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generationrandRAND_MAXremainderremainderfremainderlremquoremquofremquolrintrintfrintlroundroundfroundlscalblnscalblnfscalblnlscalbnscalbnfscalbnlsignbitsinsinfsinhsinhfsinhlsinlsqrtsqrtfsqrtlsrandtantanftanhtanhftanhltanltgammatgammaftgammaltrunctruncftrunclType-generic math_Complex_I_Imaginary_IProgram supportabortatexitat_quick_exitexitEXIT_FAILUREEXIT_SUCCESSgetenvgetenv_sjmp_buflongjmpProgram support utilitiesquick_exitraisesetjmpSIGABRTSIGFPESIGILLSIGINTsignalSIGSEGVSIGTERMsig_atomic_tSIG_DFLSIG_ERRSIG_IGNsystem_ExitStringsatofatoiatolatollbtowcc16rtombc32rtombchar16_tchar32_tisalnumisalphaisblankiscntrlisdigitisgraphislowerisprintispunctisspaceisupperiswalnumiswalphaiswblankiswcntrliswctypeiswdigitiswgraphiswloweriswprintiswpunctiswspaceiswupperiswxdigitisxdigitmblenmbrlenmbrtoc16mbrtoc32mbrtowcmbsinitmbsrtowcsmbsrtowcs_smbstate_tmbstowcsmbstowcs_smbtowcmemchrmemcmpmemcpymemcpy_smemmovememmove_smemsetmemset_sNull-terminated byte stringsNull-terminated multibyte 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文字

在头文件<wchar.h>中定义



size_t mbrlen(const char * s,size_t n,mbstate_t * ps);


(自C95以来)

size_t mbrlen(const char * restrict s,size_t n,mbstate_t * restrict ps);


(自C99以来)

确定多字节字符表示的大小(以字节为单位)。

这个函数相当于mbstate_t类型的内部隐藏对象的调用mbrtowc(nullptr,s,n,ps?ps:&internal),只是表达式ps只计算一次。

参数

s

-

指向多字节字符串的元素的指针

n

-

限制可以检查的s中的字节数

ps

-

指向保存转换状态的变量的指针

返回值

以下第一项适用:

  • 如果接下来的n个或更少的字节完成空字符或者s是空指针。 这两种情况都会重置转换状态,则返回0。

  • 返回完成有效多字节字符的字节数[1 ... n]

  • 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个字节后仍然不完整,则返回(size_t)-2

  • 如果发生编码错误,则返回(size_t)-1 。errno的价值是EILSEQ; 转换状态是未指定的。

#include <locale.h>#include <string.h>#include <stdio.h>#include <wchar.h>
 int main(void){   
    // allow mbrlen() to work with UTF-8 multibyte encoding    setlocale(LC_ALL, "en_US.utf8");    // UTF-8 narrow multibyte encoding    const char* str = u8"水";
    size_t sz = strlen(str);
 
    mbstate_t mb;    memset(&mb, 0, sizeof mb);
    int len1 = mbrlen(str, 1, &mb);    if(len1 == -2) 
        printf("The first 1 byte of %s is an incomplete multibyte char"               " (mbrlen returns -2)\n", str);
 
    int len2 = mbrlen(str+1, sz-1, &mb);    printf("The remaining %zu  bytes of %s hold %d bytes of the multibyte"           " character\n", sz-1, str, len2); 
    printf("Attempting to call mbrlen() in the middle of %s while in initial"           " shift state returns %zd\n", str, mbrlen(str+1, sz-1, &mb));}

输出:

The first 1 byte of 水 is an incomplete multibyte char (mbrlen returns -2)The remaining 2  bytes of 水 hold 2 bytes of the multibyte character
Attempting to call mbrlen() in the middle of 水 while in initial shift state returns -1

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.29.6.3.1 mbrlen函数(p:442)

  • C99标准(ISO / IEC 9899:1999):

    • 7.24.6.3.1 mbrlen函数(p:388)

扩展内容

mbrtowc(C95)

将下一个多字节字符转换为宽字符,给定状态(函数)

mblen

返回下一个多字节字符(函数)中的字节数

| mbrlen的C ++文档 |

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在头文件<wctype.h>中定义



int iswdigit(wint_t ch);


(自C95以来)

检查给定的宽字符是否对应(如果缩小)十个十进制数字字符0123456789中的一个。

参数

CH

-

宽字符

返回值

如果宽字符是数字字符,则为非零值,否则为零。

注意

iswdigitiswxdigit是唯一不受当前安装的C语言环境影响的标准宽字符分类函数。

一些语言环境提供了检测非ASCII数字的附加字符类。

#include <stdio.h>#include <wctype.h>#include <wchar.h>#include <locale.h> void test(wchar_t a3, wchar_t u3, wchar_t j3){    printf("        '%lc' '%lc' '%lc'\n", a3, u3, j3);    printf("iswdigit %d    %d   %d\n",           !!iswdigit(a3), !!iswdigit(u3), !!iswdigit(j3));    printf("jdigit:  %d    %d   %d\n", !!iswctype(a3, wctype("jdigit")),          !!iswctype(u3, wctype("jdigit")),          !!iswctype(j3, wctype("jdigit")));}
 int main(void){
    wchar_t a3 = L'3';  // the ASCII digit 3
    wchar_t u3 = L'三'; // the CJK numeral 3
    wchar_t j3 = L'3'; // the fullwidth digit 3 
    setlocale(LC_ALL, "en_US.utf8");    puts("In American locale:");    test(a3, u3, j3); 
    setlocale(LC_ALL, "ja_JP.utf8");    puts("\nIn Japanese locale:");    test(a3, u3, j3);}

输出:

In American locale:        '3' '三' '3'iswdigit 1    0   0jdigit:  0    0   0
 In Japanese locale:        '3' '三' '3'iswdigit 1    0   0jdigit:  0    0   1

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.30.2.1.5 iswdigit函数(p:449)

  • C99标准(ISO / IEC 9899:1999):

    • 7.25.2.1.5 iswdigit函数(p:395)

扩展内容

isdigit

检查一个字符是否是一个数字(功能)

| 用于iswdigit的C ++文档 |

ASCII 值  (十六进制)

字符

iscntrl  iswcntrl.

isprint  iswprint.

isspace  iswspace.

isblank  iswblank.

isgraph  iswgraph.

ispunct  iswpunct.

isalnum  iswalnum.

isalpha  iswalpha.

isupper  iswupper.

islower  iswlower.

isdigit  iswdigit.

isxdigit  iswxdigit.


0 - 8

0x00-0x08

控制码 (NUL, etc.)

≠0

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9

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tab (\t)

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space

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!"#$%&'()*+,-./

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48 - 57

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0123456789

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:;<=>?@

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65 - 70

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ABCDEF

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71 - 90

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GHIJKLMNOPQRSTUVWXYZ

0

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91 - 96

0x5B-0x60

[]^_` | 0 | ≠0 | 0 | 0 | ≠0 | ≠0 | 0 | 0 | 0 | 0 | 0 | 0 |













97 -102

0x61-0x66

abcdef

0

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103-122

0x67-0x7A

ghijklmnopqrstuvwxyz

0

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123-126

0x7B-0x7E

{|}~

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127

0x7F

退格 (DEL)

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