Added TPromise Library (#487)

tools/TPromises/tpromise.c

@@ -0,0 +1,106 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "tpromise.h"
+
+
+void *
+AwaitTPromise(
+    TPromise *promise
+    )
+{
+    pthread_mutex_lock(&promise->mutex);
+    while(!promise->resolved)
+    {   pthread_cond_wait(&promise->cond, &promise->mutex);
+    }
+    pthread_mutex_unlock(&promise->mutex);
+    return promise->data;
+}
+
+void
+DestroyTPromise(
+    TPromise *promise
+    )
+{
+    if(!promise)
+    {   return;
+    }
+
+    pthread_mutex_destroy(&promise->mutex);
+    pthread_cond_destroy(&promise->cond);
+
+    free(promise);
+}
+
+int
+IsTPromiseDone(
+    TPromise *promise
+    )
+{
+    int promise_done = 0;
+
+    if(!promise)
+    {   return promise_done;
+    }
+
+    pthread_mutex_lock(&promise->mutex);
+    if(promise->resolved)
+    {   promise_done = 1;
+    }
+    pthread_mutex_unlock(&promise->mutex);
+
+    return promise_done;
+}
+
+TPromise *
+NewTPromise(
+    void
+    )
+{
+    TPromise *promise = malloc(sizeof(*promise));
+    if(promise)
+    {
+        int status = NewTPromiseFilled(promise);
+        if(status != EXIT_SUCCESS)
+        {   
+            free(promise);
+            promise = NULL;
+        }
+    }
+    return promise;
+}
+
+int
+NewTPromiseFilled(
+    TPromise *promise_return
+    )
+{
+    if(!promise_return)
+    {   return EXIT_FAILURE;
+    }
+    const TPromise _cpy = 
+    {
+        .data = NULL,
+        .resolved = 0,
+        .mutex = PTHREAD_MUTEX_INITIALIZER,
+        .cond = PTHREAD_COND_INITIALIZER,
+    };
+    *promise_return = _cpy;
+    return EXIT_SUCCESS;
+}
+
+void
+ResolveTPromise(
+    TPromise *promise, 
+    void *data
+    )
+{
+    pthread_mutex_lock(&promise->mutex);
+    if(!promise->resolved)
+    {   
+        promise->data = data;
+        promise->resolved = 1;
+    }
+    pthread_cond_signal(&promise->cond);
+    pthread_mutex_unlock(&promise->mutex);
+}

tools/TPromises/tpromise.h

@@ -0,0 +1,101 @@
+#ifndef __THREAD__PROMISE__H__
+#define __THREAD__PROMISE__H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <pthread.h>
+
+typedef struct TPromise TPromise;
+
+struct
+TPromise
+{
+    void *data;
+    int resolved;
+    /* 4bytes pad */
+
+    pthread_mutex_t mutex;
+    pthread_cond_t cond;
+};
+
+/* (A)Waits for a promise to resolve.
+ *
+ * NOTE: NULL may be returned if ResolveTPromise() was specified as NULL data.
+ * NOTE: Awaiting a promise multiple times will not yield different results.
+ * NOTE: Attempting to await a destroyed promise is undefined.
+ *
+ * RETURN: Data from Promise.
+ */
+void *
+AwaitTPromise(
+    TPromise *promise
+    );
+
+
+/* Destroys the given promise, usage of promise after being destroyed is undefined.
+ * 
+ * NOTE: if a promise is being resolved or awaited, behaviour is undefined.
+ *
+ */
+void
+DestroyTPromise(
+    TPromise *promise
+    );
+
+/* Returns wheter or not promise has resolved its data.
+ *
+ * RETURN: true on is Done.
+ * RETURN: false otherwise.
+ */
+int
+IsTPromiseDone(
+    TPromise *promise
+    );
+
+/* Allocates and intializes a promise for use.
+ *
+ * NOTE: This is the only Failure point for TPromises. 
+ *
+ * RETURN: TPromise * on Success.
+ * RETURN: NULL on Failure.
+ */
+TPromise *
+NewTPromise(
+    void
+    );
+
+/* Intializes a promise for use.
+ *
+ * NOTE: This is the only Failure point for TPromises.
+ * NOTE: field 'promise_return' SHOULD be allocated memory, at the minimum static stack memory.
+ *       This is to avoid deadlocks in threads.
+ *
+ * RETURN: EXIT_SUCCESS on Success.
+ * RETURN: EXIT_FAILURE on Failure.
+ */
+int
+NewTPromiseFilled(
+    TPromise *promise_return
+    );
+
+/* Resolves a TPromise by updating its data.
+ *
+ * NOTE: field 'data' MAY be NULL, in such cases NULL will be set as data.
+ * NOTE: A promise may only be resolved once, further attempts to resolve a promise,
+ *       Will simply 'wakeup' the other process/thread awaiting for the response.
+ * NOTE: Attempting to resolve a destroyed promise is undefined.
+ */
+void
+ResolveTPromise(
+    TPromise *promise, 
+    void *data
+    );
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif