Converting wstring bytes to string...

I'm trying to get the bytes from a std::wstring and put them into a std::string. Unfortunately, I'm somewhat lacking when it comes to c-style string. I've made this code (and it works), but is there an easier (and more efficient) way?

Code:

---

std::string WideStringToStringStrict( const std::wstring& Text )
{
        unsigned int Size = Text.size() * sizeof( wchar_t );
        char* ctemp = new char[Size];
        memcpy( ctemp, Text.c_str(), Size );
        std::string String;
        for ( unsigned int i = 0; i < Size; ++i )
                String += ctemp[i];
        delete[] ctemp;
        return String;
};

---

Thanks.

What is this?
Do you really want to copy byte-by-byte wstring to string?
Or convert each of the wstring's element to its string's element equivalent (so the size of the string will be X times less)?

For the first one I see no point.

And you don't need any buffer for this (your code leaks memory in case the += operator throws an exception).

Code:

---


std::string wtoa(const std::wstring& wide)
{
    std::string str;
    for(std::wstring::const_iterator it = wide.begin();
        it != wide.end();
        ++it)
    {
        str.push_back(static_cast<char>(*it));
    }
    return str;
}

---

Haven't tested it, but something like this.

I couldn't resist :p
My version:

Code:

---

std::string wtoa(const std::wstring& wide)
{
    std::string out;
    std::transform(wide.begin(), wide.end(), std::back_inserter(out),
        [](wchar_t ch) -> char { return static_cast<char>(ch); });
    return out;
}

---

Of course, not tested.
By yours truly.

@kmdv: I specifically need the extra byte from the wchar_t.

@Elysia: Jesus of Nazareth, my brain overheats just trying to understand that std::transform function. Pity it won't compile.

I get the feeling that this isn't an easy (or common) task. I guess I'll have to stick with mine or try to fix it up later.

Thanks for the help.

It compiles fine. Just a small typo there: whar_t should of course be wchar_t.
Also make sure to include necessary headers:

#include <string>
#include <iterator>
#include <algorithm>

The function isn't all that complicated either. All it does is take an input range (first two parameters), an output iterator, and a function to perform the "transformation".
Then all it does is for each it in [begin, end), *out = transform(*it).

Also, in case you need the extra byte, then this should suffice:

Code:

---

std::string wtoa(const std::wstring& wide)
{
    std::string out;
    std::copy(wide.begin(), wide.end(), std::back_inserter(out));
    return out;
}

---

Code:

---

std::string wtoa (const std::wstring& wstr)
{
  return (std::string(wstr.begin(), wstr.end()));
}

---

Much better, imo.

But, all in all, I'd seriously question the idea of converting from wchar_t into char without considering encodings or even the case of a wchar_t greater than CHAR_MAX.

Quote:

---

Originally Posted by Elysia

I couldn't resist :p
My version:

Code:

---

std::string wtoa(const std::wstring& wide)
{
    std::string out;
    std::transform(wide.begin(), wide.end(), std::back_inserter(out),
        [](wchar_t ch) -> char { return static_cast<char>(ch); });
    return out;
}

---

Of course, not tested.
By yours truly.

---

What the holy hell is that?? It looks more like Groovy code than C++. Is it some kind of C++0x syntax?

Quote:

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Originally Posted by cpjust

What the holy hell is that?? It looks more like Groovy code than C++. Is it some kind of C++0x syntax?

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Lambda function syntax from the next version of C++. Considering that Ronix's suggestion should be one of the first things that come to mind, I suspect Elysia was just looking for an excuse to demonstrate the use of a lambda function ;)

Why is lambda so fugly in this language? Couldn't they use lambda or something?

Quote:

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Originally Posted by Ronix

Code:

---

std::string wtoa (const std::wstring& wstr)
{
  return (std::string(wstr.begin(), wstr.end()));
}

---

Much better, imo.

But, all in all, I'd seriously question the idea of converting from wchar_t into char without considering encodings or even the case of a wchar_t greater than CHAR_MAX.

---

Ahhh, that's even better. Damn, I didn't think of that.

Quote:

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Originally Posted by laserlight

Lambda function syntax from the next version of C++. Considering that Ronix's suggestion should be one of the first things that come to mind, I suspect Elysia was just looking for an excuse to demonstrate the use of a lambda function ;)

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Actually, I thought I'd use std::transform for this purpose instead of writing long unnecessary code that does the same thing. Why not use the standard library when you can?
But std::transform requires a function to do the conversion, or transformation, so I stuck in a lambda to do the work.

Quote:

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Originally Posted by whiteflags

Why is lambda so fugly in this language? Couldn't they use lambda or something?

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Dunno. They don't look so ugly to me.
The reason they didn't use lambda is probably to avoid introducing a new keyword.