Ledger hash skip list basic support.

src/Ledger.cpp

@@ -885,6 +885,41 @@ uint256 Ledger::getAccountRootIndex(const uint160& uAccountID)
 	return s.getSHA512Half();
 }
 
+uint256 Ledger::getLedgerHashIndex()
+{ // get the index of the node that holds the last 256 ledgers
+	Serializer s(2);
+	s.add16(spaceHashes);
+	return s.getSHA512Half();
+}
+
+uint256 Ledger::getLedgerHashIndex(uint32 desiredLedgerIndex)
+{ // get the index of the node that holds the set of 256 ledgers that includes this ledger's hash
+  // (or the first ledger after it if it's not a multiple of 256)
+	Serializer s(6);
+	s.add16(spaceHashes);
+	s.add32(desiredLedgerIndex >> 16);
+	return s.getSHA512Half();
+}
+
+int Ledger::getLedgerHashOffset(uint32 ledgerIndex)
+{ // get the offset for this ledger's hash (or the first one after it) in the every-256-ledger table
+	return (ledgerIndex >> 8) % 256;
+}
+
+int Ledger::getLedgerHashOffset(uint32 desiredLedgerIndex, uint32 currentLedgerIndex)
+{ // get the offset for this ledger's hash in the every-ledger table, -1 if not in it
+	if (desiredLedgerIndex >= currentLedgerIndex)
+		return -1;
+
+	if (currentLedgerIndex < 256)
+		return desiredLedgerIndex;
+
+	if (desiredLedgerIndex < (currentLedgerIndex - 256))
+		return -1;
+
+	return currentLedgerIndex - desiredLedgerIndex - 1;
+}
+
 uint256 Ledger::getBookBase(const uint160& uTakerPaysCurrency, const uint160& uTakerPaysIssuerID,
 	const uint160& uTakerGetsCurrency, const uint160& uTakerGetsIssuerID)
 {

src/Ledger.h

@@ -178,6 +178,12 @@ public:
 	uint256 getPrevLedgerIndex(const uint256& uHash);							// last node <hash
 	uint256 getPrevLedgerIndex(const uint256& uHash, const uint256& uBegin);	// last node <hash, >begin
 
+	// Ledger hash table function
+	static uint256 getLedgerHashIndex();
+	static uint256 getLedgerHashIndex(uint32 desiredLedgerIndex);
+	static int getLedgerHashOffset(uint32 desiredLedgerIndex);
+	static int getLedgerHashOffset(uint32 desiredLedgerIndex, uint32 currentLedgerIndex);
+
 	// index calculation functions
 	static uint256 getAccountRootIndex(const uint160& uAccountID);
 

src/LedgerFormats.cpp

@@ -86,6 +86,10 @@ static bool LEFInit()
 		<< SOElement(sfHighQualityOut,		SOE_OPTIONAL)
 		;
 
+	DECLARE_LEF(LedgerHashes, ltLEDGER_HASHES)
+		<< SOElement(sfHashes,				SOE_REQUIRED)
+		;
+
 		return true;
 }
 

src/LedgerFormats.h

@@ -14,6 +14,7 @@ enum LedgerEntryType
 	ltNICKNAME			= 'n',
 	ltOFFER				= 'o',
 	ltCONTRACT			= 'c',
+	ltLEDGER_HASHES		= 'h',
 };
 
 // Used as a prefix for computing ledger indexes (keys).
@@ -28,6 +29,7 @@ enum LedgerNameSpace
 	spaceOwnerDir		= 'O',	// Directory of things owned by an account.
 	spaceBookDir		= 'B',	// Directory of order books.
 	spaceContract		= 'c',
+	spaceHashes			= 'h',
 };
 
 enum LedgerSpecificFlags

src/SerializeProto.h

@@ -122,6 +122,7 @@
 
 	// vector of 256-bit
 	FIELD(Indexes,				VECTOR256, 1)
+	FIELD(Hashes,				VECTOR256, 2)
 
 	// inner object
 	// OBJECT/1 is reserved for end of object