utf8字符串截取

utf8字符串是變長字符串,在日常處理時字符串截取時,如果處理不好則會出現亂碼,針對這個問題下面給出一個通用utf8字符串截取的示例,下面給出的是用python和php實現根據原理可以用任何語言來實現.
 

# python
# utf8 substr
def safestrlength_utf8(sourcestr): # {{{
    i = 0;
    n = 0;
    str_length = len(sourcestr);

    while i < str_length:
        temp_str = sourcestr[i:i+1]
        ascnum = ord(temp_str)
        if ascnum >= 252:
            i = i + 6
        elif ascnum >= 248:
            i = i + 5
        elif ascnum >= 240:
            i = i + 4
        elif ascnum >= 224:
            i = i + 3
        elif ascnum >= 192:
            i = i + 2
        elif ascnum >= 65 and ascnum <= 90:
            i = i + 1
        else:
            i = i + 1
       n = n + 1
   n = n - 1
   return n

# utf8 string length
def safesubstr_utf8(sourcestr, cutlength):
    returnlist = []
    i = 0
    n = 0
    str_length = len(sourcestr)

    while (n < cutlength) and (i <= str_length):
        temp_str = sourcestr[i:i+1]
        ascnum = ord(temp_str)
        if ascnum >= 252:
            returnlist.append(sourcestr[i:i+6])
            i = i + 6
        elif ascnum >= 248:
            returnlist.append(sourcestr[i:i+5])
            i = i + 5
        elif ascnum >= 240:
            returnlist.append(sourcestr[i:i+4])
            i = i + 4
        elif ascnum >= 224:
            returnlist.append(sourcestr[i:i+3])
            i = i + 3
        elif ascnum >= 192:
            returnlist.append(sourcestr[i:i+2])
            i = i + 2
       elif ascnum >= 65 and ascnum <= 90:
            returnlist.append(sourcestr[i:i+1])
            i = i + 1
       else:
            returnlist.append(sourcestr[i:i+1])
            i = i + 1
       n = n + 1;
    return "".join(returnlist)

 

// php
// substr for utf8 string, then utf8 word is 1 length
public static function safesubstr_utf8($sourcestr, $cutlength) // {{{
{
    $returnstr = '';
    $i = 0;
    $n = 0;
    $str_length = strlen($sourcestr);

    while(($n < $cutlength) && ($i <= $str_length))
    {
        $temp_str = substr($sourcestr, $i, 1);
        $ascnum = Ord($temp_str);
        if($ascnum >= 252)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 6);
            $i = $i + 6;
        }
        elseif($ascnum >= 248)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 5);
            $i = $i + 5;
        }
        elseif($ascnum >= 240)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 4);
            $i = $i + 4;
        }
        elseif($ascnum >= 224)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 3);
            $i = $i + 3;
        }
        elseif($ascnum >= 192)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 2);
            $i = $i + 2;
        }
        elseif($ascnum >= 65 && $ascnum <= 90)
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 1);
            $i = $i + 1;
        }
        else
        {
            $returnstr = $returnstr.substr($sourcestr, $i, 1);
            $i = $i + 1;
        }
        $n++;
    }

    return $returnstr;
} // }}}

// get length for utf8 string, then utf8 word is 1 length
public static function safestrlength_utf8($sourcestr) // {{{
{
    $i = 0;
    $n = 0;
    $str_length = strlen($sourcestr);

    while($i <= $str_length)
    {
        $temp_str = substr($sourcestr, $i, 1);
        $ascnum = Ord($temp_str);
        if($ascnum >= 252)
        {
            $i = $i + 6;
        }
        elseif($ascnum >= 248)
        {
            $i = $i + 5;
        }
        elseif($ascnum >= 240)
        {
            $i = $i + 4;
        }
        elseif($ascnum >= 224)
        {
            $i = $i + 3;
        }
        elseif($ascnum >= 192)
        {
            $i = $i + 2;
        }
        elseif($ascnum >= 65 && $ascnum <= 90)
        {
            $i = $i + 1;
        }
        else
        {
            $i = $i + 1;
        }
        $n++;
    }
    $n--;
    return $n;
} // }}}

U-00000000 - U:

0xxxxxxx

U-00000080 - U-000007FF:

110xxxxx 10xxxxxx

U-00000800 - U-0000FFFF:

1110xxxx 10xxxxxx 10xxxxxx

U-00010000 - U-001FFFFF:

11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

U-00200000 - U-03FFFFFF:

111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

U-04000000 - U-7FFFFFFF:

1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx