How to trim const wchar_t*?

Question

I have const wchar_t* looks like "\n\t\t\t\tsomething\n\t\t\t\t" and I want to get "something". What is the most efficient way to do it?

[EDIT] I've worked out something like this:

typedef wchar_t XMLCh

const XMLCh* trimTabs(const XMLCh* text)
{
string dest = XMLString::transcode(text);
dest.erase(remove(dest.begin(),dest.end(),'\t'), dest.end());
dest.erase(remove(dest.begin(),dest.end(),'\n'), dest.end());
return XMLStr(dest.c_str()).getXMLStr();
}

XMLStr class which is existing already in my project helped mi a lot. I hope it's good answer. XMLString is a class from Xercesc library.

If it's const and you want your result to be null-terminated, then you have no other choice than make a copy of the result string. — Medinoc, Sep 15 '15 at 09:06
C or C++? Those are different languages with very different ways of going about it; pick one. — Angew is no longer proud of SO, Sep 15 '15 at 09:06
You're returning a pointer to the contents of a temporary `XMLStr`. That's going to blow up. Pick C++, return a `XMLStr`. object. — MSalters, Sep 15 '15 at 10:55

score 0 · Answer 1 · edited May 23 '17 at 12:22

Copy your const wchar_t* to std::wstring, and then trim it using one of the methods from What's the best way to trim std::string?. You cant trim const wchar_t*, it must be copied.

[edit]

additional comment to your updated question. With below function signature it is not possible to accomplish what you want.

const XMLCh* trimTabs(const XMLCh* text)

I dont know how the rest of your code looks like, but here the best you can do is to change to:

string trimTabs(const XMLCh* text)
{
string dest = XMLString::transcode(text);
dest.erase(remove(dest.begin(),dest.end(),'\t'), dest.end());
dest.erase(remove(dest.begin(),dest.end(),'\n'), dest.end());
return string(XMLStr(dest.c_str()).getXMLStr());
}

otherwise you are returning const wchar_t* to some temporary buffer which is undefined behaviur. I assume here your XMLStr is not managing memory in some global allocator.

score 0 · Answer 2 · answered Sep 15 '15 at 09:10

You will need new variable to store the characters, so first of all just iterate over your string and find the first and the last occurrance of non-whitespace character. You can use two pointers and iterate from the beginning and the end of a string. Then you can use this function to copy the string:

wchar_t* wcscpy (wchar_t* destination, const wchar_t* source);

You can find the description here: C++ Reference - wcscpy

How to trim const wchar_t*?

2 Answers2