Best strategy to append to binary files

thanks for the answers!

That would allow to do circular buffer in the file.

A circular buffer is roughly the idea I am thinking about: as new data comes in it gets appended. When the file is full, old data gets overwritten. This should be possible pre-allocating enough space using also the size parameter in the write() method so that I can re-write on the same file with offset in the write() method to append. However, the documentation says that I can't rewrite the same position on the same file which brings two problems:

Problem 1: I cannot rewrite older data. Workaround is to pre-allocate enough space and not overwrite. If space ends, I either create a larger file (and copy the existing content), or I give up and warn the user. I can live with the second, though not great.

Problem 2: I need to keep track of what is the last byte that was written on the file, otherwise when I read back the file I will get all the "empty" data, the 0xFF bytes. Solutions are that I either impose that 0xFF cannot be used or that I keep track of the actual size of the storage file in a separate permanent memory, but Storage (and StorageFiles) would not work for this because I cannot rewrite them.

Do you wise people have a better idea?
Gordon, maybe you can extend the current API to support overwriting already written positions?