From 32169c3855ff2f5bbf62662f036d70a956d89f6b Mon Sep 17 00:00:00 2001
From: Andrew Toth <andrewstoth@gmail.com>
Date: Sat, 21 Mar 2026 11:21:10 -0400
Subject: [PATCH] dbwrapper: accept optional testing leveldb::Env in DBParams

Allow callers to inject a custom leveldb::Env via DBParams::testing_env,
which takes priority over the memory_only in-memory environment. This
enables fuzz harnesses to supply a deterministic environment.
---
 src/dbwrapper.cpp | 12 +++++++++---
 src/dbwrapper.h   |  7 +++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index ee6419d2041..9bb85214041 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -224,16 +224,22 @@ CDBWrapper::CDBWrapper(const DBParams& params)
     DBContext().options = GetOptions(params.cache_bytes);
     DBContext().options.create_if_missing = true;
     DBContext().options.max_file_size = params.max_file_size;
-    if (params.memory_only) {
+    assert(!(params.testing_env && params.memory_only));
+    if (params.testing_env) {
+        DBContext().options.env = params.testing_env;
+    } else if (params.memory_only) {
         DBContext().penv = leveldb::NewMemEnv(leveldb::Env::Default());
         DBContext().options.env = DBContext().penv;
-    } else {
+    }
+    if (!params.memory_only) {
         if (params.wipe_data) {
             LogInfo("Wiping LevelDB in %s", fs::PathToString(params.path));
             leveldb::Status result = leveldb::DestroyDB(fs::PathToString(params.path), DBContext().options);
             HandleError(result);
         }
-        TryCreateDirectories(params.path);
+        if (!params.testing_env) {
+            TryCreateDirectories(params.path);
+        }
         LogInfo("Opening LevelDB in %s", fs::PathToString(params.path));
     }
     // PathToString() return value is safe to pass to leveldb open function,
diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index c36864004fd..3e81a27e373 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -19,6 +19,10 @@
 #include <stdexcept>
 #include <string>
 
+namespace leveldb {
+class Env;
+} // namespace leveldb
+
 static const size_t DBWRAPPER_PREALLOC_KEY_SIZE = 64;
 static const size_t DBWRAPPER_PREALLOC_VALUE_SIZE = 1024;
 static const size_t DBWRAPPER_MAX_FILE_SIZE = 32 << 20; // 32 MiB
@@ -44,6 +48,9 @@ struct DBParams {
     bool obfuscate = false;
     //! Passed-through options.
     DBOptions options{};
+    //! If non-null, use this as the leveldb::Env instead of the default.
+    //! Caller retains ownership.
+    leveldb::Env* testing_env = nullptr;
     //! Maximum LevelDB SST file size. Larger values reduce the frequency
     //! of compactions but increase their duration.
     size_t max_file_size = DBWRAPPER_MAX_FILE_SIZE;