From b0f71705955698cf1e0d1101dbe6430566b70b63 Mon Sep 17 00:00:00 2001
From: rocksonhead <30463961+rocksonhead@users.noreply.github.com>
Date: Sun, 25 Mar 2018 00:27:03 +0000
Subject: [PATCH] Fix calling multiple ZlibDecompressor in parallel causes
 adler32 checksum failure (GH #596, #600)

---
 zinflate.cpp | 60 ++++++++++++++++++++++++++++++----------------------
 zinflate.h   |  9 ++++----
 2 files changed, 40 insertions(+), 29 deletions(-)

diff --git a/zinflate.cpp b/zinflate.cpp
index 9a41462f..4df27c9d 100644
--- a/zinflate.cpp
+++ b/zinflate.cpp
@@ -612,41 +612,51 @@ void Inflator::FlushOutput()
 	}
 }
 
-struct NewFixedLiteralDecoder
+void Inflator::CreateFixedLiteralDecoder()
 {
-	HuffmanDecoder * operator()() const
-	{
-		unsigned int codeLengths[288];
-		std::fill(codeLengths + 0, codeLengths + 144, 8);
-		std::fill(codeLengths + 144, codeLengths + 256, 9);
-		std::fill(codeLengths + 256, codeLengths + 280, 7);
-		std::fill(codeLengths + 280, codeLengths + 288, 8);
-		member_ptr<HuffmanDecoder> pDecoder(new HuffmanDecoder);
-		pDecoder->Initialize(codeLengths, 288);
-		return pDecoder.release();
-	}
+	unsigned int codeLengths[288];
+	std::fill(codeLengths + 0, codeLengths + 144, 8);
+	std::fill(codeLengths + 144, codeLengths + 256, 9);
+	std::fill(codeLengths + 256, codeLengths + 280, 7);
+	std::fill(codeLengths + 280, codeLengths + 288, 8);
+	m_fixedLiteralDecoder.reset(new HuffmanDecoder);
+	m_fixedLiteralDecoder->Initialize(codeLengths, 288);
 };
 
-struct NewFixedDistanceDecoder
+void Inflator::CreateFixedDistanceDecoder()
 {
-	HuffmanDecoder * operator()() const
-	{
-		unsigned int codeLengths[32];
-		std::fill(codeLengths + 0, codeLengths + 32, 5);
-		member_ptr<HuffmanDecoder> pDecoder(new HuffmanDecoder);
-		pDecoder->Initialize(codeLengths, 32);
-		return pDecoder.release();
-	}
+	unsigned int codeLengths[32];
+	std::fill(codeLengths + 0, codeLengths + 32, 5);
+	m_fixedDistanceDecoder.reset(new HuffmanDecoder);
+	m_fixedDistanceDecoder->Initialize(codeLengths, 32);
 };
 
-const HuffmanDecoder& Inflator::GetLiteralDecoder() const
+const HuffmanDecoder& Inflator::GetLiteralDecoder()
 {
-	return m_blockType == 1 ? Singleton<HuffmanDecoder, NewFixedLiteralDecoder>().Ref() : m_dynamicLiteralDecoder;
+	if (m_blockType == 1)
+	{
+		if (m_fixedLiteralDecoder.get() == NULLPTR)
+			CreateFixedLiteralDecoder();
+		return *m_fixedLiteralDecoder;
+	}
+	else
+	{
+		return m_dynamicLiteralDecoder;
+	}
 }
 
-const HuffmanDecoder& Inflator::GetDistanceDecoder() const
+const HuffmanDecoder& Inflator::GetDistanceDecoder()
 {
-	return m_blockType == 1 ? Singleton<HuffmanDecoder, NewFixedDistanceDecoder>().Ref() : m_dynamicDistanceDecoder;
+	if (m_blockType == 1)
+	{
+		if (m_fixedDistanceDecoder.get() == NULLPTR)
+			CreateFixedDistanceDecoder();
+		return *m_fixedDistanceDecoder;
+	}
+	else
+	{
+		return m_dynamicDistanceDecoder;
+	}
 }
 
 NAMESPACE_END
diff --git a/zinflate.h b/zinflate.h
index e352aff7..b35071e5 100644
--- a/zinflate.h
+++ b/zinflate.h
@@ -133,11 +133,11 @@ private:
 	void OutputString(const byte *string, size_t length);
 	void OutputPast(unsigned int length, unsigned int distance);
 
-	static const HuffmanDecoder *FixedLiteralDecoder();
-	static const HuffmanDecoder *FixedDistanceDecoder();
+	void CreateFixedDistanceDecoder();
+	void CreateFixedLiteralDecoder();
 
-	const HuffmanDecoder& GetLiteralDecoder() const;
-	const HuffmanDecoder& GetDistanceDecoder() const;
+	const HuffmanDecoder& GetLiteralDecoder();
+	const HuffmanDecoder& GetDistanceDecoder();
 
 	enum State {PRE_STREAM, WAIT_HEADER, DECODING_BODY, POST_STREAM, AFTER_END};
 	State m_state;
@@ -148,6 +148,7 @@ private:
 	NextDecode m_nextDecode;
 	unsigned int m_literal, m_distance;	// for LENGTH_BITS or DISTANCE_BITS
 	HuffmanDecoder m_dynamicLiteralDecoder, m_dynamicDistanceDecoder;
+	member_ptr<HuffmanDecoder> m_fixedLiteralDecoder, m_fixedDistanceDecoder;
 	LowFirstBitReader m_reader;
 	SecByteBlock m_window;
 	size_t m_current, m_lastFlush;