Question

from msdn.microsoft.com – Enumerating Registry Subkeys:

http://msdn.microsoft.com/En-US/library/ms724256.aspx

// QueryKey - Enumerates the subkeys of key and its associated values.
//     hKey - Key whose subkeys and values are to be enumerated.

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

#define MAX_KEY_LENGTH 255
#define MAX_VALUE_NAME 16383

void QueryKey(HKEY hKey) 
{ 
    TCHAR    achKey[MAX_KEY_LENGTH];   // buffer for subkey name
    DWORD    cbName;                   // size of name string 
    TCHAR    achClass[MAX_PATH] = TEXT("");  // buffer for class name 
    DWORD    cchClassName = MAX_PATH;  // size of class string 
    DWORD    cSubKeys=0;               // number of subkeys 
    DWORD    cbMaxSubKey;              // longest subkey size 
    DWORD    cchMaxClass;              // longest class string 
    DWORD    cValues;              // number of values for key 
    DWORD    cchMaxValue;          // longest value name 
    DWORD    cbMaxValueData;       // longest value data 
    DWORD    cbSecurityDescriptor; // size of security descriptor 
    FILETIME ftLastWriteTime;      // last write time 

    DWORD i, retCode; 

    TCHAR  achValue[MAX_VALUE_NAME]; 
    DWORD cchValue = MAX_VALUE_NAME; 

    // Get the class name and the value count. 
    retCode = RegQueryInfoKey(
        hKey,                    // key handle 
        achClass,                // buffer for class name 
        &cchClassName,           // size of class string 
        NULL,                    // reserved 
        &cSubKeys,               // number of subkeys 
        &cbMaxSubKey,            // longest subkey size 
        &cchMaxClass,            // longest class string 
        &cValues,                // number of values for this key 
        &cchMaxValue,            // longest value name 
        &cbMaxValueData,         // longest value data 
        &cbSecurityDescriptor,   // security descriptor 
        &ftLastWriteTime);       // last write time 

    // Enumerate the subkeys, until RegEnumKeyEx fails.

    if (cSubKeys)
    {
        printf( "\nNumber of subkeys: %d\n", cSubKeys);

        for (i=0; i<cSubKeys; i++) 
        { 
            cbName = MAX_KEY_LENGTH;
            retCode = RegEnumKeyEx(hKey, i,
                     achKey, 
                     &cbName, 
                     NULL, 
                     NULL, 
                     NULL, 
                     &ftLastWriteTime); 
            if (retCode == ERROR_SUCCESS) 
            {
                _tprintf(TEXT("(%d) %s\n"), i+1, achKey);
            }
        }
    } 

    // Enumerate the key values. 

    if (cValues) 
    {
        printf( "\nNumber of values: %d\n", cValues);

        for (i=0, retCode=ERROR_SUCCESS; i<cValues; i++) 
        { 
            cchValue = MAX_VALUE_NAME; 
            achValue[0] = '\0'; 
            retCode = RegEnumValue(hKey, i, 
                achValue, 
                &cchValue, 
                NULL, 
                NULL,
                NULL,
                NULL);

            if (retCode == ERROR_SUCCESS ) 
            { 
                _tprintf(TEXT("(%d) %s\n"), i+1, achValue); 
            } 
        }
    }
}

void __cdecl _tmain(void)
{
   HKEY hTestKey;

   if( RegOpenKeyEx( HKEY_CURRENT_USER,
        TEXT("SOFTWARE\\Microsoft"),
        0,
        KEY_READ,
        &hTestKey) == ERROR_SUCCESS
      )
   {
      QueryKey(hTestKey);
   }

   RegCloseKey(hTestKey);
}

how can i modify that code at:

cchValue = MAX_VALUE_NAME; 
            achValue[0] = '\0'; 
            retCode = RegEnumValue(hKey, i, 
                achValue, 
                &cchValue, 
                NULL, 
                NULL,
                NULL,
                NULL);

            if (retCode == ERROR_SUCCESS ) 
            { 
                _tprintf(TEXT("(%d) %s\n"), i+1, achValue); 
            } 

to output to the console all the values that RegEnumValue function can return,
function at msdn:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms724865%28v=vs.85%29.aspx
i want to output these vars too:

  __out        LPTSTR lpValueName,
  __inout      LPDWORD lpcchValueName,
  __out_opt    LPDWORD lpType,
  __out_opt    LPBYTE lpData,
  __inout_opt  LPDWORD lpcbData

i have tried different things but everytime i change any of NULL var from
that function:

retCode = RegEnumValue(hKey, i,
achValue,
&cchValue,
NULL,
NULL,
NULL,
NULL);

i even don´t get achValue

thanks a lot

PD using windows 7 64 bits visual studio 2010 ultimate

Answer 1

The first of the four NULL values is lpReserved and must be set to NULL.

The second one is lpType and you should be able to get that one by itself.

The third and fourth are paired and must either be set to NULL or both non-NULL. They function much like achValue and cchValue where the first is the buffer to recieve the data and the second is a pointer to the size that must first have the size of the buffer and then gets filled in with the size of the data.

The following code works on my Vista machine:

        const DWORD maxValueBytes=300;
        BYTE valueBytes[maxValueBytes];
        DWORD valueSize=maxValueBytes;
        DWORD valueType=0;
        cchValue = MAX_VALUE_NAME;  
        achValue[0] = '\0';  
        retCode = RegEnumValue(hKey, i,  
            achValue,  
            &cchValue,  
            NULL,  
            &valueType, 
            valueBytes, 
            &valueSize); 

        if (retCode == ERROR_SUCCESS )  
        {  
            _tprintf(TEXT("(%d) %s (%d - %d bytes)\n"), i+1, achValue,valueType,valueSize);  
            switch (valueType) {
                case REG_BINARY:
                    _tprintf(TEXT("   The value is binary (0x%X, 0x%X, 0x%X ...)\n"),valueBytes[0],valueBytes[1],valueBytes[2]);
                    break;
                case REG_DWORD:
                //case REG_DWORD_LITTLE_ENDIAN:
                    _tprintf(TEXT("   The value is a DWORD (%d)\n"),*(DWORD *)valueBytes);
                    break;
                case REG_DWORD_BIG_ENDIAN:
                    _tprintf(TEXT("   The value is a DWORD (big endian) (%d)\n"),(valueBytes[0]<<24)|(valueBytes[1]<<16)|(valueBytes[2]<<8)|valueBytes[3]);
                    break;
                case REG_EXPAND_SZ:
                case REG_SZ:
                    _tprintf(TEXT("   The value is a string\n"));
                  break;
                case REG_LINK:
                    _tprintf(TEXT("   The value is a link\n"));
                  break;
                case REG_MULTI_SZ:
                    _tprintf(TEXT("   The value is a multi-string\n"));
                  break;
                case REG_NONE:
                    _tprintf(TEXT("   There is no spoon... sorry, value\n"));
                  break;
                case REG_RESOURCE_LIST:
                    _tprintf(TEXT("   The value is a resource list\n"));
                  break;
                default:
                    _tprintf(TEXT("   Unknown value type\n"));
                  break;
            }
        }
        else
        {
            _tprintf(TEXT("error reading value %d - %d\n"),i+1,retCode);
        }