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I'm trying to get the last opened directory by an open file dialog, and it seems that we can get it by first retrieving the key's name that contains the path using the first BYTE of the MRUListEx key, then the path can be obtained by reading the value of this key's name.
MRUListEx key can be find at: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedPidlMRU.
The problem is that I don't know how to properly fill the "SHITEMID" structure. (it doesn't let me access the index, and it throws a Memory access violation). I don't even know if the code below is valid in any points.
Sorry, the code is very dirty for the moment but I'll revamps it when I finally find what causes these errors.
void MyClass::OnDocumentSave(bool showSaveDlg)
{
// Do something that is not relevant here...
try {
HKEY hKey = NULL;
std::wstring regPath = LR"(Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedPidlMRU\)";
LSTATUS statusCode = RegOpenKeyExW(HKEY_CURRENT_USER, regPath.data(), 0, KEY_QUERY_VALUE, &hKey);
if (statusCode != ERROR_SUCCESS)
throw std::exception(std::string("Unable to open the specified registry key, sys err code: ") + std::to_string(statusCode));
BYTE data[MAX_PATH];
DWORD bufferSize = MAX_PATH;
statusCode = RegGetValueW(hKey, L"", L"MRUListEx", RRF_RT_REG_BINARY, NULL, &data, &bufferSize);
if (statusCode != ERROR_SUCCESS)
throw std::runtime_error(std::string("Failed at RegGetValue() Sys error code: ") + std::to_string(statusCode));
// Please note that the buffer has intentionally a fixed size here and everything is
// simplified for readability, but it uses dynamic memory allocation in the real code to
// handle errors such as ERROR_MORE_DATA
BYTE* pathData[512];
bufferSize = 512;
DWORD type = 0; // In case it matters, the returned value is 3
statusCode = RegGetValueW(hKey, L"", std::to_wstring(data[0]).c_str(), RRF_RT_REG_BINARY, &type, &pathData, &bufferSize);
if (statusCode != ERROR_SUCCESS)
throw std::runtime_error(std::string("Failed at RegGetValue() Sys error code: ") + std::to_string(statusCode));
// I don't know how to fill this structure, the documentation is very minimal,
// and I don't understand it.
int offset = sizeof(APPNAME);
SHITEMID shellIDList[2]{
// Throw a memory access violation at 0x*****, the debugger can't seems to
// get anything in pathData.
{ sizeof(USHORT) + sizeof(pathData), *pathData[0 + offset] },
{ 0, 0 } };
ITEMIDLIST idl{ shellIDList[0] };
// This is supposed give me the last path that was opened by a File Picker.
SHGetPathFromIDListW(&idl, initialDir.data());
}
catch (std::exception& e) {
// Silently set the initial directory to a hard-coded path instead of getting the registry value.
}
}
You don't seem to understand how types and simple arrays work! BYTE* pathData[512]; is not a 512 byte buffer. Use BYTE pathData[512];.
After reading into pathData, call SHGetPathFromIDList((PCIDLIST_ABSOLUTE) pathData, ...);.
That being said, that ComDlg32 key is undocumented and I don't think it stores a pidl so even if your code is corrected it is not going to work.
EnumMRUListW is a documented function you can call but it is not going to help you decode the data.
It looks to me like the location might be prefixed with the name of the .exe so as a minimum you would have to skip (lstrlenW(pathData)+1)*2 bytes before you find the real data...
