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-- (c) 2012 David Manura. Licensed under the same terms as Lua 5.1/5.2 (MIT license).
-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in
-- all copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-- THE SOFTWARE.
--
-- @author David Manura, ruki
-- @file env.lua
--
-- define module: env
local env = env or {}
-- from https://github.com/davidm/lua-inspect/blob/master/lib/luainspect/compat_env.lua
if _G.setfenv then -- Lua 5.1
env.setfenv = _G.setfenv
env.getfenv = _G.getfenv
else -- >= Lua 5.2
-- helper function for `getfenv`/`setfenv`
local function envlookup(f)
local name, val
local up = 0
local unknown
repeat
up = up + 1; name, val = debug.getupvalue(f, up)
if name == '' then unknown = true end
until name == '_ENV' or name == nil
if name ~= '_ENV' then
up = nil
if unknown then error("upvalues not readable in Lua 5.2 when debug info missing", 3) end
end
return (name == '_ENV') and up, val, unknown
end
-- helper function for `getfenv`/`setfenv`
local function envhelper(f, name)
if type(f) == 'number' then
if f < 0 then
error(("bad argument #1 to '%s' (level must be non-negative)"):format(name), 3)
elseif f < 1 then
error("thread environments unsupported in Lua 5.2", 3) --[*]
end
f = debug.getinfo(f + 2, 'f').func
elseif type(f) ~= 'function' then
error(("bad argument #1 to '%s' (number expected, got %s)"):format(name, type(f)), 2)
end
return f
end
-- [*] might simulate with table keyed by coroutine.running()
-- 5.1 style `setfenv` implemented in 5.2
function env.setfenv(f, t)
local f = envhelper(f, 'setfenv')
local up, val, unknown = envlookup(f)
if up then
debug.upvaluejoin(f, up, function() return up end, 1) -- unique upvalue [*]
debug.setupvalue(f, up, t)
else
local what = debug.getinfo(f, 'S').what
if what ~= 'Lua' and what ~= 'main' then -- not Lua func
error("'setfenv' cannot change environment of given object", 2)
end -- else ignore no _ENV upvalue (warning: incompatible with 5.1)
end
end
-- [*] http://lua-users.org/lists/lua-l/2010-06/msg00313.html
-- 5.1 style `getfenv` implemented in 5.2
function env.getfenv(f)
if f == 0 then return _G end -- simulated behavior
local f = envhelper(f or 1, 'getfenv')
local up, val = envlookup(f)
if not up then return _G end -- simulated behavior [**]
return val
end
-- [**] possible reasons: no _ENV upvalue, C function
-- register to global
_G.setfenv = env.setfenv
_G.getfenv = env.getfenv
debug.setfenv = env.setfenv
debug.getfenv = env.getfenv
end
-- return module: env
return env
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