`package `**bits**
Import Path
math/bits* (on go.dev)*
Dependency Relation
imports one package, and imported by 26 packages
Involved Source Files
Package bits implements bit counting and manipulation
functions for the predeclared unsigned integer types.
Functions in this package may be implemented directly by
the compiler, for better performance. For those functions
the code in this package will not be used. Which
functions are implemented by the compiler depends on the
architecture and the Go release.
bits_errors.go
bits_tables.go
Code Examples
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 33<<32 + 12
n1 := []uint32{33, 12}
// Second number is 21<<32 + 23
n2 := []uint32{21, 23}
// Add them together without producing carry.
d1, carry := bits.Add32(n1[1], n2[1], 0)
d0, _ := bits.Add32(n1[0], n2[0], carry)
nsum := []uint32{d0, d1}
fmt.Printf("%v + %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
// First number is 1<<32 + 2147483648
n1 = []uint32{1, 0x80000000}
// Second number is 1<<32 + 2147483648
n2 = []uint32{1, 0x80000000}
// Add them together producing carry.
d1, carry = bits.Add32(n1[1], n2[1], 0)
d0, _ = bits.Add32(n1[0], n2[0], carry)
nsum = []uint32{d0, d1}
fmt.Printf("%v + %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 33<<64 + 12
n1 := []uint64{33, 12}
// Second number is 21<<64 + 23
n2 := []uint64{21, 23}
// Add them together without producing carry.
d1, carry := bits.Add64(n1[1], n2[1], 0)
d0, _ := bits.Add64(n1[0], n2[0], carry)
nsum := []uint64{d0, d1}
fmt.Printf("%v + %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
// First number is 1<<64 + 9223372036854775808
n1 = []uint64{1, 0x8000000000000000}
// Second number is 1<<64 + 9223372036854775808
n2 = []uint64{1, 0x8000000000000000}
// Add them together producing carry.
d1, carry = bits.Add64(n1[1], n2[1], 0)
d0, _ = bits.Add64(n1[0], n2[0], carry)
nsum = []uint64{d0, d1}
fmt.Printf("%v + %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 0<<32 + 6
n1 := []uint32{0, 6}
// Second number is 0<<32 + 3
n2 := []uint32{0, 3}
// Divide them together.
quo, rem := bits.Div32(n1[0], n1[1], n2[1])
nsum := []uint32{quo, rem}
fmt.Printf("[%v %v] / %v = %v\n", n1[0], n1[1], n2[1], nsum)
// First number is 2<<32 + 2147483648
n1 = []uint32{2, 0x80000000}
// Second number is 0<<32 + 2147483648
n2 = []uint32{0, 0x80000000}
// Divide them together.
quo, rem = bits.Div32(n1[0], n1[1], n2[1])
nsum = []uint32{quo, rem}
fmt.Printf("[%v %v] / %v = %v\n", n1[0], n1[1], n2[1], nsum)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 0<<64 + 6
n1 := []uint64{0, 6}
// Second number is 0<<64 + 3
n2 := []uint64{0, 3}
// Divide them together.
quo, rem := bits.Div64(n1[0], n1[1], n2[1])
nsum := []uint64{quo, rem}
fmt.Printf("[%v %v] / %v = %v\n", n1[0], n1[1], n2[1], nsum)
// First number is 2<<64 + 9223372036854775808
n1 = []uint64{2, 0x8000000000000000}
// Second number is 0<<64 + 9223372036854775808
n2 = []uint64{0, 0x8000000000000000}
// Divide them together.
