1 files changed, 281 insertions, 0 deletions
diff --git a/libdimension/concurrency/future.c b/libdimension/concurrency/future.c
new file mode 100644
index 0000000..90ffa24
--- /dev/null
+++ b/libdimension/concurrency/future.c
@@ -0,0 +1,281 @@
+/*************************************************************************
+ * Copyright (C) 2009-2014 Tavian Barnes <tavianator@tavianator.com>     *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Future objects.
+ */
+
+#include "internal.h"
+#include "internal/concurrency.h"
+#include "internal/future.h"
+#include <pthread.h>
+
+/**
+ * Since C doesn't support anything like C++'s mutable, we fake it by casting
+ * away the constness.  This is okay since all valid dmnsn_futures live on the
+ * heap, so cannot be const.
+ */
+#define MUTATE(future) ((dmnsn_future *)(future))
+
+// Allocate a new dmnsn_future*
+dmnsn_future *
+dmnsn_new_future(void)
+{
+  dmnsn_future *future = DMNSN_MALLOC(dmnsn_future);
+  future->progress = 0;
+  future->total    = 1;
+
+  dmnsn_initialize_mutex(&future->mutex);
+  dmnsn_initialize_cond(&future->cond);
+
+  future->min_wait = 1.0;
+
+  future->nthreads = future->nrunning = 1;
+  future->npaused = 0;
+  dmnsn_initialize_cond(&future->none_running_cond);
+  dmnsn_initialize_cond(&future->all_running_cond);
+  dmnsn_initialize_cond(&future->resume_cond);
+
+  return future;
+}
+
+static void
+dmnsn_delete_future(dmnsn_future *future)
+{
+  if (future) {
+    dmnsn_destroy_cond(&future->resume_cond);
+    dmnsn_destroy_cond(&future->all_running_cond);
+    dmnsn_destroy_cond(&future->none_running_cond);
+    dmnsn_destroy_cond(&future->cond);
+    dmnsn_destroy_mutex(&future->mutex);
+    dmnsn_free(future);
+  }
+}
+
+// Join the worker thread and delete `future'.
+int
+dmnsn_future_join(dmnsn_future *future)
+{
+  void *ptr;
+  int retval = -1;
+
+  if (future) {
+    dmnsn_assert(future->npaused == 0, "Attempt to join future while paused");
+
+    // Get the thread's return value
+    dmnsn_join_thread(future->thread, &ptr);
+    if (ptr && ptr != PTHREAD_CANCELED) {
+      retval = *(int *)ptr;
+      dmnsn_free(ptr);
+    }
+
+    // Free the future object
+    dmnsn_delete_future(future);
+  }
+
+  return retval;
+}
+
+// Cancel a background thread
+void
+dmnsn_future_cancel(dmnsn_future *future)
+{
+  pthread_cancel(future->thread);
+}
+
+/**
+ * Get the current progress, without locking anything.
+ *
+ * future->mutex must be locked for this call to be safe.
+ */
+static inline double
+dmnsn_future_progress_unlocked(const dmnsn_future *future)
+{
+  return (double)future->progress/future->total;
+}
+
+// Get the current progress of the worker thread, in [0.0, 1.0]
+double
+dmnsn_future_progress(const dmnsn_future *future)
+{
+  dmnsn_future *mfuture = MUTATE(future);
+  double progress;
+
+  dmnsn_lock_mutex(&mfuture->mutex);
+    progress = dmnsn_future_progress_unlocked(mfuture);
+  dmnsn_unlock_mutex(&mfuture->mutex);
+
+  return progress;
+}
+
+// Find out whether the task is complete.
+bool
+dmnsn_future_is_done(const dmnsn_future *future)
+{
+  dmnsn_future *mfuture = MUTATE(future);
+  bool result;
+
+  dmnsn_lock_mutex(&mfuture->mutex);
+    result = future->progress == future->total;
+  dmnsn_unlock_mutex(&mfuture->mutex);
+
+  return result;
+}
+
+// Wait until dmnsn_future_progress(future) >= progress
+void
+dmnsn_future_wait(const dmnsn_future *future, double progress)
+{
+  dmnsn_future *mfuture = MUTATE(future);
+
+  dmnsn_lock_mutex(&mfuture->mutex);
+    while (dmnsn_future_progress_unlocked(mfuture) < progress) {
+      // Set the minimum waited-on value
+      if (progress < mfuture->min_wait) {
+        mfuture->min_wait = progress;
+      }
+
+      dmnsn_cond_wait_safely(&mfuture->cond, &mfuture->mutex);
+    }
+  dmnsn_unlock_mutex(&mfuture->mutex);
+}
+
+// Pause all threads working on a future.
