From 8dcf4372f4a63322c50e88f5795cf65e863b0f76 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Wed, 2 Apr 2014 22:47:49 -0400
Subject: [PATCH] Use a double-linked list for the linked blocking queue so
 insertions are done in O(1) time

---
 limelight-common/AudioStream.c         |  2 +-
 limelight-common/InputStream.c         |  2 +-
 limelight-common/LinkedBlockingQueue.c | 33 ++++++++++++++++----------
 limelight-common/LinkedBlockingQueue.h |  4 +++-
 limelight-common/VideoDepacketizer.c   |  2 +-
 limelight-common/VideoStream.c         |  2 +-
 6 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/limelight-common/AudioStream.c b/limelight-common/AudioStream.c
index b1d9ed3..2968644 100644
--- a/limelight-common/AudioStream.c
+++ b/limelight-common/AudioStream.c
@@ -33,7 +33,7 @@ void destroyAudioStream(void) {
 	entry = LbqDestroyLinkedBlockingQueue(&packetQueue);
 
 	while (entry != NULL) {
-		nextEntry = entry->next;
+		nextEntry = entry->flink;
 		free(entry->data);
 		free(entry);
 		entry = nextEntry;
diff --git a/limelight-common/InputStream.c b/limelight-common/InputStream.c
index 2ae7d6f..58580f7 100644
--- a/limelight-common/InputStream.c
+++ b/limelight-common/InputStream.c
@@ -35,7 +35,7 @@ void destroyInputStream(void) {
 	entry = LbqDestroyLinkedBlockingQueue(&packetQueue);
 
 	while (entry != NULL) {
-		nextEntry = entry->next;
+		nextEntry = entry->flink;
 		free(entry->data);
 		free(entry);
 		entry = nextEntry;
diff --git a/limelight-common/LinkedBlockingQueue.c b/limelight-common/LinkedBlockingQueue.c
index 26c9f79..8804665 100644
--- a/limelight-common/LinkedBlockingQueue.c
+++ b/limelight-common/LinkedBlockingQueue.c
@@ -21,6 +21,7 @@ int LbqInitializeLinkedBlockingQueue(PLINKED_BLOCKING_QUEUE queueHead, int sizeB
 	}
 
 	queueHead->head = NULL;
+	queueHead->tail = NULL;
 	queueHead->sizeBound = sizeBound;
 	queueHead->currentSize = 0;
 
@@ -28,14 +29,14 @@ int LbqInitializeLinkedBlockingQueue(PLINKED_BLOCKING_QUEUE queueHead, int sizeB
 }
 
 int LbqOfferQueueItem(PLINKED_BLOCKING_QUEUE queueHead, void* data) {
-	PLINKED_BLOCKING_QUEUE_ENTRY entry, lastEntry;
+	PLINKED_BLOCKING_QUEUE_ENTRY entry;
 
 	entry = (PLINKED_BLOCKING_QUEUE_ENTRY) malloc(sizeof(*entry));
 	if (entry == NULL) {
 		return LBQ_NO_MEMORY;
 	}
 
-	entry->next = NULL;
+	entry->flink = NULL;
 	entry->data = data;
 
 	PltLockMutex(&queueHead->mutex);
@@ -48,15 +49,17 @@ int LbqOfferQueueItem(PLINKED_BLOCKING_QUEUE queueHead, void* data) {
 
 	if (queueHead->head == NULL) {
 		LC_ASSERT(queueHead->currentSize == 0);
+		LC_ASSERT(queueHead->tail == NULL);
 		queueHead->head = entry;
+		queueHead->tail = entry;
+		entry->blink = NULL;
 	}
 	else {
 		LC_ASSERT(queueHead->currentSize >= 1);
-		lastEntry = queueHead->head;
-		while (lastEntry->next != NULL) {
-			lastEntry = lastEntry->next;
-		}
-		lastEntry->next = entry;
+		LC_ASSERT(queueHead->head != NULL);
+		queueHead->tail->flink = entry;
+		entry->blink = queueHead->tail;
+		queueHead->tail = entry;
 	}
 
 	queueHead->currentSize++;
@@ -86,18 +89,22 @@ int LbqWaitForQueueElement(PLINKED_BLOCKING_QUEUE queueHead, void** data) {
 		}
 
 		entry = queueHead->head;
-		queueHead->head = entry->next;
+		queueHead->head = entry->flink;
 		queueHead->currentSize--;
+		if (queueHead->head == NULL) {
+			LC_ASSERT(queueHead->currentSize == 0);
+			queueHead->tail = NULL;
+			PltClearEvent(&queueHead->containsDataEvent);
+		}
+		else {
+			LC_ASSERT(queueHead->currentSize != 0);
+			queueHead->head->blink = NULL;
+		}
 
 		*data = entry->data;
 
 		free(entry);
 
-		if (queueHead->head == NULL) {
-			LC_ASSERT(queueHead->currentSize == 0);
-			PltClearEvent(&queueHead->containsDataEvent);
-		}
-
 		PltUnlockMutex(&queueHead->mutex);
 
 		break;
diff --git a/limelight-common/LinkedBlockingQueue.h b/limelight-common/LinkedBlockingQueue.h
index 142addb..1f03efe 100644
--- a/limelight-common/LinkedBlockingQueue.h
+++ b/limelight-common/LinkedBlockingQueue.h
@@ -9,7 +9,8 @@
 #define LBQ_NO_MEMORY 3
 
 typedef struct _LINKED_BLOCKING_QUEUE_ENTRY {
-	struct _LINKED_BLOCKING_QUEUE_ENTRY *next;
+	struct _LINKED_BLOCKING_QUEUE_ENTRY *flink;
+	struct _LINKED_BLOCKING_QUEUE_ENTRY *blink;
 	void* data;
 } LINKED_BLOCKING_QUEUE_ENTRY, *PLINKED_BLOCKING_QUEUE_ENTRY;
 
@@ -19,6 +20,7 @@ typedef struct _LINKED_BLOCKING_QUEUE {
 	int sizeBound;
 	int currentSize;
 	PLINKED_BLOCKING_QUEUE_ENTRY head;
+	PLINKED_BLOCKING_QUEUE_ENTRY tail;
 } LINKED_BLOCKING_QUEUE, *PLINKED_BLOCKING_QUEUE;
 
 int LbqInitializeLinkedBlockingQueue(PLINKED_BLOCKING_QUEUE queueHead, int sizeBound);
diff --git a/limelight-common/VideoDepacketizer.c b/limelight-common/VideoDepacketizer.c
index a218e94..9d74a06 100644
--- a/limelight-common/VideoDepacketizer.c
+++ b/limelight-common/VideoDepacketizer.c
@@ -45,7 +45,7 @@ void destroyVideoDepacketizer(void) {
 	
 	entry = LbqDestroyLinkedBlockingQueue(&decodeUnitQueue);
 	while (entry != NULL) {
-		nextEntry = entry->next;
+		nextEntry = entry->flink;
 		free(entry->data);
 		free(entry);
 		entry = nextEntry;
diff --git a/limelight-common/VideoStream.c b/limelight-common/VideoStream.c
index e181560..eb6c53b 100644
--- a/limelight-common/VideoStream.c
+++ b/limelight-common/VideoStream.c
@@ -45,7 +45,7 @@ void destroyVideoStream(void) {
 	entry = LbqDestroyLinkedBlockingQueue(&packetQueue);
 
 	while (entry != NULL) {
-		nextEntry = entry->next;
+		nextEntry = entry->flink;
 		free(entry->data);
 		free(entry);
 		entry = nextEntry;