some upgrades to vmallocator.h

Make `SCP_vector`, `SCP_list`, `SCP_set`, and `SCP_multiset` subclasses of their STL counterparts.  This allows helper functions to be added to each, including the `contains()` function which is not available until C++20.  (This has minor effects on other parts of the codebase that treated `SCP_` and `std::` as synonyms.)  Since there is now a nontrivial amount of code that needs to be in a .cpp file, create vmallocator.cpp.

Note that `SCP_string` truncation has been refactored to use length rather than C-string size to be consistent with other `std::basic_string` functions.

Also, remove some enum class hashing code which is no longer necessary now that the codebase is at C++17.

code/ai/ai.h

@@ -635,6 +635,6 @@ void do_random_sidethrust(ai_info *aip, ship_info *sip);
 void ai_formation_object_recalculate_slotnums(int form_objnum, int exiting_objnum = -1);
 
 
-bool test_line_of_sight(vec3d* from, vec3d* to, std::unordered_set<int>&& excluded_object_ids = {}, float threshold = 10.0f, bool test_for_shields = false, bool test_for_hull = true, float* first_intersect_dist = nullptr, object** first_intersect_obj = nullptr);
+bool test_line_of_sight(const vec3d* from, const vec3d* to, SCP_unordered_set<int>&& excluded_object_ids = {}, float threshold = 10.0f, bool test_for_shields = false, bool test_for_hull = true, float* first_intersect_dist = nullptr, object** first_intersect_obj = nullptr);
 
 #endif

code/ai/aicode.cpp

@@ -16795,15 +16795,16 @@ void maybe_cheat_fire_synaptic(object *objp)
 	}
 }
 
-bool test_line_of_sight(vec3d* from, vec3d* to, std::unordered_set<int>&& excluded_object_ids, float threshold, bool test_for_shields, bool test_for_hull, float* first_intersect_dist, object** first_intersect_obj) {
+bool test_line_of_sight(const vec3d* from, const vec3d* to, SCP_unordered_set<int>&& excluded_object_ids, float threshold, bool test_for_shields, bool test_for_hull, float* first_intersect_dist, object** first_intersect_obj)
+{
 	bool collides = false;
 
 	for (object* objp = GET_FIRST(&obj_used_list); objp != END_OF_LIST(&obj_used_list); objp = GET_NEXT(objp)) {
 		if (objp->flags[Object::Object_Flags::Should_be_dead])
 			continue;
 
 		//Don't collision check against excluded objects
-		if (excluded_object_ids.count(OBJ_INDEX(objp)) > 0)
+		if (excluded_object_ids.contains(OBJ_INDEX(objp)))
 			continue;
 
 		int model_num = 0;

code/globalincs/systemvars.cpp

@@ -440,87 +440,3 @@ DCF(detail, "Turns on/off parts of the game for speed testing" )
 	}
 }
 #endif
-
-// Stuff that can't be included in vmallocator.h
-
-std::locale SCP_default_locale("");
-
-void SCP_tolower(char *str)
-{
-	for (; *str != '\0'; ++str)
-		*str = SCP_tolower(*str);
-}
-
-void SCP_toupper(char *str)
-{
-	for (; *str != '\0'; ++str)
-		*str = SCP_toupper(*str);
-}
-
-// this is a bit naive but it is good enough for the time being
-void SCP_totitle(char *str)
-{
-	bool prev_alpha = false;
-
-	for (; *str != '\0'; ++str)
-	{
-		bool this_alpha = (*str >= 'a' && *str <= 'z') || (*str >= 'A' && *str <= 'Z');
-
-		if (this_alpha)
-		{
-			if (prev_alpha)
-				*str = SCP_tolower(*str);
-			else
-				*str = SCP_toupper(*str);
-		}
-
-		prev_alpha = this_alpha;
-	}
-}
-
-bool lcase_equal(const SCP_string& _Left, const SCP_string& _Right)
-{
-	if (_Left.size() != _Right.size())
-		return false;
-
-	auto l_it = _Left.cbegin();
-	auto r_it = _Right.cbegin();
-
-	while (l_it != _Left.cend())
-	{
-		if (SCP_tolower(*l_it) != SCP_tolower(*r_it))
-			return false;
-
-		++l_it;
-		++r_it;
-	}
-
-	return true;
-}
-
-bool lcase_lessthan(const SCP_string& _Left, const SCP_string& _Right)
-{
-	auto l_it = _Left.cbegin();
-	auto r_it = _Right.cbegin();
-
-	while (true)
-	{
-		if (l_it == _Left.cend())
-			return (r_it != _Right.cend());
-		else if (r_it == _Right.cend())
-			return false;
-
-		auto lch = SCP_tolower(*l_it);
-		auto rch = SCP_tolower(*r_it);
-
-		if (lch < rch)
-			return true;
-		else if (lch > rch)
-			return false;
-
-		++l_it;
-		++r_it;
-	}
-
-	return true;
-}

