SystemInfo.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / Util / SystemInfo.cs / 1 / SystemInfo.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

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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