[FEATURE] IBF decompression

CHANGELOG.md

@@ -41,6 +41,11 @@ If possible, provide tooling that performs the changes, e.g. a shell-script.
   * Char literals returning std::vector are now constexpr if supported by the compiler
     ([\#3073](https://github.com/seqan/seqan3/pull/3073)).
 
+#### Search
+
+* Added a constructor to the `seqan3::interleaved_bloom_filter` for decompressing a compressed
+  `seqan3::interleaved_bloom_filter` ([\#3082](https://github.com/seqan/seqan3/pull/3082)).
+
 ## Notable Bug-fixes
 
 #### I/O

include/seqan3/search/dream_index/interleaved_bloom_filter.hpp

@@ -240,6 +240,26 @@ class interleaved_bloom_filter
         data = sdsl::bit_vector(technical_bins * bin_size_);
     }
 
+    /*!\brief Construct an uncompressed Interleaved Bloom Filter.
+     * \param[in] ibf The compressed seqan3::interleaved_bloom_filter.
+     *
+     * \attention This constructor can only be used to construct **uncompressed** Interleaved Bloom Filters.
+     *
+     * \details
+     *
+     * ### Example
+     *
+     * \include test/snippet/search/dream_index/interleaved_bloom_filter_constructor_uncompress.cpp
+     */
+    interleaved_bloom_filter(interleaved_bloom_filter<data_layout::compressed> const & ibf)
+        requires (data_layout_mode == data_layout::uncompressed)
+    {
+        std::tie(bins, technical_bins, bin_size_, hash_shift, bin_words, hash_funs) =
+            std::tie(ibf.bins, ibf.technical_bins, ibf.bin_size_, ibf.hash_shift, ibf.bin_words, ibf.hash_funs);
+
+        data = sdsl::bit_vector{ibf.data.begin(), ibf.data.end()};
+    }
+
     /*!\brief Construct a compressed Interleaved Bloom Filter.
      * \param[in] ibf The uncompressed seqan3::interleaved_bloom_filter.
      *

test/snippet/search/dream_index/interleaved_bloom_filter_constructor_uncompress.cpp

@@ -0,0 +1,18 @@
+#include <seqan3/search/dream_index/interleaved_bloom_filter.hpp>
+
+int main()
+{
+    // Construct an uncompressed Interleaved Bloom Filter.
+    seqan3::interleaved_bloom_filter ibf{seqan3::bin_count{4u}, seqan3::bin_size{128u}, seqan3::hash_function_count{3}};
+
+    // Insert the values `126`, `712` and `237` into bins `0`, `3` and `9` of the Interleaved Bloom Filter.
+    ibf.emplace(126, seqan3::bin_index{0u});
+    ibf.emplace(712, seqan3::bin_index{3u});
+    ibf.emplace(237, seqan3::bin_index{9u});
+
+    // Construct an immutable, compressed Interleaved Bloom Filter.
+    seqan3::interleaved_bloom_filter<seqan3::data_layout::compressed> ibf_compressed{ibf};
+
+    // Decompress the compressed Interleaved Bloom Filter.
+    seqan3::interleaved_bloom_filter ibf_decompressed{ibf_compressed};
+}

test/unit/search/dream_index/interleaved_bloom_filter_test.cpp

@@ -358,3 +358,23 @@ TYPED_TEST(interleaved_bloom_filter_test, serialisation)
     TypeParam ibf{TestFixture::make_ibf(seqan3::bin_count{73u}, seqan3::bin_size{1024u})};
     seqan3::test::do_serialisation(ibf);
 }
+
+TEST(interleaved_bloom_filter_test, decompression)
+{
+    seqan3::interleaved_bloom_filter ibf{seqan3::bin_count{64u}, seqan3::bin_size{1024u}};
+
+    // Only use every other bin.
+    auto take_odd = [](auto number)
+    {
+        return number & 1;
+    };
+    for (size_t bin_idx : std::views::iota(0, 64) | std::views::filter(take_odd))
+        for (size_t hash : std::views::iota(0, 64))
+            ibf.emplace(hash, seqan3::bin_index{bin_idx});
+
+    seqan3::interleaved_bloom_filter<seqan3::data_layout::compressed> ibf_compressed{ibf};
+
+    seqan3::interleaved_bloom_filter ibf_decompressed{ibf_compressed};
+
+    EXPECT_TRUE(ibf == ibf_decompressed);
+}