libs/core/luasrc/util.lua

   1 --[[
   2 LuCI - Utility library
   3
   4 Description:
   5 Several common useful Lua functions
   6
   7 FileId:
   8 $Id$
   9
  10 License:
  11 Copyright 2008 Steven Barth <steven@midlink.org>
  12
  13 Licensed under the Apache License, Version 2.0 (the "License");
  14 you may not use this file except in compliance with the License.
  15 You may obtain a copy of the License at
  16
  17         http://www.apache.org/licenses/LICENSE-2.0
  18
  19 Unless required by applicable law or agreed to in writing, software
  20 distributed under the License is distributed on an "AS IS" BASIS,
  21 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  22 See the License for the specific language governing permissions and
  23 limitations under the License.
  24
  25 ]]--
  26
  27 local io = require "io"
  28 local math = require "math"
  29 local table = require "table"
  30 local debug = require "debug"
  31 local ldebug = require "luci.debug"
  32 local string = require "string"
  33 local coroutine = require "coroutine"
  34
  35 local getmetatable, setmetatable = getmetatable, setmetatable
  36 local rawget, rawset, unpack = rawget, rawset, unpack
  37 local tostring, type, assert = tostring, type, assert
  38 local ipairs, pairs, loadstring = ipairs, pairs, loadstring
  39 local require, pcall, xpcall = require, pcall, xpcall
  40 local collectgarbage, get_memory_limit = collectgarbage, get_memory_limit
  41
  42 --- LuCI utility functions.
  43 module "luci.util"
  44
  45 --
  46 -- Pythonic string formatting extension
  47 --
  48 getmetatable("").__mod = function(a, b)
  49         if not b then
  50                 return a
  51         elseif type(b) == "table" then
  52                 return a:format(unpack(b))
  53         else
  54                 return a:format(b)
  55         end
  56 end
  57
  58
  59 --
  60 -- Class helper routines
  61 --
  62
  63 -- Instantiates a class
  64 local function _instantiate(class, ...)
  65         local inst = setmetatable({}, {__index = class})
  66
  67         if inst.__init__ then
  68                 inst:__init__(...)
  69         end
  70
  71         return inst
  72 end
  73
  74 --- Create a Class object (Python-style object model).
  75 -- The class object can be instantiated by calling itself.
  76 -- Any class functions or shared parameters can be attached to this object.
  77 -- Attaching a table to the class object makes this table shared between
  78 -- all instances of this class. For object parameters use the __init__ function.
  79 -- Classes can inherit member functions and values from a base class.
  80 -- Class can be instantiated by calling them. All parameters will be passed
  81 -- to the __init__ function of this class - if such a function exists.
  82 -- The __init__ function must be used to set any object parameters that are not shared
  83 -- with other objects of this class. Any return values will be ignored.
  84 -- @param base  The base class to inherit from (optional)
  85 -- @return              A class object
  86 -- @see                 instanceof
  87 -- @see                 clone
  88 function class(base)
  89         return setmetatable({}, {
  90                 __call  = _instantiate,
  91                 __index = base
  92         })
  93 end
  94
  95 --- Test whether the given object is an instance of the given class.
  96 -- @param object        Object instance
  97 -- @param class         Class object to test against
  98 -- @return                      Boolean indicating whether the object is an instance
  99 -- @see                         class
 100 -- @see                         clone
 101 function instanceof(object, class)
 102         local meta = getmetatable(object)
 103         while meta and meta.__index do
 104                 if meta.__index == class then
 105                         return true
 106                 end
 107                 meta = getmetatable(meta.__index)
 108         end
 109         return false
 110 end
 111
 112
 113 --
 114 -- Scope manipulation routines
 115 --
 116
 117 --- Create a new or get an already existing thread local store associated with
 118 -- the current active coroutine. A thread local store is private a table object
 119 -- whose values can't be accessed from outside of the running coroutine.
