Specs: fifo.

spec/spec-database.cr

@@ -26,10 +26,10 @@ end
 
 class SPECDB::FIFO(V) < DODB::Storage::Stacked(V)
 	property storage_dir : String
-	def initialize(storage_ext = "", @max_entries = 100_000, remove_previous_data = true)
+	def initialize(storage_ext = "", @max_entries : UInt32 = 5_000, remove_previous_data = true)
 		@storage_dir = "specdb-storage-fifo-#{@max_entries}#{storage_ext}"
 		::FileUtils.rm_rf storage_dir if remove_previous_data
-		super storage_dir
+		super storage_dir, max_entries
 	end
 
 	def rm_storage_dir

spec/test-fifo.cr

@@ -0,0 +1,41 @@
+require "spec"
+require "./db-cars.cr"
+
+describe "FIFO" do
+	it "add and remove values" do
+		fifo = FIFO(Int32).new 3 # Only 3 allowed entries.
+		(fifo << 1).should be_nil # there is still room in the stack
+		(fifo << 2).should be_nil # there is still room in the stack
+		(fifo << 3).should be_nil # last entry without exceeding the allowed size
+		(fifo << 4).should eq 1   # -> 1 (least recently used data)
+		(fifo << 4).should be_nil # -> nil (already in the stack)
+		(fifo << 2).should be_nil # -> nil (already in the stack)
+		(fifo << 5).should eq 3   # -> 3 (least recently used data)
+		fifo.data.should eq([5, 2, 4] of Int32)
+	end
+end
+
+describe "SPECDB::FIFO" do
+	it "basics, 3 values" do
+		car0 = Car.new "Corvet-0", "red", [] of String
+		car1 = Car.new "Corvet-1", "red", [] of String
+		car2 = Car.new "Corvet-2", "red", [] of String
+		car3 = Car.new "Corvet-3", "red", [] of String
+
+		db = SPECDB::FIFO(Car).new("", 3)
+
+		db.data.keys.sort.should eq([] of Int32)
+
+		db << car0
+		db.data.keys.sort.should eq([0] of Int32)
+
+		db << car1
+		db.data.keys.sort.should eq([0, 1] of Int32)
+
+		db << car2
+		db.data.keys.sort.should eq([0, 1, 2] of Int32)
+
+		db << car3
+		db.data.keys.sort.should eq([1, 2, 3] of Int32)
+	end
+end

src/dodb/storage/stacked.cr

@@ -37,7 +37,7 @@ class DODB::Storage::Stacked(V) < DODB::Storage::Cached(V)
 	property stack : FIFO(Int32)
 
 	# Initializes the `StackedDataBase` with a maximum number of entries in the cache.
-	def initialize(@directory_name : String, max_entries : UInt32 = 100_000)
+	def initialize(@directory_name : String, max_entries : UInt32)
 		@stack = FIFO(Int32).new max_entries
 		Dir.mkdir_p data_path
 		Dir.mkdir_p locks_directory

src/fifo.cr

@@ -30,7 +30,7 @@ class FIFO(V)
 	# NOTE: `#<<(v : V)` is (almost) the only function since it's enough for the intended use, feel free to improve this.
 	# WARNING: implementation is extremely simple (3 lines) and not designed to be highly efficient.
 	def <<(v : V) : V?
-		@data.select! { |x| v != v }            # remove dups
+		@data.select! { |x| v != x }            # remove dups
 		@data.unshift v                         # push on top of the stack
 		@data.pop if @data.size > @max_entries  # remove least recently used entry if `@data` is too big
 	end