[character set 6] wide string and multi byte character conversion

This paper mainly focuses on the conversion of wide characters and multi byte characters . In fact, it also involves the conversion of character sets , For your understanding , We will not introduce more here .

One 、windows

• Convert wide characters to multibytes

#include <iostream>
#include <windows.h>
using namespace std;
int main()
{
    
	wchar_t wideChar[] = L" I am a wide character ";
	// 1.  First, specify the pointer to receive the conversion result 
	char * multiByte;
	// 2.  Then call the function for the first time , Get the size of the buffer needed to store the conversion results 
	int len = WideCharToMultiByte(CP_ACP, NULL,
		wideChar,	//  The wide character string to be converted 
		-1,			//  The length to convert , Set to -1 Represents the conversion of the whole string 
		NULL,		//  First call , The receive buffer is set to NULL
		NULL,		//  The size of the receive buffer , Set to NULL Indicates that the function returns the required size 
		NULL, NULL);
	// 3.  Create a buffer of appropriate size based on the returned results 
	multiByte = new char[len];

	// 4.  The second call to the function , Make a real conversion 
	WideCharToMultiByte(CP_ACP, NULL,
		wideChar,	//  The wide character string to be converted 
		-1,			//  The length to convert , Set to -1 Represents the conversion of the whole string 
		multiByte,	//  Second call , Set as the buffer pointer to receive the conversion result 
		len,		//  Set the receive buffer size 
		NULL, NULL);
	// 5.  End of conversion , You can output and view the conversion results 
	cout << multiByte << endl;
	delete multiByte;

	system("pause");
	return 0;
}

Output

I am a wide character
Please press any key to continue . . .

• Convert multiple bytes to wide characters ：

#include <iostream>
#include <windows.h>
using namespace std;
int main()
{
    
	setlocale(LC_ALL, "chs");
	char multiByte[] = " I am a multibyte string .";
	// 1.  First, specify the pointer to receive the conversion result 
	WCHAR * wideChar;
	// 2.  Then call the function for the first time , Get the size of the buffer needed to store the conversion results 
	int len = MultiByteToWideChar(CP_ACP, NULL,
		multiByte,		//  Multibyte string to be converted 
		-1,				//  The length to convert , Set to -1 Represents the conversion of the whole string 
		NULL,			//  First call , The receive buffer is set to NULL
		0);				//  Receive buffer length , Set to 0 Represents the required length returned by the function 
	// 3.  Create a buffer of appropriate size based on the returned results 
	wideChar = new WCHAR[len];
	// 4.  The second call to the function , Make a real conversion 
	MultiByteToWideChar(CP_ACP, NULL,
		multiByte,		//  Multibyte string to be converted 
		-1,				//  The length to convert , Set to -1 Represents the conversion of the whole string 
		wideChar,		//  Second call , Set as the buffer to receive the conversion results 
		len);			//  Set the size of the receive buffer 
	// 5.  End of conversion , You can output and view the conversion results 
	wcout << wideChar << endl;
	delete wideChar;

	system("pause");
	return 0;
}

Output

I am a multibyte string .

See ： Conversion method between multibyte and wide character

Two 、linux

• iconv.h
• linux Prototype function under
• It can not only convert wide characters and multi byte characters , It can also be used to convert different character codes .

This one doesn't use much , and c++20 The corresponding function conversion is provided , Don't do too much research here , I will sort out an article later c++ 20 Provided character conversion function .

See ：linux Conversion between wide characters and multi byte characters

3、 ... and 、c Language

• c Language provides wcstombs、mbstowcs（ unsafe )

• ( Because it's not safe , stay vs2017 Can't compile , Let's use safer wcstombs_s、mbstowcs_s, Want to compile through , Can be in visual in ： Item right click – attribute – C/C++ – The preprocessor – Preprocessor definition , Add... To it _CRT_SECURE_NO_DEPRECATE that will do )

• windows and linux You can use ;

• There is 《 Four 、wchar_t》 The problems mentioned in the remarks :【 Character set II 】 Multibyte characters vs Wide characters

• wcstombs_s、mbstowcs_s It's from Microsoft ,linux It's definitely not usable .

  • wcstombs

size_t wcstombs (char* dest, const wchar_t* src, size_t max);
Convert wide-character string to multibyte string

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#define BUFFER_SIZE 50

int main()
{
    
	setlocale(LC_ALL, "chs");
	size_t ret;
	char mb[50];
	wchar_t wc[] = L" I am a wide character ";
	//wchar_t* wcStr = wc;

	/*  Convert wide character strings  */
	ret = wcstombs(mb, wc, BUFFER_SIZE);

	printf(" Number of characters to convert  = %u\n", ret);
	printf(" Multibyte characters  = %s\n\n", mb);

	return(0);
}

Output

Number of characters to convert = 14
Multibyte characters = I am a wide character

• mbstowcs

size_t mbstowcs (wchar_t* dest, const char* src, size_t max);
Convert multibyte string to wide-character string

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#define BUFFER_SIZE 50

int main()
{
    
	setlocale(LC_ALL, "chs");
	
	char mbyte[50];
	wchar_t * wbyte =NULL;

	strcpy(mbyte, " I am a multibyte character ");
	size_t mlen = strlen(mbyte);

	int dSize = mbstowcs(wbyte, mbyte, 0) + 1;

	wbyte = new wchar_t[dSize];
	wmemset(wbyte, 0, dSize);

	int len = mbstowcs(wbyte, mbyte, mlen);//mlen The length is longer than required , Will not fail .

	return(0);
}

See ：
1、wcstombs
2、mbstowcs()/wcstombs()

Four 、 The nature of wide and multibyte characters

see : What are the wide character codes and multi byte codes for Chinese characters

5、 ... and 、 other

1. Wide characters wchar_t And narrow characters char Difference and mutual transformation
2. be based on C++ Boost locale library , take utf8,utf16,utf32 Character sets are converted to and from each other
3.boost Library learning notes five Boost.Locale Character conversion gbk utf8 big5 string wstring etc.
4.windows API Realize Chinese string and GBK、Unicode、UTF-8 The three codes are converted to each other
5.boost::locale::conv:: Character encoding conversion
6. Yes C++ Local Classical analysis of