判断字符串的编码类型(GBK / UTF8)

http://blog.suraid.cn/index.php/2008/09/is-utf8/

http://www.9php.com/FAQ/cxsjl/c/2007/08/120241592512.html

http://hi.baidu.com/szimshan/blog/item/783463c348cf7d52b219a86d.html

 

GBK:

---

int isgbk(char *s, size_t ns)
{
        if(ns > 2 && (uint8_t)*s >= 0x81 && (uint8_t)*s <= 0xfe
                && (
                        ((uint8_t)*(s+1) >= 0x80 && (uint8_t)*(s+1) <= 0x7e)
                        || ((uint8_t)*(s+1) >= 0xa1 && (uint8_t)*(s+1) <= 0xfe)
                    )
          )
        {
                return 1;
        }
        return 0;
}

---

 bool isGBKCode(const string& strIn)
{
    unsigned char ch1;
    unsigned char ch2;

    if (strIn.size() >= 2)
    {
        ch1 = (unsigned char)strIn.at(0);
        ch2 = (unsigned char)strIn.at(1);
        if (ch1>=129 && ch1<=254 && ch2>=64 && ch2<=254)
            return true;
        else return false;
    }
    else return false;
}

---

 

UTF8:

---

int isutf8(char *s, size_t ns)
{
        uint8_t x = 0, i = 0, j = 0, nbytes = 0, n = 0;

        for(i = 1; i < 7; i++)
        {
                x = (uint8_t)(255 << i);
                if(((uint8_t)*s & x) == x)
                {
                        n = nbytes = (8 - i);
                        for(j = 0; (j < nbytes && j < ns); j++)
                        {
                                if((uint8_t)s[j] <= 0x80 && (uint8_t)s[j] >= 0xc0)break;
                                else n--;
                        }
                        if(n == 0) return nbytes;
                }
        }
        return 0;
}

---

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bool isUtf8(const char *buf) { int i, n; register unsigned char c; bool gotone = false;   #define F 0 /* character never appears in text */ #define T 1 /* character appears in plain ASCII text */ #define I 2 /* character appears in ISO-8859 text */ #define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */   static const unsigned char text_chars[256] = { /* BEL BS HT LF FF CR */ F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */ /* ESC */ F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */ T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */ /* NEL */ X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */ X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */ I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */ };   /* *ulen = 0; */ for (i = 0; (c = buf[i ]); i++) { if ((c & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */ /* * Even if the whole file is valid UTF-8 sequences, * still reject it if it uses weird control characters. */   if (text_chars[c] != T) return false;   } else if ((c & 0x40) == 0) { /* 10xxxxxx never 1st byte */ return false; } else { /* 11xxxxxx begins UTF-8 */ int following;   if ((c & 0x20) == 0) { /* 110xxxxx */ following = 1; } else if ((c & 0x10) == 0) { /* 1110xxxx */ following = 2; } else if ((c & 0x08) == 0) { /* 11110xxx */ following = 3; } else if ((c & 0x04) == 0) { /* 111110xx */ following = 4; } else if ((c & 0x02) == 0) { /* 1111110x */ following = 5; } else return false;   for (n = 0; n < following; n++) { i++; if (!(c = buf[i ])) goto done;   if ((c & 0x80) == 0 || (c & 0x40)) return false; } gotone = true; } } done: return gotone; /* don't claim it's UTF-8 if it's all 7-bit */ }   #undef F #undef T #undef I #undef X