Merge #19927: validation: Reduce direct g_chainman usage

72a1d5c6f3834e206719ee5121df7727aed5b786 validation: Remove review-only comments + assertions (Carl Dong)
3756853b15902d63f4b5a3129e8b5d82e84e125b docs: Move FindFilesToPrune{,Manual} doxygen comment (Carl Dong)
485899a93c6f5fff62090907efb0ac938992e1fb style: Make FindFilesToPrune{,Manual} match style guide (Carl Dong)
3f5b5f3f6db0e5716911b3fba1460ce327e8a845 validation: Move FindFilesToPrune{,Manual} to BlockManager (Carl Dong)
f8d4975ab3fcd3553843cf0862251289c88c106b validation: Move PruneOneBlockFile to BlockManager (Carl Dong)
74f73c783d46b012f375d819e2cd09c792820cd5 validation: Pass in chainman to UnloadBlockIndex (Carl Dong)
4668ded6d6ea4299d998abbb57543f37519812e2 validation: Move ~CMainCleanup logic to ~BlockManager (Carl Dong)

Pull request description:

  This PR paves the way for de-globalizing `g_chainman` entirely by removing the usage of `g_chainman` in the following functions/methods:
  - `~CMainCleanup`
  - `CChainState::FlushStateToDisk`
  - `UnloadBlockIndex`

  The remaining direct uses of `g_chainman` are as follows:
  1. In initialization codepaths:
  	- `AppTests`
  	- `AppInitMain`
  	- `TestingSetup::TestingSetup`
  2. `::ChainstateActive`
  3. `LookupBlockIndex`
  	- Note: `LookupBlockIndex` is used extensively throughout the codebase and require a much larger set of changes, therefore I've left it out of this initial PR

ACKs for top commit:
  MarcoFalke:
    re-ACK 72a1d5c6f3 👚
  jnewbery:
    utACK 72a1d5c6f3834e206719ee5121df7727aed5b786

Tree-SHA512: 944a4fa8405eecf39706ff944375d6824373aaeea849d11473f08181eff26b12f70043a8348a5b08e6e9021b243b481842fbdfbc7c3140ca795fce3688b7f5c3

1 files changed, 33 insertions, 5 deletions

diff --git a/src/validation.h b/src/validation.h
index 0da62093a3..d88bd07765 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -157,7 +157,7 @@ void LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, FlatFi
 /** Ensures we have a genesis block in the block tree, possibly writing one to disk. */
 bool LoadGenesisBlock(const CChainParams& chainparams);
 /** Unload database information */
-void UnloadBlockIndex(CTxMemPool* mempool);
+void UnloadBlockIndex(CTxMemPool* mempool, ChainstateManager& chainman);
 /** Run an instance of the script checking thread */
 void ThreadScriptCheck(int worker_num);
 /**
@@ -352,7 +352,31 @@ struct CBlockIndexWorkComparator
  * This data is used mostly in `CChainState` - information about, e.g.,
  * candidate tips is not maintained here.
  */
-class BlockManager {
+class BlockManager
+{
+    friend CChainState;
+
+private:
+    /* Calculate the block/rev files to delete based on height specified by user with RPC command pruneblockchain */
+    void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight, int chain_tip_height);
+
+    /**
+     * Prune block and undo files (blk???.dat and undo???.dat) so that the disk space used is less than a user-defined target.
+     * The user sets the target (in MB) on the command line or in config file.  This will be run on startup and whenever new
+     * space is allocated in a block or undo file, staying below the target. Changing back to unpruned requires a reindex
+     * (which in this case means the blockchain must be re-downloaded.)
+     *
+     * Pruning functions are called from FlushStateToDisk when the global fCheckForPruning flag has been set.
+     * Block and undo files are deleted in lock-step (when blk00003.dat is deleted, so is rev00003.dat.)
+     * Pruning cannot take place until the longest chain is at least a certain length (100000 on mainnet, 1000 on testnet, 1000 on regtest).
+     * Pruning will never delete a block within a defined distance (currently 288) from the active chain's tip.
+     * The block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks that were stored in the deleted files.
+     * A db flag records the fact that at least some block files have been pruned.
+     *
+     * @param[out]   setFilesToPrune   The set of file indices that can be unlinked will be returned
+     */
+    void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight, int chain_tip_height, bool is_ibd);
+
 public:
     BlockMap m_block_index GUARDED_BY(cs_main);
 
@@ -403,6 +427,9 @@ public:
     /** Create a new block index entry for a given block hash */
     CBlockIndex* InsertBlockIndex(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
+    //! Mark one block file as pruned (modify associated database entries)
+    void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
     /**
      * If a block header hasn't already been seen, call CheckBlockHeader on it, ensure
      * that it doesn't descend from an invalid block, and then add it to m_block_index.
@@ -412,6 +439,10 @@ public:
         BlockValidationState& state,
         const CChainParams& chainparams,
         CBlockIndex** ppindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    ~BlockManager() {
+        Unload();
+    }
 };
 
 /**
@@ -895,9 +926,6 @@ public:
      */
     bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& block, BlockValidationState& state, const CChainParams& chainparams, const CBlockIndex** ppindex = nullptr) LOCKS_EXCLUDED(cs_main);
 
-    //! Mark one block file as pruned (modify associated database entries)
-    void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
-
     //! Load the block tree and coins database from disk, initializing state if we're running with -reindex
     bool LoadBlockIndex(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);