From b5b53699d96ed1bcbb46120611af4740fea673f7 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 31 Aug 2018 00:22:18 +0100
Subject: Add basic support for setting the width/precision in the format
 string

---
 libadhocutil/detail/compileTimeFormatters.h        | 37 ++++++++++++++++++++++
 .../unittests/testCompileTimeFormatter.cpp         |  7 ++++
 2 files changed, 44 insertions(+)

diff --git a/libadhocutil/detail/compileTimeFormatters.h b/libadhocutil/detail/compileTimeFormatters.h
index 8579f92..00ee852 100644
--- a/libadhocutil/detail/compileTimeFormatters.h
+++ b/libadhocutil/detail/compileTimeFormatters.h
@@ -4,6 +4,7 @@
 #include "../compileTimeFormatter.h"
 #include <boost/assert.hpp>
 #include <iomanip>
+#include <type_traits>
 
 namespace AdHoc {
 #define BASICCONV(PARAMTYPE, OP, ...) \
@@ -92,6 +93,42 @@ namespace AdHoc {
 			StreamWriter::next(s, pn...);
 		}
 	};
+
+	////
+	// Width/precision embedded in format string
+	// Limitted to 3 digits at the moment
+	template<const auto & S, auto L, auto pos, typename stream, auto n0, auto nn, auto ... sn>
+	struct StreamWriter<S, L, pos, stream, typename std::enable_if<ispositivedigit(n0) && !isdigit(nn)>::type, '%', n0, nn, sn...> {
+		template<typename ... Pn>
+		static inline void write(stream & s, const Pn & ... pn)
+		{
+			constexpr auto p = (n0 - '0');
+			s << std::setw(p) << std::setprecision(p);
+			StreamWriter<S, L, pos + 1, stream, void, '%', nn, sn...>::write(s, pn...);
+		}
+	};
+	template<const auto & S, auto L, auto pos, typename stream, auto n0, auto n1, auto nn, auto ... sn>
+	struct StreamWriter<S, L, pos, stream, typename std::enable_if<ispositivedigit(n0) && isdigit(n1) && !isdigit(nn)>::type, '%', n0, n1, nn, sn...> {
+		template<typename ... Pn>
+		static inline void write(stream & s, const Pn & ... pn)
+		{
+			constexpr auto p = ((n0 - '0') * 10) + (n1 - '0');
+			s << std::setw(p) << std::setprecision(p);
+			StreamWriter<S, L, pos + 2, stream, void, '%', nn, sn...>::write(s, pn...);
+		}
+	};
+	template<const auto & S, auto L, auto pos, typename stream, auto n0, auto n1, auto n2, auto nn, auto ... sn>
+	struct StreamWriter<S, L, pos, stream, typename std::enable_if<ispositivedigit(n0) && isdigit(n1) && isdigit(n2) && !isdigit(nn)>::type, '%', n0, n1, n2, nn, sn...> {
+		template<typename ... Pn>
+		static inline void write(stream & s, const Pn & ... pn)
+		{
+			constexpr auto p = ((n0 - '0') * 100) + ((n1 - '0') * 10) + (n2 - '0');
+			s << std::setw(p) << std::setprecision(p);
+			StreamWriter<S, L, pos + 3, stream, void, '%', nn, sn...>::write(s, pn...);
+		}
+	};
+	////
+
 	StreamWriterT('.', '*') {
 		template<typename ... Pn>
 		static inline void write(stream & s, int l, const Pn & ... pn)
diff --git a/libadhocutil/unittests/testCompileTimeFormatter.cpp b/libadhocutil/unittests/testCompileTimeFormatter.cpp
index 2b9a796..138d5dc 100644
--- a/libadhocutil/unittests/testCompileTimeFormatter.cpp
+++ b/libadhocutil/unittests/testCompileTimeFormatter.cpp
@@ -329,11 +329,18 @@ GLIBC_FMT_TEST(s2, "in %s %s.", "string", "other");
 GLIBC_FMT_TEST(s3, "in %.*s.", 3, "other");
 GLIBC_FMT_TEST(s4, "in %.*s.", 5, "other");
 GLIBC_FMT_TEST(s5, "in %.*s.", 7, "other");
+GLIBC_FMT_TEST(s35, "in %3s.", "other");
+GLIBC_FMT_TEST(s55, "in %5s.", "other");
+GLIBC_FMT_TEST(s115, "in %11s.", "other");
 
 GLIBC_FMT_TEST(c1, "in %c.", 'b');
 GLIBC_FMT_TEST(c2, "in %c.", 'B');
 
 GLIBC_FMT_TEST(d1, "in %d.", 123);
+GLIBC_FMT_TEST(d01, "in %0d.", 123);
+GLIBC_FMT_TEST(d051, "in %05d.", 123);
+GLIBC_FMT_TEST(d0511, "in % 50d.", 123);
+GLIBC_FMT_TEST(d05121, "in %0510d.", 123);
 GLIBC_FMT_TEST(d2, "in %d.", 123456);
 GLIBC_FMT_TEST(d3, "in %hd.", (int16_t)-12345);
 GLIBC_FMT_TEST(d4, "in %hhd.", (int8_t)-123);
-- 
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