add utf8 library from Lua 5.3; use struct for string packing

1 files changed, 24 insertions, 0 deletions

diff --git a/compat53.lua b/compat53.lua
new file mode 100644
index 0000000..98e1a3d
--- /dev/null
+++ b/compat53.lua
@@ -0,0 +1,24 @@
+local lua_version = _VERSION:sub(-3)
+
+if lua_version ~= "5.3" then
+
+   -- load utf8 library
+   utf8 = require("compat53.utf8")
+   package.loaded["utf8"] = utf8
+   if lua_version == "5.1" then
+      utf8.charpattern = "[%z\1-\127\194-\244][\128-\191]*"
+   end
+
+   -- use Roberto's struct module for string packing/unpacking for now
+   -- maybe we'll later extract the functions from the 5.3 string
+   -- library for greater compatiblity, but it uses the 5.3 buffer API
+   -- which cannot easily be backported to Lua 5.1.
+   local ok, struct = pcall(require, "struct")
+   if ok then
+      string.pack = struct.pack
+      string.packsize = struct.size
+      string.unpack = struct.unpack
+   end
+
+end
+