From f20f4cca65d6433cb354b584ee25339f152e72ec Mon Sep 17 00:00:00 2001
From: Hisham Muhammad <hisham@gobolinux.org>
Date: Tue, 17 Jul 2018 16:00:09 -0300
Subject: fs: add filter_file

---
 src/luarocks/fs/lua.lua | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/luarocks/fs/lua.lua b/src/luarocks/fs/lua.lua
index 9da3875b..58dcf5c1 100644
--- a/src/luarocks/fs/lua.lua
+++ b/src/luarocks/fs/lua.lua
@@ -211,6 +211,36 @@ function fs_lua.modules(at)
    return modules
 end
 
+function fs_lua.filter_file(fn, input_filename, output_filename)
+   local fd, err = io.open(input_filename, "rb")
+   if not fd then
+      return nil, err
+   end
+
+   local input, err = fd:read("*a")
+   fd:close()
+   if not input then
+      return nil, err
+   end
+
+   local output, err = fn(input)
+   if not output then
+      return nil, err
+   end
+
+   fd, err = io.open(output_filename, "wb")
+   if not fd then
+      return nil, err
+   end
+
+   local ok, err = fd:write(output)
+   fd:close()
+   if not ok then
+      return nil, err
+   end
+
+   return true
+end
 
 ---------------------------------------------------------------------
 -- LuaFileSystem functions
-- 
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