Hello!
I'm having a bit of a fun problem, and I'd like you to help me with a
solution.
I want to create a custom io-backend. In my implementation all calls to
copy-file, move-file and delete-file should be captured and queued for deferred
and/or background batch processing.
The problem: the current implementation of copy-file calls WinAPI's CopyFile,
which blocks for the duration of the operation. For big files that takes time.
I want to create my own implementation that would copy the file piece by piece
in a Factor's cooperative non-blocking asynchronous background super-awesome
thread.
The solution: I have created a custom backend singleton and intercepted the
necessary methods. I'm advancing my implementation carefully one step at a
time. Currently I'm making the copy-file calculate a sha-256 hash of the file,
just to make sure it reads all of the contents correctly. Next step will be
writing the data to the new location.
Already I have a problem: with-file-reader calls (file-reader) internally,
which is hooked on io-backend. But my custom backend doesn't provide an
implementation for (file-reader). The way I want this to work is this: my
custom backend is to only intercept the methods I override (delete-file,
copy-file and move-file), and all the other methods are to be handled by the
previously installed backend. Kinda like an inheritance-type thing. Is there a
way to do this?
Is there a better approach to the whole problem?
My code so far:
USING: kernel namespaces
formatting prettyprint
checksums checksums.sha
io.backend io.files io.directories io.encodings.binary ;
IN: batch
SINGLETON: batch-io-backend
: with-batch-io-backend ( quot -- )
[ batch-io-backend io-backend ] dip with-variable ; inline
M: batch-io-backend delete-file ( path -- )
"TODO: batch delete file (%s)" sprintf . ;
M: batch-io-backend copy-file ( from to -- )
2dup "batch copy file (%s -> %s)" sprintf .
drop binary [
sha-256 initialize-checksum-state
"hello" add-checksum-bytes
get-checksum .
] with-file-reader ;
M: batch-io-backend move-file ( from to -- )
"TODO: batch move file (%s -> %s)" sprintf . ;
IN: scratchpad [ "README.md" "dst" copy-file ] with-batch-io-backend
---=====---
Александр
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