commit 89969e280953870e1a04d8a9985b32cd5c256006
Author: Cosmin Apreutesei <cosmin.apreutesei@gmail.com>
Date:   Thu Apr 29 22:24:55 2021 +0300

    unimportant

diff --git a/mysql_client.lua b/mysql_client.lua
new file mode 100644
index 0000000..0f63969
--- /dev/null
+++ b/mysql_client.lua
@@ -0,0 +1,948 @@
+-- Copyright (C) Yichun Zhang (agentzh)
+
+local tcp = require'sock'.tcp
+local sha1 = require'sha1'
+local bit = require'bit'
+
+local sub = string.sub
+local strbyte = string.byte
+local strchar = string.char
+local strfind = string.find
+local format = string.format
+local strrep = string.rep
+local null = function() end
+local band = bit.band
+local bxor = bit.bxor
+local bor = bit.bor
+local lshift = bit.lshift
+local rshift = bit.rshift
+local tohex = bit.tohex
+local concat = table.concat
+local unpack = unpack
+local setmetatable = setmetatable
+local error = error
+local tonumber = tonumber
+
+local ok, new_tab = pcall(require, 'table.new')
+if not ok then
+    new_tab = function (narr, nrec) return {} end
+end
+
+local _M = { _VERSION = '0.21' }
+
+
+-- constants
+
+local STATE_CONNECTED = 1
+local STATE_COMMAND_SENT = 2
+
+local COM_QUIT = 0x01
+local COM_QUERY = 0x03
+local CLIENT_SSL = 0x0800
+
+local SERVER_MORE_RESULTS_EXISTS = 8
+
+-- 16MB - 1, the default max allowed packet size used by libmysqlclient
+local FULL_PACKET_SIZE = 16777215
+
+-- the following charset map is generated from the following mysql query:
+--   SELECT CHARACTER_SET_NAME, ID
+--   FROM information_schema.collations
+--   WHERE IS_DEFAULT = 'Yes' ORDER BY id;
+local CHARSET_MAP = {
+    _default  = 0,
+    big5      = 1,
+    dec8      = 3,
+    cp850     = 4,
+    hp8       = 6,
+    koi8r     = 7,
+    latin1    = 8,
+    latin2    = 9,
+    swe7      = 10,
+    ascii     = 11,
+    ujis      = 12,
+    sjis      = 13,
+    hebrew    = 16,
+    tis620    = 18,
+    euckr     = 19,
+    koi8u     = 22,
+    gb2312    = 24,
+    greek     = 25,
+    cp1250    = 26,
+    gbk       = 28,
+    latin5    = 30,
+    armscii8  = 32,
+    utf8      = 33,
+    ucs2      = 35,
+    cp866     = 36,
+    keybcs2   = 37,
+    macce     = 38,
+    macroman  = 39,
+    cp852     = 40,
+    latin7    = 41,
+    utf8mb4   = 45,
+    cp1251    = 51,
+    utf16     = 54,
+    utf16le   = 56,
+    cp1256    = 57,
+    cp1257    = 59,
+    utf32     = 60,
+    binary    = 63,
+    geostd8   = 92,
+    cp932     = 95,
+    eucjpms   = 97,
+    gb18030   = 248
+}
+
+local mt = { __index = _M }
+
+
+-- mysql field value type converters
+local converters = new_tab(0, 9)
+
+for i = 0x01, 0x05 do
+    -- tiny, short, long, float, double
+    converters[i] = tonumber
+end
+converters[0x00] = tonumber  -- decimal
+-- converters[0x08] = tonumber  -- long long
+converters[0x09] = tonumber  -- int24
+converters[0x0d] = tonumber  -- year
+converters[0xf6] = tonumber  -- newdecimal
+
+
+local function _get_byte2(data, i)
+    local a, b = strbyte(data, i, i + 1)
+    return bor(a, lshift(b, 8)), i + 2
+end
+
+
+local function _get_byte3(data, i)
+    local a, b, c = strbyte(data, i, i + 2)
+    return bor(a, lshift(b, 8), lshift(c, 16)), i + 3
+end
+
+
+local function _get_byte4(data, i)
+    local a, b, c, d = strbyte(data, i, i + 3)
+    return bor(a, lshift(b, 8), lshift(c, 16), lshift(d, 24)), i + 4
+end
+
+
+local function _get_byte8(data, i)
+    local a, b, c, d, e, f, g, h = strbyte(data, i, i + 7)
+
+    -- XXX workaround for the lack of 64-bit support in bitop:
+    local lo = bor(a, lshift(b, 8), lshift(c, 16), lshift(d, 24))
+    local hi = bor(e, lshift(f, 8), lshift(g, 16), lshift(h, 24))
+    return lo + hi * 4294967296, i + 8
+
+    -- return bor(a, lshift(b, 8), lshift(c, 16), lshift(d, 24), lshift(e, 32),
