external: Add some headers from my util-headers project.

src/external/CMakeLists.txt

@@ -24,6 +24,12 @@ endif()
 add_library(xrt-external-flexkalman INTERFACE)
 target_include_directories(xrt-external-flexkalman INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/flexkalman)
 
+# FlexKalman
+add_library(xrt-external-util-headers INTERFACE)
+target_include_directories(
+	xrt-external-util-headers INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/util-headers
+	)
+
 # Glad
 add_library(xrt-external-glad INTERFACE)
 target_include_directories(xrt-external-glad INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/glad/include)

src/external/util-headers/util/Finally.h

@@ -0,0 +1,117 @@
+/** @file
+    @brief Header declaring a C++11 `finally` or "scope-guard" construct.
+
+    Inspirations are many - Alexandrescu's original and C++11 ScopeGuard, and
+    the Guideline Support Library's (GSL) `final_act`/`finally`
+    https://github.com/Microsoft/GSL/blob/0cf947db7760bf5756e4cb0d47c72a257ed527c5/include/gsl_util.h
+    come to mind, but this has been written and re-written numerous times
+    since its introduction into the C++ global consciousness, and this
+    implementation was written independently after I couldn't find a
+    previous independent implementation I had written a few weeks earlier in
+    an implementation file. -- Ryan Pavlik
+
+    See UniqueDestructionActionWrapper for a "generalized" (in some sense)
+    version of this.
+
+    Originally written for use in OSVR for Sensics <http://sensics.com/osvr>,
+    relicensed to BSL 1.0 with permission.
+
+    This header is maintained as a part of 'util-headers' - you can always
+    find the latest version online at https://github.com/rpavlik/util-headers
+
+    This GUID can help identify the project: d1dbc94e-e863-49cf-bc08-ab4d9f486613
+
+    This copy of the header is from the revision that Git calls
+    1a8444782d15cb9458052e3d8251c4f5b8e808d5
+
+    Commit date: "2022-03-11 12:11:32 -0600"
+
+    @date 2016
+
+    @author
+    Ryan Pavlik
+    <ryan.pavlik@gmail.com>
+    <http://ryanpavlik.com>
+*/
+
+// Copyright 2016, Sensics, Inc.
+//
+// SPDX-License-Identifier: BSL-1.0
+//
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef INCLUDED_Finally_h_GUID_D925FE58_9C57_448B_C0BB_19A42B3243BA
+#define INCLUDED_Finally_h_GUID_D925FE58_9C57_448B_C0BB_19A42B3243BA
+
+// Internal Includes
+// - none
+
+// Library/third-party includes
+// - none
+
+// Standard includes
+#include <utility>
+
+namespace util {
+namespace detail {
+    /// Allows you to run a callable something at the end of a scope.
+    ///
+    /// The class that provides the scope-guard behavior. Often not referred to
+    /// by name because auto is useful here, and often not created by a direct
+    /// constructor call because of the finally() convenience functions combined
+    /// with lambdas.
+    template <typename F> class FinalTask {
+    public:
+        /// Explicit constructor from something callable.
+        explicit FinalTask(F f) : f_(std::move(f)) {}
+
+        /// Move constructor - cancels the moved-from task.
+        FinalTask(FinalTask &&other) : f_(std::move(other.f_)), do_(other.do_) {
+            other.cancel();
+        }
+
+        /// non-copyable
+        FinalTask(FinalTask const &) = delete;
+
+        /// non-assignable
+        FinalTask &operator=(FinalTask const &) = delete;
+
+        /// Destructor - if we haven't been cancelled, do our callable thing.
+        ~FinalTask() {
+            if (do_) {
+                f_();
+            }
+        }
+        /// Cancel causes us to not do our final task on destruction.
+        void cancel() { do_ = false; }
+
+    private:
+        /// Our callable task to do at destruction.
+        F f_;
+        /// Whether we should actually do it.
+        bool do_ = true;
+    };
+} // namespace detail
+
+/// Creation free function for final tasks to run on scope exit. Works great
+/// when paired with lambdas (particularly with `[&]` reference capture).
+/// Use like:
+/// `auto f = finally([&]{ dothis(); });` to have `dothis()` called when `f`
+/// goes out of scope, no matter how.
+template <typename F> inline detail::FinalTask<F> finally(F &&f) {
+    /// Perfect forwarding version.
+    return detail::FinalTask<F>(std::forward<F>(f));
+}
+
+/// @overload
+template <typename F> inline detail::FinalTask<F> finally(F const &f) {
+    // Added this overload because GSL had it and GSL is supposed to be best
+    // practices guidelines...
+    return detail::FinalTask<F>(f);
+}
+
+} // namespace util
+
+#endif // INCLUDED_Finally_h_GUID_D925FE58_9C57_448B_C0BB_19A42B3243BA

