1 files changed, 15 insertions, 3 deletions

diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
index c2e903e470..eb40d45aba 100644
--- a/src/node/blockstorage.h
+++ b/src/node/blockstorage.h
@@ -24,7 +24,6 @@ class BlockValidationState;
 class CBlock;
 class CBlockFileInfo;
 class CBlockUndo;
-class CChain;
 class CChainParams;
 class Chainstate;
 class ChainstateManager;
@@ -94,7 +93,7 @@ private:
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     void FlushBlockFile(bool fFinalize = false, bool finalize_undo = false);
     void FlushUndoFile(int block_file, bool finalize = false);
-    bool FindBlockPos(FlatFilePos& pos, unsigned int nAddSize, unsigned int nHeight, CChain& active_chain, uint64_t nTime, bool fKnown);
+    bool FindBlockPos(FlatFilePos& pos, unsigned int nAddSize, unsigned int nHeight, uint64_t nTime, bool fKnown);
     bool FindUndoPos(BlockValidationState& state, int nFile, FlatFilePos& pos, unsigned int nAddSize);
 
     FlatFileSeq BlockFileSeq() const;
@@ -128,6 +127,19 @@ private:
     RecursiveMutex cs_LastBlockFile;
     std::vector<CBlockFileInfo> m_blockfile_info;
     int m_last_blockfile = 0;
+
+    // Track the height of the highest block in m_last_blockfile whose undo
+    // data has been written. Block data is written to block files in download
+    // order, but is written to undo files in validation order, which is
+    // usually in order by height. To avoid wasting disk space, undo files will
+    // be trimmed whenever the corresponding block file is finalized and
+    // the height of the highest block written to the block file equals the
+    // height of the highest block written to the undo file. This is a
+    // heuristic and can sometimes preemptively trim undo files that will write
+    // more data later, and sometimes fail to trim undo files that can't have
+    // more data written later.
+    unsigned int m_undo_height_in_last_blockfile = 0;
+
     /** Global flag to indicate we should check to see if there are
      *  block/undo files that should be deleted.  Set on startup
      *  or if we allocate more file space when we're in prune mode
@@ -202,7 +214,7 @@ public:
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
     /** Store block on disk. If dbp is not nullptr, then it provides the known position of the block within a block file on disk. */
-    FlatFilePos SaveBlockToDisk(const CBlock& block, int nHeight, CChain& active_chain, const FlatFilePos* dbp);
+    FlatFilePos SaveBlockToDisk(const CBlock& block, int nHeight, const FlatFilePos* dbp);
 
     /** Whether running in -prune mode. */
     [[nodiscard]] bool IsPruneMode() const { return m_prune_mode; }