From be65e9baa64baa501de7ac94251b8feb491560ec Mon Sep 17 00:00:00 2001
From: Dominik Drexler <dominik.drexler@gmx.net>
Date: Sat, 25 May 2024 00:42:03 +0200
Subject: [PATCH] added shrink_to_fit for bitset builder

---
 include/flatmemory/details/types/bitset.hpp | 18 ++++++++++++++++++
 tests/unit/types/bitset.cpp                 | 13 +++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/flatmemory/details/types/bitset.hpp b/include/flatmemory/details/types/bitset.hpp
index a6275a3..977d517 100644
--- a/include/flatmemory/details/types/bitset.hpp
+++ b/include/flatmemory/details/types/bitset.hpp
@@ -1062,6 +1062,24 @@ class Builder<Bitset<Block>> : public IBuilder<Builder<Bitset<Block>>>
      * Modifiers
      */
 
+    /// @brief Shrink the bitset to minimum number of blocks (at least 1) to represent its bits.
+    void shrink_to_fit()
+    {
+        int32_t last_non_default_block_index = m_blocks.size() - 1;
+
+        const Block default_block = m_default_bit_value ? BitsetOperator::block_ones : BitsetOperator::block_zeroes;
+
+        for (; last_non_default_block_index >= 0; --last_non_default_block_index)
+        {
+            if (m_blocks[last_non_default_block_index] != default_block)
+            {
+                break;
+            }
+        }
+
+        m_blocks.resize(last_non_default_block_index + 1);
+    }
+
     // Set a bit at a specific position
     void set(std::size_t position)
     {
diff --git a/tests/unit/types/bitset.cpp b/tests/unit/types/bitset.cpp
index 8054433..e04ff72 100644
--- a/tests/unit/types/bitset.cpp
+++ b/tests/unit/types/bitset.cpp
@@ -232,6 +232,19 @@ TEST(FlatmemoryTests, TypesBitsetEqualTest)
  * Modifiers
  */
 
+TEST(FlatmemoryTests, TypesBitsetShrinkToFitTest)
+{
+    // Is included in TypesBitsetGetTest
+    auto builder = Builder<Bitset<uint64_t>>(250);
+    builder.unset_all();
+    builder.set(42);
+    EXPECT_EQ(builder.get_blocks().size(), 4);
+    EXPECT_TRUE(builder.get(42));
+
+    builder.shrink_to_fit();
+    EXPECT_EQ(builder.get_blocks().size(), 1);
+}
+
 TEST(FlatmemoryTests, TypesBitsetSetTest)
 {
     // Is included in TypesBitsetGetTest