#include <Windows.h>
#include <cstdio>

VOID PrintHex(PBYTE Data, ULONG dwBytes) {
  for (ULONG i = 0; i < dwBytes; i += 16) {
    printf("%.8x: ", i);

    for (ULONG j = 0; j < 16; j++) {
      if (i + j < dwBytes) {
        printf("%.2x ", Data[i + j]);
      }
      else {
        printf("?? ");
      }
    }

    for (ULONG j = 0; j < 16; j++) {
      if (i + j < dwBytes && Data[i + j] >= 0x20 && Data[i + j] <= 0x7e) {
        printf("%c", Data[i + j]);
      }
      else {
        printf(".");
      }
    }

    printf("\n");
  }
}

int main() {
  HMODULE hAdvapi32 = LoadLibrary(L"advapi32.dll");
  DWORD (WINAPI *WmiOpenBlock)(
    _In_  GUID  *DataBlockGuid,
    _In_  ULONG DesiredAccess,
    _Out_ PVOID *DataBlockObject
    ) = (DWORD (WINAPI *)(GUID *, ULONG, PVOID *))GetProcAddress(hAdvapi32, "WmiOpenBlock");
  DWORD (WINAPI *WmiQueryAllDataW)(
    _In_      PVOID DataBlockObject,
    _Inout_   ULONG *InOutBufferSize,
    _Out_opt_ PVOID OutBuffer
    ) = (DWORD (WINAPI *)(PVOID, ULONG *, PVOID))GetProcAddress(hAdvapi32, "WmiQueryAllDataW");
  DWORD(WINAPI *WmiCloseBlock)(
    _In_ HANDLE Handle
    ) = (DWORD (WINAPI *)(HANDLE))GetProcAddress(hAdvapi32, "WmiCloseBlock");

  // Open the disk perf WMI block.
  DWORD DiskPerfGuid[] = { 0xBDD865D1, 0x11D0D7C1, 0xA00001A5, 0x102906C9 };
  HANDLE hwmi = NULL;
  DWORD st = WmiOpenBlock((GUID *)DiskPerfGuid, GENERIC_READ, &hwmi);

  if (st != ERROR_SUCCESS) {
    printf("WmiOpenBlock failed, %d\n", st);
    return 1;
  }
  
  // Request the necessary buffer size.
  DWORD InOutBufferSize = 0;
  st = WmiQueryAllDataW(hwmi, &InOutBufferSize, NULL);
  if (st != ERROR_INSUFFICIENT_BUFFER) {
    printf("WmiQueryAllDataW#1 failed, %d\n", st);
    WmiCloseBlock(hwmi);
    return 1;
  }

  // Allocate memory and read the output data in full.
  LPVOID lpBuffer = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, InOutBufferSize);
  st = WmiQueryAllDataW(hwmi, &InOutBufferSize, lpBuffer);
  if (st == ERROR_SUCCESS) {
    PrintHex((PBYTE)lpBuffer, InOutBufferSize);
  } else {
    printf("WmiQueryAllDataW#2 failed, %d\n", st);
  }

  // Free resources.
  HeapFree(GetProcessHeap(), 0, lpBuffer);
  WmiCloseBlock(hwmi);

  return 0;
}