我要评论一、前言
网上有许多的多线程断点续传操作，但总是写的很云里雾里，或者写的比较坑长。由于这几个月要负责公司的在线升级项目，所以正好顺便写了一下
代码如下：
using system;
using system.collections.generic;
using system.io;
using system.threading.tasks;
namespace testcenter
{
class program
{
static void main(string[] args)
{
string localsavepath = @"e:\test\testfile\local\1.msi"; //本地目标文件路径
fileinfo severfilepath = new fileinfo(@"e:\test\testfile\server\1.msi"); //服务器待文件路径
long filelength = severfilepath.length; //待下载文件大小
console.writeline("start configuration");
int packcount = 0; //初始化数据包个数
long packsize = 1024000; //数据包大小
if (filelength % packsize > 0)
{
packcount = (int)(filelength / packsize) + 1;
}
else
{
packcount = (int)(filelength / packsize);
}
console.writeline("start recieve");
var tasks = new task[packcount]; //多线程任务
for (int index = 0; index < packcount; index++)
{
int threadindex = index; //这步很关键，在task()里的绝对不能直接使用index
var task = new task(() =>
{
string tempfilepath = @"e:\test\testfile\temp\" + "qs_" + threadindex + "_" + packcount; //临时文件路径
using (filestream tempstream = new filestream(tempfilepath, filemode.create, fileaccess.write, fileshare.write))
{
int length = (int)math.min(packsize, filelength - threadindex * packsize);
var bytes = getfile(threadindex*packcount, length);
tempstream.write(bytes, 0, length);
tempstream.flush();
tempstream.close();
tempstream.dispose();
}
});
tasks[threadindex] = task;
task.start();
}
task.waitall(tasks); //等待所有线程完成
console.writeline("recieve end");
//检测有哪些数据包未下载
console.writeline("start compare");
directoryinfo tempdir = new directoryinfo(@"e:\test\testfile\temp"); //临时文件夹路径
list<string> comparefiles = new list<string>();
for (int i = 0; i < packcount; i++)
{
bool hasfile = false;
foreach (fileinfo tempfile in tempdir.getfiles())
{
if (tempfile.name.split('_')[1] == i.tostring())
{
hasfile = true;
break;
}
}
if (hasfile == false)
{
comparefiles.add(i.tostring());
}
}
//最后补上这些缺失的文件
if (comparefiles.count > 0)
{
foreach (string com_index in comparefiles)
{
string tempfilepath = @"e:\test\testfile\temp\" + "qs_" + com_index+ "_" + packcount;
using (filestream compstream = new filestream(tempfilepath, filemode.create, fileaccess.write, fileshare.write))
{
int length = (int)math.min(packsize, filelength - convert.toint32(com_index) * packsize);
var bytes = getfile(convert.toint32(com_index)*packcount, length);
compstream.write(bytes, 0, length);
compstream.flush();
compstream.close();
compstream.dispose();
}
}
}
console.writeline("compare end");
//准备将临时文件融合并写到1.msi中
console.writeline("start write");
using (filestream writestream = new filestream(localsavepath, filemode.create, fileaccess.write, fileshare.write))
{
foreach (fileinfo tempfile in tempdir.getfiles())
{
using (filestream readtempstream = new filestream(tempfile.fullname, filemode.open, fileaccess.read, fileshare.readwrite))
{
long onefilelength = tempfile.length;
byte[] buffer = new byte[convert.toint32(onefilelength)];
readtempstream.read(buffer, 0, convert.toint32(onefilelength));
writestream.write(buffer, 0, convert.toint32(onefilelength));
}
}
writestream.flush();
writestream.close();
writestream.dispose();
}
console.writeline("write end");
//删除临时文件
console.writeline("start delete temp files");
foreach (fileinfo tempfile in tempdir.getfiles())
{
tempfile.delete();
}
console.writeline("delete success");
console.readkey();
}
//这个方法可以放到remoting或者wcf服务中去，然后本地调用该方法即可实现多线程断点续传
public static byte[] getfile(int start, int length)
{
string severfilepath = @"e:\test\testfile\server\1.msi";
using (filestream serverstream = new filestream(severfilepath, filemode.open, fileaccess.read, fileshare.readwrite, 1024*80, true))
{
byte[] buffer = new byte[length];
serverstream.position = start;
//serverstream.seek(start, seekorigin.begin);
serverstream.read(buffer, 0, length);
return buffer;
}
}
}
}
二、讨论
1）需要注意的是第44行，不能直接使用index变量在task()里进行操作，而是要将它赋给threadindex，让threadindex在task()里，不然会直接报错，为什么呢？
2）70至108行代码可以在外面再套一层while循环，循环检测临时文件是否下完整了，然后再定义一个检测最大上限，超过这个上限就放弃本次更新，当用户的网络恢复正常后下次再做更新操作。所以说放临时文件的文件夹最好要包含版本信息，不会把2.0.0的临时文件和1.0.0的临时文件搞混。
3） filestream.position 与 filestream.seek(long offset, seekorigin seekorigin) 的作用都是获取流的指针位置，当文件路径使用绝对路径时使用position；相对路径时使用seek方法，
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
您可能感兴趣的文章:
如您对本文有疑问或者有任何想说的，请点击进行留言回复，万千网友为您解惑！
网友评论