Reading Windows Registry data in 64 bit operating system

msr_codeproject

Hi friends, here is my query... I am working on win32. I am writing an application to read some data from registry. It is working on 32 bit machines. But it is not working on 64 bit machines. I am using the below API to read the data. RegQueryValueEx(hKey, pszEntry, NULL, NULL, (LPBYTE)pData, 200) Is there any problem with the last parameter size (200). What size to be passed as parameter. Thanks in advance. Regards Sairam M.

Lost User

msr_codeproject wrote:

Is there any problem with the last parameter size (200). What size to be passed as parameter.

This parameter should be the address of (pointer to) a variable that contains the length of the buffer, as described here[^]. If this size is not large enough for the result then the call will fail and the required size will be entered into the variable. Thus if you make a call with the variable set to zero you can find out how big the buffer needs to be and allocate as appropriate. BTW I'm not sure why your question got downvoted so I have upped it to compensate.

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Mattias G

The strange thing is that your code actually worked in the 32 bit edition. Any call to RegQueryValueEx using your parameters would result in an attempt to write something at memory address 200. Not good.

Lost User

Mattias G wrote:

The strange thing is that your code actually worked

Firstly, that was the OP's code, not mine. Secondly, I don't think it did work correctly.

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Mattias G

Right, "your" was referring to the OP, naturally. Could have been more clear on that :)

Lost User

What I meant was you should have posted your reply to the OP, not to me.

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msr_codeproject

Hi Guys, my trails are not working. I am giving you the path of the key. Please write small code to read it. Key Path: HKEY_CURRENT_USER\Software\ABCD\ABCD UD PCL6_00-00-00-00-00-00\printer_ui\icc_profile\0 Name of the filed: szResId Type of the field: REG_DWORD Data at the field: 0x000084d6(34006) Now I want to read 0x000084d6. I tried in so many ways. But it wasn't worked. Help me. Regards msr_codeproject

David Crow

msr_codeproject wrote:

I tried in so many ways. But it wasn't worked. Help me.

Show the code you've tried so far.

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Electron Shepherd

The last parameter is wrong. It needs to be a pointer to a DWORD that gives the size of the buffer, not the size of the buffer itself. Currently, your code is using the value of the memory at address 200 as the buffer size, and that could be anything... Try:

DWORD cbSize = 200;

RegQueryValueEx(hKey, pszEntry, NULL, NULL, (LPBYTE)pData, &cbSize);

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Lost User

Try the following:

static PWSTR pszKeyName = L"Software\\ABCD\\ABCD UD PCL6_00-00-00-00-00-00\\printer_ui\\icc_profile";

LONG lResult;
HKEY hkMyKey;
DWORD dwDisposition;
DWORD dwType;
DWORD dwData;
DWORD dwSize;

lResult = RegCreateKeyEx(HKEY_CURRENT_USER,
pszKeyName,
0,
NULL,
0,
KEY_READ,
NULL,
&hkMyKey,
&dwDisposition
);
if (ERROR_SUCCESS == lResult)
{
dwSize = sizeof dwData;
lResult = RegGetValue(hkMyKey,
L"0",
L"szResId",
RRF_RT_ANY,
&dwType,
&dwData,
&dwSize
);
}

Note: this is a Win32 solution, I don't have access to a 64-bit system.

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MicroVirus

Richard MacCutchan wrote:

static PWSTR pszKeyName = L"Software\\ABCD\\ABCD UD PCL6_00-00-00-00-00-00\\printer_ui\\icc_profile";

I think you should make pszKeyName constant (i.e. static LPCWSTR), considering you're referencing it to memory (the string literal) that could be read-only.

Lost User

MicroVirus wrote:

I think you should make pszKeyName constant (i.e. static LPCWSTR), considering you're referencing it to memory (the string literal) that could be read-only.

This is a simple example of how to get a value from a registry key; making the keyname const will have no effect on the code I provided.

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MicroVirus

Richard MacCutchan wrote:

This is a simple example of how to get a value from a registry key; making the keyname const will have no effect on the code I provided.

True, but it's still good to realise that it should be const. If someone reads your post and decides to adapt it, having it to const to begin with could be useful. I know, I'm whining... :sigh: It's just that I feel it's an overlooked detail; I forget it myself, so that's why I find it important