Anyone know of a function to...

[Jim1981]

...return the difference between two absolute paths?

For my project, I need to pass two actual paths to a function so I can set the relative path of the second actual path passed.

For example, if I pass c:\folder1\ and c:\folder1\folder2\folder3, the function will return folder2\folder3 - as this is the difference between the two. This makes it easy to link to my second path relatively from my first path, if you see what I mean.

Thanks for any help,

Jim

[Andreas Masur]

I am not aware of such a function...so I would guess you would come up with your own one...

[Jim1981]

Okay Andreas, thanks.

If anyone has already written anything like this, it would be a real help if you could show me the function.

Thanks
Jim

[Kheun]

It's actually quite simple with std::string.

#include <string>
using namespace std;

string PathDiff(const string &first, const string &second)
{
	// Search if the second string contain the first string
	if(second.find(first) == 0)
	{
		// Removing the occurence of the first string in second string.
		return second.substr( first.length() );
	}

	return second;
}

[Jim1981]

Cheers Kheun, that's helpful.

What I need is a little more complicated than that though, because the two absolute paths will not always be on the same branch. For example, I might pass c:\folder\folder1, and c:\folder\folder2, in which case the function will need to return ..\folder2 ...etc.

It needs to be able to give the difference in any paths passed.

I am starting to write this myself now and will probably use what you have written as the template for this. I'm a little new to this though so it's not too easy for me.

Thanks
Jim

[Jim1981]

Okay, it's a little long-winded, but here is the function I have written to deal with this - if it's of use to anyone else. As I say, I'm a bit new so it's probably not written particularly well, and there may be something I've overlooked, but it seems to work

Cheers,
Jim

CString AbsolutePathDiff(CString path1, CString path2)
{
//ignore 0 as this will be the drive
	int count=1;
	int file1check=0, file2check=0;

	CString path1buf;	
	CString path2buf;	
	CString newpath;	
	CString dirsback;	

	newpath.Empty();
	dirsback.Empty();

//1. loop through both paths grabbing folders one-by-one	
	while(TRUE)
	{
		file1check=AfxExtractSubString(path1buf, path1, count, '\\');
		file2check=AfxExtractSubString(path2buf, path2, count, '\\');

//no path left to grab so break out
		if(file1check==0 && file2check==0)
		{
			break;
		}		

		if(file1check==0)
		{			
			newpath.Insert(newpath.GetLength()+1, path2buf);
			newpath.Insert(newpath.GetLength()+1, "\\");
		}
		else if(file2check==0)
		{			
			dirsback.Insert(0, "..\\");
		}
		else if(path1buf.CompareNoCase(path2buf)!=0)
		{			
			dirsback.Insert(0, "..\\");
			newpath.Insert(newpath.GetLength()+1, path2buf);
			newpath.Insert(newpath.GetLength()+1, "\\");
		}		

		count++;
	}

	newpath.Insert(0, dirsback);

	return newpath;
}

[Bob Davis]

Just some advice: I would rewrite your function to use std::string in place of CString. There's no need to lock yourself down to requiring MFC when it's not necessary.

[carribus]

CString is no longer MFC specific, and why would you want to lock yourself down to a slow std:string class? *joking*

[Andreas Masur]

CString is no longer MFC specific

Was that part of the joke?

[Jim1981]

Can't rewrite it 'cause I don't gots time!

[CJ1]

...return the difference between two absolute paths?

For my project, I need to pass two actual paths to a function so I can set the relative path of the second actual path passed.

For example, if I pass c:\folder1\ and c:\folder1\folder2\folder3, the function will return folder2\folder3 - as this is the difference between the two. This makes it easy to link to my second path relatively from my first path, if you see what I mean.

If you are programming for Windows paltforms, try the PathRelativePathTo() which is part of the SHLWAPI.dll (IE 5.0+). These are the shell APIs for IE, they are documented in MSDN, or see the shlwapi.h file in your include directory (VC++ installations).