根据 node.js 中的行数拆分文本文件

Question

在这里达到了我的理解极限。我有一个大文本文件，我需要将其分成 200 行的块（使用 mime.types 练习）。我正在使用readline，但它似乎忽略了我的pause / resume 语句。我错过了什么：

// Splits a given file into smaller subfiles by line number
var infileName = 'mime.types';
var fileCount = 1;
var count = 0;
var fs = require('fs');
var outfileName = infileName + '.' + fileCount;
var inStream = fs.createReadStream(infileName);
var outStream = fs.createWriteStream(outfileName);
var lineReader = require('readline').createInterface({
  input: inStream
});

lineReader.on('line', function(line) {
  count++;
  lineReader.pause();
  outStream.write(line + '\n');
  if (count >= 200) {
    fileCount++;
    console.log('file ', outfileName, count);
    outStream.close();
    outfileName = infileName + '.' + fileCount;
    outStream = fs.createWriteStream(outfileName);
    count = 0;
  }
  lineReader.resume();
});

lineReader.on('close', function() {
  if (count > 0) {
    console.log('Final close:', outfileName, count);
  }
  inStream.close();
  outStream.close();
  console.log('Done');
});

我也试过把stream的变化放到写操作的回调中：

lineReader.on('line', function(line) {
  count++;
  lineReader.pause();
  outStream.write(line + '\n', function() {
    if (count >= 200) {
      fileCount++;
      console.log('file ', outfileName, count);
      outStream.close();
      outfileName = infileName + '.' + fileCount;
      outStream = fs.createWriteStream(outfileName);
      count = 0;
    }
    lineReader.resume();
  });
});

两种情况的结果都是一样的：
node split file mime.types.1 1588 Done

理想情况下，我想要一个不依赖额外 npm 的解决方案

Answer 1

我摆脱了暂停/恢复。它们似乎不受 readline 流的支持。我所做的只是每 200 行提供一个新的可写流。

// Splits a given file into smaller subfiles by line number
var infileName = 'mime.types';
var fileCount = 1;
var count = 0;
var fs = require('fs');
var outStream;
var outfileName = infileName + '.' + fileCount;
newWriteStream();
var inStream = fs.createReadStream(infileName);

var lineReader = require('readline').createInterface({
    input: inStream
});

function newWriteStream(){
    outfileName = infileName + '.' + fileCount;
    outStream = fs.createWriteStream(outfileName);
    count = 0;
}

lineReader.on('line', function(line) {
    count++;
    outStream.write(line + '\n');
    if (count >= 200) {
        fileCount++;
        console.log('file ', outfileName, count);
        outStream.end();
        newWriteStream();
    }
});

lineReader.on('close', function() {
    if (count > 0) {
        console.log('Final close:', outfileName, count);
    }
    inStream.close();
    outStream.end();
    console.log('Done');
});