Concatenate two WCHAR_T arrays in C++

Question

Dealing with these insane strings and arrays is giving me a headache...

Here's my code so far

wchar_t mypath[MAX_PATH];
wchar_t temppath[MAX_PATH];

GetModuleFileName(0, mypath, MAX_PATH);
GetTempPath(MAX_PATH, temppath);
CreateDirectory(???, NULL);

The first two windows API functions use the LPWSTR variable. The third uses LPCWSTR. What's the major difference? After I get the path for the TEMP directory, I want to create a new directory inside it called "test". This means I need to append (L"test") to my "temppath" variable. Can someone give me some tips on how to use these arrays. This is what makes C++ a pain. Why couldn't everyone just settle on one data type for strings. How is wchar_t even useful? It's so hard to use and manipulate.

Thanks guys!

The Win32 API supports C, which does not have nice wrapper classes like `std::wstring` in C++. But since you are using C++, you can use `std::wstring` for your concatenation. — Remy Lebeau, Jul 05 '13 at 20:15
*This is what makes C++ a pain.* No it's not. That's what makes C a pain. — chris, Jul 05 '13 at 20:20

hmjd · Answer 1 · 2013-07-05T20:31:04.273

The first two windows API functions use the LPWSTR variable. The third uses LPCWSTR. What's the major difference?

LPCWSTR is a const version of LPWSTR:

From LPCWSTR:
```
typedef const wchar_t* LPCWSTR; 
```
From LPWSTR:
```
typedef wchar_t* LPWSTR, *PWSTR;
```

I want to create a new directory inside it called "test". This means I need to append (L"test") to my "temppath" variable.

Use a std::wostringstream:

std::wostringstream wos;
wos << temppath  << L"\\test";
std::wstring fullpath(wos.str());

or just a std::wstring (as suggested by chris in the comments):

std::wstring fullpath(std::wstring(temppath) + L"\\test");

to produce a concatenated version. Then use c_str() as the argument to CreateDirectory():

if (CreateDirectory(fullpath.c_str(), NULL) ||
    ERROR_ALREADY_EXISTS == GetLastError())
{
    // Directory created or already existed.
}
else
{
     // Failed to create directory.
}

Wouldn't `std::wstring(temppath) + L"\\test"` be easier (even better if `std::wstring` is used in the first place)? — chris, Jul 05 '13 at 20:22
@hmjd great answer! I accepted the other one though, because it was simpler, but I still +1'd this! — 43.52.4D., Jul 05 '13 at 22:06

score 4 · Accepted Answer · answered Jul 05 '13 at 20:18

4

Use PathCombine(), eg:

wchar_t temppath[MAX_PATH+1] = {0};
GetTempPath(MAX_PATH, temppath);

wchar_t mypath[MAX_PATH+8] = {0};
PathCombineW(mypath, temppath, L"test");

CreateDirectoryW(mypath, NULL);

answered Jul 05 '13 at 20:18

Remy Lebeau

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Concatenate two WCHAR_T arrays in C++

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