C/C中的mbrlen（）函数++-yiteyi-C++库

这个 mbrlen（） 给定当前转换状态ps，C/C++中的函数确定多字节字符剩余部分的字节大小（以字节为单位）。此函数的行为取决于所选C语言环境的LC_CTYPE类别。

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语法：

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: 指定要检查的最大字节数（以秒为单位）
附言： 指定指向定义转换状态的mbstate_t对象的指针

返回值： 该函数返回四个值，如下所示：

完成有效多字节字符的字节数
-1如果发生编码错误
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，在检查所有n个字节后，该字符仍然不完整

以下程序说明了上述功能： 项目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

项目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

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