lreader

按行读取任意大的文件

npm install lreader
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按行读取任意大的文件

目的

有些日志文件或者其他需要分析的文件,过于庞大,在用node一次性处理的时候,如果将其全部读入内存,可能会导致内存不足或者是进程运行缓慢。reader中的BigFileWalker就是为了解决这个问题而生。通过分批分量读取大文件,来解决大文件读取分析的问题。

用法

var reader = require('reader');
var walker = reader.createBigFileWalker(logfile, {
  offset: 10000,  //跳过前面的10000行,不传入时不会跳过
  piece: 100000   //控制每次读取的行数,默认为十万行
});

//因为walker需要等待初始化读入完数据才能够开始使用,`ready`方法可以确保在初始化完成之后再执行
walker.ready(function () {
  var result = walker.get(10);  
  //do something whith result
  result = walker.get(100);
  //当所有的数据读取完成之后,walker.finish将被置为true
  //同时walker会触发end事件:
  walker.once('end', function () {//end事件的触发,说明所有的数据都载入过了。如果再get不到就是读完了
    //do something
  });
  //如果获取不到数据,说明读取完内存中载入的数据,没有给walker CPU时间去再次载入数据。
  //一般内存中数据都足够大,除非一直采用同步的方式在处理数据,否则不会出现下面的情况
  if (!walker.finish && !result.length) {
    walker.once('readable', function () {}); //等待载入
  }
});

install

npm install lreader

Lincense

(The MIT License)

Copyright (c) 2012 dead-horse and other contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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