C++ mbrlen()用法及代码示例

在给定当前转换状态ps的情况下，C /C++中的mbrlen()函数确定多字节字符的剩余部分的大小(以字节为单位)，该字符的第一个字节由str指向。此函数的行为取决于所选C语言环境的LC_CTYPE类别。

用法:

size_t mbrlen( const char* str, size_t n, mbstate_t* ps)

参数：该函数接受三个强制性参数，如下所述：

str: 指定指向要检查的多字节字符串的第一个字节的指针
n: 指定要检查的s中的最大字节数
ps: 指定指向mbstate_t对象的指针，该对象定义了转换状态

返回值：该函数返回四个值，如下所示：

完成有效的多字节字符的字节数
如果发生编码错误，则为-1
如果s指向空字符，则为0
-2如果接下来的n个字节是可能有效的多字节字符的一部分，则在检查所有n个字节后仍不完整

以下示例程序旨在说明上述函数：
示例1:

// C++ program to illustrate 
// mbrlen() function 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to find the size of 
// the multibyte character 
void check_(const char* str, size_t n) 
{ 
    // Multibyte conversion state 
    mbstate_t ps = mbstate_t(); 
  
    // number of byte to be saved in returnV 
    int returnV = mbrlen(str, n, &ps); 
  
    if (returnV == -2) 
        cout << "Next " << n << " byte(s) doesn't"
             << " represent a complete"
             << " multibyte character" << endl; 
  
    else if (returnV == -1) 
        cout << "Next " << n << " byte(s) doesn't "
             << "represent a valid multibyte character" << endl; 
    else
        cout << "Next " << n << " byte(s) of "
             << str << "holds " << returnV << " byte"
             << " multibyte character" << endl; 
} 
  
// Driver code 
int main() 
{ 
    setlocale(LC_ALL, "en_US.utf8"); 
    char str[] = "\u10000b5"; 
  
    // test for first 1 byte 
    check_(str, 1); 
  
    // test for first 6 byte 
    check_(str, 6); 
  
    return 0; 
}

输出：

Next 1 byte(s) doesn't represent a complete multibyte character
Next 6 byte(s) of á??0b5holds 3 byte multibyte character

示例2:

// C++ program to illustrate 
// mbrlen() function 
// with empty string 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to find the size of the multibyte character 
void check_(const char* str, size_t n) 
{ 
    // Multibyte conversion state 
    mbstate_t ps = mbstate_t(); 
  
    // number of byte to be saved in returnV 
    int returnV = mbrlen(str, n, &ps); 
  
    if (returnV == -2) 
        cout << "Next " << n << " byte(s) doesn't"
             << " represent a complete"
             << " multibyte character" << endl; 
  
    else if (returnV == -1) 
        cout << "Next " << n << " byte(s) doesn't "
             << "represent a valid multibyte character" << endl; 
    else
        cout << "Next " << n << " byte(s) of "
             << str << "holds " << returnV << " byte"
             << " multibyte character" << endl; 
} 
  
// Driver code 
int main() 
{ 
    setlocale(LC_ALL, "en_US.utf8"); 
    char str[] = ""; 
  
    // test for first 1 byte 
    check_(str, 1); 
  
    // test for first 3 byte 
    check_(str, 3); 
  
    return 0; 
}

输出：

Next 1 byte(s) of holds 0 byte multibyte character
Next 3 byte(s) of holds 0 byte multibyte character

相关用法

注：本文由纯净天空筛选整理自AmanSrivastava1大神的英文原创作品 mbrlen() function in C/C++。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。