How to convert QString to LPCSTR (Unicode)

Question

how can I convert QString to LPCSTR ?

How do I do it when #ifdef UNICODE is defined and when it isn't ?

Thanks very much :)

score 13 · Accepted Answer · answered Mar 26 '11 at 16:11

13

I guess:

QString str("ddddd");
LPCSTR lstr = str.toStdString().c_str();

answered Mar 26 '11 at 16:11

snoofkin

8,725
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86

Thats if LPCSTR is const char* – snoofkin Mar 26 '11 at 16:14
2

`LPCSTR` is always defined as `char*`. You're confusing that with `LPCTSTR` (note the **T**), which can map to either `const char*` or `const wchar_t*`, depending on if `UNICODE` is defined. – Adam Rosenfield Mar 26 '11 at 18:16

score 2 · Answer 2 · answered Mar 28 '11 at 09:29

QString can always hold Unicode; LPCSTR is never Unicode. This means that you do have to consider what to do with the characters that won't fit. This isn't a "which method to use" question, but a design question.

It's quite possible that in your specific case, you absolutely know that the QString only contaisn characters from your local "ANSI" codepage (also known as ACP). In that case, the correct function is QString::toLocal8Bit ().

Alternatively, you might know that the QString only contains characters from Latin1 (ISO 8859-1). In that case, the correct function is QString::toLatin1().

You could try to call QString::toUtf8(). This will always produce a valid byte array, even if the QString contained all Unicode characters. However, formally you can't point a LPCSTR to it: UTF-8 is not a valid ACP codepage. And presumably, you want this LPCSTR to pass to another function outside your control. It's likely that function won't expect UTF-8. If it expected Unicode at all, it would take a LPCWSTR.

score 0 · Answer 3 · answered Mar 18 '13 at 18:06

I found following solution from here and it works flawlessly for me:

void fooSub(LPSTSTR X); // this is our function :-)

foo()
{
    QString text;
    if(sizeof(TCHAR) == 1)
        fooSub((LPCSTR)text.toLocal8Bit().constData()); // here you have to check, how to convert, you could also use utf8(), ...
    else
        fooSub((LPCWSTR)text.utf16());
}

score -6 · Answer 4 · answered Mar 26 '11 at 16:08

-6

LPCSTR == const char *

it's not unicode, then

LPCSTR s = (const char *)qtString;

answered Mar 26 '11 at 16:08

Mark.Ablov

857
6
6

You've misunderstood the question! – TonyK Mar 26 '11 at 16:12
I dont think (const char*)qtString converts well. – snoofkin Mar 26 '11 at 16:14
AFAIK LPCSTR is defined as TCHAR*. And TCHAR is defined either as WCHAR or CHAR according to UNICODE setting. – Sebastian Dusza Mar 26 '11 at 16:14
1

declaration in WinNT.h: `typedef __nullterminated CONST CHAR *LPCSTR, *PCSTR;` – Mark.Ablov Mar 26 '11 at 16:16
1

@Seba: That's `LPCTSTR` you're thinking of. – TonyK Mar 26 '11 at 16:28
Sorry @Mark, @TonyK my mistake :) – Sebastian Dusza Mar 26 '11 at 16:30

How to convert QString to LPCSTR (Unicode)

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