nodejs操作大文件

/*var fs=require('fs');
fs.open('D:\\nodejs\\test.txt','w');
fs.open("D:\\nodejs\\test.txt","a",0644,function(e,fd){
if(e) throw e;

fs.write(fd,"12345",0,'utf8',
function(e){
if(e) throw e;
fs.closeSync(fd);
})


});*/

var file_size = 1024*1024*1024; //1G
var buf_size = 10240;

var fs = require('fs');
var buf = new Buffer(buf_size);

// init temp buffer
var temp = new Buffer(10);
for (var i=0; i<10; i++) {
temp[i] = "1234567890";
}

// init buf
for (var i=0; i<buf_size/10-1; i++) {
temp.copy(buf, 10*i);
}
temp.copy(buf, 10*i, 0, buf_size-parseInt(buf_size/10)*10);
// write to file
fs.open('D:\\nodejs\\test.txt', 'w', 0666, function(err, fd){
if (err) throw err;

function write(err, written) {
if (err) throw err;
if (i>=file_size/buf_size) { //close the file
fs.close(fd);
} else { //continue to write
var length = buf_size;
if ((i+1)*buf_size>file_size) {
length = file_size-i*buf_size;
}
fs.write(fd, buf, 0, length, null, write);
i++;
}
}

var i=0;
write(null, 0);
});