[英]How to copy bytes from a specific offset in a file to another file at a specific offset?
Would like the most efficient way of copying, say, 1MB from an offset in file 1 to the same or different offset in file 2. Is it possible to have multiple threads doing the reads and the writes at the same time safely? 想要从文件1中的偏移量到文件2中的相同或不同偏移量的最有效方式复制,例如1MB。是否可以让多个线程安全地同时执行读取和写入操作?
To clarify, I of course want to handle file->file as stated. 为了澄清,我当然希望按照规定处理文件 - >文件。 However I also want to have multiple threads reading from a network IO bound location (internet, etc..), and then reassemble those back into a single file locally. 但是,我还希望从网络IO绑定位置(Internet等等)读取多个线程,然后将它们重新组装回本地的单个文件中。 If it makes more sense that the write operation be single-threaded that is fine too. 如果更有意义的是写操作是单线程的,那也很好。
You almost certainly don't want multiple threads doing this - you're going to be IO-bound, and you don't want the overhead of the disk seeking all over the place. 你几乎肯定不希望多个线程这样做 - 你将成为IO绑定,并且你不希望磁盘的开销在各地寻找。
I'd just do it in one thread: 我只是在一个线程中做到这一点:
You may find that some of the FileOptions
(eg SequentialScan
for the reader) could make a difference. 您可能会发现某些FileOptions
(例如读者的SequentialScan
)可能会有所不同。
EDIT: As noted in comments, it may be worth using two threads - one to read and one to write, particularly if you're using two separate drives. 编辑:如评论中所述, 可能值得使用两个线程 - 一个用于读取,一个用于写入,特别是如果您使用两个单独的驱动器。 However, it's also possible that with the operating system automatically doing prefetching etc, that wouldn't be helpful. 但是,操作系统也可以自动进行预取等操作,这样做也没有用。 It would certainly complicate the code. 它肯定会使代码复杂化。
Do you have a target time for this operation? 你有这个手术的目标时间吗? How fast does a simple implementation take compared with that target time? 与目标时间相比, 简单实现的速度有多快? I definitely wouldn't venture into multiple threads or async operations until you've established how long the simple approach takes. 在确定简单方法需要多长时间之前,我绝对不会冒险进入多线程或异步操作。
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