Using purego on darwin

[uubulb]

Is your feature request related to a problem? Please describe.
cgo implementions on darwin #66

Describe the solution you'd like
purego has relatively good support for Darwin, perhaps gopsutil can use it to replace current cgo implementations.
I tried to port perCPUTimes with purego and it seems working:

package main

import (
	"fmt"
	"unsafe"

	"github.com/ebitengine/purego"
)

const (
	KERN_SUCCESS            = 0
	PROCESSOR_CPU_LOAD_INFO = 2

	CPU_STATE_USER          = 0
	CPU_STATE_SYSTEM        = 1
	CPU_STATE_IDLE          = 2
	CPU_STATE_NICE          = 3
	CPU_STATE_MAX           = 4
)

var (
	hostProcessorInfo func(host uint32, flavor int, outProcessorCount *uint32, outProcessorInfo uintptr,
		outProcessorInfoCnt *uint32) int
	machHostSelf func() uint32
	machTaskSelf func() uint32
	vmDeallocate func(targetTask uint32, vmAddress, vmSize uintptr) int
)

var ClocksPerSec = float64(128)

type processorCpuLoadInfo struct {
	cpuTicks [CPU_STATE_MAX]uint32
}

type cpuStat struct {
	CPU    string
	User   float64
	System float64
	Nice   float64
	Idle   float64
}

func main() {
	mach, err := purego.Dlopen("/usr/lib/system/libsystem_kernel.dylib", purego.RTLD_LAZY|purego.RTLD_GLOBAL)
	if err != nil {
		fmt.Println(err)
		return
	}
	defer purego.Dlclose(mach)

	purego.RegisterLibFunc(&hostProcessorInfo, mach, "host_processor_info")
	purego.RegisterLibFunc(&machHostSelf, mach, "mach_host_self")
	purego.RegisterLibFunc(&machTaskSelf, mach, "mach_task_self")
	purego.RegisterLibFunc(&vmDeallocate, mach, "vm_deallocate")

	var count, ncpu uint32
	var cpuload *processorCpuLoadInfo

	status := hostProcessorInfo(machHostSelf(), PROCESSOR_CPU_LOAD_INFO, &ncpu,
		uintptr(unsafe.Pointer(&cpuload)), &count)

	if status != KERN_SUCCESS {
		return
	}

	defer vmDeallocate(machTaskSelf(), uintptr(unsafe.Pointer(cpuload)), uintptr(ncpu))

	ret := []cpuStat{}
	loads := unsafe.Slice(cpuload, ncpu)

	for i := 0; i < int(ncpu); i++ {
		c := cpuStat{
			CPU:    fmt.Sprintf("cpu%d", i),
			User:   float64(loads[i].cpuTicks[CPU_STATE_USER]) / ClocksPerSec,
			System: float64(loads[i].cpuTicks[CPU_STATE_SYSTEM]) / ClocksPerSec,
			Nice:   float64(loads[i].cpuTicks[CPU_STATE_NICE]) / ClocksPerSec,
			Idle:   float64(loads[i].cpuTicks[CPU_STATE_IDLE]) / ClocksPerSec,
		}

		ret = append(ret, c)
	}

	fmt.Println(ret)
}

The output values should resemble those of the cgo counterpart.

Describe alternatives you've considered
N/A

Additional context
N/A

[shirou]

Thank you for your suggestion. Yes, I completely and totally agree. I've always thought that purego is a great library for gopsutil. However, there is one problem—I don't own a mac, so I can't develop on it. I look forward to contributions from everyone!