Write out the buffer - return the accessor number
Allocate space for a write - pass this buffer to completeWrite . The data to be
written can be small
Announce that a write is complete (buffer must come from allocWrite)
Length, in bytes
The append point. The length, in units used by read/write for ids.
Read a buffer at the accessor number.
Truncate the file. The new file point should correspond to a position used by
#write, otherwise the
Decide not to perform the write
All the bytebuffers - debugging aid
A label to identify this ObjectFile
Any objects in this file?