Enumerating subkeys with CSettingsStore - visual-c++

Question

I have been looking at using CSettingsStore class.
I know how to read a value from the registry. Example:
CSettingsStore store(TRUE, TRUE);
if (store.Open(_T("Software\\TruckleSoft\\VisitsRota")))
{
if (store.Read(_T("AppPath"), m_strPathVisitsRota))
{
//yes, but is the path still valid
if (!PathFileExists(m_strPathVisitsRota))
{
// it exists
m_strPathVisitsRota = _T("");
}
}
}
Now, in the documentation is states:
The security access depends on the bReadOnly parameter. If bReadonly is FALSE, the security access will be set to KEY_ALL_ACCESS. If bReadyOnly is TRUE, the security access will be set to a combination of KEY_QUERY_VALUE, KEY_NOTIFY and KEY_ENUMERATE_SUB_KEYS.
So it implies you can enumerate sub keys. But I can't find an example explaining about to enumerate a set of key / value pairs using this class.

Answer 1

Note that KEY_ENUMERATE_SUB_KEYS is a flag which request access to enumerate the subkeys, it doesn't actually do it.
KEY_ALL_ACCESS is a combination of different flags, including KEY_ENUMERATE_SUB_KEYS. So in both cases enumeration access is requested.
To enumerate values we need ::RegEnumValue API, this method is not wrapped in CRegKey, but it doesn't matter, we can get HKEY directly.
Here is example, based on your code and Microsoft sample
void CMySettingsStore::EnumKeys(std::vector<CString>& vec)
{
vec.clear();
DWORD subkey_total;
if (ERROR_SUCCESS != RegQueryInfoKey(m_reg.m_hKey, NULL, NULL, NULL,
&subkey_total, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
return;
wchar_t buf[1024];
for (DWORD i = 0; i < subkey_total; i++)
{
DWORD len = _countof(buf);
if (ERROR_SUCCESS == m_reg.EnumKey(i, buf, &len))
vec.push_back(buf);
}
}
void CMySettingsStore::EnumValues(std::vector<CString>& vec)
{
vec.clear();
DWORD values_total;
if (ERROR_SUCCESS != RegQueryInfoKey(m_reg.m_hKey, NULL, NULL, NULL,
NULL, NULL, NULL, &values_total, NULL, NULL, NULL, NULL))
return;
wchar_t buf[1024];
for (DWORD i = 0; i < values_total; i++)
{
DWORD len = _countof(buf);
if (ERROR_SUCCESS == RegEnumValue(m_reg.m_hKey, i, buf, &len,
NULL, NULL, NULL, NULL))
vec.push_back(buf);
}
}
Udpate from Question Author
This code does not resolve all the code analysis warnings but it does add error handling and support for obtaining the value types:
#include "stdafx.h"
#include "MySettingsStore.h"
CMySettingsStore::CMySettingsStore(BOOL bAdmin, BOOL bReadOnly)
: CSettingsStore(bAdmin, bReadOnly)
{
}
bool CMySettingsStore::EnumKeys(std::vector<CString>& vec)
{
vec.clear();
DWORD subkey_total{}, lResult{};
if (RegQueryInfoKey(m_reg.m_hKey, NULL, NULL, NULL,
&subkey_total, NULL, NULL, NULL, NULL, NULL, NULL, NULL) != ERROR_SUCCESS)
{
const DWORD dwError = ::GetLastError();
AfxMessageBox(GetLastErrorAsString(dwError), MB_OK | MB_ICONWARNING);
return false;
}
wchar_t buf[1024];
for (DWORD i = 0; i < subkey_total; i++)
{
DWORD len = _countof(buf);
lResult = m_reg.EnumKey(i, buf, &len);
if(lResult == ERROR_SUCCESS || ERROR_NO_MORE_ITEMS)
vec.push_back(buf);
}
if (lResult != ERROR_NO_MORE_ITEMS)
{
const DWORD dwError = ::GetLastError();
AfxMessageBox(GetLastErrorAsString(dwError), MB_OK | MB_ICONWARNING);
return false;
}
return true;
}
bool CMySettingsStore::EnumValues(std::map<CString, DWORD>& map)
{
map.clear();
DWORD values_total{}, dwType{}, lResult{};
if (RegQueryInfoKey(m_reg.m_hKey, NULL, NULL, NULL,
NULL, NULL, NULL, &values_total, NULL, NULL, NULL, NULL) != ERROR_SUCCESS)
{
const DWORD dwError = ::GetLastError();
AfxMessageBox(GetLastErrorAsString(dwError), MB_OK | MB_ICONWARNING);
return false;
}
wchar_t buf[1024];
for (DWORD i = 0; i < values_total; i++)
{
DWORD len = _countof(buf);
lResult = RegEnumValue(m_reg.m_hKey, i, buf, &len,
NULL, &dwType, NULL, NULL);
if(lResult == ERROR_SUCCESS || lResult == ERROR_NO_MORE_ITEMS)
map.emplace(buf, dwType);
}
if (lResult != ERROR_NO_MORE_ITEMS)
{
const DWORD dwError = ::GetLastError();
AfxMessageBox(GetLastErrorAsString(dwError), MB_OK | MB_ICONWARNING);
return false;
}
return true;
}
CString CMySettingsStore::GetLastErrorAsString(DWORD dwError)
{
LPVOID lpMsgBuf{};
CString strError;
::FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
nullptr,
dwError,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR)&lpMsgBuf,
0,
nullptr);
strError = static_cast<LPTSTR>(lpMsgBuf);
LocalFree(lpMsgBuf);
return strError;
}

Answer 2

This answer is a work in progress.
Header
#pragma once
#include <afxsettingsstore.h>
#include <vector>
class CMySettingsStore :
public CSettingsStore
{
public:
CMySettingsStore(BOOL bAdmin, BOOL bReadOnly);
void EnumKey(std::vector<CString> &vecKeys);
};
Source
#include "pch.h"
#include "CMySettingsStore.h"
CMySettingsStore::CMySettingsStore(BOOL bAdmin, BOOL bReadOnly)
: CSettingsStore(bAdmin, bReadOnly)
{
}
void CMySettingsStore::EnumKey(std::vector<CString>& vecKeys)
{
DWORD dwIndex = 0;
long lResult = ERROR_SUCCESS;
vecKeys.clear();
while (lResult == ERROR_SUCCESS)
{
CString strSubKey;
DWORD dwLength = _MAX_PATH;
lResult = m_reg.EnumKey(dwIndex, strSubKey.GetBuffer(_MAX_PATH), &dwLength);
strSubKey.ReleaseBuffer();
dwIndex++;
vecKeys.push_back(strSubKey);
}
}
Test Code
Code assumes there is a CListBox control on your dialog:
CMySettingsStore mySettings(FALSE, TRUE);
if (mySettings.Open(_T("Software\\xxxx")))
{
std::vector<CString> list;
mySettings.EnumKey(list);
mySettings.Close();
for (const auto& strSubKey : list)
{
m_lbData.AddString(strSubKey);
}
}
The above works and gives me a list of subkeys for the specified key. However, I have not yet worked out how to enumerate the values in a given key.