相关疑难解决方法(0)

这就是我在完美世界中所做的事情:

fs.open('somepath', 'r+', function(err, fd) {
    fs.write(fd, 'somedata', function(err, written, string) {
       fs.rewind(fd, 0) //this doesn't exist
    })
})

这是我目前的实施:

return async.waterfall([
    function(next) {
      //opening a file descriptor to write some data
      return fs.open('somepath', 'w+', next)
    }, 
    function(fd, next) {
      //writing the data
      return fs.write(fd, 'somedata', function(err, written, string) {
        return next(null, fd)
      })
    },
    function(fd, next) {
      //closing the file descriptor
      return fs.close(fd, next)
    },
    function(next) {
      //open again to reset cursor position
      return fs.open('somepath', 'r', next)
    }
], …

我想使用node.js有效地读取一个非常大的文件的最后X个字节.这样做最有效的方法是什么？

据我所知,这样做的唯一方法是创建一个读取流并循环,直到命中字节索引.

例:

// lets assume I want the last 10 bytes;
// I would open a stream and loop until I reach the end of the file
// Once I did I would go to the last 10 bytes I kept in memory 

let f = fs.createReadStream('file.xpto'); //which is a 1gb file
let data = [];

f.on('data', function(data){
    for (d of data){
        data.push(d)
        data = data.slice(1,11); //keep only 10 elements
    }

})
f.on('end', function(){
    // check data
    console.log('Last test …