From bce1206c7002141af69266a025b039fa8ae7d65b Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 29 Jan 2018 08:19:14 -0800
Subject: [PATCH] ircd::util: Add string construction buffer closures over a
 common pattern.

---
 include/ircd/util/util.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/ircd/util/util.h b/include/ircd/util/util.h
index 3da6327a2..18eadeaef 100644
--- a/include/ircd/util/util.h
+++ b/include/ircd/util/util.h
@@ -169,6 +169,37 @@ string(const uint8_t *const &buf,
 	return string(reinterpret_cast<const char *>(buf), size);
 }
 
+/// Close over the common pattern to write directly into a post-C++11 standard
+/// string through the data() member requiring a const_cast. Closure returns
+/// the final size of the data written into the buffer.
+inline auto
+string(const size_t &size,
+       const std::function<size_t (const mutable_buffer &)> &closure)
+{
+	std::string ret(size, char{});
+	const mutable_buffer buf
+	{
+		const_cast<char *>(ret.data()), ret.size()
+	};
+
+	ret.resize(closure(buf));
+	return ret;
+}
+
+/// Close over the common pattern to write directly into a post-C++11 standard
+/// string through the data() member requiring a const_cast. Closure returns
+/// a view of the data actually written to the buffer.
+inline auto
+string(const size_t &size,
+       const std::function<string_view (const mutable_buffer &)> &closure)
+{
+	return string(size, [&closure]
+	(const mutable_buffer &buffer)
+	{
+		return ircd::size(closure(buffer));
+	});
+}
+
 //
 // Misc bang participants
 //