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.
Currently, the trunk of the official SVN repository doesn't build on Linux; the last revision that builds out-of-the-box is r199, but that revision doesn't contain any of the nifty APIs added in OS X Lion, e.g. asynchronous I/O. This repo applies some patches by Mark Heily, taken from his post to the libdispatch mailing list, along with some other fixes that I've cobbled together. It has not been exhaustively tested, but it seems to work well enough.
Patches are very welcome!
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_eventfd_np() to get a file descriptor your run-loop can monitor for reading; when it becomes readable, call eventfd_read(2) to acknowledge the wakeup, then 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.
The following does the job on Ubuntu 12.10:
sudo apt-get install libblocksruntime-dev libkqueue-dev libpthread-workqueue-dev cmake
git clone git://github.com/nickhutchinson/libdispatch.git
mkdir libdispatch-build && cd libdispatch-build
cmake ../libdispatch -DCMAKE_C_COMPILER=clang -DCMAKE_BUILD_TYPE=Release
make
sudo make install
The included test suite builds and runs on Linux (just run make check). Last I checked, a few tests failed:
- dispatch_starfish
- dispatch_vnode
Test failure results are here. The dispatch_starfish failure can probably be ignored, but the dispatch_vnode failure seems to indicate some more serious issue, possibly a bug in libkqueue. It might be best to avoid using dispatch_source_create() with DISPATCH_SOURCE_TYPE_VNODE for now...
cat << "EOF" > dispatch_test.c
#include <dispatch/dispatch.h>
#include <stdio.h>
static void timer_did_fire(void *context) { printf("Strawberry fields...\n"); }
static void write_completion_handler(dispatch_data_t unwritten_data, int error, void *context) {
if (!unwritten_data && error == 0)
printf("Dispatch I/O wrote everything to stdout. Hurrah.\n");
}
static void read_completion_handler(dispatch_data_t data, int error, void *context) {
int fd = (intptr_t)context;
close(fd);
dispatch_write_f_np(STDOUT_FILENO, data, dispatch_get_main_queue(),
NULL, write_completion_handler);
}
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);
int fd = open("dispatch_test.c", O_RDONLY);
dispatch_read_f_np(fd, SIZE_MAX, dispatch_get_main_queue(), (void *)(intptr_t)fd,
read_completion_handler);
dispatch_main();
return 0;
}
EOF
clang dispatch_test.c -I/usr/local/include/dispatch -L/usr/local/lib -ldispatch -o dispatchTest
./dispatchTest