If you're going for undocumented stuff, here is a code that can dump an MRU list like the LastVisitedPidlMRU one:
// the Shell object that can read MRU lists
static GUID CLSID_MruLongList = { 0x53bd6b4e,0x3780,0x4693,{0xaf,0xc3,0x71,0x61,0xc2,0xf3,0xee,0x9c} };
typedef enum MRULISTF
{
MRULISTF_USE_MEMCMP = 0x0,
MRULISTF_USE_STRCMPIW = 0x1,
MRULISTF_USE_STRCMPW = 0x2,
MRULISTF_USE_ILISEQUAL = 0x3,
};
typedef int (__stdcall *MRUDATALISTCOMPARE)(const BYTE*, const BYTE*, int);
MIDL_INTERFACE("00000000-0000-0000-0000-000000000000") // unknown guid but we don't care
IMruDataCompare : public IUnknown
{
public:
virtual HRESULT CompareItems(const BYTE*, int, const BYTE*, int) = 0;
};
MIDL_INTERFACE("d2c22919-91f5-4284-8807-58a2d64e561c")
IMruDataList2 : public IUnknown
{
public:
virtual HRESULT InitData(UINT uMax, MRULISTF flags, HKEY hKey, LPCWSTR pszSubKey, MRUDATALISTCOMPARE pfnCompare) = 0;
virtual HRESULT AddData(const BYTE* pData, DWORD cbData, DWORD* pdwSlot) = 0;
virtual HRESULT InsertData(const BYTE*, DWORD cbData, int* piIndex, DWORD* pdwSlot) = 0;
virtual HRESULT FindData(const BYTE* pData, DWORD cbData, int* piIndex) = 0;
virtual HRESULT GetData(int iIndex, BYTE* pData, DWORD cbData) = 0;
virtual HRESULT QueryInfo(int iIndex, DWORD* pdwSlot, DWORD* pcbData) = 0;
virtual HRESULT Delete(int iIndex) = 0;
virtual HRESULT InitData2(UINT uMax, MRULISTF flags, HKEY hKey, LPCWSTR pszSubKey, IMruDataCompare* pfnCompare) = 0;
};
int main()
{
CoInitialize(NULL);
{
CComPtr<IMruDataList2> mru;
if (SUCCEEDED(mru.CoCreateInstance(CLSID_MruLongList)))
{
const int max = 100; // get max 100 entries
mru->InitData(max, MRULISTF_USE_MEMCMP, HKEY_CURRENT_USER, L"Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\ComDlg32\\LastVisitedPidlMRU\\", nullptr);
for (auto i = 0; i < max; i++)
{
DWORD slot;
DWORD size;
// get size
if (FAILED(mru->QueryInfo(i, &slot, &size)))
continue;
// get data
// note beginning is a LPWSTR containing exe data
auto data = (LPBYTE)_alloca(size);
if (FAILED(mru->GetData(i, data, size)))
continue;
// the rest is a PIDL
auto pidl = (LPCITEMIDLIST)(data + (lstrlen((LPWSTR)data) + 1) * 2);
// get the shell item
CComPtr<IShellItem> item;
if (SUCCEEDED(SHCreateItemFromIDList(pidl, IID_PPV_ARGS(&item))))
{
// get its path
CComHeapPtr<WCHAR> path;
item->GetDisplayName(SIGDN::SIGDN_DESKTOPABSOLUTEPARSING, &path);
wprintf(L"Executable: %s LastVisited: %s\n", data, path);
}
}
}
}
CoUninitialize();
}
PS: I'm using ATL's smart classes
I finally figured out how to create an ITEMIDLIST structure, and it all works well.
Explanations:
After some test, I've concluded that this value is not necessarily updated. The application that uses a file picker needs to write to the registry to reflect changes.
For example, VS Community 2022 / VS Code updates this value, but the new Microsoft Notepad does not (not sure for the old one). Apparently, .NET applications seem to be updated automatically, though.
First, we obviously must open the key at Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedPidlMRU.
The stored data value we need is on one of the values, which has a number as a name.
The first byte of the MRUListEx value lies the last path.
HKEY hKey = NULL;
std::wstring regMRUPath = LR"(Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedPidlMRU\)";
LSTATUS statusCode = RegOpenKeyExW(HKEY_CURRENT_USER, regMRUPath.data(), 0, KEY_QUERY_VALUE, &hKey);
if (statusCode != ERROR_SUCCESS)
// Handle error
BYTE data[MAX_PATH];
DWORD bufferSize = MAX_PATH;
statusCode = RegGetValueW(hKey, L"", L"MRUListEx", RRF_RT_REG_BINARY, NULL, &data, &bufferSize);
if (statusCode != ERROR_SUCCESS)
// Handle error
std::wstring keyName = std::to_wstring(data[0]);
Now that we have the value, we can get its data.
DWORD reqBuffSize = 0;
statusCode = RegQueryValueExW(hKey, keyName.data(), NULL, NULL, NULL, &reqBuffSize);
if (statusCode != ERROR_SUCCESS)
// maybe the specified key is invalid or missing.
