coxpcall.lua

-------------------------------------------------------------------------------
-- Coroutine safe xpcall and pcall versions
--
-- Encapsulates the protected calls with a coroutine based loop, so errors can
-- be dealed without the usual Lua 5.x pcall/xpcall issues with coroutines
-- yielding inside the call to pcall or xpcall.
--
-- Authors: Roberto Ierusalimschy and Andre Carregal 
-- Contributors: Thomas Harning Jr., Ignacio Burgue�o, F�bio Mascarenhas
--
-- Copyright 2005 - Kepler Project (www.keplerproject.org)
--
-- $Id: coxpcall.lua,v 1.13 2008/05/19 19:20:02 mascarenhas Exp $
-------------------------------------------------------------------------------

require 'utils.table' -- needed for table.pack. To be removed when we switch to Lua5.2

-------------------------------------------------------------------------------
-- Implements xpcall with coroutines
-------------------------------------------------------------------------------
local performResume, handleReturnValue
local oldpcall, oldxpcall = pcall, xpcall

function handleReturnValue(err, co, status, ...)
    if not status then
        return false, err(debug.traceback(co, (...)), ...)
    end
    if coroutine.status(co) == 'suspended' then
        return performResume(err, co, coroutine.yield(...))
    else
        return true, ...
    end
end

function performResume(err, co, ...)
    return handleReturnValue(err, co, coroutine.resume(co, ...))
end    

function coxpcall(f, err, ...)
    local res, co = oldpcall(coroutine.create, f)
    if not res then
        local params = table.pack(...)
        local newf = function() return f(unpack(params, 1, params.n)) end
        co = coroutine.create(newf)
    end
    return performResume(err, co, ...)
end

-------------------------------------------------------------------------------
-- Implements pcall with coroutines
-------------------------------------------------------------------------------

local function id(trace, ...)
  return ...
end

function copcall(f, ...)
    return coxpcall(f, id, ...)
end