--- a/src/core/ngx_buf.c
+++ b/src/core/ngx_buf.c
@@ -220,6 +220,48 @@ ngx_chain_update_chains(ngx_pool_t *p, n
 }
 
 
+off_t
+ngx_chain_coalesce_file(ngx_chain_t **in, off_t limit)
+{
+    off_t         total, size, aligned, fprev;
+    ngx_fd_t      fd;
+    ngx_chain_t  *cl;
+
+    total = 0;
+
+    cl = *in;
+    fd = cl->buf->file->fd;
+
+    do {
+        size = cl->buf->file_last - cl->buf->file_pos;
+
+        if (size > limit - total) {
+            size = limit - total;
+
+            aligned = (cl->buf->file_pos + size + ngx_pagesize - 1)
+                       & ~((off_t) ngx_pagesize - 1);
+
+            if (aligned <= cl->buf->file_last) {
+                size = aligned - cl->buf->file_pos;
+            }
+        }
+
+        total += size;
+        fprev = cl->buf->file_pos + size;
+        cl = cl->next;
+
+    } while (cl
+             && cl->buf->in_file
+             && total < limit
+             && fd == cl->buf->file->fd
+             && fprev == cl->buf->file_pos);
+
+    *in = cl;
+
+    return total;
+}
+
+
 ngx_chain_t *
 ngx_chain_update_sent(ngx_chain_t *in, off_t sent)
 {