windows: add Get{Active,Maximum}ProcesorCount

Reference:
https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getactiveprocessorcount
https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getmaximumprocessorcount

Change-Id: Ifca711b82f112b395eac3b96266f63b5623881fc
Reviewed-on: https://go-review.googlesource.com/c/sys/+/374435
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Patrik Nyblom <pnyb@google.com>
Trust: Patrik Nyblom <pnyb@google.com>
Run-TryBot: Patrik Nyblom <pnyb@google.com>

windows/syscall_windows.go

@@ -363,6 +363,8 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	SetProcessWorkingSetSizeEx(hProcess Handle, dwMinimumWorkingSetSize uintptr, dwMaximumWorkingSetSize uintptr, flags uint32) (err error)
 //sys	GetCommTimeouts(handle Handle, timeouts *CommTimeouts) (err error)
 //sys	SetCommTimeouts(handle Handle, timeouts *CommTimeouts) (err error)
+//sys	GetActiveProcessorCount(groupNumber uint16) (ret uint32)
+//sys	GetMaximumProcessorCount(groupNumber uint16) (ret uint32)
 
 // Volume Management Functions
 //sys	DefineDosDevice(flags uint32, deviceName *uint16, targetPath *uint16) (err error) = DefineDosDeviceW

windows/types_windows.go

@@ -3172,3 +3172,5 @@ type ModuleInfo struct {
 	SizeOfImage uint32
 	EntryPoint  uintptr
 }
+
+const ALL_PROCESSOR_GROUPS = 0xFFFF

windows/zsyscall_windows.go

@@ -226,6 +226,7 @@ var (
 	procFreeLibrary                                          = modkernel32.NewProc("FreeLibrary")
 	procGenerateConsoleCtrlEvent                             = modkernel32.NewProc("GenerateConsoleCtrlEvent")
 	procGetACP                                               = modkernel32.NewProc("GetACP")
+	procGetActiveProcessorCount                              = modkernel32.NewProc("GetActiveProcessorCount")
 	procGetCommTimeouts                                      = modkernel32.NewProc("GetCommTimeouts")
 	procGetCommandLineW                                      = modkernel32.NewProc("GetCommandLineW")
 	procGetComputerNameExW                                   = modkernel32.NewProc("GetComputerNameExW")
@@ -251,6 +252,7 @@ var (
 	procGetLogicalDriveStringsW                              = modkernel32.NewProc("GetLogicalDriveStringsW")
 	procGetLogicalDrives                                     = modkernel32.NewProc("GetLogicalDrives")
 	procGetLongPathNameW                                     = modkernel32.NewProc("GetLongPathNameW")
+	procGetMaximumProcessorCount                             = modkernel32.NewProc("GetMaximumProcessorCount")
 	procGetModuleFileNameW                                   = modkernel32.NewProc("GetModuleFileNameW")
 	procGetModuleHandleExW                                   = modkernel32.NewProc("GetModuleHandleExW")
 	procGetNamedPipeHandleStateW                             = modkernel32.NewProc("GetNamedPipeHandleStateW")
@@ -1967,6 +1969,12 @@ func GetACP() (acp uint32) {
 	return
 }
 
+func GetActiveProcessorCount(groupNumber uint16) (ret uint32) {
+	r0, _, _ := syscall.Syscall(procGetActiveProcessorCount.Addr(), 1, uintptr(groupNumber), 0, 0)
+	ret = uint32(r0)
+	return
+}
+
 func GetCommTimeouts(handle Handle, timeouts *CommTimeouts) (err error) {
 	r1, _, e1 := syscall.Syscall(procGetCommTimeouts.Addr(), 2, uintptr(handle), uintptr(unsafe.Pointer(timeouts)), 0)
 	if r1 == 0 {
@@ -2169,6 +2177,12 @@ func GetLongPathName(path *uint16, buf *uint16, buflen uint32) (n uint32, err er
 	return
 }
 
+func GetMaximumProcessorCount(groupNumber uint16) (ret uint32) {
+	r0, _, _ := syscall.Syscall(procGetMaximumProcessorCount.Addr(), 1, uintptr(groupNumber), 0, 0)
+	ret = uint32(r0)
+	return
+}
+
 func GetModuleFileName(module Handle, filename *uint16, size uint32) (n uint32, err error) {
 	r0, _, e1 := syscall.Syscall(procGetModuleFileNameW.Addr(), 3, uintptr(module), uintptr(unsafe.Pointer(filename)), uintptr(size))
 	n = uint32(r0)