From 065dc6f8cd168e3ee6e71ddfb06f42a92abfabbd Mon Sep 17 00:00:00 2001
From: Martin Ebourne <martin@ebourne.me.uk>
Date: Wed, 7 Dec 2005 16:24:49 +0000
Subject: Merged chromi/diffopt at r116 to trunk

---
 lib/crypto/RollingChecksum.cpp | 28 ++++++++++++++++++++++++++--
 lib/crypto/RollingChecksum.h   | 25 ++++++++++++++++++-------
 2 files changed, 44 insertions(+), 9 deletions(-)

(limited to 'lib/crypto')

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;
+}
diff --git a/lib/crypto/RollingChecksum.h b/lib/crypto/RollingChecksum.h
index 99d116b9..be79c36f 100755
--- a/lib/crypto/RollingChecksum.h
+++ b/lib/crypto/RollingChecksum.h
@@ -24,7 +24,7 @@
 class RollingChecksum
 {
 public:
-	RollingChecksum(const void *data, unsigned int Length);
+	RollingChecksum(const void * const data, const unsigned int Length);
 
 	// --------------------------------------------------------------------------
 	//
@@ -35,7 +35,7 @@ public:
 	//		Created: 6/12/03
 	//
 	// --------------------------------------------------------------------------
-	inline void RollForward(uint8_t StartOfThisBlock, uint8_t LastOfNextBlock, unsigned int Length)
+	inline void RollForward(const uint8_t StartOfThisBlock, const uint8_t LastOfNextBlock, const unsigned int Length)
 	{
 		// IMPLEMENTATION NOTE: Everything is implicitly mod 2^16 -- uint16_t's will overflow nicely.
 		a -= StartOfThisBlock;
@@ -44,6 +44,17 @@ public:
 		b += a;
 	}
 
+	// --------------------------------------------------------------------------
+	//
+	// 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 RollForwardSeveral(const uint8_t * const StartOfThisBlock, const uint8_t * const LastOfNextBlock, const unsigned int Length, const unsigned int Skip);
+
 	// --------------------------------------------------------------------------
 	//
 	// Function
@@ -52,14 +63,14 @@ public:
 	//		Created: 6/12/03
 	//
 	// --------------------------------------------------------------------------	
-	inline uint32_t GetChecksum()
+	inline uint32_t GetChecksum() const
 	{
 		return ((uint32_t)a) | (((uint32_t)b) << 16);
 	}
 	
 	// Components, just in case they're handy
-	inline uint16_t GetComponent1() {return a;}
-	inline uint16_t GetComponent2() {return b;}
+	inline uint16_t GetComponent1() const {return a;}
+	inline uint16_t GetComponent2() const {return b;}
 	
 	// --------------------------------------------------------------------------
 	//
@@ -69,7 +80,7 @@ public:
 	//		Created: 6/12/03
 	//
 	// --------------------------------------------------------------------------
-	inline uint16_t GetComponentForHashing()
+	inline uint16_t GetComponentForHashing() const
 	{
 		return b;
 	}
@@ -82,7 +93,7 @@ public:
 	//		Created: 14/1/04
 	//
 	// --------------------------------------------------------------------------
-	static inline uint16_t ExtractHashingComponent(uint32_t Checksum)
+	static inline uint16_t ExtractHashingComponent(const uint32_t Checksum)
 	{
 		return Checksum >> 16;
 	}
-- 
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