Handle special characters in lua file path (umlauts) - lua

Question

I have a small lua function to check if a file exists
function file_exists( filePath )
local handler = io.open( filePath )
if handler then
io.close( handler )
return true
end
return false
end
However, this will always return false when the file path contains special chars such as German umlauts (äöü). Is there any way around this?
Thanks a lot!

Answer 1

utf8_to_cp1252 = (
function(cp1252_description)
local unicode_to_1252 = {}
for code, unicode in cp1252_description:gmatch'\n0x(%x%x)%s+0x(%x+)' do
unicode_to_1252[tonumber(unicode, 16)] = tonumber(code, 16)
end
local undefined = ('?'):byte()
return
function (utf8str)
local pos, result = 1, {}
while pos <= #utf8str do
local code, size = utf8str:byte(pos, pos), 1
if code >= 0xC0 and code < 0xFE then
local mask = 64
code = code - 128
repeat
local next_byte = utf8str:byte(pos+size, pos+size) or 0
if next_byte >= 0x80 and next_byte < 0xC0 then
code, size = (code - mask - 2) * 64 + next_byte, size+1
else
code, size = utf8str:byte(pos, pos), 1
end
mask = mask * 32
until code < mask
end
pos = pos + size
table.insert(result,
string.char(unicode_to_1252[code] or undefined))
end
return table.concat(result)
end
end
)[[
download
http://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP1252.TXT
and insert the whole text here:
#
# Name: cp1252 to Unicode table
# Unicode version: 2.0
# Table version: 2.01
..................................
0xFD 0x00FD #LATIN SMALL LETTER Y WITH ACUTE
0xFE 0x00FE #LATIN SMALL LETTER THORN
0xFF 0x00FF #LATIN SMALL LETTER Y WITH DIAERESIS
]]
Usage:
cp1252_filename = utf8_to_cp1252(your_utf8_filename)
Now you can use cp1252_filename to invoke io.open(), os.rename(), os.execute() and other functions from standard Lua library.

Answer 2

Lua and its tiny standard library is platform neutral and is not aware of correct Windows functions to read full unicode names. You can use winapi module to get some Windows-specific functions for this task. Note that it requires short name generation to be enabled on target disk.
local handler = io.open( winapi.short_path(filePath) )
if handler then
-- etc
end
It can also be easily installed through LuaRocks: luarocks install winapi.