+               -- lshift(f, 40), lshift(g, 48), lshift(h, 56)), i + 8
+end
+
+
+local function _set_byte2(n)
+    return strchar(band(n, 0xff), band(rshift(n, 8), 0xff))
+end
+
+
+local function _set_byte3(n)
+    return strchar(band(n, 0xff),
+                   band(rshift(n, 8), 0xff),
+                   band(rshift(n, 16), 0xff))
+end
+
+
+local function _set_byte4(n)
+    return strchar(band(n, 0xff),
+                   band(rshift(n, 8), 0xff),
+                   band(rshift(n, 16), 0xff),
+                   band(rshift(n, 24), 0xff))
+end
+
+
+local function _from_cstring(data, i)
+    local last = strfind(data, "\0", i, true)
+    if not last then
+        return nil, nil
+    end
+
+    return sub(data, i, last - 1), last + 1
+end
+
+
+local function _to_cstring(data)
+    return data .. "\0"
+end
+
+
+local function _to_binary_coded_string(data)
+    return strchar(#data) .. data
+end
+
+
+local function _dump(data)
+    local len = #data
+    local bytes = new_tab(len, 0)
+    for i = 1, len do
+        bytes[i] = format("%x", strbyte(data, i))
+    end
+    return concat(bytes, " ")
+end
+
+
+local function _dumphex(data)
+    local len = #data
+    local bytes = new_tab(len, 0)
+    for i = 1, len do
+        bytes[i] = tohex(strbyte(data, i), 2)
+    end
+    return concat(bytes, " ")
+end
+
+
+local function _compute_token(password, scramble)
+    if password == "" then
+        return ""
+    end
+
+    local stage1 = sha1(password)
+    local stage2 = sha1(stage1)
+    local stage3 = sha1(scramble .. stage2)
+    local n = #stage1
+    local bytes = new_tab(n, 0)
+    for i = 1, n do
+         bytes[i] = strchar(bxor(strbyte(stage3, i), strbyte(stage1, i)))
+    end
+
+    return concat(bytes)
+end
+
+
+local function _send_packet(self, req, size)
+    local sock = self.sock
+
+    self.packet_no = self.packet_no + 1
+
+    -- print("packet no: ", self.packet_no)
+
+    local packet = _set_byte3(size) .. strchar(band(self.packet_no, 255)) .. req
+
+    -- print("sending packet: ", _dump(packet))
+
+    -- print("sending packet... of size " .. #packet)
+
+    return sock:send(packet)
+end
+
+
+local function _recv_packet(self)
+    local sock = self.sock
+
+    local data, err = sock:receive(4) -- packet header
+    if not data then
+        return nil, nil, "failed to receive packet header: " .. err
+    end
+
+    --print("packet header: ", _dump(data))
+
+    local len, pos = _get_byte3(data, 1)
+
+    --print("packet length: ", len)
+
+    if len == 0 then
+        return nil, nil, "empty packet"
+    end
+
+    if len > self._max_packet_size then
+        return nil, nil, "packet size too big: " .. len
+    end
+
+    local num = strbyte(data, pos)
+
+    --print("recv packet: packet no: ", num)
+
+    self.packet_no = num
+
+    data, err = sock:receive(len)
+
+    --print("receive returned")
+
+    if not data then
+        return nil, nil, "failed to read packet content: " .. err
+    end
+
+    --print("packet content: ", _dump(data))
+    --print("packet content (ascii): ", data)
+
+    local field_count = strbyte(data, 1)
+
+    local typ
+    if field_count == 0x00 then
+        typ = "OK"
+    elseif field_count == 0xff then
+        typ = "ERR"
+    elseif field_count == 0xfe then
+        typ = "EOF"
+    else
+        typ = "DATA"
+    end
+
+    return data, typ
+end
+
+
+local function _from_length_coded_bin(data, pos)
+    local first = strbyte(data, pos)
+
+    --print("LCB: first: ", first)
+
+    if not first then
+        return nil, pos
+    end
+
+    if first >= 0 and first <= 250 then
+        return first, pos + 1
+    end
+
+    if first == 251 then
+        return null, pos + 1
