// Copyright 2018 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// CPU affinity functions

package unix

import (

	"unsafe"

)

const cpuSetSize = _CPU_SETSIZE / _NCPUBITS

// CPUSet represents a CPU affinity mask.

type CPUSet [cpuSetSize]cpuMask

func schedAffinity(trap uintptr, pid int, set *CPUSet) error {

	_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(*set)), uintptr(unsafe.Pointer(set)))

	if e != 0 {

		return errnoErr(e)

	}

	return nil

}

// SchedGetaffinity gets the CPU affinity mask of the thread specified by pid.

// If pid is 0 the calling thread is used.

func SchedGetaffinity(pid int, set *CPUSet) error {

	return schedAffinity(SYS_SCHED_GETAFFINITY, pid, set)

}

// SchedSetaffinity sets the CPU affinity mask of the thread specified by pid.

// If pid is 0 the calling thread is used.

func SchedSetaffinity(pid int, set *CPUSet) error {

	return schedAffinity(SYS_SCHED_SETAFFINITY, pid, set)

}

// Zero clears the set s, so that it contains no CPUs.

func (s *CPUSet) Zero() {

	for i := range s {

		s[i] = 0

	}

}

func cpuBitsIndex(cpu int) int {

	return cpu / _NCPUBITS

}

func cpuBitsMask(cpu int) cpuMask {

	return cpuMask(1 << (uint(cpu) % _NCPUBITS))

}

// Set adds cpu to the set s.

func (s *CPUSet) Set(cpu int) {

	i := cpuBitsIndex(cpu)

	if i < len(s) {

		s[i] |= cpuBitsMask(cpu)

	}

}

// Clear removes cpu from the set s.

func (s *CPUSet) Clear(cpu int) {

	i := cpuBitsIndex(cpu)

	if i < len(s) {

		s[i] &^= cpuBitsMask(cpu)

	}

}

// IsSet reports whether cpu is in the set s.

func (s *CPUSet) IsSet(cpu int) bool {

	i := cpuBitsIndex(cpu)

	if i < len(s) {

		return s[i]&cpuBitsMask(cpu) != 0

	}

	return false

}

// Count returns the number of CPUs in the set s.

func (s *CPUSet) Count() int {

	c := 0

	for _, b := range s {

	}

	return c

}