How can I get the byte size of std::wstring?

Question

I am using std::wstring as my Unicode style string. Now I want to get the byte size of a wstring. If I use size() method of wstring, I just get the total number of chars in my wstring. But the byte should be size() * 2. Is there an official way to get this byte size? I don't want to use size() * 2 in my program.....

I want to use in RegSetValueExW as last parameter.

score 24 · Accepted Answer · answered Feb 14 '12 at 14:40

24

Use str.size() * sizeof(wchar_t) or equivalent.

In fact, I can't think of any other platform besides Windows that has 2-byte wchar_t, 4 bytes is far more common.

answered Feb 14 '12 at 14:40

Dietrich Epp

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If you're setting a REG_SZ using RegSetValueExW, you'll want to also add a character for the null terminator: `(str.size() + 1) * sizeof(wchar_t)` – pancakes Sep 05 '17 at 02:43

Ghassen Hamrouni · Answer 2 · 2012-02-14T14:53:03.970

9

Why not :

( str.size() * sizeof(wchar_t) ) ;

Or :

( str.size() * sizeof(std::wstring::traits_type::char_type) ) ;

edited Feb 14 '12 at 14:53

answered Feb 14 '12 at 14:48

Ghassen Hamrouni

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`sizeof(char)` is guaranteed to be 1, no need to divide by it. – Feb 14 '12 at 14:49
Yes in any standard compliant compiler sizeof(char) == 1, I edited my answer. – Ghassen Hamrouni Feb 14 '12 at 14:52

score 3 · Answer 3 · answered Dec 22 '15 at 22:10

3

std::wstring s = L"Howdy, world!";
//...
std::size_t bytes_count = s.size() * sizeof s[0];

answered Dec 22 '15 at 22:10

zdf

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score -3 · Answer 4 · answered Feb 15 '12 at 16:24

-3

You can use wcslen function

MSDN link: http://msdn.microsoft.com/en-us/library/78zh94ax.aspx

Linux: http://linux.die.net/man/3/wcslen

answered Feb 15 '12 at 16:24

Yodo

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That returns number of chars, not the number of bytes, and requires a C-Style pointer, not a std::w/string. – paulm Dec 05 '12 at 16:31

How can I get the byte size of std::wstring?

4 Answers4

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