Make the inflate_streambuf rewind the input

4 files changed, 33 insertions, 1 deletions

diff --git a/include/io/izlibstream.h b/include/io/izlibstream.h
index d3c4faa14e..4c6d5def85 100644
--- a/include/io/izlibstream.h
+++ b/include/io/izlibstream.h
@@ -64,6 +64,11 @@ private:
  * This istream wraps another istream. The izlibstream will read compressed
  * data from the wrapped istream and inflate (decompress) it with zlib.
  *
+ * @note If you want to read more data from the wrapped istream after the end
+ * of the compressed data, then it must allow seeking. It is unavoidable for
+ * the izlibstream to consume more data after the compressed data.
+ * It will automatically attempt to seek the wrapped istream back to the point
+ * after the end of the compressed data.
  * @sa inflate_streambuf
  */
 class izlibstream : public std::istream
diff --git a/src/io/izlibstream.cpp b/src/io/izlibstream.cpp
index 85e04a189a..0a7512469e 100644
--- a/src/io/izlibstream.cpp
+++ b/src/io/izlibstream.cpp
@@ -78,7 +78,13 @@ inflate_streambuf::int_type inflate_streambuf::underflow()
             throw std::bad_alloc();
 
         case Z_STREAM_END:
-            stream_end = true;
+            if(!stream_end)
+            {
+                stream_end = true;
+                //In case we consumed too much, we have to rewind the input stream
+                is.clear();
+                is.seekg(-static_cast<std::streamoff>(zstr.avail_in), std::ios_base::cur);
+            }
             if(have == 0)
                 return traits_type::eof();
             break;
diff --git a/test/testfiles/trailing_data.zlib b/test/testfiles/trailing_data.zlib
new file mode 100644
index 0000000000..83848f3024
--- /dev/null
+++ b/test/testfiles/trailing_data.zlib
diff --git a/test/zlibstream_test.h b/test/zlibstream_test.h
index f8308cf7c5..e76745f80f 100644
--- a/test/zlibstream_test.h
+++ b/test/zlibstream_test.h
@@ -133,6 +133,27 @@ public:
         }
     }
 
+    void test_inflate_trailing()
+    {
+        //This file contains additional uncompressed data after the zlib-compressed data
+        std::ifstream file("trailing_data.zlib", std::ios::binary);
+        izlibstream izls(file, 32);
+        TS_ASSERT(file && izls);
+
+        std::string str;
+        izls >> str;
+        TS_ASSERT(izls);
+        TS_ASSERT(izls.eof());
+        TS_ASSERT_EQUALS(str, "foobar");
+
+        //Now read the uncompressed data
+        TS_ASSERT(file);
+        TS_ASSERT(!file.eof());
+        file >> str;
+        TS_ASSERT(!file.bad());
+        TS_ASSERT_EQUALS(str, "barbaz");
+    }
+
     void test_deflate_zlib()
     {
         //Here we assume that inflating works and has already been tested