module.exports = {
    /**
     * 文件异或加密处理
     * @param {Buffer} fileBuffer 原文件Buffer
     * @param {String} key 加密KEY
     * @param {String} sign 加密签名
     * @returns {Buffer} 加密文件Buffer
     */
    xor (fileBuffer, key = '', sign = '') {
        if (!fileBuffer) {
            Editor.log('原文件Buffer不能为空');
            return;
        }

        let keyBuffer = Buffer.from(key);
        let signBuffer = Buffer.from(sign);

        let kIndex = 0;
        let keyLen = keyBuffer.length;
        var byteLen = fileBuffer.length;
        for (let i = 0; i < byteLen; i++) {
            if (kIndex >= keyLen) {
                kIndex = 0;
            }
            fileBuffer[i] ^= keyBuffer[kIndex];
            kIndex++;
        }

        return Buffer.concat([signBuffer, fileBuffer]);
    },

    /**
     * 文件异或解密处理
     * @param {Buffer} fileBuffer 加密文件Buffer
     * @param {String} key 加密KEY
     * @param {String} sign 加密签名
     * @returns {Buffer} 原文件Buffer
     */
    rox (fileBuffer, key = '', sign = '') {
        if (!fileBuffer) {
            Editor.log('加密文件Buffer不能为空');
            return;
        }

        let keyBuffer = Buffer.from(key);
        let signBuffer = Buffer.from(sign);

        var buffer;
        var result = signBuffer.compare(fileBuffer);
        if (result < 0 || result == 0) {
            buffer = fileBuffer.slice(signBuffer.length, fileBuffer.length);
        } else {
            return fileBuffer; // 没有加密的图片
        }

        let kIndex = 0;
        let keyLen = keyBuffer.length;
        var byteLen = buffer.length;
        for (let i = 0; i < byteLen; i++) {
            if (kIndex >= keyLen) {
                kIndex = 0;
            }
            buffer[i] ^= keyBuffer[kIndex];
            kIndex++;
        }

        return buffer;
    }
};