src/external/util-headers/util/FixedLengthStringFunctions.h

@@ -0,0 +1,84 @@
+/** @file
+    @brief Header providing C++-enhanced versions of the various string
+    functions that work on fixed-length buffers, inspired by
+    https://randomascii.wordpress.com/2013/04/03/stop-using-strncpy-already/
+
+    @date 2015
+
+    This header is maintained as a part of 'util-headers' - you can always
+    find the latest version online at https://github.com/rpavlik/util-headers
+
+    This GUID can help identify the project: d1dbc94e-e863-49cf-bc08-ab4d9f486613
+
+    This copy of the header is from the revision that Git calls
+    1a8444782d15cb9458052e3d8251c4f5b8e808d5
+
+    Commit date: "2022-03-11 12:11:32 -0600"
+
+    @author
+    Sensics, Inc.
+    <http://sensics.com/osvr>
+*/
+
+// Copyright 2015, Sensics, Inc.
+// Copyright 2022, Collabora, Ltd.
+//
+// SPDX-License-Identifier: BSL-1.0
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//     (See accompanying file LICENSE_1_0.txt or copy at
+//           http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef INCLUDED_FixedLengthStringFunctions_h_GUID_34010E53_D3F3_42BD_FB36_6D00EA79C3A9
+#define INCLUDED_FixedLengthStringFunctions_h_GUID_34010E53_D3F3_42BD_FB36_6D00EA79C3A9
+
+// Internal Includes
+// - none
+
+// Library/third-party includes
+// - none
+
+// Standard includes
+#include <stddef.h>
+#include <stdexcept>
+#include <string.h>
+
+#ifdef _MSC_VER
+#define UTILHEADERS_STR_MSRUNTIME
+#else
+#include <limits.h>
+#ifndef _WIN32
+#include <sys/types.h>
+#endif
+#if defined(__KLIBC__) || defined(__BIONIC__) ||                               \
+    (!defined(__GLIBC__) && defined(_BSD_SOURCE))
+// strlcpy providers:
+// klibc
+// bionic
+// musl if _GNU_SOURCE or _BSD_SOURCE defined (_BSD_SOURCE defined by default) -
+// but not glibc!
+#define UTILHEADERS_STR_STRLCPY
+#elif defined(__DARWIN_C_LEVEL) && defined(__DARWIN_C_FULL) &&                 \
+    (__DARWIN_C_LEVEL >= __DARWIN_C_FULL)
+// Also provided in cases on Darwin
+#define UTILHEADERS_STR_STRLCPY
+#endif
+#endif
+
+namespace util {
+/// @brief Copy a string into a char array, guaranteed to null-terminate and not
+/// overrun. Does not correctly handle UTF-8 (may truncate in the middle of a
+/// codepoint).
+template <size_t N> inline void strcpy_safe(char (&dest)[N], const char *src) {
+#if defined(UTILHEADERS_STR_STRLCPY)
+    strlcpy(dest, src, N);
+#elif defined(UTILHEADERS_STR_MSRUNTIME)
+    strncpy_s(dest, src, _TRUNCATE);
+#else
+    strncpy(dest, src, N);
+    dest[N - 1] = '\0';
+#endif
+}
+} // namespace util
+
+#endif // INCLUDED_FixedLengthStringFunctions_h_GUID_34010E53_D3F3_42BD_FB36_6D00EA79C3A9

src/external/util-headers/util/Stride.h

@@ -0,0 +1,87 @@
+/**	@file
+	@brief	A class for handling "do this every n times"
+
+	This header is maintained as a part of 'util-headers' - you can always
+    find the latest version online at https://github.com/rpavlik/util-headers
+
+    This GUID can help identify the project: d1dbc94e-e863-49cf-bc08-ab4d9f486613
+
+    This copy of the header is from the revision that Git calls
+    1a8444782d15cb9458052e3d8251c4f5b8e808d5
+
+    Commit date: "2022-03-11 12:11:32 -0600"
+
+	@date
+	2009-2010
+
+	@author
+	Ryan Pavlik
+	<rpavlik@iastate.edu> and <abiryan@ryand.net>
+	http://academic.cleardefinition.com/
+	Iowa State University Virtual Reality Applications Center
+	Human-Computer Interaction Graduate Program
+*/
+
+// Copyright 2009-2010, Iowa State University.
+//
+// SPDX-License-Identifier: BSL-1.0
+//
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#pragma once
+#ifndef INCLUDED_Stride_h_GUID_eaa50b9c_e526_4656_89dc_99008d82447d
+#define INCLUDED_Stride_h_GUID_eaa50b9c_e526_4656_89dc_99008d82447d
+
+// Local includes
+// - none
+
+// Library includes
+// - none
+
+// Standard includes
+// - none
+
+namespace util {
+
+/// @addtogroup Other Other Utility Classes
+/// @{
+
+/// Handle the task of "do this every n times" in an easy way.
+	class Stride {
+		public:
+			Stride(const unsigned int n) :
+				_stride(n),
+				_step(0) { }
+
+			void advance() {
+				_step = (_step + 1) % _stride;
+			}
+
+			Stride operator++() {
+				Stride temp = *this;
+				advance();
+				return temp;
+			}
+
+			Stride & operator++(int) {
+				advance();
+				return *this;
+			}
+
+			operator bool() const {
+				return _step == 0;
+			}
+
+		private:
+			unsigned int _stride;
+			unsigned int _step;
+	};
+
+/// @}
+
+} // end of util namespace
+
+#endif // INCLUDED_Stride_h_GUID_eaa50b9c_e526_4656_89dc_99008d82447d
+