2 files changed, 33 insertions, 0 deletions
diff --git a/src/cryptonote_basic/hardfork.cpp b/src/cryptonote_basic/hardfork.cpp
index 0de09856b..447d79aee 100644
--- a/src/cryptonote_basic/hardfork.cpp
+++ b/src/cryptonote_basic/hardfork.cpp
@@ -305,6 +305,29 @@ bool HardFork::rescan_from_chain_height(uint64_t height)
   return rescan_from_block_height(height - 1);
 }
 
+void HardFork::on_block_popped(uint64_t nblocks)
+{
+  CHECK_AND_ASSERT_THROW_MES(nblocks > 0, "nblocks must be greater than 0");
+
+  CRITICAL_REGION_LOCAL(lock);
+
+  const uint64_t new_chain_height = db.height();
+  const uint64_t old_chain_height = new_chain_height + nblocks;
+  uint8_t version;
+  uint64_t height;
+  for (height = old_chain_height - 1; height >= new_chain_height; --height)
+  {
+    versions.pop_back();
+    version = db.get_hard_fork_version(height);
+    versions.push_front(version);
+  }
+
+  // does not take voting into account
+  for (current_fork_index = heights.size() - 1; current_fork_index > 0; --current_fork_index)
+    if (height >= heights[current_fork_index].height)
+      break;
+}
+
 int HardFork::get_voted_fork_index(uint64_t height) const
 {
   CRITICAL_REGION_LOCAL(lock);
diff --git a/src/cryptonote_basic/hardfork.h b/src/cryptonote_basic/hardfork.h
index a63a66976..a3fc25dfa 100644
--- a/src/cryptonote_basic/hardfork.h
+++ b/src/cryptonote_basic/hardfork.h
@@ -150,6 +150,16 @@ namespace cryptonote
     bool reorganize_from_chain_height(uint64_t height);
 
     /**
+     * @brief called when one or more blocks are popped from the blockchain
+     *
+     * The current fork will be updated by looking up the db,
+     * which is much cheaper than recomputing everything
+     *
+     * @param new_chain_height the height of the chain after popping
+     */
+    void on_block_popped(uint64_t new_chain_height);
+
+    /**
      * @brief returns current state at the given time
      *
      * Based on the approximate time of the last known hard fork,