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//go:build purego || !amd64
// +build purego !amd64
package ascii
import (
"unsafe"
)
// ValidString returns true if s contains only ASCII characters.
func ValidString(s string) bool {
p := *(*unsafe.Pointer)(unsafe.Pointer(&s))
i := uintptr(0)
n := uintptr(len(s))
for i+8 <= n {
if (*(*uint64)(unsafe.Pointer(uintptr(p) + i)) & 0x8080808080808080) != 0 {
return false
}
i += 8
}
if i+4 <= n {
if (*(*uint32)(unsafe.Pointer(uintptr(p) + i)) & 0x80808080) != 0 {
return false
}
i += 4
}
if i == n {
return true
}
p = unsafe.Pointer(uintptr(p) + i)
var x uint32
switch n - i {
case 3:
x = uint32(*(*uint16)(p)) | uint32(*(*uint8)(unsafe.Pointer(uintptr(p) + 2)))<<16
case 2:
x = uint32(*(*uint16)(p))
case 1:
x = uint32(*(*uint8)(p))
default:
return true
}
return (x & 0x80808080) == 0
}
|
