validation: Make DumpMempool(...) and LoadMempool(...) easier to test/fuzz/mock

src/validation.cpp

@@ -5010,11 +5010,11 @@ CBlockFileInfo* GetBlockFileInfo(size_t n)
 
 static const uint64_t MEMPOOL_DUMP_VERSION = 1;
 
-bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate)
+bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate, FopenFn mockable_fopen_function)
 {
     const CChainParams& chainparams = Params();
     int64_t nExpiryTimeout = gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
-    FILE* filestr = fsbridge::fopen(GetDataDir() / "mempool.dat", "rb");
+    FILE* filestr{mockable_fopen_function(GetDataDir() / "mempool.dat", "rb")};
     CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
     if (file.IsNull()) {
         LogPrintf("Failed to open mempool file from disk. Continuing anyway.\n");
@@ -5095,7 +5095,7 @@ bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate)
     return true;
 }
 
-bool DumpMempool(const CTxMemPool& pool)
+bool DumpMempool(const CTxMemPool& pool, FopenFn mockable_fopen_function, bool skip_file_commit)
 {
     int64_t start = GetTimeMicros();
 
@@ -5118,7 +5118,7 @@ bool DumpMempool(const CTxMemPool& pool)
     int64_t mid = GetTimeMicros();
 
     try {
-        FILE* filestr = fsbridge::fopen(GetDataDir() / "mempool.dat.new", "wb");
+        FILE* filestr{mockable_fopen_function(GetDataDir() / "mempool.dat.new", "wb")};
         if (!filestr) {
             return false;
         }
@@ -5141,7 +5141,7 @@ bool DumpMempool(const CTxMemPool& pool)
         LogPrintf("Writing %d unbroadcast transactions to disk.\n", unbroadcast_txids.size());
         file << unbroadcast_txids;
 
-        if (!FileCommit(file.Get()))
+        if (!skip_file_commit && !FileCommit(file.Get()))
             throw std::runtime_error("FileCommit failed");
         file.fclose();
         if (!RenameOver(GetDataDir() / "mempool.dat.new", GetDataDir() / "mempool.dat")) {

src/validation.h

@@ -1013,11 +1013,13 @@ int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Para
 /** Get block file info entry for one block file */
 CBlockFileInfo* GetBlockFileInfo(size_t n);
 
+using FopenFn = std::function<FILE*(const fs::path&, const char*)>;
+
 /** Dump the mempool to disk. */
-bool DumpMempool(const CTxMemPool& pool);
+bool DumpMempool(const CTxMemPool& pool, FopenFn mockable_fopen_function = fsbridge::fopen, bool skip_file_commit = false);
 
 /** Load the mempool from disk. */
-bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate);
+bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate, FopenFn mockable_fopen_function = fsbridge::fopen);
 
 //! Check whether the block associated with this index entry is pruned or not.
 inline bool IsBlockPruned(const CBlockIndex* pblockindex)