Modul:Homokozó/TG/StringFunctions

Homokozó/TG/StringFunctions[mi ez?] • [dokumentáció: mutat, ] • [tesztek: létrehozás]

-- basic string manipulation functionsww
local StringFunctions = {}

function StringFunctions.trim(str)
    if str.args then
        str = str.args[1]
    end
    if str == nil then
        return nil
    else
        return (str:gsub("^%s*(.-)%s*$", "%1")) -- extra brackets are necessary because gsub returns multiple values
    end
end

-- splits a string into (Unicode) characters
-- returns an iterator
-- behavior is undefined for input which is invalid UTF-8
function StringFunctions.split(str)
    local i, error = 1, false
    return function()
        if error then
            return nil
        end
        local byte = str:byte(i)
        if byte == nil then
            return nil
        end
        
        -- determine number of 1 bits before the first 0 in byte
        local leadBits, bitValue, remainder = 0, 128, byte
        while bitValue <= remainder and bitValue > 1 do
            leadBits = leadBits + 1
            remainder = remainder - bitValue
            bitValue = bitValue / 2
        end
        
        local chr, length -- the next UTF-8 character and its length in bytes
        if leadBits == 0 then -- ASCII character
            length = 1
        elseif leadBits == 1 or leadBits > 6 then -- not valid UTF-8
            error = true
            return '<error(' + i + ':' + byte + ')>'
        else
            length = leadBits
        end
        chr = str:sub(i, i + length - 1)
        i = i + length
        return chr
    end
end

-- UTF-8 aware version of string:len
function StringFunctions.len(str)
    local i = 0
    for c in StringFunctions.split(str) do
        i = i + 1
    end
    return i
end

-- UTF-8 aware version of string:sub
function StringFunctions.sub(str, i, j)
    if i < 0 then
        i = StringFunctions.len(str) + i + 1
    end
    if j and j < 0 then
        j = StringFunctions.len(str) + j + 1
    end
    
    local pos, substr = 0, ''
    for c in StringFunctions.split(str) do
        pos = pos + 1
        if pos >= i and (not j or pos <= j) then
            substr = substr .. c
        end
    end
    return substr
end

return StringFunctions