@dekkonot/int64

Int64 Luau

Available on:

• Wally as dekkonot/int64
• npm as @dekkonot/int64

Implementation of arithmetic and bitwise operations for unsigned 64-bit integers in pure Luau. Utilizes vector objects to pack the integers efficiently, meaning it avoids expensive table accesses and allocations.

Major features:

• Arithmetic (addition, subtraction, mutiplication, division, modulo, and exponentiation)
• Bitwise operations (everything implemented in bit32 as of this time except for replace/extract)
• Convenience functions for converting to and from other forms of data (hex strings, buffers, etc)

This does not implement math library functionality! Implementations of things like math.random are far beyond scope for this library, and implementation of things like math.sin are prohibitively complex and incredibly slow. It would also be very difficult to write tests for these that were appropriately exhaustive and it's irresponsible to release them into the world without tests.

This module is made as fast as is reasonably possible. However, they are still a fair bit slower than native integers; this will hopefully not be a surprise. You should expect very good performance, but it's possible that depending upon your use case storing two 32-bit integers and operating on them will be faster.

If you wish to contribute to this module, whether it be through optimizations or new functionality, please open a pull request.

API

Constructors	Destructors	Constants
from_f64	to_f64	ZERO
from_dec_string	to_dec_string	ONE
from_pair	to_pair	TWO
from_u32	to_quartet	MAX
from_buffer	to_buffer	MAX_U32
from_byte_string	write_to_buffer	MAX_F64
	to_byte_string	MAX_F32
	to_hex_string
	to_bin_string

Logical	Arithmetic	Bitwise
gt	add	band
gt_equal	sub	bor
lt	mult	bxor
lt_equal	div	bnot
	pow	lshift
		rshift
		arshift
		lrotate
		rrotate
		countlz
		countrz
		btest
		byteswap

Constructors

from_f64

int64.from_f64(f64: number): vector

Constructs a 64-bit integer from the passed f64. Put more plainly, converts a normal Luau number to a 64-bit integer.

The number is truncated into an integer first. Note that Luau numbers cannot accurately represent integers past 2 ^ 53.

from_dec_string

int64.from_dec_string(str: string): vector

Returns the provided value parsed as a 64-bit integer. Expects the provided string to contain only the digits 0-9 and will error if it does not.

Leading zeros are accepted and parsed appropriately.

Due to the implementation, the resulting integer will wrap around if it is too large to fit in a 64-bit integer rather than erroring.

from_pair

int64.from_pair(most: number, least: number): vector

Constructs a 64-bit integer from the passed u32 values.

The provided most value fills the upper 32 bits of the integer, and the provided least value fills the lower 32-bits.

from_u32

int64.from_u32(u32: number): vector

Constructs a 64-bit integer from the passed u32.

This number is truncated in a 32-bit integer, even if it is larger than the max value.

from_buffer

int64.from_buffer(buf: buffer, offset: number?): vector

Reads a u64 from the provided buffer. If offset is provided, reads from that spot in the buffer. Otherwise, reads from the beginning.

This function reads a little-endian value from the buffer.

from_byte_string

int64.from_byte_string(str: string, offset: number?): vector

Reads a u64 from the provided string. If offset is provided, reads from that point in the string. Otherwise starts at the beginning.

This function reads a little-endian value from the string.

Destructors

to_f64

int64.to_f64(u64: vector): number

Converts the provided u64 to an f64 (or put plainly: a normal Luau number).

This function does not check for precision loss. f64 values lose precision past 2 ^ 53.

to_dec_string

int64.to_dec_string(u64: vector): string

Returns the provided value as a string of decimal digits.

Equivalent to formatting normal numbers with %u or calling tostring on them.

to_pair

int64.to_pair(u64: vector): (number, number)

Converts the provided u64 into two 32-bit integers.

This returns the most significant portion of the number first.

to_quartet

int64.to_quartet(u64: vector): (number, number, number, number)

Converts the provided u64 into four 16-bit integers.

This returns the most significant portion of the number first.

to_buffer

int64.to_buffer(u64: vector): buffer

Converts the provided u64 to a buffer.

The integer is written as a little-endian value.

write_to_buffer

int64.write_to_buffer(b: buffer, u64: vector, offset: number)

Writes the provided u64 to the provided buffer. The value is written to the buffer at the provided offset.

The integer is written as a little-endian value.

to_byte_string

int64.to_byte_string(u64: vector): string

Converts the provided u64 to string of binary data.

The integer is written as if it were little-endian.

to_hex_string

int64.to_hex_string(u64: vector): string

Converts the provided u64 to a string of 16 hexadecimal digits.

The returned string will always be 16 bytes and the number is formatted as if it were big-endian. It also always uses lowercase letters.

to_bin_string

int64.to_bin_string(u64: vector): string

Converts the provided u64 to a string of 64 binary digits.

