1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
|
--!A cross-platform build utility based on Lua
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
-- Copyright (C) 2015-present, Xmake Open Source Community.
--
-- @author ruki
-- @file pairs.lua
--
-- load modules
local table = require("base/table")
-- improve pairs, wrap nil/single value
--
-- Unlike the stock lua `pairs`, this sandbox version tolerates the loop
-- body reassigning the first loop variable, e.g.:
--
-- for k, v in pairs(t) do
-- k = k:gsub("_", "-") -- safe here
-- ...
-- end
--
-- This works together with the `RDKCONST -> VDKREG` compile-time patch
-- applied to lparser.c in core/src/lua/xmake.lua (and xmake.sh): that
-- patch lifts lua 5.4+'s ban on writing to the for-in control variable,
-- and this stateful closure makes such writes harmless at runtime.
function sandbox_pairs(t)
-- exists the custom ipairs?
local is_table = type(t) == "table"
if is_table and t.pairs then
return t:pairs()
end
-- wrap table and return iterator
if not is_table then
t = t ~= nil and {t} or {}
end
-- keep `next`'s key in an upvalue so the loop body can safely reassign
-- the first loop variable. In lua 5.4+ the for-in control slot is
-- merged with the first user variable; if we threaded the key through
-- the loop it would corrupt `next` on the following iteration.
local k = nil
return function ()
local nk, nv = next(t, k)
k = nk
return nk, nv
end
end
-- load module
return sandbox_pairs
|
