From cc636d375fdd2ae26114f4acf53a58e9ea7d483a Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Thu, 7 Feb 2019 17:52:24 -0800
Subject: [PATCH] ircd::util: Improve string() suite; add flags for
 shrink_to_fit().

---
 include/ircd/util/string.h | 21 +++++++++++++++++++--
 ircd/util.cc               | 21 ++++++++++++++++++---
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/include/ircd/util/string.h b/include/ircd/util/string.h
index 5cc03e528..b36729197 100644
--- a/include/ircd/util/string.h
+++ b/include/ircd/util/string.h
@@ -17,10 +17,27 @@
 
 namespace ircd::util
 {
+	using string_closure_size = std::function<size_t (const mutable_buffer &)>;
+	using string_closure_view = std::function<string_view (const mutable_buffer &)>;
+
+	// OR this with a string size to trigger a shrink_to_fit() after closure.
+	constexpr const size_t SHRINK_TO_FIT
+	{
+		1UL << (sizeof(size_t) * 8 - 1)
+	};
+
+	// Simple string generation by copy from existing buffer.
 	std::string string(const char *const &buf, const size_t &size);
 	std::string string(const uint8_t *const &buf, const size_t &size);
-	std::string string(const size_t &size, const std::function<size_t (const mutable_buffer &)> &closure);
-	std::string string(const size_t &size, const std::function<string_view (const mutable_buffer &)> &closure);
+	std::string string(const const_buffer &);
+
+	// String generation from closure. The closure is presented a buffer of
+	// size for writing into. Closure returns how much it wrote via size or
+	// view of written portion.
+	std::string string(const size_t &size, const string_closure_size &);
+	std::string string(const size_t &size, const string_closure_view &);
+
+	// toString()'ish template suite (see defs)
 	template<class T> std::string string(const mutable_buffer &buf, const T &s);
 	template<class T> std::string string(const T &s);
 }
diff --git a/ircd/util.cc b/ircd/util.cc
index 29ad0b513..32a84d9bc 100644
--- a/ircd/util.cc
+++ b/ircd/util.cc
@@ -299,7 +299,7 @@ ircd::util::si(const uint64_t &value)
 /// a view of the data actually written to the buffer.
 std::string
 ircd::util::string(const size_t &size,
-                   const std::function<string_view (const mutable_buffer &)> &closure)
+                   const string_closure_view &closure)
 {
 	return string(size, [&closure]
 	(const mutable_buffer &buffer)
@@ -313,9 +313,14 @@ ircd::util::string(const size_t &size,
 /// the final size of the data written into the buffer.
 std::string
 ircd::util::string(const size_t &size,
-                   const std::function<size_t (const mutable_buffer &)> &closure)
+                   const string_closure_size &closure)
 {
-	std::string ret(size, char{});
+	const size_t alloc_size
+	{
+		size & ~SHRINK_TO_FIT
+	};
+
+	std::string ret(alloc_size, char{});
 	const mutable_buffer buf
 	{
 		const_cast<char *>(ret.data()), ret.size()
@@ -329,9 +334,19 @@ ircd::util::string(const size_t &size,
 	assert(consumed <= buffer::size(buf));
 	data(buf)[consumed] = '\0';
 	ret.resize(consumed);
+
+	if(size & SHRINK_TO_FIT)
+		ret.shrink_to_fit();
+
 	return ret;
 }
 
+std::string
+ircd::util::string(const const_buffer &buf)
+{
+	return string(data(buf), size(buf));
+}
+
 std::string
 ircd::util::string(const char *const &buf,
                    const size_t &size)