From 77ac97879ae869e53dc033fc5b544a46237ad01d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Mon, 17 Nov 2025 14:51:22 +0300
Subject: [PATCH] mdbx++: add `cursor::update_current()` and
 `cursor::reverse_current()`.

---
 mdbx.h++     |  5 +++++
 src/mdbx.c++ | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/mdbx.h++ b/mdbx.h++
index 6a44a6f8..c3e34466 100644
--- a/mdbx.h++
+++ b/mdbx.h++
@@ -4487,6 +4487,11 @@ public:
   inline void upsert(const slice &key, const slice &value);
   inline slice upsert_reserve(const slice &key, size_t value_length);
 
+  /// \brief Updates value associated with a key at the current cursor position.
+  void update_current(const slice &value);
+  /// \brief Reserves and returns the space to storing a value associated with a key at the current cursor position.
+  slice reverse_current(size_t value_length);
+
   inline void update(const slice &key, const slice &value);
   inline bool try_update(const slice &key, const slice &value);
   inline slice update_reserve(const slice &key, size_t value_length);
diff --git a/src/mdbx.c++ b/src/mdbx.c++
index d09cbc21..6f50fd55 100644
--- a/src/mdbx.c++
+++ b/src/mdbx.c++
@@ -1609,6 +1609,26 @@ __cold bool txn::rename_map(const ::std::string &old_name, const ::std::string &
 
 //------------------------------------------------------------------------------
 
+void cursor::update_current(const slice &value) {
+  default_buffer holder;
+  auto key = current().key;
+  if (error::boolean_or_throw(mdbx_is_dirty(handle_->txn, key.iov_base)))
+    key = holder.assign(key);
+
+  update(key, value);
+}
+
+slice cursor::reverse_current(size_t value_length) {
+  default_buffer holder;
+  auto key = current().key;
+  if (error::boolean_or_throw(mdbx_is_dirty(handle_->txn, key.iov_base)))
+    key = holder.assign(key);
+
+  return update_reserve(key, value_length);
+}
+
+//------------------------------------------------------------------------------
+
 __cold ::std::ostream &operator<<(::std::ostream &out, const slice &it) {
   out << "{";
   if (!it.is_valid())