Return error if nghttp2_gzip_inflate is invoked after Z_STREAM_END

lib/nghttp2_gzip.c

@@ -33,6 +33,7 @@ int nghttp2_gzip_inflate_new(nghttp2_gzip **inflater_ptr)
   if(*inflater_ptr == NULL) {
     return NGHTTP2_ERR_NOMEM;
   }
+  (*inflater_ptr)->finished = 0;
   (*inflater_ptr)->zst.next_in = Z_NULL;
   (*inflater_ptr)->zst.avail_in = 0;
   (*inflater_ptr)->zst.zalloc = Z_NULL;
@@ -59,6 +60,9 @@ int nghttp2_gzip_inflate(nghttp2_gzip *inflater,
                          const uint8_t *in, size_t *inlen_ptr)
 {
   int rv;
+  if(inflater->finished) {
+    return NGHTTP2_ERR_GZIP;
+  }
   inflater->zst.avail_in = *inlen_ptr;
   inflater->zst.next_in = (unsigned char*)in;
   inflater->zst.avail_out = *outlen_ptr;
@@ -69,8 +73,9 @@ int nghttp2_gzip_inflate(nghttp2_gzip *inflater,
   *inlen_ptr -= inflater->zst.avail_in;
   *outlen_ptr -= inflater->zst.avail_out;
   switch(rv) {
-  case Z_OK:
   case Z_STREAM_END:
+    inflater->finished = 1;
+  case Z_OK:
   case Z_BUF_ERROR:
     return 0;
   case Z_DATA_ERROR:

lib/nghttp2_gzip.h

@@ -33,6 +33,7 @@
 
 struct nghttp2_gzip {
   z_stream zst;
+  int8_t finished;
 };
 
 #endif /* NGHTTP2_GZIP_H */