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, 1 insertions, 1 deletions

diff --git a/modes.cpp b/modes.cpp
index f307b353..a95e7a95 100644
--- a/modes.cpp
+++ b/modes.cpp
@@ -253,7 +253,7 @@ void CBC_Decryption::ProcessData(byte *outString, const byte *inString, size_t l
 

 	// save copy now in case of in-place decryption

 	const unsigned int blockSize = BlockSize();

-	memcpy(m_temp, PtrAdd(inString,length-blockSize), blockSize);

+	memcpy(m_temp, PtrAdd(inString, length-blockSize), blockSize);

 	if (length > blockSize)

 		m_cipher->AdvancedProcessBlocks(PtrAdd(inString,blockSize), inString, PtrAdd(outString,blockSize), length-blockSize, BlockTransformation::BT_ReverseDirection|BlockTransformation::BT_AllowParallel);

 	m_cipher->ProcessAndXorBlock(inString, m_register, outString);