unicode转utf8

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场景:

1.有些字符串编码是unicode的，但是第3方库需要的是utf8字符串，这时候就需要unicode转utf8的接口了。

//unicodeתutf8#include <iostream>#include <fstream>using namespace std;#define MAX_LENGTH 1024int UniCharToUTF8(wchar_t UniChar, char* OutUTFString){int UTF8CharLength = 0;if (UniChar < 0x80){ if ( OutUTFString )OutUTFString[UTF8CharLength++] = (char)UniChar;elseUTF8CharLength++;}else if(UniChar < 0x800){if ( OutUTFString ){OutUTFString[UTF8CharLength++] = 0xc0 | ( UniChar >> 6 );OutUTFString[UTF8CharLength++] = 0x80 | ( UniChar & 0x3f );}else{UTF8CharLength += 2;}}else if(UniChar < 0x10000 ){if ( OutUTFString ){OutUTFString[UTF8CharLength++] = 0xe0 | ( UniChar >> 12 );OutUTFString[UTF8CharLength++] = 0x80 | ( (UniChar >> 6) & 0x3f );OutUTFString[UTF8CharLength++] = 0x80 | ( UniChar & 0x3f );}else{UTF8CharLength += 3;}}else if( UniChar < 0x200000 ){if ( OutUTFString ){OutUTFString[UTF8CharLength++] = 0xf0 | ( (int)UniChar >> 18 );OutUTFString[UTF8CharLength++] = 0x80 | ( (UniChar >> 12) & 0x3f );OutUTFString[UTF8CharLength++] = 0x80 | ( (UniChar >> 6) & 0x3f );OutUTFString[UTF8CharLength++] = 0x80 | ( UniChar & 0x3f );}else{UTF8CharLength += 4;}}return UTF8CharLength;}void main(){FILE* pFile=fopen("E:/project/11111/Debug/11.txt","r");fseek(pFile, 2, SEEK_SET);long int file_length = 0;int index = 1;char* pBuf;pBuf = (char*)calloc(1, MAX_LENGTH);char* curr_buf;wchar_t w_ch=fgetwc(pFile);while(!feof(pFile)){   if(file_length + 6 > index * MAX_LENGTH){index++;realloc(pBuf, index * MAX_LENGTH);}curr_buf = pBuf + file_length;file_length += UniCharToUTF8(w_ch, curr_buf);printf("%s", curr_buf);w_ch=fgetwc(pFile);   }pBuf[file_length] = '\0';fclose(pFile);getchar();}