From 8f9959387b37921a6fb82a7f182ba916dc0dd801 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 9 Dec 2016 12:18:56 +0000
Subject: Bit messy and fiddly, but removes the template string length limit of
 (just under) compile time template-depth

---
 libadhocutil/compileTimeFormatter.h                | 123 +++++++++++++++++----
 .../unittests/testCompileTimeFormatter.cpp         |   4 +-
 2 files changed, 103 insertions(+), 24 deletions(-)

diff --git a/libadhocutil/compileTimeFormatter.h b/libadhocutil/compileTimeFormatter.h
index 39254e0..1e82956 100644
--- a/libadhocutil/compileTimeFormatter.h
+++ b/libadhocutil/compileTimeFormatter.h
@@ -3,42 +3,74 @@
 #include <boost/static_assert.hpp>
 
 namespace AdHoc {
-	template <char...> struct Buffer { };
+	constexpr int WRAP_AT = 120;
 
-	template <char stop, char ...>
+	template <bool, char...> struct Buffer { };
+
+	template <char stop, int offset, char ...>
 	struct Upto {
 		template<typename stream>
-		static auto stuff(stream &, const Buffer<> & f)
+		static auto stuff(stream &, const Buffer<false> & f)
 		{
 			return f;
 		}
 	};
+	template <char stop, int offset, char s0, char... sn>
+	struct Upto<stop, offset, s0, sn...> {
+		template<typename stream, char... sm>
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
+		{
+			return Upto<stop, offset + 1, sn...>::stuff(s, Buffer<false, sm..., s0>());
+		}
+	};
+	template <char stop, int offset, char... sn>
+	struct Upto<stop, offset, stop, sn...> {
+		template<typename stream, char... sm>
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
+		{
+			char buf[] = {sm...};
+			s.write(buf, sizeof...(sm));
+			return Buffer<false, stop, sn...>();
+		}
+	};
+	template <char stop, int offset, char... sn>
+	struct Upto<stop, offset, 0, sn...> {
+		template<typename stream, char... sm>
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
+		{
+			char buf[] = {sm...};
+			s.write(buf, sizeof...(sm));
+			return Buffer<false, 0, sn...>();
+		}
+	};
 	template <char stop, char s0, char... sn>
-	struct Upto<stop, s0, sn...> {
+	struct Upto<stop, WRAP_AT, s0, sn...> {
 		template<typename stream, char... sm>
-		static auto stuff(stream & s, const Buffer<sm...> &)
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
 		{
-			return Upto<stop, sn...>::stuff(s, Buffer<sm..., s0>());
+			char buf[] = {sm...};
+			s.write(buf, sizeof...(sm));
+			return Buffer<false, s0, sn...>();
 		}
 	};
 	template <char stop, char... sn>
-	struct Upto<stop, stop, sn...> {
+	struct Upto<stop, WRAP_AT, stop, sn...> {
 		template<typename stream, char... sm>
-		static auto stuff(stream & s, const Buffer<sm...> &)
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
 		{
 			char buf[] = {sm...};
 			s.write(buf, sizeof...(sm));
-			return Buffer<stop, sn...>();
+			return Buffer<false, stop, sn...>();
 		}
 	};
 	template <char stop, char... sn>
-	struct Upto<stop, 0, sn...> {
+	struct Upto<stop, WRAP_AT, 0, sn...> {
 		template<typename stream, char... sm>
-		static auto stuff(stream & s, const Buffer<sm...> &)
+		static auto stuff(stream & s, const Buffer<false, sm...> &)
 		{
 			char buf[] = {sm...};
 			s.write(buf, sizeof...(sm));
-			return Buffer<0, sn...>();
+			return Buffer<false, 0, sn...>();
 		}
 	};
 
@@ -47,10 +79,10 @@ namespace AdHoc {
 		template<typename ... Pn>
 		static void write(stream & s, const Pn & ... pn)
 		{
-			next(s, Upto<'%', sn...>::stuff(s, Buffer<>()), pn...);
+			next(s, Upto<'%', 0, sn...>::stuff(s, Buffer<false>()), pn...);
 		}
-		template<typename ... Pn, char... ssn, template <char...> class Buffer>
-		static void next(stream & s, const Buffer<ssn...>&, const Pn & ... pn)
+		template<typename ... Pn, char... ssn, template <bool, char...> class Buffer>
+		static void next(stream & s, const Buffer<false, ssn...>&, const Pn & ... pn)
 		{
 			StreamWriter<stream, ssn...>::write(s, pn...);
 		}
@@ -90,19 +122,66 @@ namespace AdHoc {
 		static int err;
 	};
 
