From bb6b72fea40fc56dab6fdcc73994ffe9e12aacc0 Mon Sep 17 00:00:00 2001
From: JoelKatz <DavidJoelSchwartz@GMail.com>
Date: Fri, 4 Jan 2013 15:21:02 -0800
Subject: [PATCH] Make a "getNeededHashes" function to get the hashes we need
 to fill in a ledger hole.

---
 src/cpp/ripple/SHAMap.h       |  1 +
 src/cpp/ripple/SHAMapSync.cpp | 53 ++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/src/cpp/ripple/SHAMap.h b/src/cpp/ripple/SHAMap.h
index e7d4565588..6071603f58 100644
--- a/src/cpp/ripple/SHAMap.h
+++ b/src/cpp/ripple/SHAMap.h
@@ -413,6 +413,7 @@ public:
 	bool getNodeFat(const SHAMapNode& node, std::vector<SHAMapNode>& nodeIDs,
 	 std::list<std::vector<unsigned char> >& rawNode, bool fatRoot, bool fatLeaves);
 	bool getRootNode(Serializer& s, SHANodeFormat format);
+	void getNeededHashes(std::vector<uint256>& hashes, int max);
 	SMAddNode addRootNode(const uint256& hash, const std::vector<unsigned char>& rootNode, SHANodeFormat format,
 		SHAMapSyncFilter* filter);
 	SMAddNode addRootNode(const std::vector<unsigned char>& rootNode, SHANodeFormat format,
diff --git a/src/cpp/ripple/SHAMapSync.cpp b/src/cpp/ripple/SHAMapSync.cpp
index 344e2bdc1c..eb5e11b23c 100644
--- a/src/cpp/ripple/SHAMapSync.cpp
+++ b/src/cpp/ripple/SHAMapSync.cpp
@@ -19,7 +19,7 @@ void SHAMap::getMissingNodes(std::vector<SHAMapNode>& nodeIDs, std::vector<uint2
 	boost::recursive_mutex::scoped_lock sl(mLock);
 
 	assert(root->isValid());
-	
+
 	if (root->isFullBelow())
 	{
 		clearSynching();
@@ -91,6 +91,57 @@ void SHAMap::getMissingNodes(std::vector<SHAMapNode>& nodeIDs, std::vector<uint2
 	}
 }
 
+void SHAMap::getNeededHashes(std::vector<uint256>& ret, int max)
+{
+	boost::recursive_mutex::scoped_lock sl(mLock);
+
+	assert(root->isValid());
+
+	if (root->isFullBelow() || !root->isInner())
+	{
+		clearSynching();
+		return;
+	}
+
+	std::stack<SHAMapTreeNode*> stack;
+	stack.push(root.get());
+
+	while (!stack.empty())
+	{
+		SHAMapTreeNode* node = stack.top();
+		stack.pop();
+
+		int base = rand() % 256;
+		bool have_all = false;
+		for (int ii = 0; ii < 16; ++ii)
+		{ // traverse in semi-random order
+			int branch = (base + ii) % 16;
+			if (!node->isEmptyBranch(branch))
+			{
+				SHAMapNode childID = node->getChildNodeID(branch);
+				const uint256& childHash = node->getChildHash(branch);
+				SHAMapTreeNode* d;
+				try
+				{
+					d = getNodePointer(childID, childHash);
+					assert(d);
+					if (d->isInner() && !d->isFullBelow())
+						stack.push(d);
+				}
+				catch (SHAMapMissingNode&)
+				{ // node is not in the map
+					have_all = false;
+					ret.push_back(childHash);
+					if (--max <= 0)
+						return;
+				}
+			}
+		}
+		if (have_all)
+			node->setFullBelow();
+	}
+}
+
 bool SHAMap::getNodeFat(const SHAMapNode& wanted, std::vector<SHAMapNode>& nodeIDs,
 	std::list<std::vector<unsigned char> >& rawNodes, bool fatRoot, bool fatLeaves)
 { // Gets a node and some of its children