#include <iostream>
#include <string.h>

using namespace std;

typedef unsigned char   UTF8;   /* typically 8 bits */
static const char trailingBytesForUTF8[256] = {
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
};

bool isLegalUTF8(const UTF8 *source, int length) {
	UTF8 a;
	const UTF8 *srcptr = source+length;
	switch (length) {
	default: return false;
		/* Everything else falls through when "true"... */
	case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
	case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
	case 2: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;

		switch (*source) {
			/* no fall-through in this inner switch */
		case 0xE0: if (a < 0xA0) return false; break;
		case 0xED: if (a > 0x9F) return false; break;
		case 0xF0: if (a < 0x90) return false; break;
		case 0xF4: if (a > 0x8F) return false; break;
		default:   if (a < 0x80) return false;
		}

	case 1: if (*source >= 0x80 && *source < 0xC2) return false;
	}
	if (*source > 0xF4) return false;
	return true;
}
//以UTF8格式截取字符串
int cutUTF8StringLen(const UTF8* utf8)
{
	const UTF8** source = &utf8;
	
	int len = strlen((const char*)utf8);
	if(len > 20)	//超过多少字符截取
		len = 10;
	else	
		return 0;

	char *strDest = new char[21];
	const UTF8* sourceEnd = utf8 + len;
	int lenSave = 0;
	while (*source != sourceEnd) {
		int length = trailingBytesForUTF8[**source] + 1;
		if (length > (sourceEnd - *source) || !isLegalUTF8(*source, length))
			break;
		*source += length;
		lenSave += length;
	}
	return lenSave;
}

int main()
{
	string strName = "qaz@#$李中天789气味人水电费是滴水电费士大夫是";
	cout<<strlen(strName.c_str())<<endl;
	int lenSave = cutUTF8StringLen((unsigned char*)strName.c_str());
	cout<<lenSave<<endl;
	strName = strName.substr(0,lenSave);
	cout<<strName<<endl;
	return 0;
}