js实现unicode码字符串与utf8字节数据互转详解
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2023-11-14 13:49:40
js的string变量存储字符串使用的是unicode编码,要保存时必须选择其他编码后进行传输,比如转成utf-8,utf-32等。存储到数据库中为utf-8编码,读取出来...
js的string变量存储字符串使用的是unicode编码,要保存时必须选择其他编码后进行传输,比如转成utf-8,utf-32等。存储到数据库中为utf-8编码,读取出来如何转换成正确的字符串就成了问题。现在给出解决方案,可以正确支持中文、emoji表情、英文混合的字符串编码互转。
/** * created by hdwang on 2019/1/28. */ var convertutf8 = (function() { /** * unicode string to utf-8 * @param text 字符串 * @returns {*} utf-8编码 */ function tobytes(text) { var result = [], i = 0; text = encodeuri(text); while (i < text.length) { var c = text.charcodeat(i++); // if it is a % sign, encode the following 2 bytes as a hex value if (c === 37) { result.push(parseint(text.substr(i, 2), 16)) i += 2; // otherwise, just the actual byte } else { result.push(c) } } return coercearray(result); } /** * utf8 byte to unicode string * @param utf8bytes * @returns {string} */ function utf8bytetounicodestr(utf8bytes){ var unicodestr =""; for (var pos = 0; pos < utf8bytes.length;){ var flag= utf8bytes[pos]; var unicode = 0 ; if ((flag >>>7) === 0 ) { unicodestr+= string.fromcharcode(utf8bytes[pos]); pos += 1; } else if ((flag &0xfc) === 0xfc ){ unicode = (utf8bytes[pos] & 0x3) << 30; unicode |= (utf8bytes[pos+1] & 0x3f) << 24; unicode |= (utf8bytes[pos+2] & 0x3f) << 18; unicode |= (utf8bytes[pos+3] & 0x3f) << 12; unicode |= (utf8bytes[pos+4] & 0x3f) << 6; unicode |= (utf8bytes[pos+5] & 0x3f); unicodestr+= string.fromcodepoint(unicode) ; pos += 6; }else if ((flag &0xf8) === 0xf8 ){ unicode = (utf8bytes[pos] & 0x7) << 24; unicode |= (utf8bytes[pos+1] & 0x3f) << 18; unicode |= (utf8bytes[pos+2] & 0x3f) << 12; unicode |= (utf8bytes[pos+3] & 0x3f) << 6; unicode |= (utf8bytes[pos+4] & 0x3f); unicodestr+= string.fromcodepoint(unicode) ; pos += 5; } else if ((flag &0xf0) === 0xf0 ){ unicode = (utf8bytes[pos] & 0xf) << 18; unicode |= (utf8bytes[pos+1] & 0x3f) << 12; unicode |= (utf8bytes[pos+2] & 0x3f) << 6; unicode |= (utf8bytes[pos+3] & 0x3f); unicodestr+= string.fromcodepoint(unicode) ; pos += 4; } else if ((flag &0xe0) === 0xe0 ){ unicode = (utf8bytes[pos] & 0x1f) << 12;; unicode |= (utf8bytes[pos+1] & 0x3f) << 6; unicode |= (utf8bytes[pos+2] & 0x3f); unicodestr+= string.fromcharcode(unicode) ; pos += 3; } else if ((flag &0xc0) === 0xc0 ){ //110 unicode = (utf8bytes[pos] & 0x3f) << 6; unicode |= (utf8bytes[pos+1] & 0x3f); unicodestr+= string.fromcharcode(unicode) ; pos += 2; } else{ unicodestr+= string.fromcharcode(utf8bytes[pos]); pos += 1; } } return unicodestr; } function checkint(value) { return (parseint(value) === value); } function checkints(arrayish) { if (!checkint(arrayish.length)) { return false; } for (var i = 0; i < arrayish.length; i++) { if (!checkint(arrayish[i]) || arrayish[i] < 0 || arrayish[i] > 255) { return false; } } return true; } function coercearray(arg, copy) { // arraybuffer view if (arg.buffer && arg.name === 'uint8array') { if (copy) { if (arg.slice) { arg = arg.slice(); } else { arg = array.prototype.slice.call(arg); } } return arg; } // it's an array; check it is a valid representation of a byte if (array.isarray(arg)) { if (!checkints(arg)) { throw new error('array contains invalid value: ' + arg); } return new uint8array(arg); } // something else, but behaves like an array (maybe a buffer? arguments?) if (checkint(arg.length) && checkints(arg)) { return new uint8array(arg); } throw new error('unsupported array-like object'); } return { tobytes: tobytes, frombytes: utf8bytetounicodestr } })()
针对emoji的字节字符,占两个unicode字符。使用string.fromcharcode也可以实现,需要进行两次fromcharcode,没有frompointcode方便。下面展示了utf-8的4字节转换为unicode(utf-16)的过程。
//高char10位[一个unicode字符] (2+6+2=10) unicode = ((utf8bytes[pos] & 0x3)) << 8 |((utf8bytes[pos+1] & 0x3f) << 2) |((utf8bytes[pos+2] >> 4) & 0x03); //减去1f600中的1,这里减去6个0即可,低位char已经占据10位 unicode = unicode - parseint('1000000',2) //加上utf-16高char的标识符 unicode = 0xd800 + unicode; console.log(unicode); unicodestr += string.fromcharcode(unicode); //低char10位[一个unicode字符](4+6) unicode = ((utf8bytes[pos+2] & 0x0f) << 6) | (utf8bytes[pos+3] & 0x3f); //加上utf-16低char的标识符 unicode = 0xdc00 + unicode; console.log(unicode); unicodestr+= string.fromcharcode(unicode); pos += 4;
以上所述是小编给大家介绍的js实现unicode码字符串与utf8字节数据互转详解整合,希望对大家有所帮助
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