API

`#math/bits`

import: #math/bits

counts: 32 fns, 0 methods, 1 types, 0 consts, 0 ifaces

Bit length, leading zeros, rotate, add/sub/mul/div with carry.

`len`

XuAPI

pub fn len(x int) int

Purpose

len: minimum number of bits needed to represent x (0 for x == 0). Equal to 64 - leading_zeros(x), matching `bits.Len64`.

Parameters

x int: value (int)

Returns

int — a value of this type

`leading_zeros`

XuAPI

pub fn leading_zeros(x int) int

Purpose

leading_zeros: number of zero bits before the highest set bit. Binary search: each `(v >> n) == 0` test is sign-agnostic (arithmetic shift yields 0 iff the top n bits are all zero, since the sign bit is in that window), then the low bits are shifted up.

Parameters

x int: value (int)

Returns

int — a value of this type

`trailing_zeros`

XuAPI

pub fn trailing_zeros(x int) int

Purpose

trailing_zeros: number of zero bits after the lowest set bit. Binary search on the low bits; the arithmetic right shifts are safe because only the low (64-n) bits of the result are ever inspected, and those are identical for arithmetic and logical shifts.

Parameters

x int: value (int)

Returns

int — a value of this type

`ones_count`

XuAPI

pub fn ones_count(x int) int

Purpose

ones_count: population count via SWAR parallel summing of adjacent bits ( `bits.OnesCount64`, from "Hacker's Delight" ch. 5). The three mask constants m0/m1/m2 zero the sign-extension bits after the arithmetic shifts, and after the `& m2` step the value is non-negative so the trailing `+ (v >> n)` folds are plain logical shifts.

Parameters

x int: value (int)

Returns

int — a value of this type

`rotate_left`

XuAPI

pub fn rotate_left(x int, k int) int

Purpose

rotate_left: k is reduced mod 64 ( `bits.RotateLeft64`). The low part is a logical right shift by (64-s) masked to s bits; s == 0 is handled separately so no shift-by-64 is ever emitted.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type

`rotate_right`

XuAPI

pub fn rotate_right(x int, k int) int

Purpose

rotate_right: `bits.RotateRight64` (k mod 64). The low part is a logical right shift by s masked to (64-s) bits; the high part moves the low s bits to the top.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type

`reverse`

XuAPI

pub fn reverse(x int) int

Purpose

reverse: full bit reversal ( `bits.Reverse64`). 5-stage mask swap over the bit-swap masks m0/m1/m2 then the byte-swap masks m3/m4/m5 each `(v >> n) & mask` zeroes the sign extension.

Parameters

x int: value (int)

Returns

int — a value of this type

`reverse_bytes`

XuAPI

pub fn reverse_bytes(x int) int

Purpose

reverse_bytes: byte-order reversal ( `bits.ReverseBytes64`).

Parameters

x int: value (int)

Returns

int — a value of this type

`struct Carry`

XuAPI

pub struct Carry {
    pub lo int
    pub carry int
}

Purpose

Public struct `Carry`.

Parameters

lo int: field (int)
carry int: field (int)

`add64`

XuAPI

pub fn add64(x int, y int, carry_in int) Carry

Purpose

add64; returns Carry.

Parameters

x int: value (int)
y int: value (int)
carry_in int: carry_in (int)

Returns

Carry — a value of this type

`sub64`

XuAPI

pub fn sub64(x int, y int, borrow_in int) Carry

Purpose

sub64; returns Carry.

Parameters

x int: value (int)
y int: value (int)
borrow_in int: borrow_in (int)

Returns

Carry — a value of this type

`mul64`

XuAPI

pub fn mul64(x int, y int) Carry

Purpose

mul64; returns Carry.

Parameters

x int: value (int)
y int: value (int)

Returns

Carry — a value of this type

`div64`

XuAPI

pub fn div64(hi int, lo int, y int) Carry

Purpose

div64; returns Carry. Throws on failure.

Parameters

hi int: hi (int)
lo int: lo (int)
y int: value (int)

Returns

Carry — a value of this type

`len32`

XuAPI

pub fn len32(x int) int

Purpose

len32; returns int.

Parameters

x int: value (int)

Returns

int — a value of this type

`leading_zeros32`

XuAPI

pub fn leading_zeros32(x int) int

Purpose

Leading zeros32.

Parameters

x int: value (int)

Returns

int — a value of this type

`trailing_zeros32`

XuAPI

pub fn trailing_zeros32(x int) int

Purpose

Trailing zeros32.

Parameters

x int: value (int)

Returns

int — a value of this type

`ones_count32`

XuAPI

pub fn ones_count32(x int) int

Purpose

Ones count32.

Parameters

x int: value (int)

Returns

int — a value of this type

`ones_count16`

XuAPI

pub fn ones_count16(x int) int

Purpose

Ones count16.

Parameters

x int: value (int)

Returns

int — a value of this type

`ones_count8`

XuAPI

pub fn ones_count8(x int) int

Purpose

Ones count8.

Parameters

x int: value (int)

Returns

int — a value of this type

`trailing_zeros16`

XuAPI

pub fn trailing_zeros16(x int) int

Purpose

Trailing zeros16.

Parameters

x int: value (int)

Returns

int — a value of this type

`trailing_zeros8`

XuAPI

pub fn trailing_zeros8(x int) int

Purpose

Trailing zeros8.

Parameters

x int: value (int)

Returns

int — a value of this type

`len16`

XuAPI

pub fn len16(x int) int

Purpose

len16; returns int.

Parameters

x int: value (int)

Returns

int — a value of this type

`len8`

XuAPI

pub fn len8(x int) int

Purpose

len8; returns int.

Parameters

x int: value (int)

Returns

int — a value of this type

`leading_zeros16`

XuAPI

pub fn leading_zeros16(x int) int

Purpose

Leading zeros16.

Parameters

x int: value (int)

Returns

int — a value of this type

`leading_zeros8`

XuAPI

pub fn leading_zeros8(x int) int

Purpose

Leading zeros8.

Parameters

x int: value (int)

Returns

int — a value of this type

`reverse16`

XuAPI

pub fn reverse16(x int) int

Purpose

reverse16; returns int.

Parameters

x int: value (int)

Returns

int — a value of this type

`reverse8`

XuAPI

pub fn reverse8(x int) int

Purpose

reverse8; returns int.

Parameters

x int: value (int)

Returns

int — a value of this type

`reverse_bytes16`

XuAPI

pub fn reverse_bytes16(x int) int

Purpose

Reverse bytes16.

Parameters

x int: value (int)

Returns

int — a value of this type

`reverse_bytes8`

XuAPI

pub fn reverse_bytes8(x int) int

Purpose

Reverse bytes8.

Parameters

x int: value (int)

Returns

int — a value of this type

`rotate_left16`

XuAPI

pub fn rotate_left16(x int, k int) int

Purpose

Rotate left16.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type

`rotate_left8`

XuAPI

pub fn rotate_left8(x int, k int) int

Purpose

Rotate left8.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type

`rotate_right16`

XuAPI

pub fn rotate_right16(x int, k int) int

Purpose

Rotate right16.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type

`rotate_right8`

XuAPI

pub fn rotate_right8(x int, k int) int

Purpose

Rotate right8.

Parameters

x int: value (int)
k int: key or index (int)

Returns

int — a value of this type