base64.js

Posted 2020-12-16 笑看吴钩

export default {
     base64EncodeChars:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
     base64DecodeChars:new Array(-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, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1),
     keyStr:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
    /**
     * base64编码 
     * @param {Object} str 
     */
    base64encode(str) {
        var out, i, len;
        var c1, c2, c3;
        len = str.length;
        i = 0;
        out = "";
        while (i < len) {
            c1 = str.charCodeAt(i++) & 0xff;
            if (i == len) {
                out += this.base64EncodeChars.charAt(c1 >> 2);
                out += this.base64EncodeChars.charAt((c1 & 0x3) << 4);
                out += "==";
                break;
            }
            c2 = str.charCodeAt(i++);
            if (i == len) {
                out += this.base64EncodeChars.charAt(c1 >> 2);
                out += this.base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
                out += this.base64EncodeChars.charAt((c2 & 0xF) << 2);
                out += "=";
                break;
            }
            c3 = str.charCodeAt(i++);
            out += this.base64EncodeChars.charAt(c1 >> 2);
            out += this.base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
            out += this.base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));
            out += this.base64EncodeChars.charAt(c3 & 0x3F);
        }
        return out;
    },
    /** 
     * base64解码 
     * @param {Object} str 
     */
    base64decode(str) {
        var c1, c2, c3, c4;
        var i, len, out;
        len = str.length;
        i = 0;
        out = "";
        while (i < len) {
            /* c1 */
            do {
                c1 = this.base64DecodeChars[str.charCodeAt(i++) & 0xff];
            }
            while (i < len && c1 == -1);
            if (c1 == -1)
                break;
            /* c2 */
            do {
                c2 = this.base64DecodeChars[str.charCodeAt(i++) & 0xff];
            }
            while (i < len && c2 == -1);
            if (c2 == -1)
                break;
            out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
            /* c3 */
            do {
                c3 = str.charCodeAt(i++) & 0xff;
                if (c3 == 61)
                    return out;
                c3 = this.base64DecodeChars[c3];
            }
            while (i < len && c3 == -1);
            if (c3 == -1)
                break;
            out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
            /* c4 */
            do {
                c4 = str.charCodeAt(i++) & 0xff;
                if (c4 == 61)
                    return out;
                c4 = this.base64DecodeChars[c4];
            }
            while (i < len && c4 == -1);
            if (c4 == -1)
                break;
            out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
        }
        return out;
    },
    
    //将Ansi编码的字符串进行Base64编码
     encode64(input) {
        var output = "";
        var chr1, chr2, chr3 = "";
        var enc1, enc2, enc3, enc4 = "";
        var i = 0;
        do {
            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);
            enc1 = chr1 >> 2;
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            enc4 = chr3 & 63;
            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }
            output = output + this.keyStr.charAt(enc1) + this.keyStr.charAt(enc2)
            + this.keyStr.charAt(enc3) + this.keyStr.charAt(enc4);
            chr1 = chr2 = chr3 = "";
            enc1 = enc2 = enc3 = enc4 = "";
        } while (i < input.length);
        return output;
    },
    //将Base64编码字符串转换成Ansi编码的字符串
     decode64(input) {
        var output = "";
        var chr1, chr2, chr3 = "";
        var enc1, enc2, enc3, enc4 = "";
        var i = 0;
    
    
        if (input.length % 4 != 0) {
            return "";
        }
        var base64test = /[^A-Za-z0-9+/=]/g;
        if (base64test.exec(input)) {
            return "";
        }
        do {
            enc1 = this.keyStr.indexOf(input.charAt(i++));
            enc2 = this.keyStr.indexOf(input.charAt(i++));
            enc3 = this.keyStr.indexOf(input.charAt(i++));
            enc4 = this.keyStr.indexOf(input.charAt(i++));
            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;
    
    
            output = output + String.fromCharCode(chr1);
            if (enc3 != 64) {
                output += String.fromCharCode(chr2);
            }
            if (enc4 != 64) {
                output += String.fromCharCode(chr3);
            }
            chr1 = chr2 = chr3 = "";
            enc1 = enc2 = enc3 = enc4 = "";
        } while (i < input.length);
        return output;
    },
    utf16to8(str) {
        var out, i, len, c;
    
    
        out = "";
        len = str.length;
        for (i = 0; i < len; i++) {
            c = str.charCodeAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)) {
                out += str.charAt(i);
            } else if (c > 0x07FF) {
                out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
                out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            } else {
                out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            }
        }
        return out;
    },
    utf8to16(str) {
        var out, i, len, c;
        var char2, char3;
    
    
        out = "";
        len = str.length;
        i = 0;
        while (i < len) {
            c = str.charCodeAt(i++);
            switch (c >> 4) {
                case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                    // 0xxxxxxx
                    out += str.charAt(i - 1);
                    break;
                case 12: case 13:
                    // 110x xxxx   10xx xxxx
                    char2 = str.charCodeAt(i++);
                    out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
                    break;
                case 14:
                    // 1110 xxxx  10xx xxxx  10xx xxxx
                    char2 = str.charCodeAt(i++);
                    char3 = str.charCodeAt(i++);
                    out += String.fromCharCode(((c & 0x0F) << 12) |
                    ((char2 & 0x3F) << 6) |
                    ((char3 & 0x3F) << 0));
                    break;
            }
        }
        return out;
    }
}