+    end
+
+    if first == 252 then
+        pos = pos + 1
+        return _get_byte2(data, pos)
+    end
+
+    if first == 253 then
+        pos = pos + 1
+        return _get_byte3(data, pos)
+    end
+
+    if first == 254 then
+        pos = pos + 1
+        return _get_byte8(data, pos)
+    end
+
+    return nil, pos + 1
+end
+
+
+local function _from_length_coded_str(data, pos)
+    local len
+    len, pos = _from_length_coded_bin(data, pos)
+    if not len or len == null then
+        return null, pos
+    end
+
+    return sub(data, pos, pos + len - 1), pos + len
+end
+
+
+local function _parse_ok_packet(packet)
+    local res = new_tab(0, 5)
+    local pos
+
+    res.affected_rows, pos = _from_length_coded_bin(packet, 2)
+
+    --print("affected rows: ", res.affected_rows, ", pos:", pos)
+
+    res.insert_id, pos = _from_length_coded_bin(packet, pos)
+
+    --print("insert id: ", res.insert_id, ", pos:", pos)
+
+    res.server_status, pos = _get_byte2(packet, pos)
+
+    --print("server status: ", res.server_status, ", pos:", pos)
+
+    res.warning_count, pos = _get_byte2(packet, pos)
+
+    --print("warning count: ", res.warning_count, ", pos: ", pos)
+
+    local message = _from_length_coded_str(packet, pos)
+    if message and message ~= null then
+        res.message = message
+    end
+
+    --print("message: ", res.message, ", pos:", pos)
+
+    return res
+end
+
+
+local function _parse_eof_packet(packet)
+    local pos = 2
+
+    local warning_count, pos = _get_byte2(packet, pos)
+    local status_flags = _get_byte2(packet, pos)
+
+    return warning_count, status_flags
+end
+
+
+local function _parse_err_packet(packet)
+    local errno, pos = _get_byte2(packet, 2)
+    local marker = sub(packet, pos, pos)
+    local sqlstate
+    if marker == '#' then
+        -- with sqlstate
+        pos = pos + 1
+        sqlstate = sub(packet, pos, pos + 5 - 1)
+        pos = pos + 5
+    end
+
+    local message = sub(packet, pos)
+    return errno, message, sqlstate
+end
+
+
+local function _parse_result_set_header_packet(packet)
+    local field_count, pos = _from_length_coded_bin(packet, 1)
+
+    local extra
+    extra = _from_length_coded_bin(packet, pos)
+
+    return field_count, extra
+end
+
+local NOT_NULL_FLAG       = 1
+local PRI_KEY_FLAG        = 2
+local UNIQUE_KEY_FLAG     = 4
+local UNSIGNED_FLAG       = 32
+local AUTO_INCREMENT_FLAG = 512
+
+local function _parse_field_packet(data)
+    local col = new_tab(0, 2)
+    local pos
+    col.catalog, pos = _from_length_coded_str(data, 1)
+    col.db, pos = _from_length_coded_str(data, pos)
+    col.table, pos = _from_length_coded_str(data, pos)
+    col.orig_table, pos = _from_length_coded_str(data, pos)
+    col.name, pos = _from_length_coded_str(data, pos)
+    col.orig_name, pos = _from_length_coded_str(data, pos)
+    pos = pos + 1 -- ignore the filler
+    col.charsetnr, pos = _get_byte2(data, pos)
+    col.length, pos = _get_byte4(data, pos)
+    col.type = strbyte(data, pos)
+    pos = pos + 1
+    col.flags, pos = _get_byte2(data, pos)
+    col.allow_null     = band(col.flags, NOT_NULL_FLAG) == 0
+    col.pri_key        = band(col.flags, PRI_KEY_FLAG) ~= 0
+    col.unique_key     = band(col.flags, UNIQUE_KEY_FLAG) ~= 0
+    col.unsigned       = band(col.flags, UNSIGNED_FLAG) ~= 0
+    col.auto_increment = band(col.flags, AUTO_INCREMENT_FLAG) ~= 0
+    col.decimals = strbyte(data, pos)
+    pos = pos + 1
+    local default = sub(data, pos + 2)
+    if default and default ~= "" then
+        col.default = default
+    end
+    return col
+end
+
+
+local function _parse_row_data_packet(data, cols, compact)
+    local pos = 1
+    local ncols = #cols
+    local row
