C++ – Translating 32-bit paths to their WOW64 equivalents

cmfcwindowswow64

Is there any function that I can call to in a 32-bit app that would convert the paths that it thinks it's using to and from the paths that it's actually using? (For instance, call it to convert the path for a folder in Program Files to a path in Program Files (x86) or vice versa when running on a 64-bit system.) I need to do this so that, when the user is presented with a directory in the GUI (as when browsing for files or directories), he sees the real directory, rather than what the app itself thinks it sees.

We need to support both 32- and 64-bit Windows, so this should work in both environments.

Edit The need to deal with WOW64 lies in the fact that my app is the bootstrap application of an installer. By default, the product is installed under Program Files on a 32-bit system, while on a 64-bit system, it's installed under Program Files (x86). The dialogue that lets the user choose where to install the product (including on a different hard drive altogether if that's what he wants or needs); and it must work properly in both environments. Currently, it's always displaying (and browsing in) Program Files, even on 64-bit systems.

Best Answer

Is browsing through Program Files and Windows\System32 a use-case for your app? I encourage you to abandon solving this problem, as it gets really ugly. Either stay all in the 32-bit world, or recompile for x64. Living in the "in-between" world of WOW64 will make your code much more complex.

If you really want to do this, http://msdn.microsoft.com/en-us/library/aa365743(VS.85).aspx will do the trick.

Setting a bit

Use the bitwise OR operator (|) to set a bit.

number |= 1UL << n;

That will set the nth bit of number. n should be zero, if you want to set the 1st bit and so on upto n-1, if you want to set the nth bit.

Use 1ULL if number is wider than unsigned long; promotion of 1UL << n doesn't happen until after evaluating 1UL << n where it's undefined behaviour to shift by more than the width of a long. The same applies to all the rest of the examples.

Clearing a bit

Use the bitwise AND operator (&) to clear a bit.

number &= ~(1UL << n);

That will clear the nth bit of number. You must invert the bit string with the bitwise NOT operator (~), then AND it.

Toggling a bit

The XOR operator (^) can be used to toggle a bit.

number ^= 1UL << n;

That will toggle the nth bit of number.

Checking a bit

You didn't ask for this, but I might as well add it.

To check a bit, shift the number n to the right, then bitwise AND it:

bit = (number >> n) & 1U;

That will put the value of the nth bit of number into the variable bit.

Changing the nth bit to x

Setting the nth bit to either 1 or 0 can be achieved with the following on a 2's complement C++ implementation:

number ^= (-x ^ number) & (1UL << n);

Bit n will be set if x is 1, and cleared if x is 0. If x has some other value, you get garbage. x = !!x will booleanize it to 0 or 1.

To make this independent of 2's complement negation behaviour (where -1 has all bits set, unlike on a 1's complement or sign/magnitude C++ implementation), use unsigned negation.

number ^= (-(unsigned long)x ^ number) & (1UL << n);

unsigned long newbit = !!x;    // Also booleanize to force 0 or 1
number ^= (-newbit ^ number) & (1UL << n);

It's generally a good idea to use unsigned types for portable bit manipulation.

number = (number & ~(1UL << n)) | (x << n);

(number & ~(1UL << n)) will clear the nth bit and (x << n) will set the nth bit to x.

It's also generally a good idea to not to copy/paste code in general and so many people use preprocessor macros (like the community wiki answer further down) or some sort of encapsulation.

C# – How to get Program Files (x86) on Windows 64 bit

The function below will return the x86 Program Files directory in all of these three Windows configurations:

32 bit Windows
32 bit program running on 64 bit Windows
64 bit program running on 64 bit windows

static string ProgramFilesx86()
{
    if( 8 == IntPtr.Size 
        || (!String.IsNullOrEmpty(Environment.GetEnvironmentVariable("PROCESSOR_ARCHITEW6432"))))
    {
        return Environment.GetEnvironmentVariable("ProgramFiles(x86)");
    }

    return Environment.GetEnvironmentVariable("ProgramFiles");
}