Manipulating Windows Registry - c++

Question

I want every time my program runs make this process:
1- Check if there is a windows registry key called "foo"
2- If it not exists create with the value 10
3- If it exists decrement its value
4- If its value == 0 close de program
I know that i will use this functions, but i don't know how to use them:
RegCreateKeyA, RegSetValueExA
The function to create the key worked, but I can not to set the values and do not know how to do what I need.
HKEY key;
RegCreateKeyA(HKEY_CURRENT_USER,"foo",&key);
RegOpenKeyExA(HKEY_CURRENT_USER,"foo", 0, KEY_ALL_ACCESS, &key);
RegSetValueExA(key,"bar",0,REG_DWORD,(LPBYTE)10,sizeof(10));

Answer 1

Try something like this:
HKEY key;
DWORD disposition;
LONG lRet = RegCreateKeyEx(HKEY_CURRENT_USER, TEXT("foo"), 0, NULL, REG_OPTION_NON_VOLATILE, KEY_QUERY_VALUE | KEY_SET_VALUE, NULL, &key, &disposition);
if (lRet != 0)
{
// error handling...
}
else
{
DWORD value;
if (disposition == REG_CREATED_NEW_KEY)
{
value = 10;
lRet = RegSetValueEx(key, TEXT("bar"), 0, REG_DWORD, (LPBYTE)&value, sizeof(value));
if (lRet != 0)
{
// error handling...
}
}
else
{
DWORD size = sizeof(value);
lRet = RegQueryValueEx(key, TEXT("bar"), NULL, NULL, (LPBYTE)&value, &size);
if (lRet != 0)
{
// error handling...
}
else
{
if (value != 0)
{
--value;
lRet = RegSetValueEx(key, TEXT("bar"), 0, REG_DWORD, (LPBYTE)&value, sizeof(value));
if (lRet != 0)
{
// error handling...
}
}
if (value == 0)
{
// signal app to terminate...
}
}
}
RegCloseKey(key);
}