+    if compact then
+        row = new_tab(ncols, 0)
+    else
+        row = new_tab(0, ncols)
+    end
+    for i = 1, ncols do
+        local value
+        value, pos = _from_length_coded_str(data, pos)
+        local col = cols[i]
+        local typ = col.type
+        local name = col.name
+
+        --print("row field value: ", value, ", type: ", typ)
+
+        if value ~= null then
+            local conv = converters[typ]
+            if conv then
+                value = conv(value)
+            end
+        end
+
+        if compact then
+            row[i] = value
+        elseif value ~= null then
+            row[name] = value
+        end
+    end
+
+    return row
+end
+
+
+local function _recv_field_packet(self)
+    local packet, typ, err = _recv_packet(self)
+    if not packet then
+        return nil, err
+    end
+
+    if typ == "ERR" then
+        local errno, msg, sqlstate = _parse_err_packet(packet)
+        return nil, msg, errno, sqlstate
+    end
+
+    if typ ~= 'DATA' then
+        return nil, "bad field packet type: " .. typ
+    end
+
+    -- typ == 'DATA'
+
+    return _parse_field_packet(packet)
+end
+
+
+function _M.new(self)
+    local sock, err = tcp()
+    if not sock then
+        return nil, err
+    end
+    return setmetatable({ sock = sock }, mt)
+end
+
+
+function _M.set_timeout(self, timeout)
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    return sock:settimeout(timeout)
+end
+
+
+function _M.connect(self, opts)
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    local max_packet_size = opts.max_packet_size
+    if not max_packet_size then
+        max_packet_size = 1024 * 1024 -- default 1 MB
+    end
+    self._max_packet_size = max_packet_size
+
+    local ok, err
+
+    self.compact = opts.compact_arrays
+
+    local database = opts.database or ""
+    local user = opts.user or ""
+
+    local charset = CHARSET_MAP[opts.charset or "_default"]
+    if not charset then
+        return nil, "charset '" .. opts.charset .. "' is not supported"
+    end
+
+    local pool = opts.pool
+
+    local host = opts.host
+    if host then
+        local port = opts.port or 3306
+        if not pool then
+            pool = user .. ":" .. database .. ":" .. host .. ":" .. port
+        end
+
+        ok, err = sock:connect(host, port, { pool = pool })
+
+    else
+        local path = opts.path
+        if not path then
+            return nil, 'neither "host" nor "path" options are specified'
+        end
+
+        if not pool then
+            pool = user .. ":" .. database .. ":" .. path
+        end
+
+        ok, err = sock:connect("unix:" .. path, { pool = pool })
+    end
+
+    if not ok then
+        return nil, 'failed to connect: ' .. err
+    end
+
+    local reused = sock:getreusedtimes()
+
+    if reused and reused > 0 then
+        self.state = STATE_CONNECTED
+        return 1
+    end
+
+    local packet, typ, err = _recv_packet(self)
+    if not packet then
+        return nil, err
+    end
+
+    if typ == "ERR" then
+        local errno, msg, sqlstate = _parse_err_packet(packet)
+        return nil, msg, errno, sqlstate
+    end
+
+    self.protocol_ver = strbyte(packet)
+
+    --print("protocol version: ", self.protocol_ver)
+
+    local server_ver, pos = _from_cstring(packet, 2)
+    if not server_ver then
+        return nil, "bad handshake initialization packet: bad server version"
+    end
+
+    --print("server version: ", server_ver)
+
+    self._server_ver = server_ver
+
+    local thread_id, pos = _get_byte4(packet, pos)
+
+    --print("thread id: ", thread_id)
+
+    local scramble = sub(packet, pos, pos + 8 - 1)
+    if not scramble then
+        return nil, "1st part of scramble not found"
