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Difference between revisions of "cpp/string/multibyte/mbstowcs"

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< cpp‎ | string‎ | multibyte
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{{cpp/title|mbstowcs}}
 
{{cpp/title|mbstowcs}}
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{{cpp/string/multibyte/sidebar}}
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{{cpp/string/multibyte/navbar}}
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{{ddcl | header=cstdlib |
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{{ddcl|header=cstdlib|
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std::size_t mbstowcs( wchar_t* dst, const char* src, std::size_t len)
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std::size_t mbstowcs( wchar_t* dst, const char* src, std::size_t len );
 
}}
 
}}
  
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Converts a multibyte character string from the array whose first element is pointed to by {{tt|src}} to its wide character representation. Converted characters are stored in the successive elements of the array pointed to by {{tt|dst}}. No more than {{tt|len}} wide characters are written to the destination array.
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Converts a multibyte character string from the array whose first element is pointed to by {{c|src}} to its wide character representation. Converted characters are stored in the successive elements of the array pointed to by {{c|dst}}. No more than {{c|len}} wide characters are written to the destination array.
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+
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Each character is converted as if by a call to {{c|std::mbtowc}}, except that the mbtowc conversion state is unaffected. The conversion stops if:
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Each character is converted as if by a call to {{lc|std::mbtowc}}, except that the mbtowc conversion state is unaffected. The conversion stops if:
 
* The multibyte null character was converted and stored.
 
* The multibyte null character was converted and stored.
 
* An invalid (in the current C locale) multibyte character was encountered.
 
* An invalid (in the current C locale) multibyte character was encountered.
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* The next wide character to be stored would exceed {{tt|len}}.
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* The next wide character to be stored would exceed {{c|len}}.
  
 
===Notes===
 
===Notes===
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In most implementations, this function updates a global static object of type {{c|std::mbstate_t}} as it processes through the string, and cannot be called simultaneously by two threads, {{c|std::mbsrtowcs should be used in such cases.
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In most implementations, this function updates a global static object of type {{lc|std::mbstate_t}} as it processes through the string, and cannot be called simultaneously by two threads, {{lc|std::mbsrtowcs}} should be used in such cases.
  
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POSIX specifies a common extension: if {{tt|dst}} is a null pointer, this function returns the number of wide characters that would be written to {{tt|dst}}, if converted. Similar behavior is standard for {{c|std::mbsrtowcs}}.
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POSIX specifies a common extension: if {{c|dst}} is a null pointer, this function returns the number of wide characters that would be written to {{c|dst}}, if converted. Similar behavior is standard for {{lc|std::mbsrtowcs}}.
  
 
===Parameters===
 
===Parameters===
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{{param list begin}}
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{{par begin}}
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{{param list item | dst | pointer to wide character array where the wide string will be stored}}
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{{par|dst|pointer to wide character array where the wide string will be stored}}
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{{param list item | src | pointer to the first element of a null-terminated multibyte string to convert}}
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{{par|src|pointer to the first element of a null-terminated multibyte string to convert}}
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{{param list item | len | number of wide characters available in the array pointed to by dst}}
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{{par|len|number of wide characters available in the array pointed to by dst}}
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{{param list end}}
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{{par end}}
  
 
===Return value===
 
===Return value===
 
On success, returns the number of wide characters, excluding the terminating {{c|L'\0'}}, written to the destination array.
 
On success, returns the number of wide characters, excluding the terminating {{c|L'\0'}}, written to the destination array.
  
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On conversion error (if invalid multibyte character was encountered), returns {{c|static_cast<std::size_t>(-1)}}.
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On conversion error (if invalid multibyte character was encountered), returns {{c|static_cast<std::size_t> (-1)}}.
  
