The file_input_stream interface was messy: it was not fiber safe (e.g., code
doing seek() in the middle of an ongoing read_exactly()), and went against
the PIMPL philosophy.
So this patch removes the file_input_stream class, and replaces it with a
completely different design:
We now have in fstream.hh a global function:
input_stream<char>
make_file_input_stream(
lw_shared_ptr<file> file, uint64_t offset = 0,
uint64_t buffer_size = 8192);
In other words, instead of "seeking" in an input stream, we just open a new
input stream object at a particular offset of the given file. Multiple input
streams might be concurrently active on the same file.
Note how make_file_input_stream now returns a regular "input_stream", not a
subtype, and it can be used just like any normal input_stream to read the stream
starting at the given position.
This patch makes "input_stream" a "final" type: we no longer subclass it in our
code, and we shouldn't in the future because it goes against the PIMPL design
(the subclass should be of the inner workings, like the data_source_impl, not
of input_stream).
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
input_stream's constructor had an unused buf_size parameter. Such a
parameter is not needed - whenever the input_stream needs more
data it calls the underlying data_source's get(), and thus only the
data_source gets to decide the buffer size. Moreover, in some
implementations, this read buffer size will be different each time -
e.g., in a chunk-compressed file, the uncompressed chunk's size will
be different each time.
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