BYTE pathData[reqBuffSize];
statusCode = RegGetValueW(hKey, L"", keyName.data(), RRF_RT_REG_BINARY, NULL, &pathData, &reqBuffSize);
if (statusCode != ERROR_SUCCESS)
// maybe the specified key is invalid or missing.
We have another problem: The path is not directly accessible. The executable name is prefixed from the real path, so we must remove it.
Actually, it's very easy. The delimiter between the executable name and the real path is \0\0\0.
const size_t offset = (lstrlenW(reinterpret_cast<LPCWSTR>(pathData)) * sizeof(wchar_t))
+ (2 * sizeof(wchar_t));
The obtained value is not human-readable, but it actually stores a PIDL, so we can get it with SHGetPathFromIDList. The ITEMIDList is not very well documented on the Microsoft's website, but here's a way to create one of these things:
IMalloc* pMalloc;
if (FAILED(SHGetMalloc(&pMalloc)))
// handle error, failed to get a pointer to the IMalloc interface.
PIDLIST_ABSOLUTE pIdl = (PIDLIST_ABSOLUTE)pMalloc->Alloc((reqBuffSize - offset) + 1);
pIdl->mkid.cb = (sizeof(USHORT) + (reqBuffSize - offset));
memcpy_s(pIdl->mkid.abID, (reqBuffSize - offset) + 1, pathData + offset, (reqBuffSize - offset) + 1);
PIDLIST_ABSOLUTE pNext = ILGetNext(pIdl);
if (!pNext)
// handle error, failed to get a pointer to the next item
pNext->mkid.cb = 0;
initialDir.reserve(MAX_PATH * 2);
The ITEMIDList structure has two members: cb and abID. cb is the size of a USHORT + the size of the data, and abID is a pointer to the data itself.
The last ITEMIDList struct must have cb set to zero to mark the end. ILGetNext gives us a pointer to the next element.
// Finally, return the path!
std::wstring retValue;
retValue.reserve(MAX_PATH);
if (FALSE == SHGetPathFromIDList(pIdl, initialDir.data())) {
// oh no! free the allocated memory and throw an exception
}
pMalloc->Free(pIdl);
It's not as hard as it seems to be at the beginning, but if you want to get this value for use with a file picker, it's recommended to use COM instead since it's easier and less error-prone. Thank tou all for tour response and have a good day!
If you want to get the path from a specified extension, see the OpenSavePidlMRU key. It works the same, but it requires some little adjustments.
const char* Launcher::GetProjectName()
{
PVOID data;
LPDWORD pcbData;
HKEY OpenResult;
LSTATUS status = RegOpenKeyEx(HKEY_CURRENT_USER, L"Environment", NULL, KEY_READ, &OpenResult);
if (status != ERROR_SUCCESS)
{
LOG(ERROR) << "Could not found registry key 'Environment'";
}
else
{
LPCWSTR project_name_key = L"project_name";
DWORD data_type;
WCHAR value[255];
PVOID pvData = value;
DWORD size = sizeof(value);
status = RegGetValue(OpenResult, NULL, project_name_key, RRF_RT_ANY, &data_type, pvData, &size);
if (status != ERROR_SUCCESS)
{
LOG(ERROR) << "Could not found registry value 'project_name'";
}
else
{
switch (data_type)
{
case REG_DWORD:
wprintf(L"Value data: %x\n", *(DWORD*)pvData);
break;
case REG_SZ:
wprintf(L"Value data: %s\n", (PWSTR)pvData);
}
}
RegCloseKey(OpenResult);
}
return 0;
}
I'm trying to get this registry key I made named "project_name" and return it as a char* or a std::string. However, I'm getting garbage data in pvData. What am I doing wrong here? I've seen some other stackoverflow posts and tried to replicate their setup as well but nothing is working. My entire goal here is to retrieve an environment variable using the windows registry.
I think there's a mismatch of ANSI and Unicode expectations. Your code is likely compiling for ANSI, but you're passing a wide-char buffer. Let's just explicitly call the A version of the Registry functions so you can stay in the ANSI string space.
