一般情况下，如何恢复下载的工作？ [英] In general, how does resuming a download work?

问题描述

我使用的是互联网下载管理器。它恢复从早期的暂停点下载的能力。其他下载管理器，如Firefox的也提供这种能力。如何将这些算法一般的工作？如何他们通常跟踪，他们已经离开，并让服务器知道形式，其中以恢复？

I'm using "Internet Download Manager". It has the ability to resume a download from an earlier paused point. Other download managers, such as Firefox's also offer this ability. How do these algorithms work in general? How does they normally keep track of where they've left off, and allow servers to know form where to resume?

推荐答案

有没有算法。

看 2616 ，其中包括HTTP / 1.1，对于各种范围支持它;这是一个客户端程序如何告诉服务器跳过一些[兆]字节，从而恢复离开的地方下载。但是，服务器的可以的忽略范围检索请求从而阻止/禁止续传。

Look at RFC 2616, which covers HTTP/1.1, for the various range support it has; this is how a client program can tell the server to skip a number of [mega]bytes and thus "resume" the download where it left off. However, servers may ignore Range Retrieval Requests and thereby thwart/prohibit resuming downloads.

记住何处恢复是留给客户端，但被平凡存储为字节数已下载字段某处。

Remembering where to resume is left up to the client, but is trivially stored as a "number of bytes already downloaded" field somewhere.

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