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Assert for negative `field` in bit32 polyfill 

This more closely matches the behavior of lua5.2.
This commit is contained in:
Guldoman 2022-01-12 19:56:09 +01:00
parent 51975472a9
commit e51c76c72b
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1 changed files with 9 additions and 4 deletions
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13
data/core/bit.lua
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@ -11,18 +11,23 @@ local function mask(n)
return (~((ALLONES << 1) << ((n) - 1)))
end
local function check_args(field, width)
assert(field >= 0, "field cannot be negative")
assert(width > 0, "width must be positive")
assert(field + width < LUA_NBITS and field + width >= 0,
"trying to access non-existent bits")
end
function bit.extract(n, field, width)
local w = width or 1
assert(w > 0, "width must be positive")
assert(field + w < LUA_NBITS and field + w >= 0, "trying to access non-existent bits")
check_args(field, w)
local m = trim(n)
return m >> field & mask(w)
end
function bit.replace(n, v, field, width)
local w = width or 1
assert(w > 0, "width must be positive")
assert(field + w < LUA_NBITS and field + w >= 0, "trying to access non-existent bits")
check_args(field, w)
local m = trim(n)
local x = v & mask(width);
return m & ~(mask(w) << field) | (x << field)