From f85ec313de2cb723b1ca004866f031635e0162e2 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Fri, 29 Nov 2019 11:38:19 +0100
Subject: [PATCH] os/vfs.h: handle zero-sized files

The 'File_content' class failed to consider zero-sized files.

Fixes #3557
---
 repos/os/include/os/vfs.h | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/repos/os/include/os/vfs.h b/repos/os/include/os/vfs.h
index 5070f68e49..094b3072fc 100644
--- a/repos/os/include/os/vfs.h
+++ b/repos/os/include/os/vfs.h
@@ -498,8 +498,15 @@ class Genode::File_content
 		template <typename FN>
 		void xml(FN const &fn) const
 		{
-			try { fn(Xml_node(_buffer.ptr, _buffer.size)); }
-			catch (Xml_node::Invalid_syntax) { fn(Xml_node("<empty/>")); }
+			try {
+				if (_buffer.size) {
+					fn(Xml_node(_buffer.ptr, _buffer.size));
+					return;
+				}
+			}
+			catch (Xml_node::Invalid_syntax) { }
+
+			fn(Xml_node("<empty/>"));
 		}
 
 		/**
@@ -510,6 +517,9 @@ class Genode::File_content
 		template <typename STRING, typename FN>
 		void for_each_line(FN const &fn) const
 		{
+			if (_buffer.size == 0)
+				return;
+
 			char const *src           = _buffer.ptr;
 			char const *curr_line     = src;
 			size_t      curr_line_len = 0;
@@ -538,9 +548,15 @@ class Genode::File_content
 
 		/**
 		 * Call functor 'fn' with the data pointer and size in bytes
+		 *
+		 * If the buffer has a size of zero, 'fn' is not called.
 		 */
 		template <typename FN>
-		void bytes(FN const &fn) const { fn((char const *)_buffer.ptr, _buffer.size); }
+		void bytes(FN const &fn) const
+		{
+			if (_buffer.size)
+				fn((char const *)_buffer.ptr, _buffer.size);
+		}
 };