Warning

Work in progress. API is unstable.

caldav.h - Header-only C/C++ CalDAV client library

A minimal CalDAV client for C and C++ projects. The only dependency is libcurl for making HTTP requests.

Features:

• Calendar Management:
  • Automatic discovery via /.well-known/caldav/
  • Fetch calendars with properties: Name, Description, Color
  • Create, update, and delete calendars
  • Change tracking with CTags
• Event Management:
  • Get events with iCalendar data (RFC 5545)
  • Create, update, and delete events
  • Change tracking with ETags
• Simple API: Clean, consistent interface with full documentation
• Header-Only: Single stb-style header file that you can put it directly in your project.

Usage

#define CALDAV_DEBUG          // Define for debug logs
#define CALDAV_IMPLEMENTATION // Define in **ONE** source file to include the implementation
#include "caldav.h"

#include <stdio.h>

#define USERNAME "vlad"
#define PASSWORD "1234"
#define URL      "localhost:8080" // Nextcloud
// #define URL      "localhost:5232" // Radicale

// Event iCal data
#define EXAMPLE_EVENT_UID "123e4567-e89b-12d3-a456-426614174010"
const char *example_event = "BEGIN:VCALENDAR\n"
                            "VERSION:2.0\n"
                            "PRODID:-//Example//CalDAV Test//EN\n"
                            "BEGIN:VTODO\n"
                            "UID:" EXAMPLE_EVENT_UID "\n"
                            "DTSTAMP:20260107T120000Z\n"
                            "SUMMARY:Test event created via CalDAV\n"
                            "DESCRIPTION:Created via CalDAV\n"
                            "END:VTODO\n"
                            "END:VCALENDAR\n";

int main() {
  // Connect to the server
  CalDAVClient *client = caldav_client_new(URL, USERNAME, PASSWORD);
  if (!client) {
    fprintf(stderr, "Failed to create client\n");
    return 1;
  }
  // Pull calendars from the server
  caldav_client_pull_calendars(client);
  // Create new VTODO calendar
  bool created = caldav_client_create_calendar(client, "my-calendar-uuid", "Calendar Name", "My calendar description",
                                               "#181818ff", CALDAV_COMPONENT_SET_VTODO);
  if (!created) {
    fprintf(stderr, "Failed to create calendar\n");
    return 1;
  }
  // Loop calendars
  for (size_t i = 0; i < client->calendars->count; ++i) {
    // Get calendar from calendar list
    CalDAVCalendar *calendar = client->calendars->items[i];
    // Check only VTODO calendars
    if (!(calendar->component_set & CALDAV_COMPONENT_SET_VTODO)) continue;
    // Print calendar information
    caldav_calendar_print(calendar);
    // Update calendar properties
    bool updated = caldav_request_calendar_update(calendar, "Changed Name", "Changed description", "#FFFFFFFF");
    if (!updated) {
      fprintf(stderr, "Failed to update calendar\n");
      return 1;
    }
    // Print new calendar information
    caldav_calendar_print(calendar);
    // Pull calendar events from the server
    caldav_calendar_pull_events(client->calendars->items[i]);
    // Create new event
    caldav_calendar_create_event(client->calendars->items[i], EXAMPLE_EVENT_UID, example_event);
    // Print all events
    for (size_t j = 0; j < client->calendars->items[i]->events->count; ++j)
      caldav_event_print(client->calendars->items[i]->events->items[j]);
    // Delete first event
    CalDAVEvent *first_event = calendar->events->items[0];
    caldav_event_delete(first_event);
    if (!first_event->deleted) {
      fprintf(stderr, "Failed to delete event\n");
      return 1;
    }
  }
  // Delete last calendar
  bool deleted = caldav_calendar_delete(client->calendars->items[client->calendars->count - 1]);
  if (!deleted) {
    fprintf(stderr, "Failed to delete calendar\n");
    return 1;
  }
  // Cleanup client
  caldav_client_free(client);

  return 0;
}

Documentation

Look inside caldav.h. All functions have comments.

Building and Testing

To build the shared library, run the following command:

gcc -x c -shared -o libcaldavh.so caldav.h

To run the example, run the following command:

gcc -Wall -Wextra -Wpedantic -o example example.c -lcurl -g && ./example

Make sure to change the URL, USERNAME and PASSWORD in example.c to your own CalDAV server.

Contributing

Pull requests are welcome!

License

This project is licensed under the Zlib license - see the LICENSE file for details.

TODO

• Autodiscovery of CalDAV URL
• Calendars
  • Getting properties
    • URL
    • CTag
    • Name
    • Description
    • Color
  • Updating
    • Fetch created
    • Fetch changed
    • Fetch deleted
    • Push properties
      • Name
      • Description
      • Color
  • Deleting
• Events
  • Getting
    • URL
    • ETag
    • iCal
  • Updating
    • Fetch created
    • Fetch changed
    • Fetch deleted
    • Push new ical
  • Deleting