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Rather more robust nr_elements_in_seq.

This commit is contained in:
Jon Michael Aanes 2017-10-22 12:23:19 +02:00
parent a13c6351c1
commit ef0a4c82ed
2 changed files with 32 additions and 9 deletions

View File

@ -39,10 +39,10 @@ local LEAF_VALUE_TYPES = {
['boolean'] = true,
}
local SHORT_STRING_MAX_LEN = 7
local MINIMUM_NUMBER_OF_SET_ELEMENTS = 2
local RECURSIVE_TOSTRING_TIMEOUT = 10
local SHORT_STRING_MAX_LEN = 7 -- Range: [0, ∞[
local MINIMUM_NUMBER_OF_SET_ELEMENTS = 2 -- Range: [1, ∞[
local ALLOWED_HOLE_SIZE_IN_SEQUENCE = 1 -- Range: [0, ∞[. Set to 0, to completely disallow holes in sequences.
local RECURSIVE_TOSTRING_TIMEOUT = 10 -- Range: [1, ∞[. High values may result in crashes on specially-crafted input.
--------------------------------------------------------------------------------
@ -98,6 +98,8 @@ local function largest_number_index (t)
end
local function nr_elements_in_table (t)
-- Determines the total number of elements in the table.
assert(type(t) == 'table')
--
local k, count = nil, -1
@ -108,16 +110,30 @@ local function nr_elements_in_table (t)
end
local function nr_elements_in_seq (t)
-- Determines the number of elements in the sequence part of the table.
-- Allows holes of size `ALLOWED_HOLE_SIZE_IN_SEQUENCE`, before stopping.
-- This function works even when the given table's metamethods throws errors.
--
-- Returns:
-- * Number: number of elements
-- * Boolean: whether the table has holes.
assert(type(t) == 'table')
if getmetatable(t) and getmetatable(t).__index then
return 0, false -- FIXME: Temporary stopgap for when __index throws an
-- error. I think we need to clone the numbers part of the table, to
-- fix this.
-- We don't want to crash if the __index metamethod throws an error, so we
-- copy the pairs with number keys into a fresh table, which we then operate
-- on lower down.
if debug.getmetatable(t) and debug.getmetatable(t).__index then
local t_prime = {}
for k, v in pairs(t) do
if type(k) == 'number' then t_prime[k] = v end
end
t = t_prime
end
-- Now we run though the table, from 1 and up.
local i, last_elem_i, nr_elems, has_holes = 0, 0, 0, false
while i <= last_elem_i + 2 do
while i <= last_elem_i + 1 + ALLOWED_HOLE_SIZE_IN_SEQUENCE do
i = i + 1
if t[i] ~= nil then
last_elem_i, nr_elems = i, nr_elems + 1

View File

@ -229,6 +229,13 @@ SUITE:addTest('Can count elements, even though metatable.__index throws errors',
assert_equal(2, info[input].seq_elems)
end)
SUITE:addTest('Can count elements, even though metatable.__index throws errors and __metatable returns bogus', function ()
local input = setmetatable({ 'hi', 'hello' }, {__index = function (_, k) error('Undefined access on key: '..k) end, __metatable = {}})
local info = analyze_structure(input, math.huge)
assert_equal(2, info[input].seq_elems)
end)
--------------------------------------------------------------------------------
-- Uniform structure