 
===Example===
 
===Example===
 
{{example
 
{{example
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|
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|code=
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| code=
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−
#include <iostream>
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#include <clocale>
 
#include <clocale>
 
#include <cstdlib>
 
#include <cstdlib>
 +
#include <iostream>
 +
 
int main()
 
int main()
 
{
 
{
 
     std::setlocale(LC_ALL, "en_US.utf8");
 
     std::setlocale(LC_ALL, "en_US.utf8");
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     const char* mbstr = u8"z\u00df\u6c34\U0001d10b"; // or u8"zß水𝄋"
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    std::wcout.imbue(std::locale("en_US.utf8"));
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                         // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";
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     const char* mbstr = "z\u00df\u6c34\U0001f34c"; // or u8"zß水🍌"
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                         // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c";
 
     wchar_t wstr[5];
 
     wchar_t wstr[5];
 
     std::mbstowcs(wstr, mbstr, 5);
 
     std::mbstowcs(wstr, mbstr, 5);
 
     std::wcout << "wide string: " << wstr << '\n';
 
     std::wcout << "wide string: " << wstr << '\n';
 
}
 
}
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| output=
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|output=
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wide string: zß水𝄋
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wide string: zß水🍌
 
}}
 
}}
  
 
===See also===
 
===See also===
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{{dcl list begin}}
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{{dsc begin}}
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{{dcl list template | cpp/string/multibyte/dcl list mbsrtowcs}}
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{{dsc inc|cpp/string/multibyte/dsc mbsrtowcs}}
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{{dcl list template | cpp/string/multibyte/dcl list wcstombs}}
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{{dsc inc|cpp/string/multibyte/dsc wcstombs}}
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{{dcl list template | cpp/locale/codecvt/dcl list do_in}}
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{{dsc inc|cpp/locale/codecvt/dsc do_in}}
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{{dcl list see c | c/string/multibyte/mbstowcs}}
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{{dsc see c|c/string/multibyte/mbstowcs}}
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{{dcl list end}}
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{{dsc end}}
 +
 
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 10:01, 19 October 2023

 
C++
 
Strings library
 
Null-terminated multibyte strings
Wide/multibyte conversions
mbstowcs
(C++20)
(C++11)
(C++11)    
Types
 
Defined in header <cstdlib>
std::size_t mbstowcs( wchar_t* dst, const char* src, std::size_t len );

Converts a multibyte character string from the array whose first element is pointed to by src to its wide character representation. Converted characters are stored in the successive elements of the array pointed to by dst. No more than len wide characters are written to the destination array.

Each character is converted as if by a call to std::mbtowc, except that the mbtowc conversion state is unaffected. The conversion stops if:

  • The multibyte null character was converted and stored.
  • An invalid (in the current C locale) multibyte character was encountered.
  • The next wide character to be stored would exceed len.

Contents

[edit] Notes

In most implementations, this function updates a global static object of type std::mbstate_t as it processes through the string, and cannot be called simultaneously by two threads, std::mbsrtowcs should be used in such cases.

POSIX specifies a common extension: if dst is a null pointer, this function returns the number of wide characters that would be written to dst, if converted. Similar behavior is standard for std::mbsrtowcs.

[edit] Parameters

dst - pointer to wide character array where the wide string will be stored
src - pointer to the first element of a null-terminated multibyte string to convert
len - number of wide characters available in the array pointed to by dst

[edit] Return value

On success, returns the number of wide characters, excluding the terminating L'\0', written to the destination array.

On conversion error (if invalid multibyte character was encountered), returns static_cast<std::size_t> (-1).

[edit] Example

Run this code
#include <clocale>
#include <cstdlib>
#include <iostream>
 
int main()
{
    std::setlocale(LC_ALL, "en_US.utf8");
    std::wcout.imbue(std::locale("en_US.utf8"));
    const char* mbstr = "z\u00df\u6c34\U0001f34c"; // or u8"zß水🍌"
                        // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c";
    wchar_t wstr[5];
    std::mbstowcs(wstr, mbstr, 5);
    std::wcout << "wide string: " << wstr << '\n';
}

Output: 

wide string: zß水🍌

[edit] See also

 converts a narrow multibyte character string to wide string, given state
(function) [edit]
converts a wide string to narrow multibyte character string
(function) [edit]
[virtual]
 converts a string from ExternT to InternT, such as when reading from file
(virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
C documentation for mbstowcs
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