if not modules then modules = { } end modules ['l-io'] = {
    version   = 1.001,
    comment   = "companion to luat-lib.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

local io = io
local byte, find, gsub, format = string.byte, string.find, string.gsub, string.format
local concat = table.concat
local type = type

if string.find(os.getenv("PATH"),";") then
    io.fileseparator, io.pathseparator = "\\", ";"
else
    io.fileseparator, io.pathseparator = "/" , ":"
end

function io.loaddata(filename,textmode) -- return nil if empty
    local f = io.open(filename,(textmode and 'r') or 'rb')
    if f then
        local data = f:read('*all')
        f:close()
        if #data > 0 then
            return data
        end
    end
end

function io.savedata(filename,data,joiner)
    local f = io.open(filename,"wb")
    if f then
        if type(data) == "table" then
            f:write(concat(data,joiner or ""))
        elseif type(data) == "function" then
            data(f)
        else
            f:write(data or "")
        end
        f:close()
        io.flush()
        return true
    else
        return false
    end
end

function io.loadlines(filename,n) -- return nil if empty
    local f = io.open(filename,'r')
    if f then
        if n then
            local lines = { }
            for i=1,n do
                local line = f:read("*lines")
                if line then
                    lines[#lines+1] = line
                else
                    break
                end
            end
            f:close()
            lines = concat(lines,"\n")
            if #lines > 0 then
                return lines
            end
        else
            local line = f:read("*line") or ""
            assert(f:close())
            if #line > 0 then
                return line
            end
        end
    end
end

function io.loadchunk(filename,n)
    local f = io.open(filename,'rb')
    if f then
        local data = f:read(n or 1024)
        f:close()
        if #data > 0 then
            return data
        end
    end
end

function io.exists(filename)
    local f = io.open(filename)
    if f == nil then
        return false
    else
        assert(f:close())
        return true
    end
end

function io.size(filename)
    local f = io.open(filename)
    if f == nil then
        return 0
    else
        local s = f:seek("end")
        assert(f:close())
        return s
    end
end

function io.noflines(f)
    if type(f) == "string" then
        local f = io.open(filename)
        local n = f and io.noflines(f) or 0
        assert(f:close())
        return n
    else
        local n = 0
        for _ in f:lines() do
            n = n + 1
        end
        f:seek('set',0)
        return n
    end
end

local nextchar = {
    [ 4] = function(f)
        return f:read(1,1,1,1)
    end,
    [ 2] = function(f)
        return f:read(1,1)
    end,
    [ 1] = function(f)
        return f:read(1)
    end,
    [-2] = function(f)
        local a, b = f:read(1,1)
        return b, a
    end,
    [-4] = function(f)
        local a, b, c, d = f:read(1,1,1,1)
        return d, c, b, a
    end
}

function io.characters(f,n)
    if f then
        return nextchar[n or 1], f
    end
end

local nextbyte = {
    [4] = function(f)
        local a, b, c, d = f:read(1,1,1,1)
        if d then
            return byte(a), byte(b), byte(c), byte(d)
        end
    end,
    [3] = function(f)
        local a, b, c = f:read(1,1,1)
        if b then
            return byte(a), byte(b), byte(c)
        end
    end,
    [2] = function(f)
        local a, b = f:read(1,1)
        if b then
            return byte(a), byte(b)
        end
    end,
    [1] = function (f)
        local a = f:read(1)
        if a then
            return byte(a)
        end
    end,
    [-2] = function (f)
        local a, b = f:read(1,1)
        if b then
            return byte(b), byte(a)
        end
    end,
    [-3] = function(f)
        local a, b, c = f:read(1,1,1)
        if b then
            return byte(c), byte(b), byte(a)
        end
    end,
    [-4] = function(f)
        local a, b, c, d = f:read(1,1,1,1)
        if d then
            return byte(d), byte(c), byte(b), byte(a)
        end
    end
}

function io.bytes(f,n)
    if f then
        return nextbyte[n or 1], f
    else
        return nil, nil
    end
end

function io.ask(question,default,options)
    while true do
        io.write(question)
        if options then
            io.write(format(" [%s]",concat(options,"|")))
        end
        if default then
            io.write(format(" [%s]",default))
        end
        io.write(format(" "))
        io.flush()
        local answer = io.read()
        answer = gsub(answer,"^%s*(.*)%s*$","%1")
        if answer == "" and default then
            return default
        elseif not options then
            return answer
        else
            for k=1,#options do
                if options[k] == answer then
                    return answer
                end
            end
            local pattern = "^" .. answer
            for k=1,#options do
                local v = options[k]
                if find(v,pattern) then
                    return v
                end
            end
        end
    end
end