Fix memory stats on Darwin, non-CGO

mem/mem_darwin.go

@@ -3,12 +3,29 @@
 package mem
 
 import (
+	"encoding/binary"
 	"strconv"
 	"strings"
+	"syscall"
 
 	"github.com/shirou/gopsutil/internal/common"
 )
 
+func getHwMemsize() (uint64, error) {
+	totalString, err := syscall.Sysctl("hw.memsize")
+	if err != nil {
+		return 0, err
+	}
+
+	// syscall.sysctl() helpfully assumes the result is a null-terminated string and
+	// removes the last byte of the result if it's 0 :/
+	totalString += "\x00"
+
+	total := uint64(binary.LittleEndian.Uint64([]byte(totalString)))
+
+	return total, nil
+}
+
 // SwapMemory returns swapinfo.
 func SwapMemory() (*SwapMemoryStat, error) {
 	var ret *SwapMemoryStat

mem/mem_darwin_cgo.go

@@ -9,7 +9,6 @@ package mem
 import "C"
 
 import (
-	"encoding/binary"
 	"fmt"
 	"syscall"
 	"unsafe"
@@ -30,14 +29,10 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 	}
 
 	pageSize := uint64(syscall.Getpagesize())
-
-	totalString, err := syscall.Sysctl("hw.memsize")
+	total, err := getHwMemsize()
 	if err != nil {
 		return nil, err
 	}
-	// syscall.sysctl() helpfully removes the last byte of the result if it's 0 :/
-	totalString += "\x00"
-	total := uint64(binary.LittleEndian.Uint64([]byte(totalString)))
 	totalCount := C.natural_t(total / pageSize)
 
 	availableCount := vmstat.inactive_count + vmstat.free_count

mem/mem_darwin_nocgo.go

@@ -8,8 +8,6 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
-
-	"github.com/shirou/gopsutil/internal/common"
 )
 
 // Runs vm_stat and returns Free and inactive pages
@@ -67,11 +65,7 @@ func parseVMStat(out string, vms *VirtualMemoryStat) error {
 func VirtualMemory() (*VirtualMemoryStat, error) {
 	ret := &VirtualMemoryStat{}
 
-	t, err := common.DoSysctrl("hw.memsize")
-	if err != nil {
-		return nil, err
-	}
-	total, err := strconv.ParseUint(t[0], 10, 64)
+	total, err := getHwMemsize()
 	if err != nil {
 		return nil, err
 	}
@@ -83,8 +77,8 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 	ret.Available = ret.Free + ret.Inactive
 	ret.Total = total
 
-	ret.Used = ret.Total - ret.Free
-	ret.UsedPercent = float64(ret.Total-ret.Available) / float64(ret.Total) * 100.0
+	ret.Used = ret.Total - ret.Available
+	ret.UsedPercent = 100 * float64(ret.Used) / float64(ret.Total)
 
 	return ret, nil
 }