bit32

The complete bit32 library. All operations work on 32-bit unsigned integers (inputs are truncated to 32 bits; results are in 0..4294967295). This is the library for combining EConVarFlag values.

Basic operations

bit32.band(...), bit32.bor(...), bit32.bxor(...)

AND, OR, XOR over any number of arguments.

print(bit32.band(0xFF, 0x0F))      --> 15
print(bit32.bor(128, 256))         --> 384  (FCVAR_ARCHIVE | FCVAR_NOTIFY)
print(bit32.bxor(0xFF, 0xF0))      --> 15
print(bit32.bor(1, 2, 4, 8))       --> 15

bit32.bnot(x)

Bitwise NOT.

print(bit32.bnot(0))     --> 4294967295
print(bit32.bnot(0xFF))  --> 4294967040

bit32.btest(...)

true when band(...) of the arguments is nonzero — the idiomatic flag check.

local flags = bit32.bor(128, 256)     -- ARCHIVE | NOTIFY
print(bit32.btest(flags, 128))        --> true
print(bit32.btest(flags, 16384))      --> false (CHEAT not set)

Shifts and rotates

bit32.lshift(x, disp), bit32.rshift(x, disp)

Logical shifts (left fills with zeros; right fills with zeros — no sign extension). Negative disp shifts the other way.

print(bit32.lshift(1, 7))    --> 128
print(bit32.rshift(384, 7))  --> 3
print(bit32.lshift(1, -1))   --> 0  (acts as rshift 1)

bit32.arshift(x, disp)

Arithmetic right shift — fills with the sign bit, treating x as signed.

print(bit32.rshift(0x80000000, 4))  --> 134217728  (zero-filled)
print(bit32.arshift(0x80000000, 4)) --> 4026531840 (sign-filled)

bit32.lrotate(x, disp), bit32.rrotate(x, disp)

Bit rotation (no bits lost).

print(bit32.lrotate(0x80000001, 1))  --> 3           (0x00000003)
print(bit32.rrotate(0x80000001, 1))  --> 3221225472  (0xC0000000)

Note

Results are always 0..2^32-1. When you need the signed view of a result, convert: local signed = r >= 2^31 and r - 2^32 or r.

Field extraction

bit32.extract(n, field, width?)

Reads a width-bit field (default 1) starting at bit field.

print(bit32.extract(384, 7))        --> 1  (bit 7 = ARCHIVE is set)
print(bit32.extract(0xFF, 4, 4))    --> 15 (the high nibble)

bit32.replace(n, v, field, width?)

Returns n with the field overwritten by v.

print(bit32.replace(0, 1, 7))       --> 128  (set bit 7)
print(bit32.replace(0xFF, 0, 4, 4)) --> 240  (clear high nibble)

Counting (Luau)

bit32.countlz(x)

Leading zero count.

print(bit32.countlz(1))         --> 31
print(bit32.countlz(0x80000000)) --> 0

bit32.countrz(x)

Trailing zero count.

print(bit32.countrz(384))  --> 7   (384 = 0b110000000)
print(bit32.countrz(0))    --> 32

Byte order (Luau)

bit32.byteswap(n)

Reverses the four bytes.

print(bit32.byteswap(0x00112233)) --> 573785173  (0x33221100)