 120 -- @return      Table value representing the corresponding thread local store
 121 function threadlocal()
 122         local tbl = {}
 123
 124         local function get(self, key)
 125                 local c = coroutine.running()
 126                 local thread = coxpt[c] or c or 0
 127                 if not rawget(self, thread) then
 128                         return nil
 129                 end
 130                 return rawget(self, thread)[key]
 131         end
 132
 133         local function set(self, key, value)
 134                 local c = coroutine.running()
 135                 local thread = coxpt[c] or c or 0
 136                 if not rawget(self, thread) then
 137                         rawset(self, thread, {})
 138                 end
 139                 rawget(self, thread)[key] = value
 140         end
 141
 142         setmetatable(tbl, {__index = get, __newindex = set, __mode = "k"})
 143
 144         return tbl
 145 end
 146
 147
 148 --
 149 -- Debugging routines
 150 --
 151
 152 --- Write given object to stderr.
 153 -- @param obj   Value to write to stderr
 154 -- @return              Boolean indicating whether the write operation was successful
 155 function perror(obj)
 156         return io.stderr:write(tostring(obj) .. "\n")
 157 end
 158
 159 --- Recursively dumps a table to stdout, useful for testing and debugging.
 160 -- @param t     Table value to dump
 161 -- @param maxdepth      Maximum depth
 162 -- @return      Always nil
 163 function dumptable(t, maxdepth, i, seen)
 164         i = i or 0
 165         seen = seen or setmetatable({}, {__mode="k"})
 166
 167         for k,v in pairs(t) do
 168                 perror(string.rep("\t", i) .. tostring(k) .. "\t" .. tostring(v))
 169                 if type(v) == "table" and (not maxdepth or i < maxdepth) then
 170                         if not seen[v] then
 171                                 seen[v] = true
 172                                 dumptable(v, maxdepth, i+1, seen)
 173                         else
 174                                 perror(string.rep("\t", i) .. "*** RECURSION ***")
 175                         end
 176                 end
 177         end
 178 end
 179
 180
 181 --
 182 -- String and data manipulation routines
 183 --
 184
 185 --- Escapes all occurrences of the given character in given string.
 186 -- @param s     String value containing unescaped characters
 187 -- @param c     String value with character to escape (optional, defaults to "\")
 188 -- @return      String value with each occurrence of character escaped with "\"
 189 function escape(s, c)
 190         c = c or "\\"
 191         return s:gsub(c, "\\" .. c)
 192 end
 193
 194 --- Create valid XML PCDATA from given string.
 195 -- @param value String value containing the data to escape
 196 -- @return              String value containing the escaped data
 197 local function _pcdata_repl(c)
 198         local i = string.byte(c)
 199
 200         if ( i >= 0x00 and i <= 0x08 ) or ( i >= 0x0B and i <= 0x0C ) or
 201            ( i >= 0x0E and i <= 0x1F ) or ( i == 0x7F )
 202         then
 203                 return ""
 204
 205         elseif ( i == 0x26 ) or ( i == 0x27 ) or ( i == 0x22 ) or
 206                ( i == 0x3C ) or ( i == 0x3E )
 207         then
 208                 return string.format("&#%i;", i)
 209         end
 210
 211         return c
 212 end
 213
 214 function pcdata(value)
 215         return value and tostring(value):gsub("[&\"'<>%c]", _pcdata_repl)
 216 end
 217
 218 --- Strip HTML tags from given string.
 219 -- @param value String containing the HTML text
 220 -- @return      String with HTML tags stripped of
 221 function striptags(s)
 222         return pcdata(s:gsub("</?[A-Za-z][A-Za-z0-9:_%-]*[^>]*>", " "):gsub("%s+", " "))
 223 end
 224
 225 --- Splits given string on a defined separator sequence and return a table
 226 -- containing the resulting substrings. The optional max parameter specifies
 227 -- the number of bytes to process, regardless of the actual length of the given
 228 -- string. The optional last parameter, regex, specifies whether the separator
 229 -- sequence is interpreted as regular expression.