quo, rem = bits.Div64(n1[0], n1[1], n2[1])
nsum = []uint64{quo, rem}
fmt.Printf("[%v %v] / %v = %v\n", n1[0], n1[1], n2[1], nsum)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("LeadingZeros16(%016b) = %d\n", 1, bits.LeadingZeros16(1))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("LeadingZeros32(%032b) = %d\n", 1, bits.LeadingZeros32(1))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("LeadingZeros64(%064b) = %d\n", 1, bits.LeadingZeros64(1))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("LeadingZeros8(%08b) = %d\n", 1, bits.LeadingZeros8(1))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("Len16(%016b) = %d\n", 8, bits.Len16(8))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("Len32(%032b) = %d\n", 8, bits.Len32(8))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("Len64(%064b) = %d\n", 8, bits.Len64(8))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("Len8(%08b) = %d\n", 8, bits.Len8(8))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 0<<32 + 12
n1 := []uint32{0, 12}
// Second number is 0<<32 + 12
n2 := []uint32{0, 12}
// Multiply them together without producing overflow.
hi, lo := bits.Mul32(n1[1], n2[1])
nsum := []uint32{hi, lo}
fmt.Printf("%v * %v = %v\n", n1[1], n2[1], nsum)
// First number is 0<<32 + 2147483648
n1 = []uint32{0, 0x80000000}
// Second number is 0<<32 + 2
n2 = []uint32{0, 2}
// Multiply them together producing overflow.
hi, lo = bits.Mul32(n1[1], n2[1])
nsum = []uint32{hi, lo}
fmt.Printf("%v * %v = %v\n", n1[1], n2[1], nsum)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 0<<64 + 12
n1 := []uint64{0, 12}
// Second number is 0<<64 + 12
n2 := []uint64{0, 12}
// Multiply them together without producing overflow.
hi, lo := bits.Mul64(n1[1], n2[1])
nsum := []uint64{hi, lo}
fmt.Printf("%v * %v = %v\n", n1[1], n2[1], nsum)
// First number is 0<<64 + 9223372036854775808
n1 = []uint64{0, 0x8000000000000000}
// Second number is 0<<64 + 2
n2 = []uint64{0, 2}
// Multiply them together producing overflow.
hi, lo = bits.Mul64(n1[1], n2[1])
nsum = []uint64{hi, lo}
fmt.Printf("%v * %v = %v\n", n1[1], n2[1], nsum)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("OnesCount(%b) = %d\n", 14, bits.OnesCount(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("OnesCount16(%016b) = %d\n", 14, bits.OnesCount16(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("OnesCount32(%032b) = %d\n", 14, bits.OnesCount32(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("OnesCount64(%064b) = %d\n", 14, bits.OnesCount64(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("OnesCount8(%08b) = %d\n", 14, bits.OnesCount8(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%016b\n", 19)
fmt.Printf("%016b\n", bits.Reverse16(19))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%032b\n", 19)
fmt.Printf("%032b\n", bits.Reverse32(19))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%064b\n", 19)
fmt.Printf("%064b\n", bits.Reverse64(19))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%08b\n", 19)
fmt.Printf("%08b\n", bits.Reverse8(19))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%016b\n", 15)
fmt.Printf("%016b\n", bits.ReverseBytes16(15))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%032b\n", 15)
fmt.Printf("%032b\n", bits.ReverseBytes32(15))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%064b\n", 15)
fmt.Printf("%064b\n", bits.ReverseBytes64(15))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%016b\n", 15)
fmt.Printf("%016b\n", bits.RotateLeft16(15, 2))
fmt.Printf("%016b\n", bits.RotateLeft16(15, -2))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%032b\n", 15)
fmt.Printf("%032b\n", bits.RotateLeft32(15, 2))
fmt.Printf("%032b\n", bits.RotateLeft32(15, -2))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%064b\n", 15)
fmt.Printf("%064b\n", bits.RotateLeft64(15, 2))
fmt.Printf("%064b\n", bits.RotateLeft64(15, -2))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("%08b\n", 15)
fmt.Printf("%08b\n", bits.RotateLeft8(15, 2))
fmt.Printf("%08b\n", bits.RotateLeft8(15, -2))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 33<<32 + 23
n1 := []uint32{33, 23}
// Second number is 21<<32 + 12
n2 := []uint32{21, 12}
// Sub them together without producing carry.
