node实现大文件断点上传

大文件的断点上传主要是利用HTTP协议的Range请求头来实现，其中Range请求头用于指定请求的数据范围，可以用于服务器响应部分内容或者支持分块下载。通过Range请求头，客户端可以在上传文件时只上传文件的某个部分，或者在上传过程中出现中断后可以继续从中断处继续上传。

以下是用Node.js实现大文件断点上传的示例代码：

const fs = require('fs');
const http = require('http');

const FILE_PATH = '/path/to/large/file';
const PORT = 3000;

const server = http.createServer((req, res) => {
  if (req.url === '/upload') {
    const range = req.headers.range;
    if (range) {
      const parts = range.replace(/bytes=/, '').split('-');
      const start = parseInt(parts[0], 10);
      const end = parts[1] ? parseInt(parts[1], 10) : fs.statSync(FILE_PATH).size - 1;
      const chunkSize = (end - start) + 1;
      const fileStream = fs.createReadStream(FILE_PATH, { start, end });
      res.writeHead(206, {
        'Content-Range': `bytes ${start}-${end}/${fs.statSync(FILE_PATH).size}`,
        'Accept-Ranges': 'bytes',
        'Content-Length': chunkSize,
        'Content-Type': 'application/octet-stream'
      });
      fileStream.pipe(res);
    } else {
      const fileStream = fs.createReadStream(FILE_PATH);
      res.writeHead(200, {
        'Content-Length': fs.statSync(FILE_PATH).size,
        'Content-Type': 'application/octet-stream'
      });
      fileStream.pipe(res);
    }
  }
});

server.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

在客户端实现文件上传时，需要分段上传每个文件分片，并记录当前上传进度。如果上传过程中出现中断，可以记录已上传的分片，下次继续上传时从中断处继续上传。以下是客户端实现文件上传的示例代码：

const fs = require('fs');
const http = require('http');
const path = require('path');

const FILE_PATH = '/path/to/large/file';
const CHUNK_SIZE = 1024 * 1024; // 1MB
const PORT = 3000;

let uploadedBytes = 0;
let totalBytes = fs.statSync(FILE_PATH).size;
let fileStream;

const uploadChunk = (start, end) => {
  const options = {
    hostname: 'localhost',
    port: PORT,
    path: '/upload',
    method: 'POST',
    headers: {
      'Content-Type': 'application/octet-stream',
      'Content-Length': end - start + 1,
      'Content-Range': `bytes ${start}-${end}/${totalBytes}`
    }
  };
  const req = http.request(options, (res) => {
    if (res.statusCode === 200 || res.statusCode === 206) {
      uploadedBytes += end - start + 1;
      console.log(`Uploaded ${uploadedBytes} bytes of ${totalBytes} bytes`);
      if (uploadedBytes === totalBytes) {
        console.log('Upload complete!');
      } else {
        uploadNextChunk();
      }
    } else {
      console.error(`Error uploading chunk ${start}-${end}: ${res.statusCode} ${res.statusMessage}`);
    }
  });
  fileStream.pipe(req);
};

const uploadNextChunk = () => {
  if (uploadedBytes === totalBytes) {
    return;
  }
  const start = uploadedBytes;
  const end = Math.min(start + CHUNK_SIZE - 1, totalBytes - 1);
  console.log(`Uploading chunk ${start}-${end}`);
  fileStream = fs.createReadStream(FILE_PATH, { start, end });
  uploadChunk(start, end);
};

const startUpload = () => {
  console.log(`Starting upload of ${path.basename(FILE_PATH)} (${totalBytes} bytes)`);
  uploadNextChunk();
};

startUpload();

注意，以上代码只是示例代码，实际项目中还需要考虑错误处理、性能优化、安全性等问题。