#define WINVER 0x0500
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <stdio.h>
#pragma comment(lib, "advapi32.lib")

// These are internal.
#include <winternl.h>
#include <windef.h>
extern "C" {
	typedef NTSTATUS (WINAPI *PNtSetSystemInformation)(IN SYSTEM_INFORMATION_CLASS, OUT PVOID, IN ULONG);
	
	#define SystemCacheInformation 0x15
	
	typedef struct _SYSTEM_CACHE_INFORMATION {
		unsigned long CurrentSize;
		unsigned long PeakSize;
		unsigned long PageFaultCount;
		unsigned long MinimumWorkingSet;
		unsigned long MaximumWorkingSet;
		unsigned long Unused1;
		unsigned long Unused2;
		unsigned long Unused3;
		unsigned long Unused4;
	} SYSTEM_CACHE_INFORMATION, *PSYSTEM_CACHE_INFORMATION;
}
// End of internal.

int main(int argc, const char* argv[]) {
	// Open the process' token so we can enable the privilege needed.
	HANDLE hToken;
	if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken)) {
		unsigned int err = GetLastError();
		printf("OpenProcessToken error: %u\n", err);
		return err;
	}
	
	// Map the privilege name to it's logon-local ID.
	LUID luid;
	if (!LookupPrivilegeValue(NULL, SE_INCREASE_QUOTA_NAME, &luid)) {
		unsigned int err = GetLastError();
		printf("LookupPrivilegeValue error: %u\n", err);
		return err;
	}
	
	// Try to enable the privilege. If we're not in Administrators, this will
	// almost certainly fail.
	TOKEN_PRIVILEGES tp;
	tp.PrivilegeCount = 1;
	tp.Privileges[0].Luid = luid;
	tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
	if (!AdjustTokenPrivileges(hToken, FALSE, &tp, sizeof(TOKEN_PRIVILEGES), (PTOKEN_PRIVILEGES)NULL, (PDWORD)NULL)) {
		unsigned int err = GetLastError();
		printf("AdjustTokenPrivileges error: %u\n", err);
		return err;
	}
	if (GetLastError() == ERROR_NOT_ALL_ASSIGNED) {
		printf("The token does not have the specified privilege.\n");
		return GetLastError();
	}
	
	// Get the internal API we're going to use and set the working set values
	// to the special values that tell it to clear the file system cache.
	PNtSetSystemInformation NtSetSystemInformation;
	NtSetSystemInformation = (PNtSetSystemInformation)GetProcAddress(LoadLibrary("ntdll.dll"), "NtSetSystemInformation");
	SYSTEM_CACHE_INFORMATION info;
	info.MinimumWorkingSet = 0xFFFFFFFF;
	info.MaximumWorkingSet = 0xFFFFFFFF;
	unsigned int rv = NtSetSystemInformation((SYSTEM_INFORMATION_CLASS)SystemCacheInformation, &info, sizeof(info));
	if (rv != 0) {
		printf("NtSetSystemInformation error: %u\n", rv);
		return rv;
	}
	
	return 0;
}