code/globalincs/vmallocator.cpp

@@ -0,0 +1,128 @@
+// Stuff that can't be included in vmallocator.h
+
+#include "globalincs/vmallocator.h"
+
+std::locale SCP_default_locale("");
+
+void SCP_tolower(SCP_string &str)
+{
+	std::for_each(str.begin(), str.end(), [](char &ch) { ch = SCP_tolower(ch); });
+}
+
+void SCP_toupper(SCP_string &str)
+{
+	std::for_each(str.begin(), str.end(), [](char &ch) { ch = SCP_toupper(ch); });
+}
+
+void SCP_tolower(char *str)
+{
+	for (; *str != '\0'; ++str)
+		*str = SCP_tolower(*str);
+}
+
+void SCP_toupper(char *str)
+{
+	for (; *str != '\0'; ++str)
+		*str = SCP_toupper(*str);
+}
+
+// in-place modification of string to title case; this is a bit naive but it is good enough for the time being
+void SCP_totitle(char *str)
+{
+	bool prev_alpha = false;
+
+	for (; *str != '\0'; ++str)
+	{
+		bool this_alpha = (*str >= 'a' && *str <= 'z') || (*str >= 'A' && *str <= 'Z');
+
+		if (this_alpha)
+		{
+			if (prev_alpha)
+				*str = SCP_tolower(*str);
+			else
+				*str = SCP_toupper(*str);
+		}
+
+		prev_alpha = this_alpha;
+	}
+}
+
+// in-place modification of string to title case; same naive algorithm as above
+void SCP_totitle(SCP_string &str)
+{
+	SCP_string title_str;
+	bool prev_alpha = false;
+
+	std::for_each(str.begin(), str.end(), [&prev_alpha](char &ch)
+	{
+		bool this_alpha = (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z');
+
+		if (this_alpha)
+		{
+			if (prev_alpha)
+				ch = SCP_tolower(ch);
+			else
+				ch = SCP_toupper(ch);
+		}
+
+		prev_alpha = this_alpha;
+	});
+}
+
+bool SCP_truncate(SCP_string &str, size_t len)
+{
+	if (str.length() > len)
+	{
+		str.resize(len);
+		return true;
+	}
+	else
+		return false;
+}
+
+bool lcase_equal(const SCP_string& _Left, const SCP_string& _Right)
+{
+	if (_Left.size() != _Right.size())
+		return false;
+
+	auto l_it = _Left.cbegin();
+	auto r_it = _Right.cbegin();
+
+	while (l_it != _Left.cend())
+	{
+		if (SCP_tolower(*l_it) != SCP_tolower(*r_it))
+			return false;
+
+		++l_it;
+		++r_it;
+	}
+
+	return true;
+}
+
+bool lcase_lessthan(const SCP_string& _Left, const SCP_string& _Right)
+{
+	auto l_it = _Left.cbegin();
+	auto r_it = _Right.cbegin();
+
+	while (true)
+	{
+		if (l_it == _Left.cend())
+			return (r_it != _Right.cend());
+		else if (r_it == _Right.cend())
+			return false;
+
+		auto lch = SCP_tolower(*l_it);
+		auto rch = SCP_tolower(*r_it);
+
+		if (lch < rch)
+			return true;
+		else if (lch > rch)
+			return false;
+
+		++l_it;
+		++r_it;
+	}
+
+	return true;
+}