From 7e9a7a6fd6214e42cd31a74c699843a7fad4ed33 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 29 Jul 2023 13:49:35 +0100
Subject: Centralise lots of value conversion functions

---
 icespider/core/Jamfile.jam            |  3 +-
 icespider/core/ihttpRequest.h         | 37 ++++----------------
 icespider/core/util.cpp               |  7 ++++
 icespider/core/util.h                 | 63 +++++++++++++++++++++++++++++++++++
 icespider/core/xwwwFormUrlEncoded.cpp |  6 ++--
 5 files changed, 80 insertions(+), 36 deletions(-)

diff --git a/icespider/core/Jamfile.jam b/icespider/core/Jamfile.jam
index 0654c78..26a30f6 100644
--- a/icespider/core/Jamfile.jam
+++ b/icespider/core/Jamfile.jam
@@ -2,7 +2,7 @@ lib adhocutil : : : : <include>/usr/include/adhocutil ;
 lib slicer : : : : <include>/usr/include/slicer ;
 lib stdc++fs ;
 
-obj util-test : util-test.cpp ;
+obj util-test : util-test.cpp : <use>adhocutil ;
 
 obj routeOptions : routeOptions.ice : <toolset>tidy:<checker>none ;
 lib icespider-core :
@@ -17,6 +17,7 @@ lib icespider-core :
 	<implicit-dependency>routeOptions
 	: :
 	<include>.
+	<use>adhocutil
 	<library>../common//icespider-common
 	<implicit-dependency>../common//icespider-common
 	<implicit-dependency>routeOptions
diff --git a/icespider/core/ihttpRequest.h b/icespider/core/ihttpRequest.h
index 99de25a..6876c2b 100644
--- a/icespider/core/ihttpRequest.h
+++ b/icespider/core/ihttpRequest.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "exceptions.h"
+#include "util.h"
 #include <Ice/Current.h>
 #include <boost/lexical_cast.hpp>
 #include <c++11Helpers.h>
@@ -60,36 +61,12 @@ namespace IceSpider {
 
 		virtual std::ostream & dump(std::ostream & s) const = 0;
 
-		static_assert(std::is_constructible_v<std::string, std::string_view>);
-		static_assert(std::is_convertible_v<std::string_view, std::string_view>);
-
 		template<typename T, typename K>
 		[[nodiscard]] inline std::optional<T>
 		getFrom(const K key, OptionalString (IHttpRequest::*src)(const K) const) const
 		{
 			if (auto v = (this->*src)(key)) {
-				if constexpr (std::is_convertible<std::string_view, T>::value) {
-					return *v;
-				}
-				else if constexpr (std::is_constructible<T, std::string_view>::value) {
-					return std::optional<T> {std::in_place, *v};
-				}
-				else if constexpr (requires(T out) { std::from_chars(v->begin(), v->end(), out); }) {
-					if (T out {}; std::from_chars(v->begin(), v->end(), out).ec == std::errc {}) {
-						return out;
-					}
-					else {
-						throw Http400_BadRequest();
-					}
-				}
-				else {
-					try {
-						return boost::lexical_cast<T>(*v);
-					}
-					catch (const boost::bad_lexical_cast & e) {
-						throw Http400_BadRequest();
-					}
-				}
+				return convert<T>(*v);
 			}
 			else {
 				return std::nullopt;
@@ -117,13 +94,11 @@ namespace IceSpider {
 			if (!map) {
 				return {};
 			}
-			auto i = map->find(key);
-			if (i == map->end()) {
-				return {};
-			}
-			else {
-				return boost::lexical_cast<T>(i->second);
+
+			if (const auto i = map->find(key); i != map->end()) {
+				return convert<T>(i->second);
 			}
+			return {};
 		}
 
 		void responseRedirect(const std::string_view url, const OptionalString & = {}) const;
diff --git a/icespider/core/util.cpp b/icespider/core/util.cpp
index 62de195..b330f79 100644
--- a/icespider/core/util.cpp
+++ b/icespider/core/util.cpp
@@ -1,6 +1,13 @@
 #include "util.h"
+#include "exceptions.h"
 
