X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=dragonstd%2Fflag.h;fp=dragonstd%2Fflag.h;h=ba6a859e644a91ec449d5d7f0b9f9a3f258f0549;hb=ae5dd6c930ccef19ad313aa903f0528aa803ee80;hp=0000000000000000000000000000000000000000;hpb=7d8cdeeb49fc6fa0b4b7ac9c3bb3e1fb27f4f0bf;p=dragonstd.git

diff --git a/dragonstd/flag.h b/dragonstd/flag.h
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+++ b/dragonstd/flag.h
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+/*
+	Flag
+	----
+
+	A flag is a data structure that can be used to syncronize a boolean across multiple
+		threads.
+
+	The flag's state can be set, read and waited for in a thread safe manner.
+*/
+
+#ifndef _DRAGONSTD_FLAG_H_ // include guard
+#define _DRAGONSTD_FLAG_H_
+
+#include <pthread.h>   // for pthread_mutex_t, pthread_cond_t
+#include <stdatomic.h> // for atomic_bool
+#include <stdbool.h>   // for bool
+#include "list.h"      // for List
+
+typedef struct {
+	/* protected */
+	atomic_bool set;     // whether the flag is set
+	/* private */
+	pthread_cond_t cnd;  // main condition variable
+	pthread_mutex_t mtx; // mutex to protect the main condition variable
+	List cvs;            // condition variables
+} Flag;
+
+void flag_ini(Flag *flag);
+/*
+	Initializes the flag.
+
+	The flag should be uninitialized or deleted before passed to this function.
+	This function should be called before any other function is called on the flag.
+*/
+
+void flag_dst(Flag *flag);
+/*
+	Destroy the flag.
+
+	The refcount is unusable until reinitialized afterwards.
+*/
+
+void flag_sub(Flag *flag, pthread_cond_t *cnd);
+/*
+	[Thread Safe]
+	Subscribe condition variable cnd to flag.
+
+	The condition variable will be triggered when the flag is set.
+*/
+
+void flag_uns(Flag *flag, pthread_cond_t *cnd);
+/*
+	[Thread Safe]
+	Unsubscribe condition variable cnd from flag.
+
+	The condition variable will no longer be triggered when the flag is set.
+*/
+
+void flag_set(Flag *flag);
+/*
+	[Thread Safe]
+	Sets the flag.
+
+	This changes the flag state to be true and wakes up any threads waiting for it.
+	Afterwards, **the state cannot be changed back**.
+
+	This function can be called multiple times.
+*/
+
+void flag_slp(Flag *flag);
+/*
+	[Thread Safe]
+	Waits for the flag to be true.
+
+	This will sleep until the flag's state is changed to true, unless it is already set to
+		true.
+*/
+
+#endif // _DRAGONSTD_FLAG_H_