d1, carry := bits.Sub32(n1[1], n2[1], 0)
d0, _ := bits.Sub32(n1[0], n2[0], carry)
nsum := []uint32{d0, d1}
fmt.Printf("%v - %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
// First number is 3<<32 + 2147483647
n1 = []uint32{3, 0x7fffffff}
// Second number is 1<<32 + 2147483648
n2 = []uint32{1, 0x80000000}
// Sub them together producing carry.
d1, carry = bits.Sub32(n1[1], n2[1], 0)
d0, _ = bits.Sub32(n1[0], n2[0], carry)
nsum = []uint32{d0, d1}
fmt.Printf("%v - %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
// First number is 33<<64 + 23
n1 := []uint64{33, 23}
// Second number is 21<<64 + 12
n2 := []uint64{21, 12}
// Sub them together without producing carry.
d1, carry := bits.Sub64(n1[1], n2[1], 0)
d0, _ := bits.Sub64(n1[0], n2[0], carry)
nsum := []uint64{d0, d1}
fmt.Printf("%v - %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
// First number is 3<<64 + 9223372036854775807
n1 = []uint64{3, 0x7fffffffffffffff}
// Second number is 1<<64 + 9223372036854775808
n2 = []uint64{1, 0x8000000000000000}
// Sub them together producing carry.
d1, carry = bits.Sub64(n1[1], n2[1], 0)
d0, _ = bits.Sub64(n1[0], n2[0], carry)
nsum = []uint64{d0, d1}
fmt.Printf("%v - %v = %v (carry bit was %v)\n", n1, n2, nsum, carry)
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("TrailingZeros16(%016b) = %d\n", 14, bits.TrailingZeros16(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("TrailingZeros32(%032b) = %d\n", 14, bits.TrailingZeros32(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("TrailingZeros64(%064b) = %d\n", 14, bits.TrailingZeros64(14))
}
package main
import (
"fmt"
"math/bits"
)
func main() {
fmt.Printf("TrailingZeros8(%08b) = %d\n", 14, bits.TrailingZeros8(14))
}
Package-Level Functions* (total 49)*
Add returns the sum with carry of x, y and carry: sum = x + y + carry.
The carry input must be 0 or 1; otherwise the behavior is undefined.
The carryOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
Add32 returns the sum with carry of x, y and carry: sum = x + y + carry.
The carry input must be 0 or 1; otherwise the behavior is undefined.
The carryOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
Add64 returns the sum with carry of x, y and carry: sum = x + y + carry.
The carry input must be 0 or 1; otherwise the behavior is undefined.
The carryOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
Div returns the quotient and remainder of (hi, lo) divided by y:
quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
half in parameter hi and the lower half in parameter lo.
Div panics for y == 0 (division by zero) or y <= hi (quotient overflow).
Div32 returns the quotient and remainder of (hi, lo) divided by y:
quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
half in parameter hi and the lower half in parameter lo.
Div32 panics for y == 0 (division by zero) or y <= hi (quotient overflow).
Div64 returns the quotient and remainder of (hi, lo) divided by y:
quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
half in parameter hi and the lower half in parameter lo.
Div64 panics for y == 0 (division by zero) or y <= hi (quotient overflow).
LeadingZeros returns the number of leading zero bits in x; the result is UintSize for x == 0.
LeadingZeros16 returns the number of leading zero bits in x; the result is 16 for x == 0.
LeadingZeros32 returns the number of leading zero bits in x; the result is 32 for x == 0.
LeadingZeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.
LeadingZeros8 returns the number of leading zero bits in x; the result is 8 for x == 0.
Len returns the minimum number of bits required to represent x; the result is 0 for x == 0.
Len16 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
Len32 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
Len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
Len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
Mul returns the full-width product of x and y: (hi, lo) = x * y
with the product bits' upper half returned in hi and the lower
half returned in lo.
