cl-btree has relatively high code coverage with unit tests but it is still considered unstable because of low usage rate.
There is two types of B-trees implemented. Default type uses 32-bit unsigned integers as keys and values. The other type uses string as keys and values. The string B-tree can store anything readable as keys and values. The size of key strings or values is not fixed. String B-tree uses simply prin1 to write and read to read keys and values from cl-swap-file block stream.
Here is a sample session for using string B-tree:
(let ((btree (b-tree:open "/tmp/b-tree-test.db" :type :string :block-size 64 :if-exists :append))) (b-tree:insert btree 'my-key "This is a test value.") (b-tree:search btree 'my-key)) (b-tree:close btree))
cl-btree uses cl-swap-file for storing disk blocks on to file.
Download it from https://sourceforge.net/projects/cl-btree/files/
cl-btree no longer depends on cl-unit-test.