opal/class: add a new class: opal_interval_tree_t

This commit adds a new class to opal: opal_interval_tree_t. This is a
thread-safe impelementation of a 1-dimensional interval tree. The data
structure is intended to provide a faster implementation of the
registration cache VMA tree.

The thread safety is provided by a relativistic red-black tree
implementation. This structure provides support for multiple-reader,
and single writer. There is one caveat, an item may appear in the tree
twice while the tree is being updated. Care needs to be taken to avoid
issues associated with this "feature". I don't anticipate a problem
with the current VMA tree usage.

Signed-off-by: Nathan Hjelm <[email protected]>

Author: hjelmn

opal/class/Makefile.am

@@ -11,7 +11,7 @@
 # Copyright (c) 2004-2005 The Regents of the University of California.
 #                         All rights reserved.
 # Copyright (c) 2014 Cisco Systems, Inc.  All rights reserved.
-# Copyright (c) 2014-2015 Los Alamos National Security, LLC. All rights
+# Copyright (c) 2014-2018 Los Alamos National Security, LLC. All rights
 #                         reserved.
 # $COPYRIGHT$
 #
@@ -38,7 +38,8 @@ headers += \
         class/opal_pointer_array.h \
         class/opal_value_array.h \
         class/opal_ring_buffer.h \
-        class/opal_rb_tree.h
+        class/opal_rb_tree.h \
+        class/opal_interval_tree.h
 
 lib@OPAL_LIB_PREFIX@open_pal_la_SOURCES += \
         class/opal_bitmap.c \
@@ -54,4 +55,5 @@ lib@OPAL_LIB_PREFIX@open_pal_la_SOURCES += \
         class/opal_pointer_array.c \
         class/opal_value_array.c \
         class/opal_ring_buffer.c \
-        class/opal_rb_tree.c
+        class/opal_rb_tree.c \
+        class/opal_interval_tree.c