Various performance tweaks to CCoinsView

* Pass txid's to CCoinsView functions by reference instead of by value
* Add a method to swap CCoins, and use it in some places to avoid a
  allocating copy + destruct.
* Optimize CCoinsViewCache::FetchCoins to do only a single search
  through the backing map.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/txdb.cpp b/src/txdb.cpp
index 78fa0279b..ca4e6c9bd 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -22,17 +22,17 @@ void static BatchWriteHashBestChain(CLevelDBBatch &batch, const uint256 &hash) {
 CCoinsViewDB::CCoinsViewDB(size_t nCacheSize, bool fMemory, bool fWipe) : db(GetDataDir() / "coins", nCacheSize, fMemory, fWipe) {
 }
 
-bool CCoinsViewDB::GetCoins(uint256 txid, CCoins &coins) { 
+bool CCoinsViewDB::GetCoins(const uint256 &txid, CCoins &coins) { 
     return db.Read(make_pair('c', txid), coins); 
 }
 
-bool CCoinsViewDB::SetCoins(uint256 txid, const CCoins &coins) {
+bool CCoinsViewDB::SetCoins(const uint256 &txid, const CCoins &coins) {
     CLevelDBBatch batch;
     BatchWriteCoins(batch, txid, coins);
     return db.WriteBatch(batch);
 }
 
-bool CCoinsViewDB::HaveCoins(uint256 txid) {
+bool CCoinsViewDB::HaveCoins(const uint256 &txid) {
     return db.Exists(make_pair('c', txid)); 
 }