Reimplement CBlockLocator's chain-related logic in CChain.

This removes a few unused CBlockLocator methods, and moves the
construction and fork-finding logic to CChain (which can do these
more efficiently, as it has a height-indexable chain available).
It also makes CBlockLocator independent from the validation code.

5 files changed, 54 insertions, 108 deletions

diff --git a/src/db.h b/src/db.h
index b3f269f3da..8736031da4 100644
--- a/src/db.h
+++ b/src/db.h
@@ -16,7 +16,7 @@
 #include <db_cxx.h>
 
 class CAddrMan;
-class CBlockLocator;
+struct CBlockLocator;
 class CDiskBlockIndex;
 class CMasterKey;
 class COutPoint;
diff --git a/src/init.cpp b/src/init.cpp
index dcd65198c3..fce5992255 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -116,7 +116,7 @@ void Shutdown()
     {
         LOCK(cs_main);
         if (pwalletMain)
-            pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
+            pwalletMain->SetBestChain(chainActive.GetLocator());
         if (pblocktree)
             pblocktree->Flush();
         if (pcoinsTip)
@@ -912,7 +912,7 @@ bool AppInit2(boost::thread_group& threadGroup)
                 strErrors << _("Cannot write default address") << "\n";
         }
 
-        pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
+        pwalletMain->SetBestChain(chainActive.GetLocator());
     }
 
     LogPrintf("%s", strErrors.str().c_str());
@@ -928,7 +928,7 @@ bool AppInit2(boost::thread_group& threadGroup)
         CWalletDB walletdb(strWalletFile);
         CBlockLocator locator;
         if (walletdb.ReadBestBlock(locator))
-            pindexRescan = locator.GetBlockIndex();
+            pindexRescan = chainActive.FindFork(locator);
         else
             pindexRescan = chainActive.Genesis();
     }
@@ -939,7 +939,7 @@ bool AppInit2(boost::thread_group& threadGroup)
         nStart = GetTimeMillis();
         pwalletMain->ScanForWalletTransactions(pindexRescan, true);
         LogPrintf(" rescan      %15"PRI64d"ms\n", GetTimeMillis() - nStart);
-        pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
+        pwalletMain->SetBestChain(chainActive.GetLocator());
         nWalletDBUpdated++;
     }
 
diff --git a/src/main.cpp b/src/main.cpp
index 732a828524..cfa99b34b8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -190,105 +190,61 @@ void UnregisterNodeSignals(CNodeSignals& nodeSignals)
 
 //////////////////////////////////////////////////////////////////////////////
 //
-// CBlockLocator implementation
+// CChain implementation
 //
 
-CBlockLocator::CBlockLocator(uint256 hashBlock)
-{
-    std::map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashBlock);
-    if (mi != mapBlockIndex.end())
-        Set((*mi).second);
+CBlockIndex *CChain::SetTip(CBlockIndex *pindex) {
+    if (pindex == NULL) {
+        vChain.clear();
+        return NULL;
+    }
+    vChain.resize(pindex->nHeight + 1);
+    while (pindex && vChain[pindex->nHeight] != pindex) {
+        vChain[pindex->nHeight] = pindex;
+        pindex = pindex->pprev;
+    }
+    return pindex;
 }
 
-void CBlockLocator::Set(const CBlockIndex* pindex)
-{
-    vHave.clear();
+CBlockLocator CChain::GetLocator(const CBlockIndex *pindex) const {
     int nStep = 1;
-    while (pindex)
-    {
-        vHave.push_back(pindex->GetBlockHash());
+    std::vector<uint256> vHave;
+    vHave.reserve(32);
 
-        // Exponentially larger steps back
-        for (int i = 0; pindex && i < nStep; i++)
+    if (!pindex)
+        pindex = Tip();
+    while (pindex) {
+        vHave.push_back(pindex->GetBlockHash());
+        // Stop when we have added the genesis block.
+        if (pindex->nHeight == 0)
+            break;
+        // Exponentially larger steps back, plus the genesis block.
+        int nHeight = std::max(pindex->nHeight - nStep, 0);
+        // In case pindex is not in this chain, iterate pindex->pprev to find blocks.
+        while (pindex->nHeight > nHeight && !Contains(pindex))
             pindex = pindex->pprev;
+        // If pindex is in this chain, use direct height-based access.
+        if (pindex->nHeight > nHeight)
+            pindex = (*this)[nHeight];
         if (vHave.size() > 10)
             nStep *= 2;
     }
-    vHave.push_back(Params().HashGenesisBlock());
-}
 
-int CBlockLocator::GetDistanceBack()
-{
-    // Retrace how far back it was in the sender's branch
-    int nDistance = 0;
-    int nStep = 1;
-    BOOST_FOREACH(const uint256& hash, vHave)
-    {
-        std::map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hash);
-        if (mi != mapBlockIndex.end())
-        {
-            CBlockIndex* pindex = (*mi).second;
-            if (chainActive.Contains(pindex))
-                return nDistance;
-        }
-        nDistance += nStep;
-        if (nDistance > 10)
-            nStep *= 2;
-    }
-    return nDistance;
+    return CBlockLocator(vHave);
 }
 