The returned string will always be 64 bytes and the number is formatted as if it were big-endian.

Constants

ZERO

A constant representing the 64-bit representation of 0.

ONE

A constant representating the 64-bit representation of 1.

TWO

A constant representating the 64-bit representation of 2.

MAX

A constant representing the maximum possible 64-bit value (18446744073709551615, or 2 ^ 64 - 1).

MAX_U32

A constant representing the maximum possible 32-bit value (4294967295, or 2 ^ 32 - 1).

MAX_F64

A constant representing the maximum integer that is exactly representable by a normal Luau number (9007199254740992 or 2 ^ 53).

MAX_F32

A constant representing the maximum integer that is exactly representable by a 32-bit floating point value (16777216, or 2 ^ 24).

Logical

gt

int64.gt(lhs: vector, rhs: vector): boolean

Returns whether lhs is greater than rhs.

gt_equal

int64.gt_equal(lhs: vector, rhs: vector): boolean

Returns whether lhs is greater than or equal to rhs.

lt

int64.lt(lhs: vector, rhs: vector): boolean

Returns whether lhs is less than rhs.

lt_equal

int64.lt_equal(lhs: vector, rhs: vector): boolean

Returns whether lhs is less than or equal to rhs.

Arithmetic

add

int64.add(augend: vector, addend: vector): vector

Calculates the sum of the two provided values. Equivalent to + for normal integers.

If the sum is equal to or greater than 2 ^ 64, the returned value will overflow rather than expanding beyond 64 bits.

sub

int64.sub(minuend: vector, subtrahend: vector): vector

Calculates the difference of the two provided values. Equivalent to - for normal integers.

If the difference is less than 0, the returned value will overflow rather than going negative.

mult

int64.mult(multiplier: vector, multiplicand: vector): vector

Calculates the product of the two provided values. Equivalent to * for normal integers.

If the product is greater than or equal to 2 ^ 64, the returned value will overflow rather than expanding beyond 64 bits.

div

int64.div(dividend: vector, divisor: vector): (vector, vector)

Calculates the quotient of the two provided values and returns it, along with the remainder.

Equivalent to // and % for normal integers. This function will error if divisor is 0.

pow

int64.pow(base: vector, power: number): vector

Calculates the result of base raised to power. Equivalent to ^ for normal integers. power is interpreted as a 32-bit integer.

If the result is greater than or equal to 2 ^ 64, the returned value will overflow rather than expanding beyond 64 bits.

Additionally, 0 ^ 0 is treated as being 1.

Bitwise

band

int64.band(lhs: vector, rhs: vector): vector

Computes the bitwise AND of the two provide values.

This does not accept a vararg like the bit32 equivalent for performance reasons.

bor

int64.bor(lhs: vector, rhs: vector): vector

Computes the bitwise OR of the two provide values.

This does not accept a vararg like the bit32 equivalent for performance reasons.

bxor

int64.bxor(lhs: vector, rhs: vector): vector

Computes the bitwise XOR of the two provide values.

This does not accept a vararg like the bit32 equivalent for performance reasons.

bnot

int64.bnot(u64: vector): vector

Computes the bitwise negation of the provided value.

lshift

int64.lshift(u64: vector, n: number): vector

Shifts the provided u64 logically left by n bits.

This function will error if n is negative.

rshift

int64.rshift(u64: vector, n: number): vector

Shifts the provided u64 logically right by n bits.

This function will error if n is negative.

arshift

bit64.arshift(u64: vector, n: number): vector

Shifts the provided u64 arithmetically right by n bits. Since these numbers are unsigned, this effectively just copies the most significant bit into the empty space rather than filling them with zeros.

This function will error if n is negative.

lrotate

int64.lrotate(u64: vector, n: number): vector

Rotates the bits of the provided u64 left by n bits.

If n is negative, this is equivalent to rrotate. Otherwise, if n is greater than 64-bits, it will wrap around.

rrotate

int64.rrotate(u64: vector, n: number): vector

Rotates the bits of the provided u64 right by n bits.

If n is negative, this is equivalent to lrotate. Otherwise, if n is greater than 64-bits, it will wrap around.

countlz

int64.countlz(u64: vector): number

Returns the number of consecutive zero bits in the provided u64 starting from the left-most (most significant) bit.

countrz

int64.countrz(u64: vector): number

Returns the number of consecutive zero bits in the provided u64 starting from the right-most (least significant) bit.

btest

int64.btest(lhs: vector, rhs: vector): boolean

Returns a boolean describing whether the bitwise AND of lhs and rhs are different than zero.

This does not accept a vararg like the bit32 equivalent for performance reasons.

byteswap

int64.byteswap(u64: vector): vector

Returns the provided u64 with the order of bytes swapped.