From 277957c10e96a23f822b2e6ae22c8d126a93141a Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Thu, 22 Nov 2012 00:28:24 -0600
Subject: [PATCH 1/1] Use pthread condition variables instead of semaphores

(Unnamed semaphores are not implemented on Mac OS X...)
---
 src/write.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/src/write.c b/src/write.c
index 29a8f21f..5b586cee 100644
--- a/src/write.c
+++ b/src/write.c
@@ -43,7 +43,6 @@
 #include "xpress.h"
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
-#include <semaphore.h>
 #include <pthread.h>
 #endif
 
@@ -547,13 +546,14 @@ out:
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
 struct shared_queue {
-	sem_t filled_slots;
-	sem_t empty_slots;
-	pthread_mutex_t lock;
+	unsigned size;
 	unsigned front;
 	unsigned back;
+	unsigned filled_slots;
 	void **array;
-	unsigned size;
+	pthread_mutex_t lock;
+	pthread_cond_t msg_avail_cond;
+	pthread_cond_t space_avail_cond;
 };
 
 static int shared_queue_init(struct shared_queue *q, unsigned size)
@@ -561,46 +561,52 @@ static int shared_queue_init(struct shared_queue *q, unsigned size)
 	q->array = CALLOC(sizeof(q->array[0]), size);
 	if (!q->array)
 		return WIMLIB_ERR_NOMEM;
-
-	sem_init(&q->filled_slots, 0, 0);
-	sem_init(&q->empty_slots, 0, size);
-	pthread_mutex_init(&q->lock, NULL);
+	q->filled_slots = 0;
 	q->front = 0;
 	q->back = size - 1;
 	q->size = size;
+	pthread_mutex_init(&q->lock, NULL);
+	pthread_cond_init(&q->msg_avail_cond, NULL);
+	pthread_cond_init(&q->space_avail_cond, NULL);
 	return 0;
 }
 
 static void shared_queue_destroy(struct shared_queue *q)
 {
-	sem_destroy(&q->filled_slots);
-	sem_destroy(&q->empty_slots);
-	pthread_mutex_destroy(&q->lock);
 	FREE(q->array);
+	pthread_mutex_destroy(&q->lock);
+	pthread_cond_destroy(&q->msg_avail_cond);
+	pthread_cond_destroy(&q->space_avail_cond);
 }
 
 static void shared_queue_put(struct shared_queue *q, void *obj)
 {
-	sem_wait(&q->empty_slots);
 	pthread_mutex_lock(&q->lock);
+	while (q->filled_slots == q->size)
+		pthread_cond_wait(&q->space_avail_cond, &q->lock);
 
 	q->back = (q->back + 1) % q->size;
 	q->array[q->back] = obj;
+	q->filled_slots++;
 
-	sem_post(&q->filled_slots);
+	pthread_cond_broadcast(&q->msg_avail_cond);
 	pthread_mutex_unlock(&q->lock);
 }
 
 static void *shared_queue_get(struct shared_queue *q)
 {
-	sem_wait(&q->filled_slots);
+	void *obj;
+
 	pthread_mutex_lock(&q->lock);
+	while (q->filled_slots == 0)
+		pthread_cond_wait(&q->msg_avail_cond, &q->lock);
 
-	void *obj = q->array[q->front];
+	obj = q->array[q->front];
 	q->array[q->front] = NULL;
 	q->front = (q->front + 1) % q->size;
+	q->filled_slots--;
 
-	sem_post(&q->empty_slots);
+	pthread_cond_broadcast(&q->space_avail_cond);
 	pthread_mutex_unlock(&q->lock);
 	return obj;
 }
-- 
2.43.0