js实现unicode码字符串与utf8字节数据互转

2020-02-02 作者:网站首页   |   浏览(88)

时间: 2019-01-29阅读: 477标签: 码

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;

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