package com.zhexiao.kafka.component;

import org.apache.kafka.common.utils.Bytes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/**
 * 读取文件数据
 *
 * @author zhe.xiao
 * @date 2020/09/11
 * @description 上传图片保存到本地
 */
@Component
public class ReadFile {
    private static final Logger log = LoggerFactory.getLogger(ReadFile.class);


    /**
     * 读取文件并转为字节数组
     *
     * @param filepath
     * @return 字节数组
     */
    public byte[] readBinary(String filepath) {
        File file = new File(filepath);
        if (!file.exists()) {
            log.error("文件不存在, filepath={}", filepath);
            return Bytes.EMPTY;
        }

        try (

                FileInputStream fis = new FileInputStream(filepath);
                FileChannel fisChannel = fis.getChannel();
                ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream((int) fisChannel.size());
        ) {
            //分配缓冲区，设定每次读的字节数
            ByteBuffer byteBuffer = ByteBuffer.allocate(4);

            //读取数据
            int len = 0;
            while ((len = fisChannel.read(byteBuffer)) > 0) {
                //上面把数据写入到了buffer，所以可知上面的buffer是写模式，调用flip把buffer切换到读模式，读取数据
                byteBuffer.flip();
                byteArrayOutputStream.write(byteBuffer.array(), 0, len);
                byteBuffer.clear();
            }

            return byteArrayOutputStream.toByteArray();
        } catch (Exception e) {
            log.info("读取文件异常,e={}", e.getMessage());
            return Bytes.EMPTY;
        }
    }
}