From c280ccd33b3d85dbd2e5a3edd4fbeeded65a2288 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Sun, 20 Sep 2020 06:08:15 -0400
Subject: [PATCH] Clear stream errors in FileStore::MaxRetrievable (GH #968)

---
 files.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/files.cpp b/files.cpp
index 2d05e03f..22af7097 100644
--- a/files.cpp
+++ b/files.cpp
@@ -65,10 +65,19 @@ lword FileStore::MaxRetrievable() const
 	if (!m_stream)
 		return 0;
 
+	// Clear error bits due to seekg(). Also see
+	// https://github.com/weidai11/cryptopp/pull/968
 	std::streampos current = m_stream->tellg();
 	std::streampos end = m_stream->seekg(0, std::ios::end).tellg();
 	m_stream->clear();
 	m_stream->seekg(current);
+	m_stream->clear();
+
+	// Return max for a non-seekable stream
+	// https://www.cplusplus.com/reference/istream/istream/tellg/
+	if (end == static_cast<std::streampos>(-1))
+		return LWORD_MAX;
+
 	return end-current;
 }