 230 -- @param str           String value containing the data to split up
 231 -- @param pat           String with separator pattern (optional, defaults to "\n")
 232 -- @param max           Maximum times to split (optional)
 233 -- @param regex         Boolean indicating whether to interpret the separator
 234 --                                      pattern as regular expression (optional, default is false)
 235 -- @return                      Table containing the resulting substrings
 236 function split(str, pat, max, regex)
 237         pat = pat or "\n"
 238         max = max or #str
 239
 240         local t = {}
 241         local c = 1
 242
 243         if #str == 0 then
 244                 return {""}
 245         end
 246
 247         if #pat == 0 then
 248                 return nil
 249         end
 250
 251         if max == 0 then
 252                 return str
 253         end
 254
 255         repeat
 256                 local s, e = str:find(pat, c, not regex)
 257                 max = max - 1
 258                 if s and max < 0 then
 259                         t[#t+1] = str:sub(c)
 260                 else
 261                         t[#t+1] = str:sub(c, s and s - 1)
 262                 end
 263                 c = e and e + 1 or #str + 1
 264         until not s or max < 0
 265
 266         return t
 267 end
 268
 269 --- Remove leading and trailing whitespace from given string value.
 270 -- @param str   String value containing whitespace padded data
 271 -- @return              String value with leading and trailing space removed
 272 function trim(str)
 273         return (str:gsub("^%s*(.-)%s*$", "%1"))
 274 end
 275
 276 --- Count the occurences of given substring in given string.
 277 -- @param str           String to search in
 278 -- @param pattern       String containing pattern to find
 279 -- @return                      Number of found occurences
 280 function cmatch(str, pat)
 281         local count = 0
 282         for _ in str:gmatch(pat) do count = count + 1 end
 283         return count
 284 end
 285
 286 --- Parse certain units from the given string and return the canonical integer
 287 -- value or 0 if the unit is unknown. Upper- or lower case is irrelevant.
 288 -- Recognized units are:
 289 --      o "y"   - one year   (60*60*24*366)
 290 --  o "m"       - one month  (60*60*24*31)
 291 --  o "w"       - one week   (60*60*24*7)
 292 --  o "d"       - one day    (60*60*24)
 293 --  o "h"       - one hour       (60*60)
 294 --  o "min"     - one minute (60)
 295 --  o "kb"  - one kilobyte (1024)
 296 --  o "mb"      - one megabyte (1024*1024)
 297 --  o "gb"      - one gigabyte (1024*1024*1024)
 298 --  o "kib" - one si kilobyte (1000)
 299 --  o "mib"     - one si megabyte (1000*1000)
 300 --  o "gib"     - one si gigabyte (1000*1000*1000)
 301 -- @param ustr  String containing a numerical value with trailing unit
 302 -- @return              Number containing the canonical value
 303 function parse_units(ustr)
 304
 305         local val = 0
 306
 307         -- unit map
 308         local map = {
 309                 -- date stuff
 310                 y   = 60 * 60 * 24 * 366,
 311                 m   = 60 * 60 * 24 * 31,
 312                 w   = 60 * 60 * 24 * 7,
 313                 d   = 60 * 60 * 24,
 314                 h   = 60 * 60,
 315                 min = 60,
 316
 317                 -- storage sizes
 318                 kb  = 1024,
 319                 mb  = 1024 * 1024,
 320                 gb  = 1024 * 1024 * 1024,
 321
 322                 -- storage sizes (si)
 323                 kib = 1000,
 324                 mib = 1000 * 1000,
 325                 gib = 1000 * 1000 * 1000
 326         }
 327
 328         -- parse input string
 329         for spec in ustr:lower():gmatch("[0-9%.]+[a-zA-Z]*") do
 330
 331                 local num = spec:gsub("[^0-9%.]+$","")
 332                 local spn = spec:gsub("^[0-9%.]+", "")
 333
 334                 if map[spn] or map[spn:sub(1,1)] then
 335                         val = val + num * ( map[spn] or map[spn:sub(1,1)] )
 336                 else
 337                         val = val + num
 338                 end
 339         end
 340
 341
 342         return val
 343 end
 344
 345 -- also register functions above in the central string class for convenience
 346 string.escape      = escape
 347 string.pcdata      = pcdata
 348 string.striptags   = striptags
 349 string.split       = split
 350 string.trim        = trim
 351 string.cmatch      = cmatch
 352 string.parse_units = parse_units
 353
 354
 355 --- Appends numerically indexed tables or single objects to a given table.
