--- a/src/http/ngx_http_filter.h
+++ b/src/http/ngx_http_filter.h
@@ -2,9 +2,19 @@
 #define _NGX_HTTP_FILTER_H_INCLUDED_
 
 
-#define NGX_HTTP_FILTER_ERROR  -1
-#define NGX_HTTP_FILTER_AGAIN   0
-#define NGX_HTTP_FILTER_DONE    1
+#include <ngx_core.h>
+
+#define NGX_HTTP_FILTER_NEED_IN_MEMORY  1
+#define NGX_HTTP_FILTER_NEED_TEMP       2
+
+typedef struct {
+    int         (*next_filter)(ngx_http_request_t *r, ngx_chain_t *ch);
+    ngx_hunk_t   *hunk;
+    ngx_chain_t  *in;
+    ngx_chain_t   out;
+    size_t        hunk_size;
+    unsigned      last;
+} ngx_http_filter_ctx_t;
 
 
 #endif /* _NGX_HTTP_FILTER_H_INCLUDED_ */