On Thu, Aug 26, 2010 at 2:04 PM, Darin Fisher da...@chromium.org wrote:
I noticed that FileWriter.truncate() can only be used to shorten a file, and
there does not seem to be a good way to grow a file using FileWriter without
appending data to it. By contrast, the POSIX ftruncate function can be used
to grow a file (zero padding it):
From ftruncate(2):
If the file previously was larger than this size, the extra data is lost.
If the file previously
was shorter, it is extended, and the extended part reads as null bytes
('\0').
I see no reason we can't add this; I just left it off for simplicity,
but your use case makes sense.
I think there are use cases for wanting to grow a file in advance of writing
data to it. For example, you might implement a system that downloads chunks
of a file in parallel using multiple XMLHttpRequest objects. The chunks may
arrive out-of-order.
A possible alternative API would be to support seeking beyond the end of the
file or writing to a starting offset that is beyond the length fo the file.
It may also be reasonable to support all of those in addition to truncating
to an offset greater than the length of the file.
I think this may be a little messier, and there's no reason to make up
a new paradigm when the POSIX one is well-known and sufficient.
If nobody objects, I'll just add it.
Eric
