Author Topic: What does "Append" mean?  (Read 1950 times)

Offline Donk

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What does "Append" mean?
« on: November 21, 2016, 08:35:02 am »
What does "Append" mean?
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Offline Ixen

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Re: What does "Append" mean?
« Reply #1 on: November 26, 2016, 10:22:35 am »
I was going to write that it means the destination file will have the missing 3 bytes appended. But it's much more tricky, and in that specific scenario, with disabled buffering (settings) it will replace the destination file.
That comes from the requirements related to the n-buffering operations, where reads and writes has to be aligned to a sector size boundary (CH uses 4k blocks). In this case, when you schedule "append", ch rewinds the destination file to the nearest multiple of 4k, and then appends the data.
Basically it comes down to the naming of the button. It should be named something like "Resume copying". I'm filing it under https://dev.copyhandler.com/browse/CH-316

Offline Donk

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Re: What does "Append" mean?
« Reply #2 on: November 26, 2016, 10:39:33 am »
Thank you.

Quote
I was going to write that it means the destination file will have the missing 3 bytes appended.
OK, and what does it mean when those bytes are appended to that file? Is there a way to get the identical file in destination like the source file, so the identical (content) copy of the source?


Quote
That comes from the requirements related to the n-buffering operations, where reads and writes has to be aligned to a sector size boundary (CH uses 4k blocks). In this case, when you schedule "append", ch rewinds the destination file to the nearest multiple of 4k, and then appends the data.
Basically it comes down to the naming of the button. It should be named something like "Resume copying". I'm filing it under https://dev.copyhandler.com/browse/CH-316
Very sorry, I have any idea of anything, so I cannot understand that, seems to be for experts only. Actually I would not know what "Resume copying" (exactly) means, start copying the file (or more or whatever) again? From the beginning, start again to copy the rest? Or so?

Many thanks, also for the link
Windows 10 Home, 64bit

Offline Ixen

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Re: What does "Append" mean?
« Reply #3 on: November 26, 2016, 10:52:16 am »
OK, and what does it mean when those bytes are appended to that file? Is there a way to get the identical file in destination like the source file, so the identical (content) copy of the source?
If you want to be sure you have the same file after copying, choose "Overwrite" - it will start copying that file again.
The "Append" option (or using your words "copy the rest") would consider the part of destination file that already exists as if it was partially copied previously, and will just copy the remaining part. That option will give you the same files after copying (assuming that the file was previously copied from the same source file and nobody modified the destination file between copyings).

Hopefully that would answer you question.

Offline Donk

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Re: What does "Append" mean?
« Reply #4 on: November 26, 2016, 11:07:07 am »
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The "Append" option (or using your words "copy the rest") would consider the part of destination file that already exists as if it was partially copied previously, and will just copy the remaining part. That option will give you the same files after copying (assuming that the file was previously copied from the same source file and nobody modified the destination file between copyings)

So it sounds like this option would be useful for big files, e.g., you have a 5 GB file and 4,5 GB are already copied, resume would mean just copy 0,5 GB instead of using "Overwrite" what would mean copy 5 GB, the entire file. In both cases the destination files would be identical by content, so when you would check both of the copied files the checksum would be the same?
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Offline Ixen

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Re: What does "Append" mean?
« Reply #5 on: November 26, 2016, 11:39:36 am »
It is exactly as you described :)

Offline Donk

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Re: What does "Append" mean?
« Reply #6 on: November 26, 2016, 11:45:35 am »
Alright, many thanks!
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