aux/math: Add simple string hashing function

src/xrt/auxiliary/CMakeLists.txt

@@ -4,8 +4,9 @@
 set(MATH_SOURCE_FILES
 	math/m_api.h
 	math/m_base.cpp
-	math/m_optics.c
 	math/m_eigen_interop.h
+	math/m_hash.cpp
+	math/m_optics.c
 	math/m_quatexpmap.cpp
 	)
 

src/xrt/auxiliary/math/m_api.h

@@ -36,6 +36,25 @@ extern "C" {
  */
 
 
+/*
+ *
+ * Hash functions.
+ *
+ */
+
+/*!
+ * Generate a hash value from the given string, trailing zero not included.
+ *
+ * Hashing function used is not specified so no garantee of staying the same
+ * between different versions of the software, or even when the same version
+ * is compiled on different platforms/libc++ as it might use std::hash.
+ *
+ * @ingroup aux_math
+ */
+size_t
+math_hash_string(const char *str_c, size_t length);
+
+
 /*
  *
  * Vector functions

src/xrt/auxiliary/math/m_hash.cpp

@@ -0,0 +1,20 @@
+// Copyright 2019, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Hashing fuction.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @ingroup aux_math
+ */
+
+#include <string>
+#include "m_api.h"
+
+
+extern "C" size_t
+math_hash_string(const char *str_c, size_t length)
+{
+	std::string str = std::string(str_c, length);
+	std::hash<std::string> str_hash;
+	return str_hash(str);
+}