Add GetKeyBirthTimes to wallet

Compute safe lower bounds on the birth times of all wallet keys. For
pool keys or keys with metadata, the actually stored birth time is
used. For all others, the birth times are inferred from the wallet
transactions.

src/wallet.cpp

@@ -1846,7 +1846,7 @@ void CReserveKey::ReturnKey()
     vchPubKey = CPubKey();
 }
 
-void CWallet::GetAllReserveKeys(set<CKeyID>& setAddress)
+void CWallet::GetAllReserveKeys(set<CKeyID>& setAddress) const
 {
     setAddress.clear();
 
@@ -1908,3 +1908,53 @@ void CWallet::ListLockedCoins(std::vector<COutPoint>& vOutpts)
     }
 }
 
+void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64> &mapKeyBirth) const {
+    mapKeyBirth.clear();
+
+    // get birth times for keys with metadata
+    for (std::map<CKeyID, CKeyMetadata>::const_iterator it = mapKeyMetadata.begin(); it != mapKeyMetadata.end(); it++)
+        if (it->second.nCreateTime)
+            mapKeyBirth[it->first] = it->second.nCreateTime;
+
+    // map in which we'll infer heights of other keys
+    CBlockIndex *pindexMax = FindBlockByHeight(std::max(0, nBestHeight - 144)); // the tip can be reorganised; use a 144-block safety margin
+    std::map<CKeyID, CBlockIndex*> mapKeyFirstBlock;
+    std::set<CKeyID> setKeys;
+    GetKeys(setKeys);
+    BOOST_FOREACH(const CKeyID &keyid, setKeys) {
+        if (mapKeyBirth.count(keyid) == 0)
+            mapKeyFirstBlock[keyid] = pindexMax;
+    }
+    setKeys.clear();
+
+    // if there are no such keys, we're done
+    if (mapKeyFirstBlock.empty())
+        return;
+
+    // find first block that affects those keys, if there are any left
+    std::vector<CKeyID> vAffected;
+    for (std::map<uint256, CWalletTx>::const_iterator it = mapWallet.begin(); it != mapWallet.end(); it++) {
+        // iterate over all wallet transactions...
+        const CWalletTx &wtx = (*it).second;
+        std::map<uint256, CBlockIndex*>::const_iterator blit = mapBlockIndex.find(wtx.hashBlock);
+        if (blit != mapBlockIndex.end() && blit->second->IsInMainChain()) {
+            // ... which are already in a block
+            int nHeight = blit->second->nHeight;
+            BOOST_FOREACH(const CTxOut &txout, wtx.vout) {
+                // iterate over all their outputs
+                ::ExtractAffectedKeys(*this, txout.scriptPubKey, vAffected);
+                BOOST_FOREACH(const CKeyID &keyid, vAffected) {
+                    // ... and all their affected keys
+                    std::map<CKeyID, CBlockIndex*>::iterator rit = mapKeyFirstBlock.find(keyid);
+                    if (rit != mapKeyFirstBlock.end() && nHeight < rit->second->nHeight)
+                        rit->second = blit->second;
+                }
+                vAffected.clear();
+            }
+        }
+    }
+
+    // Extract block timestamps for those keys
+    for (std::map<CKeyID, CBlockIndex*>::const_iterator it = mapKeyFirstBlock.begin(); it != mapKeyFirstBlock.end(); it++)
+        mapKeyBirth[it->first] = it->second->nTime - 7200; // block times can be 2h off
+}