 356 -- @param src   Target table
 357 -- @param ...   Objects to insert
 358 -- @return              Target table
 359 function append(src, ...)
 360         for i, a in ipairs({...}) do
 361                 if type(a) == "table" then
 362                         for j, v in ipairs(a) do
 363                                 src[#src+1] = v
 364                         end
 365                 else
 366                         src[#src+1] = a
 367                 end
 368         end
 369         return src
 370 end
 371
 372 --- Combines two or more numerically indexed tables and single objects into one table.
 373 -- @param tbl1  Table value to combine
 374 -- @param tbl2  Table value to combine
 375 -- @param ...   More tables to combine
 376 -- @return              Table value containing all values of given tables
 377 function combine(...)
 378         return append({}, ...)
 379 end
 380
 381 --- Checks whether the given table contains the given value.
 382 -- @param table Table value
 383 -- @param value Value to search within the given table
 384 -- @return              Boolean indicating whether the given value occurs within table
 385 function contains(table, value)
 386         for k, v in pairs(table) do
 387                 if value == v then
 388                         return k
 389                 end
 390         end
 391         return false
 392 end
 393
 394 --- Update values in given table with the values from the second given table.
 395 -- Both table are - in fact - merged together.
 396 -- @param t                     Table which should be updated
 397 -- @param updates       Table containing the values to update
 398 -- @return                      Always nil
 399 function update(t, updates)
 400         for k, v in pairs(updates) do
 401                 t[k] = v
 402         end
 403 end
 404
 405 --- Retrieve all keys of given associative table.
 406 -- @param t     Table to extract keys from
 407 -- @return      Sorted table containing the keys
 408 function keys(t)
 409         local keys = { }
 410         if t then
 411                 for k, _ in kspairs(t) do
 412                         keys[#keys+1] = k
 413                 end
 414         end
 415         return keys
 416 end
 417
 418 --- Clones the given object and return it's copy.
 419 -- @param object        Table value to clone
 420 -- @param deep          Boolean indicating whether to do recursive cloning
 421 -- @return                      Cloned table value
 422 function clone(object, deep)
 423         local copy = {}
 424
 425         for k, v in pairs(object) do
 426                 if deep and type(v) == "table" then
 427                         v = clone(v, deep)
 428                 end
 429                 copy[k] = v
 430         end
 431
 432         return setmetatable(copy, getmetatable(object))
 433 end
 434
 435
 436 --- Create a dynamic table which automatically creates subtables.
 437 -- @return      Dynamic Table
 438 function dtable()
 439         return setmetatable({}, { __index =
 440                 function(tbl, key)
 441                         return rawget(tbl, key)
 442                          or rawget(rawset(tbl, key, dtable()), key)
 443                 end
 444         })
 445 end
 446
 447
 448 -- Serialize the contents of a table value.
 449 function _serialize_table(t, seen)
 450         assert(not seen[t], "Recursion detected.")
