feat: Provide an access object for SMBIOS information (#51)

lib/google/cloud/env/compute_smbios.rb

@@ -0,0 +1,138 @@
+# frozen_string_literal: true
+
+# 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 "google/cloud/env/lazy_value"
+
+module Google
+  module Cloud
+    class Env
+      ##
+      # Access to the SMBIOS information needed to determine if this Ruby
+      # process is running on a Google compute platform.
+      #
+      # This information lives at a file system path on Linux, but in the
+      # Registry on Windows.
+      #
+      # You can provide an override to "mock out" the behavior of this object.
+      #
+      class ComputeSMBIOS
+        ##
+        # Create an SMBIOS access object
+        #
+        def initialize
+          @product_name_cache = LazyValue.new { load_product_name }
+          @override_product_name = nil
+        end
+
+        ##
+        # Read the product name. On a Google compute platform, this should
+        # include the word "Google".
+        #
+        # This method may read the file system (on Linux) or registry (on
+        # Windows) the first time it is called, but it will cache the result
+        # for subsequent calls.
+        #
+        # @return [String] Product name, or the empty string if not found.
+        #
+        def product_name
+          @override_product_name || @product_name_cache.get.first
+        end
+
+        ##
+        # The source of the product name data. Will be one of the following:
+        #
+        # * `:linux` - The data comes from the Linux SMBIOS under /sys
+        # * `:windows` - The data comes from the Windows Registry
+        # * `:error` - The data could not be obtained
+        # * `:override` - The data comes from an override
+        #
+        # This method may read the file system (on Linux) or registry (on
+        # Windows) the first time it is called, but it will cache the result
+        # for subsequent calls.
+        #
+        # @return [Symbol] The source
+        #
+        def product_name_source
+          @override_product_name ? :override : @product_name_cache.get.last
+        end
+
+        ##
+        # Determine whether the SMBIOS state suggests that we are running on a
+        # Google compute platform.
+        #
+        # This method may read the file system (on Linux) or registry (on
+        # Windows) the first time it is called, but it will cache the result
+        # for subsequent calls.
+        #
+        # @return [true,false]
+        #
+        def google_compute?
+          product_name.include? "Google"
+        end
+
+        ##
+        # The current override value for the product name, either a string
+        # value, or nil to disable mocking.
+        #
+        # @return [nil,String]
+        #
+        attr_accessor :override_product_name
+
+        ##
+        # Run the given block with the product name mock modified. This is
+        # generally used for debugging/testing/mocking.
+        #
+        # @param override_name [nil,String]
+        #
+        def with_override_product_name override_name
+          old_override = @override_product_name
+          begin
+            @override_product_name = override_name
+            yield
+          ensure
+            @override_product_name = old_override
+          end
+        end
+
+        private
+
+        # @private The Windows registry key path
+        WINDOWS_KEYPATH = "SYSTEM\\HardwareConfig\\Current"
+        # @private The Windows registry key name
+        WINDOWS_KEYNAME = "SystemProductName"
+        # @private The Linux file path
+        LINUX_FILEPATH = "/sys/class/dmi/id/product_name"
+
+        private_constant :WINDOWS_KEYPATH, :WINDOWS_KEYNAME, :LINUX_FILEPATH
+
+        def load_product_name
+          require "win32/registry"
+          Win32::Registry::HKEY_LOCAL_MACHINE.open WINDOWS_KEYPATH do |reg|
+            return [reg[WINDOWS_KEYNAME].to_s, :windows]
+          end
+        rescue LoadError
+          begin
+            File.open LINUX_FILEPATH do |file|
+              return [file.readline(chomp: true), :linux]
+            end
+          rescue IOError, SystemCallError
+            ["", :error]
+          end
+        end
+      end
+    end
+  end
+end

test/google/cloud/env/compute_smbios_test.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+# 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 "helper"
+require "google/cloud/env/compute_smbios"
+
+describe Google::Cloud::Env::ComputeSMBIOS do
+  let(:compute_smbios) { Google::Cloud::Env::ComputeSMBIOS.new }
+
+  it "gets data on Linux" do
+    skip unless `uname`.strip == "Linux"
+    assert_kind_of String, compute_smbios.product_name
+    assert_equal :linux, compute_smbios.product_name_source
+  end
+
+  it "gets data on Windows" do
+    skip unless ::RbConfig::CONFIG["host_os"] =~ /mswin|msys|mingw|cygwin|bccwin|wince|emc/
+    assert_kind_of String, compute_smbios.product_name
+    assert_equal :windows, compute_smbios.product_name_source
+  end
+
+  it "overrides product_name" do
+    refute_equal "My Product", compute_smbios.product_name
+    refute_equal :override, compute_smbios.product_name_source
+    compute_smbios.override_product_name = "My Product"
+    assert_equal "My Product", compute_smbios.product_name
+    assert_equal :override, compute_smbios.product_name_source
+    compute_smbios.override_product_name = nil
+    refute_equal "My Product", compute_smbios.product_name
+    refute_equal :override, compute_smbios.product_name_source
+  end
+
+  it "overrides product_name in a block" do
+    refute_equal "My Product", compute_smbios.product_name
+    refute_equal :override, compute_smbios.product_name_source
+    compute_smbios.with_override_product_name "My Product" do
+      assert_equal "My Product", compute_smbios.product_name
+      assert_equal :override, compute_smbios.product_name_source
+    end
+    refute_equal "My Product", compute_smbios.product_name
+    refute_equal :override, compute_smbios.product_name_source
+  end
+end