+    end
+
+    pos = pos + 9 -- skip filler
+
+    -- two lower bytes
+    local capabilities  -- server capabilities
+    capabilities, pos = _get_byte2(packet, pos)
+
+    -- print(format("server capabilities: %#x", capabilities))
+
+    self._server_lang = strbyte(packet, pos)
+    pos = pos + 1
+
+    --print("server lang: ", self._server_lang)
+
+    self._server_status, pos = _get_byte2(packet, pos)
+
+    --print("server status: ", self._server_status)
+
+    local more_capabilities
+    more_capabilities, pos = _get_byte2(packet, pos)
+
+    capabilities = bor(capabilities, lshift(more_capabilities, 16))
+
+    --print("server capabilities: ", capabilities)
+
+    -- local len = strbyte(packet, pos)
+    local len = 21 - 8 - 1
+
+    --print("scramble len: ", len)
+
+    pos = pos + 1 + 10
+
+    local scramble_part2 = sub(packet, pos, pos + len - 1)
+    if not scramble_part2 then
+        return nil, "2nd part of scramble not found"
+    end
+
+    scramble = scramble .. scramble_part2
+    --print("scramble: ", _dump(scramble))
+
+    local client_flags = 0x3f7cf;
+
+    local ssl_verify = opts.ssl_verify
+    local use_ssl = opts.ssl or ssl_verify
+
+    if use_ssl then
+        if band(capabilities, CLIENT_SSL) == 0 then
+            return nil, "ssl disabled on server"
+        end
+
+        -- send a SSL Request Packet
+        local req = _set_byte4(bor(client_flags, CLIENT_SSL))
+                    .. _set_byte4(self._max_packet_size)
+                    .. strchar(charset)
+                    .. strrep("\0", 23)
+
+        local packet_len = 4 + 4 + 1 + 23
+        local bytes, err = _send_packet(self, req, packet_len)
+        if not bytes then
+            return nil, "failed to send client authentication packet: " .. err
+        end
+
+        local ok, err = sock:sslhandshake(false, nil, ssl_verify)
+        if not ok then
+            return nil, "failed to do ssl handshake: " .. (err or "")
+        end
+    end
+
+    local password = opts.password or ""
+
+    local token = _compute_token(password, scramble)
+
+    --print("token: ", _dump(token))
+
+    local req = _set_byte4(client_flags)
+                .. _set_byte4(self._max_packet_size)
+                .. strchar(charset)
+                .. strrep("\0", 23)
+                .. _to_cstring(user)
+                .. _to_binary_coded_string(token)
+                .. _to_cstring(database)
+
+    local packet_len = 4 + 4 + 1 + 23 + #user + 1
+        + #token + 1 + #database + 1
+
+    -- print("packet content length: ", packet_len)
+    -- print("packet content: ", _dump(concat(req, "")))
+
+    local bytes, err = _send_packet(self, req, packet_len)
+    if not bytes then
+        return nil, "failed to send client authentication packet: " .. err
+    end
+
+    --print("packet sent ", bytes, " bytes")
+
+    local packet, typ, err = _recv_packet(self)
+    if not packet then
+        return nil, "failed to receive the result packet: " .. err
+    end
+
+    if typ == 'ERR' then
+        local errno, msg, sqlstate = _parse_err_packet(packet)
+        return nil, msg, errno, sqlstate
+    end
+
+    if typ == 'EOF' then
+        return nil, "old pre-4.1 authentication protocol not supported"
+    end
+
+    if typ ~= 'OK' then
+        return nil, "bad packet type: " .. typ
+    end
+
+    self.state = STATE_CONNECTED
+
+    return 1
+end
+
+
+function _M.set_keepalive(self, ...)
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    if self.state ~= STATE_CONNECTED then
+        return nil, "cannot be reused in the current connection state: "
+                    .. (self.state or "nil")
+    end
+
+    self.state = nil
+    return sock:setkeepalive(...)