 451         seen[t] = true
 452
 453         local data  = ""
 454         local idata = ""
 455         local ilen  = 0
 456
 457         for k, v in pairs(t) do
 458                 if type(k) ~= "number" or k < 1 or math.floor(k) ~= k or ( k - #t ) > 3 then
 459                         k = serialize_data(k, seen)
 460                         v = serialize_data(v, seen)
 461                         data = data .. ( #data > 0 and ", " or "" ) ..
 462                                 '[' .. k .. '] = ' .. v
 463                 elseif k > ilen then
 464                         ilen = k
 465                 end
 466         end
 467
 468         for i = 1, ilen do
 469                 local v = serialize_data(t[i], seen)
 470                 idata = idata .. ( #idata > 0 and ", " or "" ) .. v
 471         end
 472
 473         return idata .. ( #data > 0 and #idata > 0 and ", " or "" ) .. data
 474 end
 475
 476 --- Recursively serialize given data to lua code, suitable for restoring
 477 -- with loadstring().
 478 -- @param val   Value containing the data to serialize
 479 -- @return              String value containing the serialized code
 480 -- @see                 restore_data
 481 -- @see                 get_bytecode
 482 function serialize_data(val, seen)
 483         seen = seen or setmetatable({}, {__mode="k"})
 484
 485         if val == nil then
 486                 return "nil"
 487         elseif type(val) == "number" then
 488                 return val
 489         elseif type(val) == "string" then
 490                 return "%q" % val
 491         elseif type(val) == "boolean" then
 492                 return val and "true" or "false"
 493         elseif type(val) == "function" then
 494                 return "loadstring(%q)" % get_bytecode(val)
 495         elseif type(val) == "table" then
 496                 return "{ " .. _serialize_table(val, seen) .. " }"
 497         else
 498                 return '"[unhandled data type:' .. type(val) .. ']"'
 499         end
 500 end
 501
 502 --- Restore data previously serialized with serialize_data().
 503 -- @param str   String containing the data to restore
 504 -- @return              Value containing the restored data structure
 505 -- @see                 serialize_data
 506 -- @see                 get_bytecode
 507 function restore_data(str)
 508         return loadstring("return " .. str)()
 509 end
 510
 511
 512 --
 513 -- Byte code manipulation routines
 514 --
 515
 516 --- Return the current runtime bytecode of the given data. The byte code
 517 -- will be stripped before it is returned.
 518 -- @param val   Value to return as bytecode
 519 -- @return              String value containing the bytecode of the given data
 520 function get_bytecode(val)
 521         local code
 522
 523         if type(val) == "function" then
 524                 code = string.dump(val)
 525         else
 526                 code = string.dump( loadstring( "return " .. serialize_data(val) ) )
 527         end
 528
 529         return code and strip_bytecode(code)
 530 end
 531
 532 --- Strips unnescessary lua bytecode from given string. Information like line
 533 -- numbers and debugging numbers will be discarded. Original version by
 534 -- Peter Cawley (http://lua-users.org/lists/lua-l/2008-02/msg01158.html)
 535 -- @param code  String value containing the original lua byte code
 536 -- @return              String value containing the stripped lua byte code
 537 function strip_bytecode(code)
 538         local version, format, endian, int, size, ins, num, lnum = code:byte(5, 12)
 539         local subint
 540         if endian == 1 then
 541                 subint = function(code, i, l)
 542                         local val = 0
 543                         for n = l, 1, -1 do
 544                                 val = val * 256 + code:byte(i + n - 1)
 545                         end
 546                         return val, i + l
 547                 end
 548         else
 549                 subint = function(code, i, l)
 550                         local val = 0
 551                         for n = 1, l, 1 do
 552                                 val = val * 256 + code:byte(i + n - 1)
 553                         end
 554                         return val, i + l
 555                 end
 556         end
 557
 558         local function strip_function(code)
 559                 local count, offset = subint(code, 1, size)
