libdispatch for Linux

pthreads getting you down? libdispatch, aka Grand Central Dispatch (GCD) is Apple's high-performance event-handling library, introduced in OS X Snow Leopard. It provides asynchronous task queues, monitoring of file descriptor read and write-ability, asynchronous I/O (for sockets and regular files), readers-writer locks, parallel for-loops, sane signal handling, periodic timers, semaphores and more. You'll want to read over Apple's API reference.

Changes from Apple's official version

I've added the ability to integrate libdispatch's main queue with third-party run-loops, e.g. GLib's GMainLoop. Call dispatch_get_main_queue_handle_np() to get a file descriptor your run-loop can monitor for reading; when it becomes readable call dispatch_main_queue_drain_np() to execute the pending tasks.

I've also added missing _f variants for several functions in data.h and io.h that took Objective-C blocks only: look for the functions with _np appended to them. Although you can make full use of libdispatch with compilers like GCC that don't support blocks, it is not advisable to build libdispatch itself with anything other than Clang, as the dispatch i/o portion cannot be built without compiler support for blocks.

Build/Runtime Requirements

• libBlocksRuntime
• libpthread_workqueue
• libkqueue

Build Requirements

• CMake >= 2.8.12
• Python2 >= 2.6
• Clang >= 3.4

Getting Started:

On Ubuntu 14.04, the required dependencies are available via apt-get.

sudo apt-get install libblocksruntime-dev libkqueue-dev libpthread-workqueue-dev cmake

git clone git://github.com/nickhutchinson/libdispatch.git && cd libdispatch
mkdir libdispatch-build && cd libdispatch-build
../configure
make
sudo make install

Known Issues

• 2014-10-01 - Dispatch Sources of type DISPATCH_SOURCE_TYPE_VNODE are unreliable, and should be avoided for now.

Testing with CTest

ctest -j $(nproc) --output-on-failure

Demo

forever.c

#include <dispatch/dispatch.h>
#include <stdio.h>

static void timer_did_fire(void *context) {
    printf("Strawberry fields...\n");
}

int main(int argc, const char *argv[]) {
    dispatch_source_t timer = dispatch_source_create(
        DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());

    dispatch_source_set_event_handler_f(timer, timer_did_fire);
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC,
                              0.5 * NSEC_PER_SEC);
    dispatch_resume(timer);
    dispatch_main();
}

> clang forever.c -I/usr/local/include -L/usr/local/lib -ldispatch -o forever
> ./forever

Strawberry fields...
Strawberry fields...
Strawberry fields...
Strawberry fields...
[...]

Credits

This port was made possible by Mark Heily and others who contributed the libpthread_workqueue and libkqueue libraries that libdispatch depends on, as well as numerous portability patches floating around the official libdispatch mailing list, notably http://lists.macosforge.org/pipermail/libdispatch-dev/2012-August/000676.html.