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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<uchar.h>中定义



size_t c32rtomb（char * s，char32_t c32，mbstate_t * ps）;


（自C11以来）

将单个代码点从其可变长度的32位宽字符表示（通常为UTF-32）转换为其窄多字节字符表示形式。

如果s不是空指针，则函数确定存储c32的多字节字符表示（包括任何移位序列）所需的字节数，并将多字节字符表示存储在第一个元素由s指向的字符数组中。 该函数最多可以写入MB_CUR_MAX个字节。

如果s是空指针，那么对于某些内部缓冲区buf，调用等价于c32rtomb（buf，U'\ 0'，ps）。

如果c32是空宽字符U'\ 0'，则存储空字节，之前是恢复初始移位状态所必需的任何移位序列，并且更新转换状态参数* ps以表示初始移位状态。

如果定义了宏__STDC_UTF_32__，则该函数使用的32位编码为UTF-32; 否则，它是实现定义的。 在任何情况下，此函数使用的多字节字符编码均由当前活动的C语言环境指定。

参数

s

-

指向多字节字符将被存储在其中的窄字符数组的指针

C32

-

要转换的32位宽字符

PS

-

指向解释多字节字符串时使用的转换状态对象的指针

返回值

成功时，返回写入字符数组的第一个元素由s指向的字节数（包括任何移位序列）。 该值可以是0，例如：处理多char32_t单元序列中的前导char32_t单元时（不发生在UTF-32中）。

失败时（如果c32不是有效的32位宽字符）则返回-1，将EILSEQ存储在errno中，并使* ps处于未指定状态。

例

#include <stdio.h>#include <locale.h>#include <uchar.h>#include <stdlib.h>
 mbstate_t state;int main(void){    setlocale(LC_ALL, "en_US.utf8");
    char32_t in[] = U"zß水?"; // or "z\u00df\u6c34\U0001F34C"
    size_t in_sz = sizeof in / sizeof *in; 
    printf("Processing %zu UTF-32 code units: [ ", in_sz);    for(size_t n = 0; n < in_sz; ++n) printf("%#x ", in[n]);    puts("]");
 
    char out[MB_CUR_MAX * in_sz];
    char *p = out;    for(size_t n = 0; n < in_sz; ++n) {
        int rc = c32rtomb(p, in[n], &state); 
        if(rc == -1) break;
        p += rc;    }
 
    size_t out_sz = p - out;    printf("into %zu UTF-8 code units: [ ", out_sz);    for(size_t x = 0; x < out_sz; ++x) printf("%#x ", +(unsigned char)out[x]);    puts("]");}

输出：

Processing 5 UTF-32 code units: [ 0x7a 0xdf 0x6c34 0x1f34c 0 ]into 11 UTF-8 code units: [ 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c 0 ]

参考

  • C11标准（ISO / IEC 9899：2011）：

    • 7.28.1.4 c32rtomb函数（p：401）

扩展内容

mbrtoc32（C11）

从一个窄多字节字符串（函数）生成下一个32位宽字符

| c32rtomb的C ++文档 |

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