 560                 local stripped = { string.rep("\0", size) }
 561                 local dirty = offset + count
 562                 offset = offset + count + int * 2 + 4
 563                 offset = offset + int + subint(code, offset, int) * ins
 564                 count, offset = subint(code, offset, int)
 565                 for n = 1, count do
 566                         local t
 567                         t, offset = subint(code, offset, 1)
 568                         if t == 1 then
 569                                 offset = offset + 1
 570                         elseif t == 4 then
 571                                 offset = offset + size + subint(code, offset, size)
 572                         elseif t == 3 then
 573                                 offset = offset + num
 574                         elseif t == 254 or t == 9 then
 575                                 offset = offset + lnum
 576                         end
 577                 end
 578                 count, offset = subint(code, offset, int)
 579                 stripped[#stripped+1] = code:sub(dirty, offset - 1)
 580                 for n = 1, count do
 581                         local proto, off = strip_function(code:sub(offset, -1))
 582                         stripped[#stripped+1] = proto
 583                         offset = offset + off - 1
 584                 end
 585                 offset = offset + subint(code, offset, int) * int + int
 586                 count, offset = subint(code, offset, int)
 587                 for n = 1, count do
 588                         offset = offset + subint(code, offset, size) + size + int * 2
 589                 end
 590                 count, offset = subint(code, offset, int)
 591                 for n = 1, count do
 592                         offset = offset + subint(code, offset, size) + size
 593                 end
 594                 stripped[#stripped+1] = string.rep("\0", int * 3)
 595                 return table.concat(stripped), offset
 596         end
 597
 598         return code:sub(1,12) .. strip_function(code:sub(13,-1))
 599 end
 600
 601
 602 --
 603 -- Sorting iterator functions
 604 --
 605
 606 function _sortiter( t, f )
 607         local keys = { }
 608
 609         for k, v in pairs(t) do
 610                 keys[#keys+1] = k
 611         end
 612
 613         local _pos = 0
 614
 615         table.sort( keys, f )
 616
 617         return function()
 618                 _pos = _pos + 1
 619                 if _pos <= #keys then
 620                         return keys[_pos], t[keys[_pos]]
 621                 end
 622         end
 623 end
 624
 625 --- Return a key, value iterator which returns the values sorted according to
 626 -- the provided callback function.
 627 -- @param t     The table to iterate
 628 -- @param f A callback function to decide the order of elements
 629 -- @return      Function value containing the corresponding iterator
 630 function spairs(t,f)
 631         return _sortiter( t, f )
 632 end
 633
 634 --- Return a key, value iterator for the given table.
 635 -- The table pairs are sorted by key.
 636 -- @param t     The table to iterate
 637 -- @return      Function value containing the corresponding iterator
 638 function kspairs(t)
 639         return _sortiter( t )
 640 end
 641
 642 --- Return a key, value iterator for the given table.
 643 -- The table pairs are sorted by value.
 644 -- @param t     The table to iterate
 645 -- @return      Function value containing the corresponding iterator
 646 function vspairs(t)
 647         return _sortiter( t, function (a,b) return t[a] < t[b] end )
 648 end
 649
 650
 651 --
 652 -- System utility functions
 653 --
 654
 655 --- Test whether the current system is operating in big endian mode.
 656 -- @return      Boolean value indicating whether system is big endian
 657 function bigendian()
 658         return string.byte(string.dump(function() end), 7) == 0
 659 end
 660
 661 --- Execute given commandline and gather stdout.
 662 -- @param command       String containing command to execute
 663 -- @return                      String containing the command's stdout
 664 function exec(command)
 665         local pp   = io.popen(command)
 666         local data = pp:read("*a")
 667         pp:close()
 668
 669         return data
 670 end
 671
 672 --- Return a line-buffered iterator over the output of given command.
