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//------------------------------------------------------------------------------
// <copyright file="SystemInfo.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.Util {
internal static class SystemInfo {
static int _trueNumberOfProcessors;
static internal int GetNumProcessCPUs() {
if (_trueNumberOfProcessors == 0) {
UnsafeNativeMethods.SYSTEM_INFO si;
UnsafeNativeMethods.GetSystemInfo(out si);
if (si.dwNumberOfProcessors == 1) {
_trueNumberOfProcessors = 1;
}
else {
// KERNEL32.DLL:GetCurrentProcess() always returns -1 under NT
// Note: not really a handle (no need to CloseHandle())
IntPtr processHandle = UnsafeNativeMethods.INVALID_HANDLE_VALUE;
IntPtr processAffinityMask;
IntPtr systemAffinityMask;
int returnCode = UnsafeNativeMethods.GetProcessAffinityMask(
processHandle, out processAffinityMask, out systemAffinityMask);
if (returnCode == 0) {
_trueNumberOfProcessors = 1;
}
else {
// if cpu affinity is set to a single processor busy waiting is a waste of time
int numProcessors = 0;
if (IntPtr.Size == 4) {
uint mask = (uint) processAffinityMask;
for (; mask != 0; mask >>= 1) {
if ((mask & 1) == 1) {
++numProcessors;
}
}
}
else {
ulong mask = (ulong) processAffinityMask;
for (; mask != 0; mask >>= 1) {
if ((mask & 1) == 1) {
++numProcessors;
}
}
}
_trueNumberOfProcessors = numProcessors;
}
}
}
Debug.Assert(_trueNumberOfProcessors > 0);
return _trueNumberOfProcessors;
}
}
}
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