From 615c1adfb07b9b466173166dc2e53ace540e4b32 Mon Sep 17 00:00:00 2001
From: James O'Beirne <james.obeirne@pm.me>
Date: Wed, 16 Jun 2021 16:27:20 -0400
Subject: refactor: wrap CCoinsViewCursor in unique_ptr

Specifically with CCoinsViewDB, if a raw cursor is allocated and
not freed, a cryptic leveldb assertion failure occurs on
CCoinsViewDB destruction.

See: https://github.com/google/leveldb/issues/142#issuecomment-414418135
---
 src/txdb.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'src/txdb.cpp')

diff --git a/src/txdb.cpp b/src/txdb.cpp
index 762f71feb1..bd0e9f7317 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -168,9 +168,10 @@ bool CBlockTreeDB::ReadLastBlockFile(int &nFile) {
     return Read(DB_LAST_BLOCK, nFile);
 }
 
-CCoinsViewCursor *CCoinsViewDB::Cursor() const
+std::unique_ptr<CCoinsViewCursor> CCoinsViewDB::Cursor() const
 {
-    CCoinsViewDBCursor *i = new CCoinsViewDBCursor(const_cast<CDBWrapper&>(*m_db).NewIterator(), GetBestBlock());
+    auto i = std::make_unique<CCoinsViewDBCursor>(
+        const_cast<CDBWrapper&>(*m_db).NewIterator(), GetBestBlock());
     /* It seems that there are no "const iterators" for LevelDB.  Since we
        only need read operations on it, use a const-cast to get around
        that restriction.  */
-- 
cgit v1.2.3


From 0f8a5a4dd530549d37c43da52c923ac3b2af1a03 Mon Sep 17 00:00:00 2001
From: James O'Beirne <james.obeirne@pm.me>
Date: Fri, 18 Jun 2021 14:14:15 -0400
Subject: move-only(ish): don't expose CCoinsViewDBCursor

No need for this to be a part of the header anymore.

Includes a small reference type style change.
---
 src/txdb.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'src/txdb.cpp')

diff --git a/src/txdb.cpp b/src/txdb.cpp
index bd0e9f7317..e6469ee159 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -168,6 +168,28 @@ bool CBlockTreeDB::ReadLastBlockFile(int &nFile) {
     return Read(DB_LAST_BLOCK, nFile);
 }
 
+/** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */
+class CCoinsViewDBCursor: public CCoinsViewCursor
+{
+public:
+    CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256&hashBlockIn):
+        CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
+    ~CCoinsViewDBCursor() {}
+
+    bool GetKey(COutPoint &key) const override;
+    bool GetValue(Coin &coin) const override;
+    unsigned int GetValueSize() const override;
+
+    bool Valid() const override;
+    void Next() override;
+
+private:
+    std::unique_ptr<CDBIterator> pcursor;
+    std::pair<char, COutPoint> keyTmp;
+
+    friend class CCoinsViewDB;
+};
+
 std::unique_ptr<CCoinsViewCursor> CCoinsViewDB::Cursor() const
 {
     auto i = std::make_unique<CCoinsViewDBCursor>(
-- 
cgit v1.2.3


From 7ad414f4bfa74595ee5726e66f3527045c02a977 Mon Sep 17 00:00:00 2001
From: James O'Beirne <james.obeirne@pm.me>
Date: Fri, 18 Jun 2021 14:15:39 -0400
Subject: doc: add comment about CCoinsViewDBCursor constructor

---
 src/txdb.cpp | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'src/txdb.cpp')

diff --git a/src/txdb.cpp b/src/txdb.cpp
index e6469ee159..4b76bee5ab 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -172,6 +172,8 @@ bool CBlockTreeDB::ReadLastBlockFile(int &nFile) {
 class CCoinsViewDBCursor: public CCoinsViewCursor
 {
 public:
+    // Prefer using CCoinsViewDB::Cursor() since we want to perform some
+    // cache warmup on instantiation.
     CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256&hashBlockIn):
         CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
     ~CCoinsViewDBCursor() {}
-- 
cgit v1.2.3