Fix CTR mode when using FileSource (GH #683, GH #1010)

We think this is another instance problem that surfaced under GH #683 when inString==outString. It violates aliasing rules and the compiler begins removing code.

The ultimate workaround was to add a member variable m_tempOutString as scratch space when inString==outString. We did not loose much in the way of perforamce for some reason. It looks like AES/CTR lost about 0.03-0.05 cpb.

When combined with the updated xorbuf from GH #1020, the net result was a speedup of 0.1-0.6 cpb. In fact, some ciphers like RC6, gained almost 5 cpb.

1 files changed, 4 insertions, 1 deletions

diff --git a/strciphr.h b/strciphr.h
index 7a71159a..bf9463cf 100644
--- a/strciphr.h
+++ b/strciphr.h
@@ -388,7 +388,8 @@ protected:
 	inline byte * KeystreamBufferBegin() {return this->m_buffer.data();}

 	inline byte * KeystreamBufferEnd() {return (PtrAdd(this->m_buffer.data(), this->m_buffer.size()));}

 

-	AlignedSecByteBlock m_buffer;

+	// m_tempOutString added due to GH #1010

+	AlignedSecByteBlock m_buffer, m_tempOutString;

 	size_t m_leftOver;

 };

 

@@ -633,6 +634,8 @@ protected:
 

 	void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);

 

+	// m_tempOutString added due to GH #1010

+	AlignedSecByteBlock m_tempOutString;

 	size_t m_leftOver;

 };