diff --git a/osi/include/fixed_queue.h b/osi/include/fixed_queue.h
index 52862bf..6902d6b 100644
--- a/osi/include/fixed_queue.h
+++ b/osi/include/fixed_queue.h
@@ -21,6 +21,8 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
+#include "osi/include/list.h"
+
 struct fixed_queue_t;
 typedef struct fixed_queue_t fixed_queue_t;
 typedef struct reactor_t reactor_t;
@@ -28,6 +30,11 @@
 typedef void (*fixed_queue_free_cb)(void *data);
 typedef void (*fixed_queue_cb)(fixed_queue_t *queue, void *context);
 
+// Initializes a fixed |queue| with the given |capacity|. If more elements than
+// |capacity| are added to the queue, the caller is blocked until space is
+// made available in the queue. Returns false on failure.
+bool fixed_queue_init(fixed_queue_t *queue, size_t capacity);
+
 // Creates a new fixed queue with the given |capacity|. If more elements than
 // |capacity| are added to the queue, the caller is blocked until space is
 // made available in the queue. Returns NULL on failure. The caller must free
@@ -42,6 +49,9 @@
 // not be NULL.
 bool fixed_queue_is_empty(fixed_queue_t *queue);
 
+// Returns the length of the |queue|. |queue| may not be NULL.
+size_t fixed_queue_length(fixed_queue_t *queue);
+
 // Returns the maximum number of elements this queue may hold. |queue| may
 // not be NULL.
 size_t fixed_queue_capacity(fixed_queue_t *queue);
@@ -69,9 +79,27 @@
 void *fixed_queue_try_dequeue(fixed_queue_t *queue);
 
 // Returns the first element from |queue|, if present, without dequeuing it.
-// This function will never block the caller. Returns NULL if there are no elements
-// in the queue. |queue| may not be NULL.
-void *fixed_queue_try_peek(fixed_queue_t *queue);
+// This function will never block the caller. Returns NULL if there are no
+// elements in the queue. |queue| may not be NULL.
+void *fixed_queue_try_peek_first(fixed_queue_t *queue);
+
+// Returns the last element from |queue|, if present, without dequeuing it.
+// This function will never block the caller. Returns NULL if there are no
+// elements in the queue. |queue| may not be NULL.
+void *fixed_queue_try_peek_last(fixed_queue_t *queue);
+
+// Tries to remove a |data| element from the middle of the |queue|. This
+// function will never block the caller. If the |data| element is found
+// in the queue, a pointer to the removed data is returned, otherwise NULL.
+void *fixed_queue_try_remove_from_queue(fixed_queue_t *queue, void *data);
+
+// Returns the iterateable list with all entries in the |queue|. This function
+// will never block the caller. |queue| may not be NULL.
+//
+// NOTE: The return result of this function is not thread safe: the list could
+// be modified by another thread, and the result would be unpredictable.
+// Hence, the usage of this function is discouraged.
+list_t *fixed_queue_get_list(fixed_queue_t *queue);
 
 // This function returns a valid file descriptor. Callers may perform one
 // operation on the fd: select(2). If |select| indicates that the file