Re: [Boost-users] [iostreams] problem with gzip_compressor

From: Tiago de Paula Peixoto (tiago_at_[hidden])
Date: 2005-10-30 22:40:21

On 10/30/2005 10:34 PM, Jonathan Turkanis wrote:
> gzip_compressor works as follows: The first time you write data to it, it writes
> the gzip header information to the downstream Sink, and then writes the
> beginning of the compressed data. When the filter is closed, it writes any
> compressed data that has been buffered, plus the gzip footer, which consists of
> a checksum and the length of the uncompressed data.
> 
> In the above example, the filter is automatically closed at the end of main;
> this causes the gzip footer to be written. But since no data was ever
> compressed, the gzip header has never been written.
> 
> I guess this is a bug of some sort.  What behavior would you expect in this
> case? It seems to me it would make the most sense to output data in the gzip
> format representing a 0-length file.
> 

That would also make sense to me, but it would be inconsistent with the
bzip2_compressor behavior, which doesn't write any footer if there was
no header.

And also it would create an impossibility of just visiting a file in
append mode, without writing any data to it. This could be fixed if
gzip_compressor were seekable. Is this possible to be implemented? Is
this an intended feature?

-- 
Tiago de Paula Peixoto <tiago_at_[hidden]>