1 files changed, 120 insertions, 0 deletions
diff --git a/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb b/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb
new file mode 100644
index 0000000000..53870b9177
--- /dev/null
+++ b/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb
@@ -0,0 +1,120 @@
+require_relative '../../../spec_helper'
+require 'stringio'
+require 'zlib'
+
+describe "Zlib::GzipReader#ungetbyte" do
+  before :each do
+    @data = '12345abcde'
+    @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
+            76, 74, 78, 73, 5, 0, 157, 5, 0, 36, 10, 0, 0, 0].pack('C*')
+    @io = StringIO.new @zip
+  end
+
+  describe 'at the start of the stream' do
+    before :each do
+      @gz = Zlib::GzipReader.new(@io)
+    end
+
+    describe 'with an integer' do
+      it 'prepends the byte to the stream' do
+        @gz.ungetbyte 0x21
+        @gz.read.should == '!12345abcde'
+      end
+
+      it 'decrements pos' do
+        @gz.ungetbyte 0x21
+        @gz.pos.should == -1
+      end
+    end
+
+    quarantine! do # https://bugs.ruby-lang.org/issues/13675
+      describe 'with nil' do
+        it 'does not prepend anything to the stream' do
+          @gz.ungetbyte nil
+          @gz.read.should == '12345abcde'
+        end
+
+        it 'does not decrement pos' do
+          @gz.ungetbyte nil
+          @gz.pos.should == 0
+        end
+      end
+    end
+  end
+
+  describe 'in the middle of the stream' do
+    before :each do
+      @gz = Zlib::GzipReader.new(@io)
+      @gz.read 5
+    end
+
+    describe 'with an integer' do
+      it 'inserts the corresponding character into the stream' do
+        @gz.ungetbyte 0x21
+        @gz.read.should == '!abcde'
+      end
+
+      it 'decrements pos' do
+        @gz.ungetbyte 0x21
+        @gz.pos.should == 4
+      end
+    end
+
+    quarantine! do # https://bugs.ruby-lang.org/issues/13675
+      describe 'with nil' do
+        it 'does not insert anything into the stream' do
+          @gz.ungetbyte nil
+          @gz.read.should == 'abcde'
+        end
+
+        it 'does not decrement pos' do
+          @gz.ungetbyte nil
+          @gz.pos.should == 5
+        end
+      end
+    end
+  end
+
+  describe 'at the end of the stream' do
+    before :each do
+      @gz = Zlib::GzipReader.new(@io)
+      @gz.read
+    end
+
+    describe 'with an integer' do
+      it 'appends the corresponding character to the stream' do
+        @gz.ungetbyte 0x21
+        @gz.read.should == '!'
+      end
+
+      it 'decrements pos' do
+        @gz.ungetbyte 0x21
+        @gz.pos.should == 9
+      end
+
+      it 'makes eof? false' do
+        @gz.ungetbyte 0x21
+        @gz.eof?.should == false
+      end
+    end
+
+    quarantine! do # https://bugs.ruby-lang.org/issues/13675
+      describe 'with nil' do
+        it 'does not append anything to the stream' do
+          @gz.ungetbyte nil
+          @gz.read.should == ''
+        end
+
+        it 'does not decrement pos' do
+          @gz.ungetbyte nil
+          @gz.pos.should == 10
+        end
+
+        it 'does not make eof? false' do
+          @gz.ungetbyte nil
+          @gz.eof?.should == true
+        end
+      end
+    end
+  end
+end