Enumerating subkeys with CSettingsStore

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;
}