Hexdump in Lua

hexdump.lua

-- Hexdump the input data using the same style as 'hexdump -C'.
-- Supports Lua 5.1 and above.
-- Credit: http://lua-users.org/wiki/HexDump
function hexdump(data)
    if type(data) ~= "string" then
        return nil, "expected string type, but given " .. type(data)
    end

    local pieces = {}
    local i = 1

    for byte = 1, #data, 16 do
        local chunk = string.sub(data, byte, byte + 15)
        pieces[i] = string.format("%08x  ", byte - 1)
        i = i + 1
        local n = 0
        chunk:gsub(".", function (c)
            pieces[i] = string.format("%02x ", string.byte(c))
            i = i + 1
            n = n + 1
            if n == 8 then
                pieces[i] = " "
                i = i + 1
            end
        end)
        if n < 8 then
            pieces[i] = " "
            i = i + 1
        end
        pieces[i] = string.rep(" ", 3 * (16 - #chunk))
        i = i + 1
        pieces[i] = " |" .. chunk:gsub("[^%w%p ]", ".") .. "|\n"
        i = i + 1
    end

    pieces[i] = string.format("%08x", #data)  -- no '\n' at the end

    return table.concat(pieces)
end

Example:

-- Test
-- NOTE: escape sequence \ddd, where ddd is a sequence of up to three *decimal* digits.
--       (from: Lua Reference Manual: Lexical Conventions)
local data = "hello world\nyo\3\0045\02042\200\255 ho\0"
print(hexdump(data))

Output:

00000000  68 65 6c 6c 6f 20 77 6f  72 6c 64 0a 79 6f 03 04  |hello world.yo..|
00000010  35 14 34 32 c8 ff 20 68  6f 00                    |5.42.. ho.|
0000001a