Getting Process ID

#include <Windows.h>
#include <ntstatus.h>

#define NT_SUCCESS(Status) ((NTSTATUS)(Status) >= 0)

enum SYSTEM_INFORMATION_CLASS { SystemProcessInformation = 5 };

struct SYSTEM_PROCESS_INFORMATION
{
    ULONG NextEntryOffset;
    DWORD unused0[14];
    WCHAR* ImageName;
    DWORD unused1;
    HANDLE UniqueProcessId;
};

extern "C" NTSTATUS __stdcall NtQuerySystemInformation(SYSTEM_INFORMATION_CLASS systemInformationClass, void* pSystemInformation, ULONG systemInformationLength, ULONG* pReturnLength);

DWORD GetProcessID(wstring const& ImageName)
{
    size_t size = 0x10000;
    string Data;
    Data.resize(size);

    NTSTATUS status;
    while ((status = NtQuerySystemInformation(SystemProcessInformation, (char*)Data.data(), (ULONG)Data.size(), nullptr)) == STATUS_INFO_LENGTH_MISMATCH)
        Data.resize(size *= 2);

    if (!NT_SUCCESS(status))
        throw runtime_error("NtQuerySystemInformation failed");

    auto pProcessInfo = (SYSTEM_PROCESS_INFORMATION*)Data.data();
    while (true)
    {
        if (pProcessInfo->ImageName && !_wcsicmp(pProcessInfo->ImageName, ImageName.c_str()))
            return (DWORD)pProcessInfo->UniqueProcessId;

        if (!pProcessInfo->NextEntryOffset)
            break;

        pProcessInfo = (SYSTEM_PROCESS_INFORMATION*)((byte*)pProcessInfo + pProcessInfo->NextEntryOffset);
    }

    throw runtime_error("process not found");
}