+void
+dmnsn_future_pause(dmnsn_future *future)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    while (future->nrunning < future->nthreads) {
+      dmnsn_cond_wait_safely(&future->all_running_cond, &future->mutex);
+    }
+    ++future->npaused;
+    while (future->nrunning > 0) {
+      dmnsn_cond_wait_safely(&future->none_running_cond, &future->mutex);
+    }
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+// Resume all threads working on a future.
+void
+dmnsn_future_resume(dmnsn_future *future)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    dmnsn_assert(future->npaused > 0, "dmnsn_future_resume() without matching dmnsn_future_pause()");
+    if (--future->npaused == 0) {
+      dmnsn_cond_broadcast(&future->resume_cond);
+    }
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+// Set the total number of loop iterations
+void
+dmnsn_future_set_total(dmnsn_future *future, size_t total)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    future->total = total;
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+static void
+dmnsn_future_increment_cleanup(void *ptr)
+{
+  dmnsn_future *future = ptr;
+  ++future->nrunning;
+  dmnsn_unlock_mutex_impl(&future->mutex);
+}
+
+// Increment the number of completed loop iterations
+void
+dmnsn_future_increment(dmnsn_future *future)
+{
+  // Allow a thread to be canceled whenever it increments a future object --
+  // this is close to PTHREAD_CANCEL_ASYNCHRONOUS but allows consistent state
+  // on cancellation
+  pthread_testcancel();
+
+  dmnsn_lock_mutex(&future->mutex);
+    ++future->progress;
+
+    if (dmnsn_future_progress_unlocked(future) >= future->min_wait) {
+      future->min_wait = 1.0;
+      dmnsn_cond_broadcast(&future->cond);
+    }
+
+    if (future->npaused > 0) {
+      dmnsn_assert(future->nrunning > 0, "More worker threads than expected");
+
+      if (--future->nrunning == 0) {
+        dmnsn_cond_broadcast(&future->none_running_cond);
+      }
+
+      pthread_cleanup_push(dmnsn_future_increment_cleanup, future);
+        do {
+          dmnsn_cond_wait(&future->resume_cond, &future->mutex);
+        } while (future->npaused > 0);
+      pthread_cleanup_pop(false);
+
+      if (++future->nrunning == future->nthreads) {
+        dmnsn_cond_broadcast(&future->all_running_cond);
+      }
+    }
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+// Immediately set to 100% completion
+void
+dmnsn_future_finish(dmnsn_future *future)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    future->progress = future->total;
+    future->nthreads = future->nrunning = 0;
+    dmnsn_cond_broadcast(&future->cond);
+    dmnsn_cond_broadcast(&future->none_running_cond);
+    dmnsn_cond_broadcast(&future->all_running_cond);
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+// Set the number of threads
+void
+dmnsn_future_set_nthreads(dmnsn_future *future, unsigned int nthreads)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    dmnsn_assert(future->nrunning == future->nthreads,
+                 "dmnsn_future_set_nthreads() called with paused threads");
+    future->nthreads = future->nrunning = nthreads;
+  dmnsn_unlock_mutex(&future->mutex);
+}
+
+// Notify completion of a worker thread
+void
+dmnsn_future_finish_thread(dmnsn_future *future)
+{
+  dmnsn_lock_mutex(&future->mutex);
+    dmnsn_assert(future->nthreads > 0,
+                 "dmnsn_future_finish_thread() called with no threads");
+    --future->nthreads;
+
+    dmnsn_assert(future->nrunning > 0,
+                 "dmnsn_future_finish_thread() called with no running threads");
+    if (--future->nrunning == 0) {
+      dmnsn_cond_broadcast(&future->none_running_cond);
+    }
+  dmnsn_unlock_mutex(&future->mutex);
+}