From b45306a01219305fcc907ea6e938c1a9494fca25 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 10 Apr 2019 13:38:47 -0700
Subject: [PATCH] ircd::buffer: Additional assertions; simplify unique_buffer
 operations; minor cleanup.

---
 include/ircd/buffer/buffer_base.h   | 56 +++++++++++++++++++----------
 include/ircd/buffer/unique_buffer.h | 30 +++++++---------
 2 files changed, 49 insertions(+), 37 deletions(-)

diff --git a/include/ircd/buffer/buffer_base.h b/include/ircd/buffer/buffer_base.h
index 0160c738d..2bb8f1e64 100644
--- a/include/ircd/buffer/buffer_base.h
+++ b/include/ircd/buffer/buffer_base.h
@@ -20,21 +20,21 @@ struct ircd::buffer::buffer
 	using iterator = it;
 	using value_type = typename std::remove_pointer<iterator>::type;
 
-	explicit operator const it &() const;
-	operator string_view() const;
-	explicit operator std::string_view() const;
-	explicit operator std::string() const;
-
 	auto &begin() const                { return std::get<0>(*this);            }
 	auto &begin()                      { return std::get<0>(*this);            }
 	auto &end() const                  { return std::get<1>(*this);            }
 	auto &end()                        { return std::get<1>(*this);            }
 
+	bool null() const;
+	bool empty() const;                // For boost::spirit conceptual compliance.
+
 	auto &operator[](const size_t &i) const;
 	auto &operator[](const size_t &i);
 
-	// For boost::spirit conceptual compliance.
-	auto empty() const                 { return ircd::buffer::empty(*this);    }
+	explicit operator const it &() const;
+	explicit operator std::string_view() const;
+	explicit operator std::string() const;
+	operator string_view() const;
 
 	buffer(const it &start, const it &stop);
 	buffer(const it &start, const size_t &size);
@@ -59,18 +59,10 @@ ircd::buffer::buffer<it>::buffer(const it &start,
 {}
 
 template<class it>
-auto &
-ircd::buffer::buffer<it>::operator[](const size_t &i)
+ircd::buffer::buffer<it>::operator string_view()
 const
 {
-	return *(begin() + i);
-}
-
-template<class it>
-auto &
-ircd::buffer::buffer<it>::operator[](const size_t &i)
-{
-	return *(begin() + i);
+	return { reinterpret_cast<const char *>(data(*this)), size(*this) };
 }
 
 template<class it>
@@ -88,10 +80,36 @@ const
 }
 
 template<class it>
-ircd::buffer::buffer<it>::operator string_view()
+auto &
+ircd::buffer::buffer<it>::operator[](const size_t &i)
+{
+	assert(begin() + i < end());
+	return *(begin() + i);
+}
+
+template<class it>
+auto &
+ircd::buffer::buffer<it>::operator[](const size_t &i)
 const
 {
-	return { reinterpret_cast<const char *>(data(*this)), size(*this) };
+	assert(begin() + i < end());
+	return *(begin() + i);
+}
+
+template<class it>
+bool
+ircd::buffer::buffer<it>::empty()
+const
+{
+	return null() || std::distance(begin(), end()) == 0;
+}
+
+template<class it>
+bool
+ircd::buffer::buffer<it>::null()
+const
+{
+	return !begin();
 }
 
 template<class it>
diff --git a/include/ircd/buffer/unique_buffer.h b/include/ircd/buffer/unique_buffer.h
index 94e3d59e0..877c14054 100644
--- a/include/ircd/buffer/unique_buffer.h
+++ b/include/ircd/buffer/unique_buffer.h
@@ -26,7 +26,7 @@ struct ircd::buffer::unique_buffer
 
 	unique_buffer(const size_t &size, const size_t &align = 0);
 	explicit unique_buffer(const buffer &);
-	unique_buffer();
+	unique_buffer() = default;
 	unique_buffer(unique_buffer &&) noexcept;
 	unique_buffer(const unique_buffer &) = delete;
 	unique_buffer &operator=(unique_buffer &&) noexcept;
@@ -34,14 +34,6 @@ struct ircd::buffer::unique_buffer
 	~unique_buffer() noexcept;
 };
 
-template<class buffer>
-ircd::buffer::unique_buffer<buffer>::unique_buffer()
-:buffer
-{
-	nullptr, nullptr
-}
-{}
-
 template<class buffer>
 ircd::buffer::unique_buffer<buffer>::unique_buffer(const buffer &src)
 :unique_buffer
@@ -49,9 +41,11 @@ ircd::buffer::unique_buffer<buffer>::unique_buffer(const buffer &src)
 	size(src)
 }
 {
+	assert(this->begin() != nullptr);
+	assert(size(src) == size(*this));
 	const mutable_buffer dst
 	{
-		const_cast<char *>(data(*this)), size(*this)
+		const_cast<char *>(this->begin()), size(src)
 	};
 
 	copy(dst, src);
@@ -72,10 +66,10 @@ ircd::buffer::unique_buffer<buffer>::unique_buffer(unique_buffer &&other)
 noexcept
 :buffer
 {
-	std::move(static_cast<buffer &>(other))
+	other.release()
 }
 {
-	get<0>(other) = nullptr;
+	assert(std::get<0>(other) == nullptr);
 }
 
 template<class buffer>
@@ -85,8 +79,8 @@ noexcept
 {
 	this->~unique_buffer();
 
-	static_cast<buffer &>(*this) = std::move(static_cast<buffer &>(other));
-	get<0>(other) = nullptr;
+	static_cast<buffer &>(*this) = other.release();
+	assert(std::get<0>(other) == nullptr);
 
 	return *this;
 }
@@ -95,15 +89,15 @@ template<class buffer>
 ircd::buffer::unique_buffer<buffer>::~unique_buffer()
 noexcept
 {
-	std::free(const_cast<char *>(data(*this)));
+	std::free(const_cast<char *>(this->begin()));
 }
 
 template<class buffer>
 buffer
 ircd::buffer::unique_buffer<buffer>::release()
 {
-	const buffer ret{static_cast<buffer>(*this)};
-	static_cast<buffer &>(*this) = buffer{};
+	const buffer ret{*this};
+	this->begin() = nullptr;
 	return ret;
 }
 
@@ -136,6 +130,6 @@ ircd::buffer::aligned_alloc(const size_t &align,
 
 	return std::unique_ptr<char, decltype(&std::free)>
 	{
-		reinterpret_cast<char *>(ret), std::free
+		reinterpret_cast<char *>(ret), &std::free
 	};
 }