Instead of this:
WCHAR value[255];
PVOID pvData = value;
DWORD size = sizeof(value);
status = RegGetValue(OpenResult, NULL, project_name_key, RRF_RT_ANY, &data_type, pvData, &size);
Use this:
char value[255];
DWORD size = sizeof(value);
status = RegGetValueA(OpenResult, NULL, project_name_key, RRF_RT_ANY, &data_type, value, &size);
Then, return a std::string as follows:
Declare your function to return a string, not a pointer:
const std::string Launcher::GetProjectName()
Then simply return value as a string;
return std::string(value);
I am trying to write&read from the windows register:
Writting:
std::string path = "c:\\"
LPCTSTR str_data = TEXT(path.c_str());
auto size = static_cast<DWORD>(strlen(str_data));
LONG setRes = RegSetValueEx(*key, TEXT("DumpFolder"), 0, REG_EXPAND_SZ, (LPBYTE)str_data, size);
Reading:
char str_data[1028];
DWORD keyType;
DWORD size;
auto sk = TEXT("SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps");
auto status = RegGetValue(HKEY_LOCAL_MACHINE, sk, TEXT("DumpFolder"), RF_RT_REG_EXPAND_SZ, &keyType, str_data, &size);
Writing appears to work fine, at least it looks fine in regedit.exe.
Reading fails with ERROR_INVALID_PARAMETER = 87. If I change RF_RT_REG_EXPAND_SZ to RRF_RT_ANY, it works in debug mode, but still fails in release with error code ERROR_MORE_DATA = 234. I tried:
std::string path = "c:\\";
path = path + "\0" (it should be null terminated anyway
but it doesn't help
UPDATE
First of all, thanks for answers, I understand the thing a little better now. Unfortunately, I am still unable to read the string successfully.
Here is the test example combined from the answer below:
HKEY registry_key;
LPCTSTR sk = "SOFTWARE\\Microsoft\\Windows\\Windows Error Reporting";
// open registry key
auto openRes = RegOpenKey(HKEY_CURRENT_USER, sk, ®istry_key);
// set default dump options
HKEY default_key;
auto createRes = RegCreateKey(registry_key, "LocalDumps", &default_key);
if (createRes != ERROR_SUCCESS) {
auto b = createRes;
}
std::string path = "c:\\";
LONG setRes = RegSetValueExA(default_key, "DumpFolder", 0, REG_EXPAND_SZ, (LPCBYTE)path.c_str(), path.size() + 1);
std::string str_data;
DWORD size = 0;
const char *sak = "SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps";
auto status = RegGetValueA(HKEY_CURRENT_USER, sak, "DumpFolder", RRF_RT_REG_EXPAND_SZ, NULL, NULL, &size);
if ((status == ERROR_SUCCESS) && (size > 1)) {
str_data.resize(size - 1);
status = RegGetValueA(HKEY_CURRENT_USER, sk, "DumpFolder", RRF_RT_REG_EXPAND_SZ, NULL, &str_data[0], &size);
}
Writing again works fine (checked in regedit, and the return error code). On the other hand, reading the size of string register sets the size to 0 and returns error code 87 = ERROR_INVALID_PARAMETER.
Apparently, I am still missing something. (the project is set to multy-byte character set)
SOLUTION
After fixing things proposed by the answers below, the following code worked for me:
#include <Windows.h>
#include <string>
#include <iostream>
#define reg_type HKEY_LOCAL_MACHINE
void main() {
const std::string reg_path = "Software\\Microsoft\\Windows\\Windows Error Reporting\\LocalDumps";
const std::string dump_folder = "DumpFolder";
const std::string path = "c:\\";
// WRITING
HKEY default_key;
auto status = RegCreateKeyExA(reg_type, reg_path.c_str(), 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE | KEY_QUERY_VALUE, NULL, &default_key, NULL);
if (status != ERROR_SUCCESS) {
std::cout << "Creating key failed.";
return;
}
status = RegSetValueExA(default_key, dump_folder.c_str(), 0, REG_EXPAND_SZ, (LPCBYTE)path.c_str(), path.size() + 1);
if (status != ERROR_SUCCESS) {
std::cout << "Setting key value failed.";
return;
}
// READING
std::string str_data;
DWORD size = 0;
status = RegGetValueA(default_key, "", dump_folder.c_str(), RRF_NOEXPAND | RRF_RT_REG_EXPAND_SZ, NULL, NULL, &size);
if ((status == ERROR_SUCCESS) && (size > 1)){
str_data.resize(size - 1);
status = RegGetValueA(default_key, "", dump_folder.c_str(), RRF_NOEXPAND | RRF_RT_REG_EXPAND_SZ, NULL, &str_data[0], &size);
std::cout << "Successfully read key value: " << str_data;
} else {
std::cout << "Unable to retrive value. Error: " << status;
}
RegCloseKey(default_key);
}
I found, that RegGetValueA should be called with a
RRF_NOEXPAND | RRF_RT_REG_EXPAND_SZ
flag, which appears strange, but is described in header where it is defined, so I guess it is correct. If using only
RRF_RT_REG_EXPAND_SZ
error 87 occurs ERROR_INVALID_PARAMETER.