 673 -- @param command       String containing the command to execute
 674 -- @return                      Iterator
 675 function execi(command)
 676         local pp = io.popen(command)
 677
 678         return pp and function()
 679                 local line = pp:read()
 680
 681                 if not line then
 682                         pp:close()
 683                 end
 684
 685                 return line
 686         end
 687 end
 688
 689 -- Deprecated
 690 function execl(command)
 691         local pp   = io.popen(command)
 692         local line = ""
 693         local data = {}
 694
 695         while true do
 696                 line = pp:read()
 697                 if (line == nil) then break end
 698                 data[#data+1] = line
 699         end
 700         pp:close()
 701
 702         return data
 703 end
 704
 705 --- Returns the absolute path to LuCI base directory.
 706 -- @return              String containing the directory path
 707 function libpath()
 708         return require "nixio.fs".dirname(ldebug.__file__)
 709 end
 710
 711
 712 --
 713 -- Coroutine safe xpcall and pcall versions modified for Luci
 714 -- original version:
 715 -- coxpcall 1.13 - Copyright 2005 - Kepler Project (www.keplerproject.org)
 716 --
 717 -- Copyright © 2005 Kepler Project.
 718 -- Permission is hereby granted, free of charge, to any person obtaining a
 719 -- copy of this software and associated documentation files (the "Software"),
 720 -- to deal in the Software without restriction, including without limitation
 721 -- the rights to use, copy, modify, merge, publish, distribute, sublicense,
 722 -- and/or sell copies of the Software, and to permit persons to whom the
 723 -- Software is furnished to do so, subject to the following conditions:
 724 --
 725 -- The above copyright notice and this permission notice shall be
 726 -- included in all copies or substantial portions of the Software.
 727 --
 728 -- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 729 -- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 730 -- OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 731 -- IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 732 -- DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 733 -- TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
 734 -- OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 735
 736 local performResume, handleReturnValue
 737 local oldpcall, oldxpcall = pcall, xpcall
 738 coxpt = {}
 739 setmetatable(coxpt, {__mode = "kv"})
 740
 741 -- Identity function for copcall
 742 local function copcall_id(trace, ...)
 743   return ...
 744 end
 745
 746 --- This is a coroutine-safe drop-in replacement for Lua's "xpcall"-function
 747 -- @param f             Lua function to be called protected
 748 -- @param err   Custom error handler
 749 -- @param ...   Parameters passed to the function
 750 -- @return              A boolean whether the function call succeeded and the return
 751 --                              values of either the function or the error handler
 752 function coxpcall(f, err, ...)
 753         local res, co = oldpcall(coroutine.create, f)
 754         if not res then
 755                 local params = {...}
 756                 local newf = function() return f(unpack(params)) end
 757                 co = coroutine.create(newf)
 758         end
 759         local c = coroutine.running()
 760         coxpt[co] = coxpt[c] or c or 0
 761
 762         return performResume(err, co, ...)
 763 end
 764
 765 --- This is a coroutine-safe drop-in replacement for Lua's "pcall"-function
 766 -- @param f             Lua function to be called protected
 767 -- @param ...   Parameters passed to the function
 768 -- @return              A boolean whether the function call succeeded and the returns
 769 --                              values of the function or the error object
 770 function copcall(f, ...)
 771         return coxpcall(f, copcall_id, ...)
 772 end
 773
 774 -- Handle return value of protected call
 775 function handleReturnValue(err, co, status, ...)
 776         if not status then
 777                 return false, err(debug.traceback(co, (...)), ...)
 778         end
 779         if coroutine.status(co) == 'suspended' then
 780                 return performResume(err, co, coroutine.yield(...))
 781         else
 782                 return true, ...
 783         end
 784 end
 785
 786 -- Resume execution of protected function call
 787 function performResume(err, co, ...)
 788         if get_memory_limit and get_memory_limit() > 0 and
 789            collectgarbage("count") > (get_memory_limit() * 0.8)
 790         then
 791                 collectgarbage("collect")
 792         end
 793
 794         return handleReturnValue(err, co, coroutine.resume(co, ...))
 795 end