-	template <const char * const & S, int offset, char s0, char ... sn>
+	template <const char * const & S, int offset, int roffset, char s0, char ... sn>
 	struct Parser {
 		static auto parse()
 		{
-			return Parser<S, offset + 1, S[offset + 1], sn..., s0>::parse();
+			return append(innerparse());
+		}
+		static auto innerparse()
+		{
+			return Parser<S, offset + 1, roffset + 1, S[offset + 1], sn..., s0>::innerparse();
+		}
+		template<char...ssn>
+		static auto append(const Buffer<true, ssn...> & b)
+		{
+			return join(b, Parser<S, offset + 1 + WRAP_AT, 0, S[offset + 1 + WRAP_AT]>::parse());
+		}
+		template<char...ssn>
+		static auto append(const Buffer<false, ssn...> & b)
+		{
+			return b;
+		}
+		template<bool more, char...ssn, char...ssm>
+		static auto join(const Buffer<true, ssn...> &, const Buffer<more, ssm...> &)
+		{
+			return Buffer<more, ssn..., ssm...>();
+		}
+	};
+
+	template <const char * const & S, int offset, char s0, char ... sn>
+	struct Parser<S, offset, WRAP_AT, s0, sn...> {
+		static auto parse()
+		{
+			return Buffer<true, sn..., s0>();
+		}
+		static auto innerparse()
+		{
+			return Buffer<true, sn..., s0>();
 		}
 	};
 
 	template <const char * const & S, int offset, char ... sn>
-	struct Parser<S, offset, 0, sn...> {
+	struct Parser<S, offset, WRAP_AT, 0, sn...> {
 		static auto parse()
 		{
-			return Buffer<sn..., 0>();
+			return Buffer<false, sn...>();
+		}
+		static auto innerparse()
+		{
+			return Buffer<false, sn...>();
+		}
+	};
+
+	template <const char * const & S, int offset, int roffset, char ... sn>
+	struct Parser<S, offset, roffset, 0, sn...> {
+		static auto parse()
+		{
+			return Buffer<false, sn..., 0>();
+		}
+		static auto innerparse()
+		{
+			return Buffer<false, sn..., 0>();
 		}
 	};
 
@@ -111,11 +190,11 @@ namespace AdHoc {
 		template<typename stream, typename ... Pn>
 		static void write(stream & s, const Pn & ... pn)
 		{
-			run(Parser<S, 0, *S>::parse(), s, pn...);
+			run(Parser<S, 0, 0, *S>::parse(), s, pn...);
 		}
 
-		template<typename stream, char...ssn, template<char...> class Buffer, typename ... Pn>
-		static void run(const Buffer<ssn...> &, stream & s, const Pn & ... pn)
+		template<typename stream, char...ssn, template<bool, char...> class Buffer, typename ... Pn>
+		static void run(const Buffer<false, ssn...> &, stream & s, const Pn & ... pn)
 		{
 			StreamWriter<stream, ssn...>::write(s, pn...);
 		}
diff --git a/libadhocutil/unittests/testCompileTimeFormatter.cpp b/libadhocutil/unittests/testCompileTimeFormatter.cpp
index f19ee0a..00f1e6f 100644
--- a/libadhocutil/unittests/testCompileTimeFormatter.cpp
+++ b/libadhocutil/unittests/testCompileTimeFormatter.cpp
@@ -136,11 +136,11 @@ BOOST_AUTO_TEST_CASE ( customMultiArgRightAlign )
 	BOOST_REQUIRE_EQUAL(buf3.str(), "value              123.45");
 }
 
-extern constexpr const char * formatStringLong = "                                                                                                                            ";
+extern constexpr const char * formatStringLong = "                                                                                                                                                                                                                                                      ";
 BOOST_AUTO_TEST_CASE ( longFormatString )
 {
 	std::stringstream buf;
   Formatter<formatStringLong>::write(buf);
-	BOOST_REQUIRE_EQUAL(buf.str().length(), 124);
+	BOOST_REQUIRE_EQUAL(buf.str().length(), 246);
 }
 
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