Add close and closed? methods to Tabix class with corresponding tests

Author: kojix2

lib/hts/tabix.rb

@@ -68,6 +68,7 @@ def build_index(index_name = nil, min_shift: 0)
     end
 
     def load_index(index_name = nil)
+      check_closed
       if index_name
         LibHTS.tbx_index_load2(@file_name, index_name)
       else
@@ -76,14 +77,17 @@ def load_index(index_name = nil)
     end
 
     def index_loaded?
+      check_closed
       !@idx.null?
     end
 
     def name2id(name)
+      check_closed
       LibHTS.tbx_name2id(@idx, name)
     end
 
     def seqnames
+      check_closed
       nseq = FFI::MemoryPointer.new(:int)
       LibHTS.tbx_seqnames(@idx, nseq).then do |pts|
         pts.read_array_of_pointer(nseq.read_int).map(&:read_string)
@@ -101,6 +105,20 @@ def query(region, start = nil, end_ = nil, &block)
       end
     end
 
+    def close
+      return if closed?
+
+      # @idx is an internal index (LibHTS::Tbx, a ManagedStruct).
+      # Do not call tbx_destroy here; the FFI finalizer will
+      # release the underlying C struct when @idx becomes unreachable.
+      @idx = nil
+      super
+    end
+
+    def closed?
+      @hts_file.nil? || @hts_file.null?
+    end
+
     private
 
     def queryi(id, start, end_, &block)
@@ -131,5 +149,9 @@ def query_yield(qiter)
         LibHTS.hts_itr_destroy(qiter)
       end
     end
+
+    def check_closed
+      raise IOError, "closed Tabix" if closed?
+    end
   end
 end

test/tabix_test.rb

@@ -27,6 +27,14 @@ def test_file_format
     assert_equal "vcf", @bcf.file_format
   end
 
+  def test_close
+    assert_equal false, @bcf.closed?
+    @bcf.close
+    assert_equal true, @bcf.closed?
+    # second close should be no-op
+    assert_nil @bcf.close
+  end
+
   def test_name2id
     assert_equal 0, @bcf.name2id("poo")
   end