-CBlockIndex *CBlockLocator::GetBlockIndex()
-{
+CBlockIndex *CChain::FindFork(const CBlockLocator &locator) const {
     // Find the first block the caller has in the main chain
-    BOOST_FOREACH(const uint256& hash, vHave)
-    {
+    BOOST_FOREACH(const uint256& hash, locator.vHave) {
         std::map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hash);
         if (mi != mapBlockIndex.end())
         {
             CBlockIndex* pindex = (*mi).second;
-            if (chainActive.Contains(pindex))
+            if (Contains(pindex))
                 return pindex;
         }
     }
-    return chainActive.Genesis();
-}
-
-uint256 CBlockLocator::GetBlockHash()
-{
-    // Find the first block the caller has in the main chain
-    BOOST_FOREACH(const uint256& hash, vHave)
-    {
-        std::map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hash);
-        if (mi != mapBlockIndex.end())
-        {
-            CBlockIndex* pindex = (*mi).second;
-            if (chainActive.Contains(pindex))
-                return hash;
-        }
-    }
-    return Params().HashGenesisBlock();
-}
-
-int CBlockLocator::GetHeight()
-{
-    CBlockIndex* pindex = GetBlockIndex();
-    if (!pindex)
-        return 0;
-    return pindex->nHeight;
-}
-
-CBlockIndex *CChain::SetTip(CBlockIndex *pindex) {
-    if (pindex == NULL) {
-        std::vector<CBlockIndex*>().swap(vChain);
-        return NULL;
-    }
-    vChain.resize(pindex->nHeight + 1);
-    while (pindex && vChain[pindex->nHeight] != pindex) {
-        vChain[pindex->nHeight] = pindex;
-        pindex = pindex->pprev;
-    }
-    return pindex;
+    return Genesis();
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -2156,10 +2112,7 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
 
     // Update best block in wallet (so we can detect restored wallets)
     if ((pindexNew->nHeight % 20160) == 0 || (!fIsInitialDownload && (pindexNew->nHeight % 144) == 0))
-    {
-        const CBlockLocator locator(pindexNew);
-        ::SetBestChain(locator);
-    }
+        ::SetBestChain(chainActive.GetLocator(pindexNew));
 
     // New best block
     nTimeBestReceived = GetTime();
@@ -2525,7 +2478,7 @@ void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd)
     pnode->pindexLastGetBlocksBegin = pindexBegin;
     pnode->hashLastGetBlocksEnd = hashEnd;
 
-    pnode->PushMessage("getblocks", CBlockLocator(pindexBegin), hashEnd);
+    pnode->PushMessage("getblocks", chainActive.GetLocator(pindexBegin), hashEnd);
 }
 
 bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp)
@@ -3653,7 +3606,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         vRecv >> locator >> hashStop;
 
         // Find the last block the caller has in the main chain
-        CBlockIndex* pindex = locator.GetBlockIndex();
+        CBlockIndex* pindex = chainActive.FindFork(locator);
 
         // Send the rest of the chain
         if (pindex)
@@ -3698,7 +3651,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         else
         {
             // Find the last block the caller has in the main chain
-            pindex = locator.GetBlockIndex();
+            pindex = chainActive.FindFork(locator);
             if (pindex)
                 pindex = chainActive.Next(pindex);
         }
diff --git a/src/main.h b/src/main.h
index 46d629044a..1cddbae567 100644
--- a/src/main.h
+++ b/src/main.h
@@ -22,6 +22,7 @@ class CBlock;
 class CBlockIndex;
 class CKeyItem;
 class CReserveKey;
+class CBlockLocator;
 
 class CAddress;
 class CInv;
@@ -1033,6 +1034,12 @@ public:
 
     /** Set/initialize a chain with a given tip. Returns the forking point. */
     CBlockIndex *SetTip(CBlockIndex *pindex);
+
+    /** Return a CBlockLocator that refers to a block in this chain (by default the tip). */
+    CBlockLocator GetLocator(const CBlockIndex *pindex = NULL) const;
+
+    /** Find the last common block between this chain and a locator. */
+    CBlockIndex *FindFork(const CBlockLocator &locator) const;
 };
 
 /** The currently-connected chain of blocks. */
@@ -1051,13 +1058,6 @@ protected:
 public:
     CBlockLocator() {}
 
-    explicit CBlockLocator(const CBlockIndex* pindex)
-    {
-        Set(pindex);
-    }
-
-    explicit CBlockLocator(uint256 hashBlock);
-
     CBlockLocator(const std::vector<uint256>& vHaveIn)
     {
         vHave = vHaveIn;
@@ -1080,16 +1080,7 @@ public:
         return vHave.empty();
     }
 
-    /** Given a block initialises the locator to that point in the chain. */
-    void Set(const CBlockIndex* pindex);
-    /** Returns the distance in blocks this locator is from our chain head. */
-    int GetDistanceBack();
-    /** Returns the first best-chain block the locator contains. */
-    CBlockIndex* GetBlockIndex();
-    /** Returns the hash of the first best chain block the locator contains. */
-    uint256 GetBlockHash();
-    /** Returns the height of the first best chain block the locator has. */
-    int GetHeight();
+    friend class CChain;
 };
 
 
diff --git a/src/rpcwallet.cpp b/src/rpcwallet.cpp
index 433cc8b735..f7341f7b69 100644
--- a/src/rpcwallet.cpp
+++ b/src/rpcwallet.cpp
@@ -1169,7 +1169,9 @@ Value listsinceblock(const Array& params, bool fHelp)
         uint256 blockId = 0;
 
         blockId.SetHex(params[0].get_str());
-        pindex = CBlockLocator(blockId).GetBlockIndex();
+        std::map<uint256, CBlockIndex*>::iterator it = mapBlockIndex.find(blockId);
+        if (it != mapBlockIndex.end())
+            pindex = it->second;
     }
 
     if (params.size() > 1)