Add (partial) spec for IO::Buffer#valid?

Author: trinistr

core/io/buffer/valid_spec.rb

@@ -0,0 +1,92 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#valid?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  # Non-slices are always valid
+  context "with a non-slice buffer" do
+    it "is true for a regular buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a 0-size buffer" do
+      @buffer = IO::Buffer.new(0)
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a freed buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.free
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a freed file-backed buffer" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.valid?.should be_true
+        @buffer.free
+        @buffer.valid?.should be_true
+      end
+    end
+
+    it "is true for a freed string-backed buffer" do
+      @buffer = IO::Buffer.for("hello")
+      @buffer.valid?.should be_true
+      @buffer.free
+      @buffer.valid?.should be_true
+    end
+  end
+
+  # "A buffer becomes invalid if it is a slice of another buffer (or string)
+  # which has been freed or re-allocated at a different address."
+  context "with a slice buffer" do
+    it "is true for a slice of a live buffer" do
+      @buffer = IO::Buffer.new(4)
+      slice = @buffer.slice(0, 2)
+      slice.valid?.should be_true
+    end
+
+    it "is false for a slice of a transferred buffer" do
+      buffer = IO::Buffer.new(4)
+      slice = buffer.slice(0, 2)
+      @buffer = buffer.transfer
+      slice.valid?.should be_false
+    end
+
+    it "is false for a slice of a freed buffer" do
+      @buffer = IO::Buffer.new(4)
+      slice = @buffer.slice(0, 2)
+      @buffer.free
+      slice.valid?.should be_false
+    end
+
+    it "is false for a slice of a freed file-backed buffer" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        slice = @buffer.slice(0, 2)
+        slice.valid?.should be_true
+        @buffer.free
+        slice.valid?.should be_false
+      end
+    end
+
+    it "is true for a slice of a freed string-backed buffer while string is alive" do
+      @buffer = IO::Buffer.for("alive")
+      slice = @buffer.slice(0, 2)
+      slice.valid?.should be_true
+      @buffer.free
+      slice.valid?.should be_true
+    end
+
+    # There probably should be a test with a garbage-collected string,
+    # but it's not clear how to force that.
+    # Also, a test for re-allocated memory, as #transfer does not
+    # change the address.
+
+    it "needs to be reviewed for spec completeness"
+  end
+end