[patch] Slice filter: support for empty file.

[胡聪 (hucc)]

Hi,

>416 will be returned when the request has no Range HEADER and the target file is
>empty.  Apparently, it does not conform to the HTTP protocol. Empty file seems
>inevitable in the CDN service where Nginx is heavily used.
>
># HG changeset patch
># User hucongcong <hucong.c at foxmail.com>
># Date 1497892764 -28800
>#      Tue Jun 20 01:19:24 2017 +0800
># Node ID 79d38b2d27d4eb92395cf1ff43bbfe23498bc69a
># Parent  d1816a2696de8c2faa1cd913a151e5f62a8620f3
>Slice filter: support for empty file.

The following modifications may be more appropriate.

# HG changeset patch
# User hucongcong <hucong.c at foxmail.com>
# Date 1497926137 -28800
#      Tue Jun 20 10:35:37 2017 +0800
# Node ID e42abb7e28c4f0dd3d66cb81aa2623e7fae8b4da
# Parent  a39bc74873faf9e5bea616561b43f6ecc55229f9
Slice filter: support for empty file.

diff -r a39bc74873fa -r e42abb7e28c4 src/http/modules/ngx_http_slice_filter_module.c
--- a/src/http/modules/ngx_http_slice_filter_module.c   Mon Jun 19 14:25:42 2017 +0300
+++ b/src/http/modules/ngx_http_slice_filter_module.c   Tue Jun 20 10:35:37 2017 +0800
@@ -114,7 +114,21 @@ ngx_http_slice_header_filter(ngx_http_re
     }

     if (r->headers_out.status != NGX_HTTP_PARTIAL_CONTENT) {
+
         if (r == r->main) {
+            if (r->headers_in.range == NULL
+                && r->headers_out.status == NGX_HTTP_RANGE_NOT_SATISFIABLE)
+            {
+                r->header_only = 1;
+                ngx_str_null(&r->headers_out.content_type);
+
+                r->headers_out.status = NGX_HTTP_OK;
+                r->headers_out.status_line.len = 0;
+                r->headers_out.content_length_n = 0;
+                r->headers_out.content_range->hash = 0;
+                r->headers_out.content_range = NULL;
+            }
+
             ngx_http_set_ctx(r, NULL, ngx_http_slice_filter_module);
             return ngx_http_next_header_filter(r);
         }