On the writing side:
std::string uses char elements, but TCHAR maps to either char or wchar_t depending on whether your code is compiled with UNICODE defined or not.
The TEXT() macro only works with compile-time literals, you can't use it with runtime data. TEXT(path.c_str()) is an invalid type-cast, and won't even compile if UNICODE is enabled.
You are clearly working with char data, so you should be using the char-based API functions instead of the TCHAR-based functions.
You are also not following one of the most important rules of RegSetValueEx():
For string-based types, such as REG_SZ, the string must be null-terminated. With the REG_MULTI_SZ data type, the string must be terminated with two null characters... The size of the information pointed to by the lpData parameter, in bytes. If the data is of type REG_SZ, REG_EXPAND_SZ, or REG_MULTI_SZ, cbData must include the size of the terminating null character or characters.
std::string::c_str() returns a pointer to null-terminated data, but you are not including the null terminator when reporting the size of the data you are writing to the Registry. RegGetValue() knows how to deal with that mistake, but RegGetValueEx() does not. You might not be the only person to ever read the value, so make sure you include the null terminator properly.
Try this instead:
std::string path = "c:\\";
LONG setRes = RegSetValueExA(*key, "DumpFolder", 0, REG_EXPAND_SZ, (LPCBYTE)path.c_str(), path.size()+1);
On the reading side:
You are getting errors because you are not telling RegGetValue() how large your str_data buffer is. You have to set your size variable to the size of str_data, in bytes, before you pass it in.
Try this instead:
char str_data[1028];
DWORD size = sizeof(str_data);
DWORD dwFlags = RRF_RT_REG_EXPAND_SZ;
// NOTE: when using RRF_RT_REG_EXPAND_SZ, RRF_NOEXPAND is *required* prior to Windows 8.1!
auto status = RegGetValueA(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps", "DumpFolder", RRF_RT_REG_EXPAND_SZ | RRF_NOEXPAND, NULL, str_data, &size);
Alternatively:
std:string str_data;
DWORD size = 0;
const char *sk = "SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps";
// NOTE: when using RRF_RT_REG_EXPAND_SZ, RRF_NOEXPAND is *required* prior to Windows 8.1!
const DWORD dwFlags = RRF_RT_REG_EXPAND_SZ | RRF_NOEXPAND;
auto status = RegGetValueA(HKEY_LOCAL_MACHINE, sk, "DumpFolder", dwFlags, NULL, NULL, &size);
if ((status == ERROR_SUCCESS) && (size > 1))
{
str_data.resize(size-1);
status = RegGetValueA(HKEY_LOCAL_MACHINE, sk, "DumpFolder", dwFlags, NULL, &str_data[0], &size);
}
UPDATE: your new code fails because you have introduced new bugs.
You are using legacy Registry functions that are meant for 16bit apps. You need to use RegOpenKeyEx/RegCreateKeyEx instead of RegOpenKey/RegCreateKey, and then you can specify only the specific access rights that you actually need (create subkeys, set values, read values, etc). Even better, RegCreateKeyEx() creates missing keys for you, so you don't need to manually open a parent key separately just to create a new subkey.
