mirror of
https://github.com/wader/fq.git
synced 2024-12-25 06:12:30 +03:00
29 lines
1.1 KiB
Go
29 lines
1.1 KiB
Go
package bitio
|
|
|
|
import "fmt"
|
|
|
|
// ReverseBytes64 reverses the bytes part of the lowest nBits.
|
|
// Similar to bits.ReverseBytes64 but only rotates the lowest bytes and rest of bytes will be zero.
|
|
func ReverseBytes64(nBits int, n uint64) uint64 {
|
|
switch {
|
|
case nBits <= 8:
|
|
return n
|
|
case nBits <= 16:
|
|
return n&0xff00>>8 | n&0xff<<8
|
|
case nBits <= 24:
|
|
return n&0xff<<16 | n&0xff00 | n&0xff0000>>16
|
|
case nBits <= 32:
|
|
return n&0xff<<24 | n&0xff00<<8 | n&0xff0000>>8 | n&0xff000000>>24
|
|
case nBits <= 40:
|
|
return n&0xff<<32 | n&0xff00<<16 | n&0xff0000 | n&0xff000000>>16 | n&0xff00000000>>32
|
|
case nBits <= 48:
|
|
return n&0xff<<40 | n&0xff00<<24 | n&0xff0000<<8 | n&0xff000000>>8 | n&0xff00000000>>24 | n&0xff0000000000>>40
|
|
case nBits <= 56:
|
|
return n&0xff<<48 | n&0xff00<<32 | n&0xff0000<<16 | n&0xff000000 | n&0xff00000000>>16 | n&0xff0000000000>>32 | n&0xff000000000000>>48
|
|
case nBits <= 64:
|
|
return n&0xff<<56 | n&0xff00<<40 | n&0xff0000<<24 | n&0xff000000<<8 | n&0xff00000000>>8 | n&0xff0000000000>>24 | n&0xff000000000000>>40 | n&0xff00000000000000>>56
|
|
default:
|
|
panic(fmt.Sprintf("unsupported bit length %d", nBits))
|
|
}
|
|
}
|