Add GetConfigured

GetConfigured returns the number of configured CPUs in the system. This
matches what getconf _SC_NPROCESSORS_CONF returns on a Unix system.

README.md

@@ -4,10 +4,10 @@
 [![GitHub Action Status](https://github.com/tklauser/numcpus/workflows/Tests/badge.svg)](https://github.com/tklauser/numcpus/actions?query=workflow%3ATests)
 [![Go Report Card](https://goreportcard.com/badge/github.com/tklauser/numcpus)](https://goreportcard.com/report/github.com/tklauser/numcpus)
 
-Package numcpus provides information about the number of CPU.
+Package numcpus provides information about the number of CPU in a system.
 
-It gets the number of CPUs (online, offline, present, possible or kernel
-maximum) on a Linux, Darwin, FreeBSD, NetBSD, OpenBSD,  DragonflyBSD or
+It gets the number of CPUs (online, offline, present, possible, configured or
+kernel maximum) on a Linux, Darwin, FreeBSD, NetBSD, OpenBSD,  DragonflyBSD or
 Solaris/Illumos system.
 
 On Linux, the information is retrieved by reading the corresponding CPU
@@ -45,5 +45,5 @@ func main() {
 
 ## References
 
-* [Linux kernel sysfs documenation for CPU attributes](https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-devices-system-cpu)
+* [Linux kernel sysfs documentation for CPU attributes](https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-devices-system-cpu)
 * [Linux kernel CPU topology documentation](https://www.kernel.org/doc/Documentation/cputopology.txt)

numcpus.go

@@ -30,6 +30,13 @@ import "errors"
 // ErrNotSupported is the error returned when the function is not supported.
 var ErrNotSupported = errors.New("function not supported")
 
+// GetConfigured returns the number of CPUs configured on the system. This
+// function should return the same value as `getconf _SC_NPROCESSORS_CONF` on a
+// unix system.
+func GetConfigured() (int, error) {
+	return getConfigured()
+}
+
 // GetKernelMax returns the maximum number of CPUs allowed by the kernel
 // configuration. This function is only supported on Linux systems.
 func GetKernelMax() (int, error) {

numcpus_bsd.go

@@ -23,6 +23,11 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+func getConfigured() (int, error) {
+	n, err := unix.SysctlUint32("hw.ncpu")
+	return int(n), err
+}
+
 func getKernelMax() (int, error) {
 	return 0, ErrNotSupported
 }

numcpus_linux.go

@@ -16,6 +16,7 @@ package numcpus
 
 import (
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -55,6 +56,28 @@ func parseCPURange(cpus string) (int, error) {
 	return n, nil
 }
 
+func getConfigured() (int, error) {
+	d, err := os.Open(sysfsCPUBasePath)
+	if err != nil {
+		return 0, err
+	}
+	defer d.Close()
+	fis, err := d.Readdir(-1)
+	if err != nil {
+		return 0, err
+	}
+	count := 0
+	for _, fi := range fis {
+		if name := fi.Name(); fi.IsDir() && strings.HasPrefix(name, "cpu") {
+			_, err := strconv.ParseInt(name[3:], 10, 64)
+			if err == nil {
+				count++
+			}
+		}
+	}
+	return count, nil
+}
+
 func getKernelMax() (int, error) {
 	buf, err := ioutil.ReadFile(filepath.Join(sysfsCPUBasePath, "kernel_max"))
 	if err != nil {

numcpus_solaris.go

@@ -26,6 +26,11 @@ const (
 	_SC_NPROCESSORS_MAX  = 516
 )
 
+func getConfigured() (int, error) {
+	n, err := unix.Sysconf(_SC_NPROCESSORS_CONF)
+	return int(n), err
+}
+
 func getKernelMax() (int, error) {
 	n, err := unix.Sysconf(_SC_NPROCESSORS_MAX)
 	return int(n), err

numcpus_test.go

@@ -51,6 +51,18 @@ func testGetconf(t *testing.T, got int, name, getconfWhich string) {
 	}
 }
 
+func TestGetConfigured(t *testing.T) {
+	n, err := numcpus.GetConfigured()
+	if errors.Is(err, numcpus.ErrNotSupported) {
+		t.Skipf("GetConfigured not supported on %s", runtime.GOOS)
+	} else if err != nil {
+		t.Fatalf("GetConfigured: %v", err)
+	}
+	t.Logf("Configured = %v", n)
+
+	testGetconf(t, n, "GetConfigured", "_NPROCESSORS_CONF")
+}
+
 func TestGetKernelMax(t *testing.T) {
 	n, err := numcpus.GetKernelMax()
 	if errors.Is(err, numcpus.ErrNotSupported) {

numcpus_unsupported.go

@@ -17,6 +17,10 @@
 
 package numcpus
 
+func getConfigured() (int, error) {
+	return 0, ErrNotSupported
+}
+
 func getKernelMax() (int, error) {
 	return 0, ErrNotSupported
 }