+int svm_fifo_enqueue_nowait (svm_fifo_t * f, u32 max_bytes,
+ const u8 * copy_from_here);
+int svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset,
+ u32 required_bytes, u8 * copy_from_here);
+int svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_here);
+
+int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
+int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
+void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
+int svm_fifo_segments (svm_fifo_t * f, svm_fifo_segment_t * fs);
+void svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_segment_t * fs);
+void svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer);
+void svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len);
+void svm_fifo_add_subscriber (svm_fifo_t * f, u8 subscriber);
+void svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber);
+format_function_t format_svm_fifo;
+
+/**
+ * Max contiguous chunk of data that can be read
+ */
+always_inline u32
+svm_fifo_max_read_chunk (svm_fifo_t * f)
+{
+ return ((f->tail > f->head) ? (f->tail - f->head) : (f->nitems - f->head));
+}
+
+/**
+ * Max contiguous chunk of data that can be written
+ */
+always_inline u32
+svm_fifo_max_write_chunk (svm_fifo_t * f)
+{
+ return ((f->tail >= f->head) ? (f->nitems - f->tail) : (f->head - f->tail));
+}
+
+/**
+ * Advance tail pointer
+ *
+ * Useful for moving tail pointer after external enqueue.
+ */
+always_inline void
+svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 bytes)
+{
+ ASSERT (bytes <= svm_fifo_max_enqueue (f));
+ f->tail = (f->tail + bytes) % f->nitems;
+ clib_atomic_fetch_add_rel (&f->cursize, bytes);
+}