This function's execution time does not depend on the inputs.
Mul32 returns the 64-bit product of x and y: (hi, lo) = x * y
with the product bits' upper half returned in hi and the lower
half returned in lo.
This function's execution time does not depend on the inputs.
Mul64 returns the 128-bit product of x and y: (hi, lo) = x * y
with the product bits' upper half returned in hi and the lower
half returned in lo.
This function's execution time does not depend on the inputs.
OnesCount returns the number of one bits ("population count") in x.
OnesCount16 returns the number of one bits ("population count") in x.
OnesCount32 returns the number of one bits ("population count") in x.
OnesCount64 returns the number of one bits ("population count") in x.
OnesCount8 returns the number of one bits ("population count") in x.
Rem returns the remainder of (hi, lo) divided by y. Rem panics for
y == 0 (division by zero) but, unlike Div, it doesn't panic on a
quotient overflow.
Rem32 returns the remainder of (hi, lo) divided by y. Rem32 panics
for y == 0 (division by zero) but, unlike Div32, it doesn't panic
on a quotient overflow.
Rem64 returns the remainder of (hi, lo) divided by y. Rem64 panics
for y == 0 (division by zero) but, unlike Div64, it doesn't panic
on a quotient overflow.
Reverse returns the value of x with its bits in reversed order.
Reverse16 returns the value of x with its bits in reversed order.
Reverse32 returns the value of x with its bits in reversed order.
Reverse64 returns the value of x with its bits in reversed order.
Reverse8 returns the value of x with its bits in reversed order.
ReverseBytes returns the value of x with its bytes in reversed order.
This function's execution time does not depend on the inputs.
ReverseBytes16 returns the value of x with its bytes in reversed order.
This function's execution time does not depend on the inputs.
ReverseBytes32 returns the value of x with its bytes in reversed order.
This function's execution time does not depend on the inputs.
ReverseBytes64 returns the value of x with its bytes in reversed order.
This function's execution time does not depend on the inputs.
RotateLeft returns the value of x rotated left by (k mod UintSize) bits.
To rotate x right by k bits, call RotateLeft(x, -k).
This function's execution time does not depend on the inputs.
RotateLeft16 returns the value of x rotated left by (k mod 16) bits.
To rotate x right by k bits, call RotateLeft16(x, -k).
This function's execution time does not depend on the inputs.
RotateLeft32 returns the value of x rotated left by (k mod 32) bits.
To rotate x right by k bits, call RotateLeft32(x, -k).
This function's execution time does not depend on the inputs.
RotateLeft64 returns the value of x rotated left by (k mod 64) bits.
To rotate x right by k bits, call RotateLeft64(x, -k).
This function's execution time does not depend on the inputs.
RotateLeft8 returns the value of x rotated left by (k mod 8) bits.
To rotate x right by k bits, call RotateLeft8(x, -k).
This function's execution time does not depend on the inputs.
Sub returns the difference of x, y and borrow: diff = x - y - borrow.
The borrow input must be 0 or 1; otherwise the behavior is undefined.
The borrowOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
Sub32 returns the difference of x, y and borrow, diff = x - y - borrow.
The borrow input must be 0 or 1; otherwise the behavior is undefined.
The borrowOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
Sub64 returns the difference of x, y and borrow: diff = x - y - borrow.
The borrow input must be 0 or 1; otherwise the behavior is undefined.
The borrowOut output is guaranteed to be 0 or 1.
This function's execution time does not depend on the inputs.
TrailingZeros returns the number of trailing zero bits in x; the result is UintSize for x == 0.
TrailingZeros16 returns the number of trailing zero bits in x; the result is 16 for x == 0.
TrailingZeros32 returns the number of trailing zero bits in x; the result is 32 for x == 0.
TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
TrailingZeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
Package-Level Constants* (only one)*
UintSize is the size of a uint in bits.

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