From f86b129ea622e138d24a5e757f367aa02ccfffe7 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 23 Sep 2019 18:07:18 -0700
Subject: [PATCH] ircd::json::stack: Add class member counters; assertions;
 conditions.

---
 include/ircd/json/stack.h | 19 +++++++----
 ircd/json.cc              | 66 +++++++++++++++++++++++++++++----------
 2 files changed, 62 insertions(+), 23 deletions(-)

diff --git a/include/ircd/json/stack.h b/include/ircd/json/stack.h
index 21b108b81..d6fbc1e44 100644
--- a/include/ircd/json/stack.h
+++ b/include/ircd/json/stack.h
@@ -54,6 +54,8 @@ struct ircd::json::stack
 	flush_callback flusher;
 	std::exception_ptr eptr;
 	checkpoint *cp {nullptr};
+	size_t appended {0};
+	size_t flushed {0};
 	size_t hiwat;                      ///< autoflush watermark
 	size_t lowat;                      ///< flush(false) call min watermark
 
@@ -308,9 +310,9 @@ ircd::json::stack::member::append(const json::tuple<T...> &t)
 		_post_append();
 	}};
 
-	s->append(serialized(t), [this, &t](mutable_buffer buf)
+	s->append(serialized(t), [&t](mutable_buffer buf)
 	{
-		return size(stringify(buf, t));
+		return ircd::size(stringify(buf, t));
 	});
 }
 
@@ -326,7 +328,7 @@ ircd::json::stack::array::append(const json::tuple<T...> &t)
 
 	s->append(serialized(t), [&t](mutable_buffer buf)
 	{
-		return size(stringify(buf, t));
+		return ircd::size(stringify(buf, t));
 	});
 }
 
@@ -336,10 +338,15 @@ ircd::json::stack::object::append(const json::tuple<T...> &t)
 {
 	for_each(t, [this](const auto &name, const auto &_value)
 	{
-		const json::value value(_value);
-		if(defined(value)) json::stack::member
+		const json::value value
 		{
-			*this, name, value
+			_value
 		};
+
+		if(defined(value))
+			json::stack::member
+			{
+				*this, name, value
+			};
 	});
 }
diff --git a/ircd/json.cc b/ircd/json.cc
index 77f408a37..b7c4739c8 100644
--- a/ircd/json.cc
+++ b/ircd/json.cc
@@ -722,9 +722,11 @@ void
 ircd::json::stack::append(const string_view &s)
 noexcept
 {
-	append(size(s), [&s](const mutable_buffer &buf)
+	append(s.size(), [&s]
+	(const mutable_buffer &buf)
 	{
-		return copy(buf, s);
+		assert(ircd::size(buf) >= s.size());
+		return ircd::copy(buf, s);
 	});
 }
 
@@ -733,7 +735,7 @@ ircd::json::stack::append(const size_t &expect,
                           const window_buffer::closure &closure)
 noexcept try
 {
-	if(unlikely(failed()))
+	if(!expect || failed())
 		return;
 
 	// Since all appends are atomic, we need to have buffer available to print
@@ -763,18 +765,27 @@ noexcept try
 	}
 
 	// Print the JSON to the buffer and advance the window pointer
-	buf([&expect, &closure]
-	(const mutable_buffer &buf)
+	const const_buffer appended
 	{
-		const size_t ret
+		buf([&expect, &closure](const mutable_buffer &buf)
 		{
-			closure(buf)
-		};
+			const size_t appended
+			{
+				closure(buf)
+			};
 
-		assert(ret <= size(buf));
-		assert(ret == expect);
-		return ret;
-	});
+			assert(appended <= size(buf));
+			assert(appended == expect);
+			return const_buffer
+			{
+				data(buf), appended
+			};
+		})
+	};
+
+	this->appended += expect;
+	assert(size(appended) >= expect);
+	assert(this->appended >= size(appended));
 
 	// Conditions to courtesy flush after a sufficiently large dump; when
 	// there's no buffer remaining we'll inevitably have to flush; the call
@@ -816,7 +827,7 @@ noexcept try
 	if(!force && cp)
 		return false;
 
-	if(cp)
+	if(unlikely(cp))
 	{
 		const size_t invalidated
 		{
@@ -841,6 +852,7 @@ noexcept try
 	};
 
 	assert(data(flushed) == data(buf.completed())); // Can only flush front sry
+	this->flushed += size(flushed);
 	buf.shift(size(flushed));
 	return true;
 }
@@ -865,18 +877,38 @@ ircd::json::stack::invalidate_checkpoints()
 void
 ircd::json::stack::clear()
 {
-	rewind(buf.consumed());
+	const size_t rewound
+	{
+		rewind(buf.consumed())
+	};
+
 	this->eptr = std::exception_ptr{};
 }
 
 size_t
 ircd::json::stack::rewind(const size_t &bytes)
 {
-	const size_t before(buf.consumed());
-	const size_t &amount(std::min(bytes, before));
-	const size_t after(size(buf.rewind(amount)));
+	const size_t before
+	{
+		buf.consumed()
+	};
+
+	assert(appended >= before);
+	const size_t &amount
+	{
+		std::min(bytes, before)
+	};
+
+	assert(appended >= amount);
+	const size_t after
+	{
+		size(buf.rewind(amount))
+	};
+
 	assert(before >= after);
 	assert(before - after == amount);
+	appended -= amount;
+	assert(appended >= after);
 	return amount;
 }