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Is there a O(1) way in windows API to concatenate 2 files?
O(1) with respect to not having to read in the entire second file and write it out to the file you want to append to. So as opposed to O(n) bytes processed.
I think this should be possible at the file system driver level, and I don’t think there is a user mode API available for this, but I thought I’d ask.
If the ‘new file’ is only going to be read by your application, then you can get away without actually concatenating them on disk.
You can just implement a stream interface that behaves as if the two files have been concatenated, and then use that stream as opposed to what ever the default filestream implementation used by your app framework is.
If that won’t work for you, and you are using windows, you could always create a re parse point and a file system filter. I believe if you create a ‘mini filter’ that it will run in user mode, but I’m not sure.
You can probably find more information about it here:
http://www.microsoft.com/whdc/driver/filterdrv/default.mspx