naruse	2017-07-14 18:17:55 +0900 (Fri, 14 Jul 2017)

  New Revision: 59333

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=59333

  Log:
    Zlib::GzipReader#pos underflows after calling #ungetbyte or #ungetc at start of file [Bug #13616]
    
    patched by Andrew Haines <andrew@h...> [ruby-core:81488]

  Modified files:
    trunk/ext/zlib/zlib.c
    trunk/test/zlib/test_zlib.rb
Index: test/zlib/test_zlib.rb
===================================================================
--- test/zlib/test_zlib.rb	(revision 59332)
+++ test/zlib/test_zlib.rb	(revision 59333)
@@ -663,6 +663,18 @@ if defined? Zlib https://github.com/ruby/ruby/blob/trunk/test/zlib/test_zlib.rb#L663
       }
     end
 
+    def test_ungetc_at_start_of_file
+      s = "".dup
+      w = Zlib::GzipWriter.new(StringIO.new(s))
+      w << "abc"
+      w.close
+      r = Zlib::GzipReader.new(StringIO.new(s))
+
+      r.ungetc ?!
+
+      assert_equal(-1, r.pos, "[ruby-core:81488][Bug #13616]")
+    end
+
     def test_open
       Tempfile.create("test_zlib_gzip_reader_open") {|t|
         t.close
Index: ext/zlib/zlib.c
===================================================================
--- ext/zlib/zlib.c	(revision 59332)
+++ ext/zlib/zlib.c	(revision 59333)
@@ -3393,7 +3393,14 @@ static VALUE https://github.com/ruby/ruby/blob/trunk/ext/zlib/zlib.c#L3393
 rb_gzfile_total_out(VALUE obj)
 {
     struct gzfile *gz = get_gzfile(obj);
-    return rb_uint2inum(gz->z.stream.total_out - ZSTREAM_BUF_FILLED(&gz->z));
+    uLong total_out = gz->z.stream.total_out;
+    long buf_filled = ZSTREAM_BUF_FILLED(&gz->z);
+
+    if (total_out >= (uLong)buf_filled) {
+        return rb_uint2inum(total_out - buf_filled);
+    } else {
+        return LONG2FIX(-(buf_filled - total_out));
+    }
 }
 
 /*

--
ML: ruby-changes@q...
Info: http://www.atdot.net/~ko1/quickml/