feat: Add LRU hash (#970)

Author: diptanshumittal

.github/workflows/ci-common.yml

@@ -7,6 +7,10 @@ on:
     branches:
       - main
   workflow_dispatch:
+
+env:
+  MT_COMPAT: true
+
 jobs:
   CI:
     if: ${{ github.repository == 'googleapis/gapic-generator-ruby' }}

.github/workflows/ci.yml

@@ -9,6 +9,10 @@ on:
       - main
   workflow_dispatch:
 
+env:
+  MT_COMPAT: true
+
+
 jobs:
   tests:
     if: ${{ github.repository == 'googleapis/gapic-generator-ruby' }}

gapic-common/lib/gapic/generic_lro/operation.rb

@@ -90,7 +90,7 @@ def initialize operation, client:, polling_method_name:, operation_status_field:
       #
       def results
         return error if error?
-        return response if response?
+        response if response?
       end
 
       ##

gapic-common/lib/gapic/lru_hash.rb

@@ -0,0 +1,106 @@
+# Copyright 2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Gapic
+  ##
+  # @private
+  #
+  # Linked list based hash maintaining the order of
+  # access/creation of the keys.
+  #
+  class LruHash
+    def initialize size = 1
+      raise ArgumentError, "The size of LRU hash can't be < 1" unless size > 1
+      @start = nil
+      @end = nil
+      @size = size
+      @cache = {}
+    end
+
+    def get key
+      return nil unless @cache.key? key
+      node = @cache[key]
+      move_to_top node
+      node.value
+    end
+
+    def put key, value
+      if @cache.key? key
+        node = @cache[key]
+        node.value = value
+        move_to_top node
+      else
+        remove_tail if @cache.size >= @size
+        new_node = Node.new key, value
+        insert_at_top new_node
+        @cache[key] = new_node
+      end
+    end
+
+    private
+
+    def move_to_top node
+      return if node.equal? @start
+
+      if node.equal? @end
+        @end = node.prev
+        @end.next = nil
+      else
+        node.prev.next = node.next
+        node.next.prev = node.prev
+      end
+
+      node.prev = nil
+      node.next = @start
+      @start.prev = node
+      @start = node
+    end
+
+    def remove_tail
+      @cache.delete @end.key
+      @end = @end.prev
+      @end.next = nil if @end
+    end
+
+    def insert_at_top node
+      if @start.nil?
+        @start = node
+        @end = node
+      else
+        node.next = @start
+        @start.prev = node
+        @start = node
+      end
+    end
+
+    ##
+    # @private
+    #
+    # Node class for linked list.
+    #
+    class Node
+      attr_accessor :key
+      attr_accessor :value
+      attr_accessor :prev
+      attr_accessor :next
+
+      def initialize key, value
+        @key = key
+        @value = value
+        @prev = nil
+        @next = nil
+      end
+    end
+  end
+end

gapic-common/lib/gapic/operation.rb

@@ -102,7 +102,7 @@ def initialize grpc_op, client, result_type: nil, metadata_type: nil, options: {
     #   `Google::Rpc::Status` will be returned.
     def results
       return error if error?
-      return response if response?
+      response if response?
     end
 
     ##

gapic-common/lib/gapic/rest/grpc_transcoder.rb

@@ -218,7 +218,7 @@ def extract_scalar_value! request_hash, field_path, regex
 
         # Covers the case where in `foo.bar.baz`, `baz` is still a submessage or an array.
         return nil if value.is_a?(::Hash) || value.is_a?(::Array)
-        return value.to_s if value.to_s =~ regex
+        value.to_s if value.to_s =~ regex
       end
 
       # Finds a value in the hash by path.

gapic-common/test/gapic/lru_hash_test.rb

@@ -0,0 +1,54 @@
+# Copyright 2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require "test_helper"
+require "gapic/lru_hash"
+
+##
+# Tests LRU hash class
+#
+class LruHashTest < Minitest::Test
+  def test_hash_size_exceed
+    lru_cache = Gapic::LruHash.new 3
+    lru_cache.put 1, "one"
+    lru_cache.put 2, "two"
+    lru_cache.put 3, "three"
+    lru_cache.put 4, "four"
+    assert lru_cache.get(1).nil?
+    assert_equal "four", lru_cache.get(4)
+  end
+
+  def test_hash_size_value
+    assert_raises ArgumentError do
+      Gapic::LruHash.new 0
+    end
+    assert_raises ArgumentError do
+      Gapic::LruHash.new(-1)
+    end
+  end
+
+  def test_hash_removes_lru_value
+    lru_cache = Gapic::LruHash.new 3
+    lru_cache.put 1, "one"
+    lru_cache.put 2, "two"
+    lru_cache.put 3, "three"
+    lru_cache.get 3
+    lru_cache.get 2
+    lru_cache.get 1
+
+    lru_cache.put 4, "four"
+    assert lru_cache.get(3).nil?
+    assert_equal "four", lru_cache.get(4)
+  end
+end