Re: State of Lua and GNU gettext?

["J.Jørgen von Bargen" <jjvb.primus@...>]

Am 25.03.2010 13:47, schrieb Dinu Gherman:
> So I did some research (including archives of this list) to find out
> if Lua supported GNU gettext which I think can safely be considered
> a standard which is backed by many tools. Unfortunately, I haven't
> found a definitive conclusion other than GNU gettext not supporting
> Lua and Lua not providing standard tools for handling gettext files
> (.pot/.po/.mo).
At least I can provide a little function, I'm using.
It loads an mo-file and returns a lua table (or nil + an error message).
Feedback and suggestions are welcome.
Regards J.Jørgen von Bargen
---8<---snip---8<---snip---8<---snip---8<---snip---8<---snip---8<---snip---8<---snip---8<---snip

-----------------------------------------------------------
-- load an mo file and return a lua table
-- @param mo_file name of the file to load
-- @return table on success
-- @return nil,string on failure
-- @copyright J.Jørgen von Bargen
-- @licence I provide this as public domain
-- @see http://www.gnu.org/software/hello/manual/gettext/MO-Files.html
-----------------------------------------------------------

function load_mo_file(mo_file)
    --------------------------------
    -- open file and read data
    --------------------------------
    local fd,err=io.open(mo_file,"rb")
    if not fd then return nil,err end
    local mo_data=fd:read("*all")
    fd:close()

    --------------------------------
    -- precache some functions
    --------------------------------
    local byte=string.byte
    local sub=string.sub

    --------------------------------
    -- check format
    --------------------------------
    local peek_long --localize
    local magic=sub(mo_data,1,4)
    -- intel magic 0xde120495
    if magic=="\222\018\004\149" then
        peek_long=function(offs)
            local a,b,c,d=byte(mo_data,offs+1,offs+4)
            return ((d*256+c)*256+b)*256+a
        end
    -- motorola magic = 0x950412de
    elseif magic=="\149\004\018\222" then
        peek_long=function(offs)
            local a,b,c,d=byte(mo_data,offs+1,offs+4)
            return ((a*256+b)*256+c)*256+d
        end
    else
        return nil,"no valid mo-file"
    end

    --------------------------------
    -- version
    --------------------------------
    local V=peek_long(4)
    if V~=0 then
        return nul,"unsupported version"
    end

    ------------------------------
    -- get number of offsets of table
    ------------------------------
    local N,O,T=peek_long(8),peek_long(12),peek_long(16)
    ------------------------------
    -- traverse and get strings
    ------------------------------
    local hash={}
    for nstr=1,N do
        local ol,oo=peek_long(O),peek_long(O+4) O=O+8
        local tl,to=peek_long(T),peek_long(T+4) T=T+8
        hash[sub(mo_data,oo+1,oo+ol)]=sub(mo_data,to+1,to+tl)
    end
    return hash    -- return table
end
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usage:

    local mo_data=assert(load_mo_file("appl.mo"))
    print(mo_data["again"])
   -- nochmal
    print(mo_data["nixda"])
   -- nil

You could also change "return hash" to

    return function(text)
        return hash[text] or text
    end

then you'll get a kind of gettext function

    local gettext=assert(load_mo_file("appl.mo"))
    print(gettext"again")
   -- nochmal
    print(gettext"nixda")
    -- nixda

with a slight modification this will be ready-to-use for the xgettext tool:

    _=assert(load_mo_file("appl.mo"))
    print(_("again"))
    print(_("nixda"))