Also, you changed HKEY_LOCAL_MACHINE to HKEY_CURRENT_USER, but not consistently. Some of your steps use one root, other steps use the other root. You are not able to read back the value you are writing because you are not reading from the same key you wrote to.
Try this instead:
LPCSTR sk = "SOFTWARE\\Microsoft\\Windows\\Windows Error Reporting\\LocalDumps";
HKEY default_key;
auto status = RegCreateKeyExA(HKEY_LOCAL_MACHINE, sk, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_SET_VALUE, NULL, &default_key, NULL);
if (status == ERROR_SUCCESS)
{
std::string path = "c:\\";
status = RegSetValueExA(default_key, "DumpFolder", 0, REG_EXPAND_SZ, (LPCBYTE)path.c_str(), path.size() + 1);
RegCloseKey(default_key);
}
LPCSTR sk = "SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps";
std::string str_data;
DWORD size = 0;
// NOTE: when using RRF_RT_REG_EXPAND_SZ, RRF_NOEXPAND is *required* prior to Windows 8.1!
const DWORD dwFlags = RRF_RT_REG_EXPAND_SZ | RRF_NOEXPAND;
auto status = RegGetValueA(HKEY_LOCAL_MACHINE, sk, "DumpFolder", dwFlags, NULL, NULL, &size);
if ((status == ERROR_SUCCESS) && (size > 1))
{
str_data.resize(size - 1);
status = RegGetValueA(HKEY_LOCAL_MACHINE, sk, "DumpFolder", dwFlags, NULL, &str_data[0], &size);
}
On the other hand, when you have to make multiple API calls to read a value (ie, to query the size, then query the data), you should explicitly open the parent key first:
const char *sk = "SOFTWARE\\Microsoft\\Windows\\Windows Error reporting\\LocalDumps";
std:string str_data;
HKEY default_key;
auto status = RegOpenKeyExA(HKEY_LOCAL_MACHINE, sk, 0, KEY_QUERY_VALUE, &dumps_key);
if (status == ERROR_SUCCESS)
{
DWORD size = 0;
// NOTE: when using RRF_RT_REG_EXPAND_SZ, RRF_NOEXPAND is *required* prior to Windows 8.1!
const DWORD dwFlags = RRF_RT_REG_EXPAND_SZ | RRF_NOEXPAND;
status = RegGetValueA(default_key, "", "DumpFolder", dwFlags, NULL, NULL, &size);
if ((status == ERROR_SUCCESS) && (size > 1))
{
str_data.resize(size-1);
status = RegGetValueA(default_key, "", "DumpFolder", dwFlags, NULL, &str_data[0], &size);
}
RegCloseKey(default_key);
}
i try to read the Registry in my NPAPI-Plugin:
bool ScriptablePluginObject::Invoke(NPObject* obj, NPIdentifier methodName, const NPVariant* args, uint32_t argCount, NPVariant* result) {
ScriptablePluginObject *thisObj = (ScriptablePluginObject*) obj;
char* name = npnfuncs->utf8fromidentifier(methodName);
LPCWSTR game_path = getRegKey(L"SOFTWARE\\World of RPG", L"Path");
MessageBox(NULL, game_path, L"Debugging", MB_TOPMOST);
/* ... */
}
LPCWSTR ScriptablePluginObject::getRegKey(LPCWSTR location, LPCWSTR name) {
HKEY hKey;
LPBYTE folder = new BYTE[MAX_PATH];
DWORD dwSize = sizeof(folder);
long registry = RegOpenKeyEx(HKEY_LOCAL_MACHINE, location, 0, KEY_READ | KEY_WOW64_64KEY, &hKey);
long entry = RegQueryValueEx(hKey, name, NULL, REG_NONE, folder, &dwSize);
if(registry != ERROR_SUCCESS) {
return L"Error1";
}
if(entry != ERROR_SUCCESS) {
return L"Error2";
}
RegCloseKey(hKey);
folder[dwSize / sizeof(folder[0])] = '\0';
return (LPCWSTR) folder;
}
But it's returned every call Error2. I've tried a lot of changes:
change the Path (with Start and/or Ending \\)
change parameters
I Want to get the Path of HKEY_LOCAL_MACHINE\SOFTWARE\World of RPG\Path:
Anyone can help me? What i'm doing wrong?
