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-- Until Lua 5.2 support is dropped, we can't use the native operators directly
-- https://pastebin.com/fepexfdU - assumed public domain license
--[[ Backwards compat for Lua 5.3; only loaded in 5.3 because package.loaded is
prepopulated with the existing global bit32 in 5.2. ]]
local bit32 = {}
-------------------------------------------------------------------------------
local function fold(init, op, ...)
local result = init
local args = table.pack(...)
for i = 1, args.n do
result = op(result, args[i])
end
return result
end
local function trim(n)
return n & 0xFFFFFFFF
end
local function mask(w)
return ~(0xFFFFFFFF << w)
end
function bit32.arshift(x, disp)
return x // (2 ^ disp)
end
function bit32.band(...)
return fold(0xFFFFFFFF, function(a, b) return a & b end, ...)
end
function bit32.bnot(x)
return ~x
end
function bit32.bor(...)
return fold(0, function(a, b) return a | b end, ...)
end
function bit32.btest(...)
return bit32.band(...) ~= 0
end
function bit32.bxor(...)
return fold(0, function(a, b) return a ~ b end, ...)
end
local function fieldargs(f, w)
w = w or 1
assert(f >= 0, "field cannot be negative")
assert(w > 0, "width must be positive")
assert(f + w <= 32, "trying to access non-existent bits")
return f, w
end
function bit32.extract(n, field, width)
local f, w = fieldargs(field, width)
return (n >> f) & mask(w)
end
function bit32.replace(n, v, field, width)
local f, w = fieldargs(field, width)
local m = mask(w)
return (n & ~(m << f)) | ((v & m) << f)
end
function bit32.lrotate(x, disp)
if disp == 0 then
return x
elseif disp < 0 then
return bit32.rrotate(x, -disp)
else
disp = disp & 31
x = trim(x)
return trim((x << disp) | (x >> (32 - disp)))
end
end
function bit32.lshift(x, disp)
return trim(x << disp)
end
function bit32.rrotate(x, disp)
if disp == 0 then
return x
elseif disp < 0 then
return bit32.lrotate(x, -disp)
else
disp = disp & 31
x = trim(x)
return trim((x >> disp) | (x << (32 - disp)))
end
end
function bit32.rshift(x, disp)
return trim(x >> disp)
end
-------------------------------------------------------------------------------
return bit32
|