 namespace IceSpider {
+	void
+	conversion_failure()
+	{
+		throw Http400_BadRequest();
+	}
+
 	void
 	remove_trailing(std::string_view & in, const char c)
 	{
diff --git a/icespider/core/util.h b/icespider/core/util.h
index f4d559b..d31c7da 100644
--- a/icespider/core/util.h
+++ b/icespider/core/util.h
@@ -2,8 +2,11 @@
 
 #include <Ice/Optional.h>
 #include <array>
+#include <boost/lexical_cast.hpp>
+#include <charconv>
 #include <optional>
 #include <string_view>
+#include <visibility.h>
 
 namespace std::experimental::Ice {
 	template<typename T, typename TF>
@@ -116,6 +119,66 @@ private:
 };
 
 namespace IceSpider {
+	[[noreturn]] DLL_PUBLIC void conversion_failure();
+
+	static_assert(std::is_constructible_v<std::string, std::string_view>);
+	static_assert(std::is_convertible_v<std::string_view, std::string_view>);
+
+	template<typename T>
+	inline T
+	from_chars(const std::string_view v, T && out)
+	{
+		if (std::from_chars(v.begin(), v.end(), out).ec != std::errc {}) {
+			conversion_failure();
+		}
+		return out;
+	}
+
+	template<typename T>
+	inline T
+	lexical_cast(const std::string_view v)
+	{
+		try {
+			return boost::lexical_cast<T>(v);
+		}
+		catch (const boost::bad_lexical_cast & e) {
+			conversion_failure();
+		}
+	}
+
+	template<typename T>
+	inline void
+	convert(const std::string_view v, T & out)
+	{
+		if constexpr (std::is_assignable_v<std::string_view, T>) {
+			out = v;
+		}
+		if constexpr (requires { std::from_chars(v.begin(), v.end(), out); }) {
+			from_chars(v, out);
+		}
+		else {
+			out = lexical_cast<T>(v);
+		}
+	}
+
+	template<typename T>
+	inline T
+	convert(const std::string_view v)
+	{
+		if constexpr (std::is_convertible_v<std::string_view, T>) {
+			return v;
+		}
+		else if constexpr (std::is_constructible_v<T, std::string_view>) {
+			return T {v};
+		}
+		else if constexpr (requires(T out) { std::from_chars(v.begin(), v.end(), out); }) {
+			return from_chars<T>(v, {});
+		}
+		else {
+			return lexical_cast<T>(v);
+		}
+	}
+
 	void remove_trailing(std::string_view & in, const char c);
 	void remove_leading(std::string_view & in, const char c);
 }
diff --git a/icespider/core/xwwwFormUrlEncoded.cpp b/icespider/core/xwwwFormUrlEncoded.cpp
index 73f77b8..639b07a 100644
--- a/icespider/core/xwwwFormUrlEncoded.cpp
+++ b/icespider/core/xwwwFormUrlEncoded.cpp
@@ -1,11 +1,11 @@
 #include "xwwwFormUrlEncoded.h"
 #include "exceptions.h"
+#include "util.h"
 #include <Ice/Config.h>
 #include <algorithm>
 #include <array>
 #include <boost/algorithm/string/compare.hpp>
 #include <boost/algorithm/string/finder.hpp>
-#include <charconv>
 #include <cstddef>
 #include <cstdint>
 #include <factory.h>
@@ -181,9 +181,7 @@ namespace IceSpider {
 	/* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
 	void set(T & t) const override \
 	{ \
-		if (const auto v = s.value(); std::from_chars(v.begin(), v.end(), t).ec != std::errc {}) { \
-			throw Http400_BadRequest(); \
-		} \
+		convert<T>(s, t); \
 	}
 
 		SET(Ice::Byte);
-- 
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