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90 lines
3.6 KiB
C++
90 lines
3.6 KiB
C++
// Handles IO that may hang.
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#ifndef FISH_IOTHREAD_H
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#define FISH_IOTHREAD_H
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#include <pthread.h>
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#include <functional>
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#include <type_traits>
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/// Runs a command on a thread.
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///
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/// \param handler The function to execute on a background thread. Accepts an arbitrary context
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/// pointer, and returns an int, which is passed to the completionCallback.
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/// \param completionCallback The function to execute on the main thread once the background thread
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/// is complete. Accepts an int (the return value of handler) and the context.
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/// \param context A arbitary context pointer to pass to the handler and completion callback.
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/// \return A sequence number, currently not very useful.
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int iothread_perform_base(int (*handler)(void *), void (*completionCallback)(void *, int),
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void *context);
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/// Gets the fd on which to listen for completion callbacks.
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///
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/// \return A file descriptor on which to listen for completion callbacks.
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int iothread_port(void);
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/// Services one iothread competion callback.
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void iothread_service_completion(void);
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/// Waits for all iothreads to terminate.
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void iothread_drain_all(void);
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// Internal implementation
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int iothread_perform_impl(std::function<void(void)> &&func, std::function<void(void)> &&completion);
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// Template helpers
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// This is the glue part of the handler-completion handoff
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// In general we can just allocate an object, move the result of the handler into it,
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// and then call the completion with that object. However if our type is void,
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// this won't work (new void() fails!). So we have to use this template.
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// The type T is the return type of HANDLER and the argument to COMPLETION
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template <typename T>
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struct _iothread_trampoline {
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template <typename HANDLER, typename COMPLETION>
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static int perform(const HANDLER &handler, const COMPLETION &completion) {
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T *result = new T(); // TODO: placement new?
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return iothread_perform_impl([=]() { *result = handler(); },
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[=]() {
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completion(std::move(*result));
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delete result;
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});
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}
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};
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// Void specialization
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template <>
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struct _iothread_trampoline<void> {
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template <typename HANDLER, typename COMPLETION>
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static int perform(const HANDLER &handler, const COMPLETION &completion) {
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return iothread_perform_impl(handler, completion);
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}
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};
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// iothread_perform invokes a handler on a background thread, and then a completion function
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// on the main thread. The value returned from the handler is passed to the completion.
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// In other words, this is like COMPLETION(HANDLER()) except the handler part is invoked
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// on a background thread.
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template <typename HANDLER, typename COMPLETION>
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int iothread_perform(const HANDLER &handler, const COMPLETION &completion) {
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return _iothread_trampoline<decltype(handler())>::perform(handler, completion);
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}
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// variant of iothread_perform without a completion handler
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inline int iothread_perform(std::function<void(void)> &&func) {
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return iothread_perform_impl(std::move(func), {});
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}
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/// Performs a function on the main thread, blocking until it completes.
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void iothread_perform_on_main(std::function<void(void)> &&func);
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/// Creates a pthread, manipulating the signal mask so that the thread receives no signals.
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/// The pthread runs \p func.
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/// \returns true on success, false on failure.
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bool make_pthread(pthread_t *result, void *(*func)(void *), void *param);
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bool make_pthread(pthread_t *result, std::function<void(void)> &&func);
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/// \returns a thread ID for this thread.
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/// Thread IDs are never repeated.
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uint64_t thread_id();
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#endif
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