTC of today).
         */
        if (!(result = gcal_get_updated_events(gcal, &event_array, NULL)))
                printf("updated events: %d\n", (int)event_array.length);

        /* Cleanup */
        gcal_cleanup_events(&event_array);
        gcal_delete(gcal);

        return 0;

}

Add a new contact from a raw XML file, checking for error codes

#include <stdio.h>
#include <gcalendar.h>
#include <gcal_status.h>

int main(int argc, char *argv[])
{
        char *super_contact = NULL;
        const char filename[] = "supercontact.xml";
        gcal_t gcal;
        int result;

        gcal = gcal_new(GCONTACT);
        result = gcal_get_authentication(gcal, "username", "password");

        /* find_load_file is a function that will magically load the contents
         * of a XML file into a string.
         */
        if (find_load_file(filename, &super_contact))
                exit(-1);

        result = gcal_add_xmlentry(gcal, super_contact, NULL);
        if (result == -1)
                /* Check for errors and print status code */
                printf("Failed adding a new contact! HTTP code: %d"
                "\nmsg: %s\n", gcal_status_httpcode(gcal),
                gcal_status_msg(gcal));

        /* Cleanup */
        free(super_contact);
        gcal_delete(gcal);

        return 0;
}