Merged chromi/diffopt at r116 to trunk

1 files changed, 26 insertions, 2 deletions

diff --git a/lib/crypto/RollingChecksum.cpp b/lib/crypto/RollingChecksum.cpp
index 75bad7df..a2954e3a 100755
--- a/lib/crypto/RollingChecksum.cpp
+++ b/lib/crypto/RollingChecksum.cpp
@@ -20,11 +20,11 @@
 //		Created: 6/12/03
 //
 // --------------------------------------------------------------------------
-RollingChecksum::RollingChecksum(const void *data, unsigned int Length)
+RollingChecksum::RollingChecksum(const void * const data, const unsigned int Length)
 	: a(0),
 	  b(0)
 {
-	uint8_t *block = (uint8_t *)data;
+	const uint8_t *block = (const uint8_t *)data;
 	for(unsigned int x = Length; x >= 1; --x)
 	{
 		a += (*block);
@@ -34,5 +34,29 @@ RollingChecksum::RollingChecksum(const void *data, unsigned int Length)
 	}
 }
 
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    RollingChecksum::RollForwardSeveral(uint8_t*, uint8_t*, unsigned int, unsigned int)
+//		Purpose: Move the checksum forward a block, given a pointer to the first byte of the current block,
+//				 and a pointer just after the last byte of the current block and the length of the block and of the skip.
+//		Created: 7/14/05
+//
+// --------------------------------------------------------------------------
+void RollingChecksum::RollForwardSeveral(const uint8_t * const StartOfThisBlock, const uint8_t * const LastOfNextBlock, const unsigned int Length, const unsigned int Skip)
+{
+	// IMPLEMENTATION NOTE: Everything is implicitly mod 2^16 -- uint16_t's will overflow nicely.
+	unsigned int i;
+	uint16_t sumBegin=0, j,k;
 
+	for(i=0; i < Skip; i++)
+	{
+		j = StartOfThisBlock[i];
+		k = LastOfNextBlock[i];
+		sumBegin += j;
+		a += (k - j);
+		b += a;
+	}
 
+	b -= Length * sumBegin;
+}