+end
+
+
+function _M.get_reused_times(self)
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    return sock:getreusedtimes()
+end
+
+
+function _M.close(self)
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    self.state = nil
+
+    local bytes, err = _send_packet(self, strchar(COM_QUIT), 1)
+    if not bytes then
+        return nil, err
+    end
+
+    return sock:close()
+end
+
+
+function _M.server_ver(self)
+    return self._server_ver
+end
+
+
+local function send_query(self, query)
+    if self.state ~= STATE_CONNECTED then
+        return nil, "cannot send query in the current context: "
+                    .. (self.state or "nil")
+    end
+
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    self.packet_no = -1
+
+    local cmd_packet = strchar(COM_QUERY) .. query
+    local packet_len = 1 + #query
+
+    local bytes, err = _send_packet(self, cmd_packet, packet_len)
+    if not bytes then
+        return nil, err
+    end
+
+    self.state = STATE_COMMAND_SENT
+
+    --print("packet sent ", bytes, " bytes")
+
+    return bytes
+end
+_M.send_query = send_query
+
+
+local function read_result(self, est_nrows)
+    if self.state ~= STATE_COMMAND_SENT then
+        return nil, "cannot read result in the current context: "
+                    .. (self.state or "nil")
+    end
+
+    local sock = self.sock
+    if not sock then
+        return nil, "not initialized"
+    end
+
+    local packet, typ, err = _recv_packet(self)
+    if not packet then
+        return nil, err
+    end
+
+    if typ == "ERR" then
+        self.state = STATE_CONNECTED
+
+        local errno, msg, sqlstate = _parse_err_packet(packet)
+        return nil, msg, errno, sqlstate
+    end
+
+    if typ == 'OK' then
+        local res = _parse_ok_packet(packet)
+        if res and band(res.server_status, SERVER_MORE_RESULTS_EXISTS) ~= 0 then
+            return res, "again"
+        end
+
+        self.state = STATE_CONNECTED
+        return res
+    end
+
+    if typ ~= 'DATA' then
+        self.state = STATE_CONNECTED
+
+        return nil, "packet type " .. typ .. " not supported"
+    end
+
+    -- typ == 'DATA'
+
+    --print("read the result set header packet")
+
+    local field_count, extra = _parse_result_set_header_packet(packet)
+
+    --print("field count: ", field_count)
+
+    local cols = new_tab(field_count, 0)
+    for i = 1, field_count do
+        local col, err, errno, sqlstate = _recv_field_packet(self)
+        if not col then
+            return nil, err, errno, sqlstate
+        end
+
+        cols[i] = col
+    end
+
+    local packet, typ, err = _recv_packet(self)
+    if not packet then
+        return nil, err
+    end
+
+    if typ ~= 'EOF' then
+        return nil, "unexpected packet type " .. typ .. " while eof packet is "
+            .. "expected"
+    end
+
+    -- typ == 'EOF'
+
+    local compact = self.compact
+
+    local rows = new_tab(est_nrows or 4, 0)
+    local i = 0
+    while true do
+        --print("reading a row")
+
+        packet, typ, err = _recv_packet(self)
+        if not packet then
+            return nil, err
+        end
+
+        if typ == 'EOF' then
+            local warning_count, status_flags = _parse_eof_packet(packet)
+
+            --print("status flags: ", status_flags)
+
+            if band(status_flags, SERVER_MORE_RESULTS_EXISTS) ~= 0 then
+                return rows, "again", cols
+            end
+
+            break
+        end
+
+        -- if typ ~= 'DATA' then
+            -- return nil, 'bad row packet type: ' .. typ
+        -- end
+
+        -- typ == 'DATA'
+
+        local row = _parse_row_data_packet(packet, cols, compact)
+        i = i + 1
+        rows[i] = row
+    end
+
+    self.state = STATE_CONNECTED
+
+    return rows, nil, cols
+end
+_M.read_result = read_result
+
+
+function _M.query(self, query, est_nrows)
+    local bytes, err = send_query(self, query)
+    if not bytes then
+        return nil, "failed to send query: " .. err
+    end
+
+    return read_result(self, est_nrows)
+end
+
+
+function _M.set_compact_arrays(self, value)
+    self.compact = value
+end
+
+local qmap = {
+    ['\0' ] = '\\0',
+    ['\b' ] = '\\b',
+    ['\n' ] = '\\n',
+    ['\r' ] = '\\r',
+    ['\t' ] = '\\t',
+    ['\26'] = '\\Z',
+    ['\\' ] = '\\\\',
+    ['\'' ] = '\\\'',
+    ['\"' ] = '\\"',
+}
+function _M.quote(s)
+    return s:gsub('[%z\b\n\r\t\26\\\'\"]', qmap)
+end
+
+return _M