Here's the sample I mentioned in the comments above:
#include <stdlib.h>
#include <stdio.h>
#include <tchar.h>
#include <windows.h>
LSTATUS ReadRegistry ( LPCWSTR sPath, LPCWSTR sKey, LPWSTR pBuffer, DWORD *pBufferSize );
int _tmain(int argc, _TCHAR* argv[])
{
const int BUFFER_SIZE = 1024;
WCHAR sBuffer[BUFFER_SIZE]; // 2048 bytes
DWORD nBufferSize = BUFFER_SIZE * sizeof ( WCHAR );
ZeroMemory ( sBuffer, nBufferSize );
LSTATUS nResult = ReadRegistry ( L"SOFTWARE\\7-Zip", L"Path64",
sBuffer, &nBufferSize );
// check nResult for ERROR_SUCCESS to know if the call succeeded or not
return 0;
}
LSTATUS ReadRegistry ( LPCWSTR sPath, LPCWSTR sKey, LPWSTR pBuffer, LPDWORD pBufferSize )
{
HKEY hKey;
LSTATUS nResult = ::RegOpenKeyEx ( HKEY_LOCAL_MACHINE, sPath,
0, KEY_READ | KEY_WOW64_64KEY, &hKey );
if ( nResult == ERROR_SUCCESS )
{
nResult = ::RegQueryValueEx ( hKey, sKey, NULL, NULL,
(LPBYTE) pBuffer, pBufferSize );
RegCloseKey ( hKey );
}
return ( nResult );
}
Notice how the ReadRegistry function doesn't allocate memory - it takes a buffer and fills it with data. It's a lot easier to deal with memory if you always have the caller allocate memory. If the callee allocates memory, the caller may not know how memory was allocated and it may not know how to free it. (Of course, you can always assume the use of new and delete but things are simpler if only one side does this consistently. If the caller allocates memory, it'll know how to free it. The callee only needs to put data in the allocated space.
Also, notice how the return value of the API functions is checked before proceeding to the next call - this is important because this tells you if you got a useful registry handle back or not and whether you need to close it or not.
(This sample is really just C, not C++ but it still applies.)
In getRegKey(), your folder variable is a pointer, so sizeof(folder) is 4 (if compiling for 32bit) or 8 (if compiling for 64bit). Thus RegQueryValueEx() fails with an ERROR_MORE_DATA error code.
You are also using the wrong data type for the array. You need to use WCHAR instead of BYTE.
Change this:
LPBYTE folder = new BYTE[MAX_PATH];
DWORD dwSize = sizeof(folder);
To this:
LPWSTR folder = new WCHAR[MAX_PATH];
DWORD dwSize = sizeof(WCHAR) * MAX_PATH;
With that said, you are leaking the memory pointed to by folder, since you never delete[] it.
I am writing a simple C++ program to grab a Windows registry value on a 64 bit machine.
The problem is it only works for about 50% of the registry's and for the other half "ret" does not return ERROR_SUCCESS(0).
My question is to why I am getting these inconsistent returns and also when I attempt to make the path longer than two directories it also break.
ex.
keypath = TEXT("SOFTWARE\\Perl\\ASDF");
Here is my code.
LPCTSTR keypath = TEXT("SOFTWARE\\Perl");
HKEY key = NULL;
LONG ret = ERROR_SUCCESS;
DWORD BufferSize = TOTALBYTES;
DWORD cbData;
DWORD dwRet;
DWORD type;
char registry[256] = {'\0'};
ret = RegOpenKeyEx(HKEY_LOCAL_MACHINE, keypath, 0, KEY_QUERY_VALUE, &key);
PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize );
cbData = BufferSize;
if (ret == ERROR_SUCCESS)
{
dwRet = RegQueryValueEx( key,
TEXT("BinDir"),
NULL,
&type,
(LPBYTE) PerfData,
&cbData );
RegCloseKey(key);
printf("\nFinal buffer size is %d\n", BufferSize);
int i = 0;
while ((*PerfData).Signature[i] != NULL)
{
registry[i] = (char)(*PerfData).Signature[i];
i++;
}
printf("registery: %s\n", registry);
}
editing in fixes.